THOMAS E. BOWM The Distribution of

Calanoid Copepods off

r

 the Southeastern

W United States Between

Cape Hatteras and j

Southern Florida

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 96
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SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 96

Thomas E. Bowman The Distribution of

Calanoid Copepods off

the Southeastern

United States Between

Cape Hatteras and

Southern Florida

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

1971
ABSTRACT

Bowman, Thomas E. The Distribution of Calanoid Copepods off the Southeastern

United States Between Cape Hatteras and Southern Florida. Smithsonian Contributions to Zoology, number 96, 58 pages, 1971.—About 100 species of epipelagic

calanoid copepods occur in waters off the southeastern coast of the United States.

From inshore waters seaward the species diversity increases from less than 10

species/station in coastal waters to more than 40 species/station in some oceanic

stations. The species composition changes concomitantly, and, using the FagerMcGowan index of association, coastal, shelf, and oceanic associations have been

identified, each with characteristic indicator species. The seaward gradient in

diversity is explained by Sanders' stability-time hypothesis. The calanoid fauna

south of Cape Hatteras is compared with the fauna north of Cape Hatteras.

Two species of Paracalanus, P. quasimodo, new species, and P. indicus, new

rank (=P. parvus var. indicus), both formerly referred to P. parvus, are described

and compared with the more northern P. parvus. Taxonomic remarks are given

concerning Rhincalanus cornutus, Pleuromamma gracilis and P. piseki, and

Heterorhabdus papilliger.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

UNITED STATES GOVERNMENT PRINTING OFFICE

WASHINGTON: 1971

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 • Price 65 cents (paper cover)
Thomas E. Bowman The Distribution of

Calanoid Copepods off

the Southeastern

United States Between

Gape Hatteras and

Southern Florida

Introduction

In Atlantic waters along the east coast of the United

States much less attention has been given to the

plankton in the region south of Cape Hatteras than

to that in the region north of Cape Hatteras. South of

Cape Hatteras the species of chaetognaths and their

distribution have been discussed by Bumpus and

Pierce (1955) and Pierce and Wass (1962), and the

association of pteropod species with the three water

masses off Cape Hatteras has been analyzed by Chen

and Hillman (1970). Investigations of planktonic

copepods have been for the most part taxonomic

studies, especially of Florida Current species (summarized in Owre and Foyo 1967) or analyses of

vertical movements (e.g., Moore and O'Berry 1957).

An overall survey of the patterns of copepod distribution was not possible until an adequate program of plankton sampling could be carried out.

Owing to interests in the relatively unexplored

area south of Cape Hatteras by the U. S. Fish and

Wildlife Service, the Navy Hydrographic Office,

and the Office of Naval Research, a program to investigate these waters was developed in the early

1950s. A pattern of 16 transects forty miles apart,

each transect containing 3-6 stations twenty miles

apart, was established (Figure 1). The lines extended seaward beyond the axis of the Gulf Stream,

and 9 special stations were set up farther offshore.

The 97-foot vessel Theodore N. Gill, with accomThomas E. Bowman, Division of Crustacea, National Museum

of Natural History, Smithsonian Institution, Washington,

D.C. 20560.

modations for eight scientists and ten crew, made

a series of nine cruises over the station grid between

January 1953 and December 1954, making oceanographic measurements and plankton collections at

each station.

STATION POSITIONS

REGULAR O

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FIGURE 1.—Basic station plan.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Methods

The basic physical biological and chemical data,

together with procedures and methods, have been

published for each cruise. This paper is limited to

Cruises 1-4 (February-November 1953), for which

the relevant information is given by Anderson,

Gehringer, and Cohen (1956a, 1956b), and Anderson and Gehringer (1957a, 1957b).

Plankton tows were made during Cruises 1 and

2 with a standard half-meter no. 1 silk net with an

Atlas-type current meter suspended in the mouth

to measure the amount of water filtered. During

Cruises 3 and 4 (and later cruises) tows were made

with the all-metal, half-meter Gulf III sampler

(Arnold and Gehringer 1952), except when adverse

sea conditions made it unsafe to tow the Gulf III

and the silk net was substituted. Nets were towed

obliquely starting at 70 m (100 m of cable out), or

less in shallow water, and retrieved at the rate necessary to bring them to the surface in about 20 minutes. The silk net was towed at 1-2 knots, the Gulf

III at 5-6 knots. Plankton samples were preserved in

5 percent buffered formalin.

Aliquots of 40 ml, comprising 10 percent of the

total sample, were sent to me by William W. Anderson, Director of the Bureau of Commercial Fisheries, South Atlantic Fisheries Investigations, Brunswick, Georgia. Subsamples of the aliquots were removed with a 2 ml Stempel pipet and placed in a

plastic, rectangular counting chamber for enumeration of the calanoid copepod species. Depending

on the abundance of the plankters, from 1-3 2 ml

subsamples (0.5 to 1.5 percent of the entire sample)

were enumerated. Usually 100 or more, sometimes

several hundred, copepods were counted and identified, the number depending on the species diversity. The number of each species counted was corrected to the number per 100 m3

 of water strained.

The remainder of the original 40 ml aliquot was

examined and species not present in the subsample

were noted.

Both the 40 ml aliquots and the counts of calanoids made from them are permanently stored in

the Division of Crustacea, Smithsonian Institution,

where they are available to interested investigators.

Circulation

The circulation in the area surveyed by the Gill

has been discussed by Bumpus (1955), Bumpus and

Pierce (1955), Pierce and Wass (1962), and Gray

and Cerame-Vivas (1963), hence only a brief summary is given here.

The dominant offshore feature is the Gulf Stream

(Florida Current), which has an average velocity

greater than 150 cm/sec. West of this lies the Carolinian Coastal water, composed of Florida Current

water plus river-runoff water, which extends from

Cape Hatteras to off Daytona Beach or at times to

off Cape Kennedy. Carolinian Coastal water is more

saline than most coastal water, because (1) there is

less runoff, (2) the runoff enters from sounds rather

than from river mouths, and (3) the Florida Current frequently makes broad excursions over the

shelf.

Between Cape Hatteras and Cape Cod the shelf

water is known as Virginian Coastal water and is

colder and less saline than Carolinian Coastal

water. It drifts slowly southward along the coast at

about 3-20 miles/day, due to a dynamic current induced by the addition of fresh water from river

runoff. Such a south-flowing dynamic current is

very transient in Carolinian Coastal water; it is

restricted to a very narrow portion of the shelf

and develops only during periods of substantial runoff. There is usually little motion, mostly a drift

to the northeast.

There is no regular communication between the

two coastal waters, but Virginian water may be

driven around Cape Hatteras by the northeast

winds which are common from November to May.

Between the Gulf Stream and the Virginian

Coastal water is a slowly revolving (about 10 cm/

sec) gyre of slope water. This water has essentially

the same characteristics as Gulf Stream water but

has a slightly lower salinity, due to admixture with

coastal water. No slope water intervenes between

the Gulf Stream and Carolinian Coastal water.

The eastern border of the Florida Current merges

with the Sargasso Sea, without any sharp boundary.

T-S curves are not distinctive enough to separate

the two water masses in the boundary zone, but

they can be distinguished by plotting dissolved 02

against sigma-t. The special stations show intrusion

of Sargasso Sea water, while the regular stations

near the axis of the Gulf Stream do not. In the upper 100 meters the two water masses cannot be distinguished on any basis, and analysis of the Gill

samples has not brought to light any consistent differences in the calanoid fauna.
NUMBER 96

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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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NUMBER 96

Seasonal Changes in Temperature and Salinity

Figures 2 and 3 show the distribution of surface

temperature and surface salinity during the four

cruises. In February—March strong gradients of both

temperature and salinity were present, roughly

parallel to the coastline. Temperatures ranged from

12°C near the coast to over 24°C in the Gulf

Stream, and the 36%O isohaline was well inside the

20-fathom line. By April-May the inshore surface

water was warmer and the 36%o isohaline had

moved offshore. The surface temperature range

over the area was now from about 20°C to 26°C.

The salinity range was about the same as in

February-March, but a layer of water of reduced

salinity extended out to about the 100-fathom line

northward from the Savannah section. In JulyAugust the surface waters reached their greatest

uniformity in temperature. Salinity distribution

was similar to that in the spring, except that it

was higher at the most shoreward stations. In the

fall the temperature and salinity gradients were

again well formed. An especially strong salinity

gradient off the Florida coast presumably resulted

from heavy runoff in the area, reported in the U. S.

Weather Bureau's Climatological Data—National

Summary for September 1953 as follows:

The heavy rains over the peninsular portion of Florida

during August and September caused high stages on several

streams. The St. Johns River experienced Tecord flooding.

Pasture and farm lands along the banks of the Kissimmce

River were flooded and heavy discharge from the river caused

Lake Okeechobee to rise to 0.6 feet above desirable level.

Lake Istokpoga overflowed and inundated farm roads. Localized flooding was reported in low-lying sections of Miami and

other cities on the coastal ridge.

Flood conditions still existed in Florida when

Hurricane Hazel crossed the Florida Peninsula

from Charlotte Harbor on the west coast to near

Vero Beach on the east coast on 9 October. The effects of the rains that fell during Hazel are reported

in Climatological Data—National Summary for

October 1953:

As a result of the above-normal rainfall in this area since

May, the soil was saturated, lakes were full, and some streams,

particularly the St. Johns and Kissimmee Rivers, were already

overflowing at the end of September. The 3- to 5-inch rains

which fell during the passage of this storm augmented these

flood conditions, and the resulting damage which included

the total loss of some plantings, and damage to roads,

sewers, and drainage systems was estimated to be at least

$9,000,000.

The stations of Cruise 4 off the Florida coast were

occupied between 12 October and 22 October,

shortly after the passage of Hurricane Hazel, and

the effects of the flood conditions are evident in the

salinity chart. As we shall see, the lowered salinity

had a marked effect on the distribution of copepods

in this region.

The Species of Calanoid Copepods

About one hundred species were identified in the

samples. They are listed below in taxonomic order.

Calanidae

Calanus gracilis Dana

Calanus minor (Claus)

Calanus robustior Giesbrecht

Calanus tenuicornis Dana

Undinula vulgaris (Dana)

Eucalanidae

Eucalanus attenuatus (Dana)

Eucalanus crassus Giesbrecht

Eucalanus elongatus (Dana)

Eucalanus monachus (Giesbrecht)

Eucalanus pileatus Giesbrecht

Eucalanus subtenuis Giesbrecht

Mecynocera clausi Thompson

Rhincalanus cornutus (Dana)

Para calanidae

Acrocalanus andersoni Bowman

Acrocalanus longicornis Giesbrecht

Calocalanus contractus Farran

Calocalanus gracilis Tanaka

Calocalanus pavo (Dana)

Calocalanus pavoninus Farran

Calocalanus plumulosus (Claus)

Calocalanus styliremis Giesbrecht

Paracalanus aculeatus Giesbrecht

Paracalanus crassirostris Dahl

Paracalanus indicus Wolfenden

Paracalanus pygmaeus (Claus)

Paracalanus quasimodo, new species

Pseudocalanidae

Clausocalanus furcatus (Brady)

Clausocalanus species1

Ctenocalanus vanus Giesbrecht

Aetideidae

Euaetidius gicsbrechti (Cleve)

Euchirella amoena Giesbrecht

1

 Frost and Fleminger's (1968) monograph on Clausocalanus had not appeared at the time the copepods were

being enumerated, and only the distinctive C. furcatus can be

considered to have been reliably identified.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Euchirella curticauda Giesbrecht

Euchirella messinensis (Claus)

Euchirella pulchra (Lubbock)

Euchirella rostrata (Claus)

Undeuchaeta major Giesbrecht

Undeuchaeta plumosa (Lubbock)

Euchaetidae

Euchaeta marina (Prestandrea)

Phaennidae

Phaenna spinifera Claus

Xanthocalanus agilis Giesbrecht

Scolecithricidae

Lophothrix latipes (T. Scott)

Scaphocalanus curtus (Farran)

Scaphocalanus echinatus (Farran)

Scolecithricella ctenopus (Giesbrecht)

Scolecithricella dentata (Giesbrecht)

Scolecithricella tenuiserrata (Giesbrecht)

Scolecithrix bradyi Giesbrecht

Scolecithrix danae (Lubbock)

Scottocalanus securifrons (T. Scott)

Temoridae

Temora stylifera (Dana)

Temora turbinata (Dana)

Temoropia mayumbaensis T. Scott

Metridiidae

Pleuromamma abdominalis (Lubbock)

Pleuromamma gracilis (Claus)

Pleuromamma piseki Farren

Pleuromamma xiphias (Giesbrecht)

Gentropagidae

Centropages furcatus (Dana)

Centropages hamatus (Lilljeborg)

Centropages typicus Kr^yer

Centropages violaceous (Claus)

Pseudodiaptomidae

Pseudodiaptomus coronatus Williams

Lucicutiidae

Lucicutia flavicornis (Claus)

Lucicutia gnussae Grice

Heterorhabdidae

Heterorhabdus papilliger (Claus)

Augaptilidae

Haloptilus longicornis (Claus)

Haloptilus oxycephalus (Giesbrecht)

Haloptilus spiniceps (Giesbrecht)

Arietellidae

Arietellus setosus Giesbrecht

Candaciidae

Candacia armata (Boeck)

Candacia bipinnata (Giesbrecht)

Candacia curta (Dana)

Candacia ethiopica (Dana)

Candacia longimana (Claus)

Candacia pachydactyla (Dana)

Canadacia paenelongimana Fleminger & Bowman

Paracandacia bispinosa (Claus)

Paracandacia simplex (Giesbrecht)

Pontellidae

Anomalocera ornata Sutcliffe

Calanopia americana F. Dahl

Labidocera acutifrons (Dana)

Labidocera aestiva Wheeler

Labidocera nerii (Kr^yer)

Labidocera scotti Giesbrecht

Pontella meadi Wheeler

Pontella securifer Brady

Pontella spinipes Giesbrecht

Pontellina plumata (Dana)

Pontellopsis perspicax (Dana)

Pontellopsis regalis (Dana)

Pontellopsis villosa Brady

Acartiidae

Acartia danae Giesbrecht

Acartia negligens Dana

Acartia tonsa Giesbrecht

All but about a dozen of the above species may

be identified with the aid of Rose (1933) or Owre

and Foyo (1967). Taxonomic considerations are

not the principal objective of the present paper,

and they are dealt with only when problems were

encountered, namely in the genera Paracalanus,

Pleuromamma, and Heterorhabdus.

Zonation and Species Associations

The most striking aspect of the distribution of the

copepods was the marked inshore-offshore zonation.

Certain species were restricted to coastal waters;

others were found only in oceanic waters. Along

with the change in species composition in samples

collected at progressively greater distances from

shore was an increase in the number of species in a

sample. The extremes were a station where only

Acartia tonsa was collected (Cruise 1, Station 23)

and one which yielded 42 species of calanoids

(Cruise 3, Station 48). The maps in Figure 4 show

clearly the inshore-offshore zonation in numbers of

species.

It was evident that the species associations in

coastal and shelf waters differed from those in

oceanic waters. To identify these associations, I

have used the affinity index of Fager and McGowan

(1963):

C _ 1

AB 2B

where C is the number of joint occurrences of a

pair of species; A is the total number of occurrences
NUMBER 96

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FIGURE 4.—Number of species of calanoid copepods, Cruises 1-4.
8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

of species A; B is the total number of occurrences

of species B and A ^B .

It was not practical to compute affinity indexes

between all possible pairs of the 94 species, and I

therefore restricted my analysis to 13 species which

were consistently present in the samples in significant numbers. From the 78 affinity indices computed from the 13 species for each cruise, dendrograms were constructed by the methods of Mountford (1962). The results, shown in Figures 5-6, are

remarkably consistent in that almost identical

groupings of species were obtained in the separate

analyses made for each of the four cruises. This

consistency confirms the validity of the method

used. From the shore outward the following calanoid associations can be identified.

1. A coastal association of two species, Acartia

tonsa and Labidocera aestiva. Acartia tonsa is a

widely distributed estuarine species tolerant of wide

ranges in salinity. Labidocera aestiva is less euryhaline but well known as a coastal species. The association of the two species is not high (affinity indices 0.56, 0.33, 0.56, and 0.51 for Cruises 1-4) and

is not statistically significant on Cruise 2. One might

argue for separating the coastal assemblage into the

estuarine A. tonsa and the coastal L. aestiva.

2. A shelf association of four species: Paracalanus

parvus, Centropages furcatus, Eucalanus pileatus,

and Temora turbinata. On Cruise 2, Labidocera

aestiva joins this association, and on Cruise 4, T.

turbinata leaves it to join the oceanic association.

The remaining three species are consistently associated.

3. An oceanic association of the other seven species. These species branch in various ways in the

four dendrograms but occur together consistently.

They form a rather tightly knit group, with the

exception of Lucicutia fiavicornis, which has the

lowest association with the other species of any

member of the oceanic association.

Of the 81 species for which affinity indices were

not computed, almost all of them could be placed

in the oceanic association by their distribution patterns. The higher number of species in offshore

stations has already been mentioned. The distribution of selected genera and species will be considered later in this paper.

A calanoid association is a reliable indicator of

the presence of coastal, shelf, and oceanic water at

a given locality. This is shown diagrammatically in

Figure 7. For simplicity the lines of stations are

arranged in parallel rows as though the coastline

were vertical, and stations between the main lines

are omitted. Each station is represented by a pie

diagram that shows the percentage of coastal

(black), shelf (stippled), and oceanic (white) indicator species. Nine of the thirteen species represented in the dendrograms (Figures 5-6) were

used in constructing the pie diagrams, as follows:

Coastal: Acartia tonsa, Labidocera aestive.

Shelf: Centropages furcatus, Eucalanus pileatus,

Paracalanus parvus.

Oceanic: Calanus minor, Undinula vulgaris, Euchaeta marina, Clausocalanus furcatus.

In calculations of percentages, the combined

number of those of the nine species present at any

station was considered 100 percent.

The pie diagrams show, as expected, a shift from

coastal to shelf to oceanic indicator species as we

move away from the coast (to the right in the diagrams) . They indicate the extent to which Carolinian Coastal water, the habitat of the shelf species,

has received incursions of Florida Current water,

the habitat of the oceanic species, or brackish water

from the sounds and river mouths, in which the

coastal species thrive. Rarely does a station have

only shelf species; usually there is an admixture of

oceanic and /or coastal species. Pure oceanic stations, however, are common. Stations dominated by

coastal species are few and in general close to shore.

The two stations most frequently dominated by

coastal species were Station 11, at Cape Kennedy,

and Station 23, at Jacksonville Beach near the

mouth of the St. Johns River.

Figure 8 shows for each of the four cruises a

vertical section through the line of stations 40-44,

lying off Charleston, South Carolina, with temperature profiles plotted. As in Figure 7, pie diagrams

illustrate the seaward changes in the percentages of

coastal, shelf, and oceanic species.

Seasonal changes in distribution will be discussed

in the section on distribution of the individual

species.

Species Diversity

I have already pointed out the greater numbers of

calanoid species at the oceanic stations compared
NUMBER 96

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FICURE 5.—Dendrograms from affinity indices (vertical scale) among 13 common calanoids. Cruises

1 (above) and 2 (below).
10

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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3 (above) and 4 (below).
NUMBER 96 11

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FIGURE 7.—Percentages of coastal (black), shelf (stippled), and oceanic (white) indicator species,

Cruises 1-4. For explanation see text.
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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FIGURE 8.-Vertical secuons for Cruises \-A through Stations 40-44, off Charleston, South Carolina

with temperature profiles in degrees centigrade and depths in meters. Pie diagrams show percentages of coastal (black), shelf (stippled), and oceanic (white) indicator species.
NUMBER 96 13

with the smaller numbers in shelf waters and the

very small numbers along the coast. In other words,

the species diversity, i.e., the absolute number of

species present, is greatest in oceanic waters and

least in coastal water.

Under many conditions, diversity is directly correlated with sample size, especially in small samples.

This effect led Sanders (1968) to devise his rarefaction method, which allows comparison of diversity in samples of different sizes. Fortunately it is

not necessary here to resort to Sanders' technique or

the other mathematical strategems discussed in his

paper. The net tows made during the Gill cruises

commonly filtered between 100 and 200 cubic meters of water, sometimes much more, and the numbers of calanoids collected were very great, amounting to several hundred thousand in some samples.

Although the size of the samples varied greatly, it

is safe to say that all but an insignificant number

of the calanoid species at each station were collected

and enumerated. The simplest and most direct expression of diversity, the number of species, is not

affected by sample size in the Gill collections. The

charts in Figure 4 may be considered as charts of

species diversity.

40i—

30

fe 20

Dominance Diversity or Equitability

A second concept of diversity is the extent to which

the species in a sample are equally abundant. This

dominance diversity or equitability is greatest when

the species of a sample occur in equal numbers and

minimal when the specimens of a sample are most

unequally divided among the species. Most of the

commonly used measurements of diversity take into

account the equitability as well as the number of

species. Lloyd and Ghelardi (1964) presented a

method for calculating the equitability component

(e) of diversity measured by the Shannon-Wiener

information function. Sanders (1968) demonstrated

that c is not independent of sample size but decreases with increasing sample size. He also found

only a weak correlation between the rank in dominance diversity (judged from cumulative frequency

curves) and the rank in species diversity. Moreover,

species diversity faithfully reflected the type of

environment, but dominance diversity did not.

A rough estimate of equitability is the percent

of all the calanoid species in a sample that together comprises half the total number of calanoid

specimens in that sample. In Figure 9 this measure-

•• • •

• 99

20 30 40

% SPECIES MAKING 50 % OF SAMPLE

50 60

FIGURE 9.—Relationship between equitability and species diversity. Each dot represents 1 station

of Cruise 2.
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

>25 SPECIES

Sta. 1 2 6 7 26 39 41 48 49 50 51 62 73 74

Sta. 11 45 46 55 56 57

iHh

FICURE 10.—Relative percentage of 15 species of calanoids at two groups of stations from Cruise 1.

Above: stations with > 25 calanoid species. Below: stations with < 10 calanoid species. 1, Acartia

tonsa; 2, Labidocera aestiva; 3, Centropages furcatus; 4, Paracalanus "paruus"; 5, Eucalanus pileatus; 6, Temora stylifera; 7, Temora turbinata; 8, Paracalanus aculeatus; 9, Clausocalanus furcatus; 10, Calanus minor; 11, Undinula vulgaris; 12, Euchaeta marina; 13, Lucicutia flavicornis; 14,

Pleuromamma gracilis; 15, Pleuromamma adbominalis.
NUMBER 96 15

ment is plotted against the number of species for

the stations of Cruise 2. It can be seen that equitability measured in this way is much more variable

in the samples with few species (coastal and shelf

samples), than in the oceanic samples. In the latter

samples 20-40 percent of the species commonly

make up half the sample, so the specimens in the

samples are far from being equally divided among

the component species.

A way of showing visually the degree of equitability is by a series of bar graphs indicating the

percentage composition by species of samples from

different stations. In Figure 10, bar graphs are

given for two groups of stations from Cruise 1: (1)

stations with less than 10 species of calanoids

(coastal and shelf stations); (2) stations with 25 or

more species (oceanic stations). The rather low

equitability at both groups of stations is evident.

Despite the high species diversity at the oceanic

stations, a few species tend to dominate the samples

numerically. Commonly these are the seven species

used to construct the affinity diagrams (Figures 5-6)

plus Pleuromamma gracilis and P. abdominalis.

The 9 Special Stations, on the eastern Gulf

Stream edge of the western Sargasso Sea, are farthest

removed from the influence of coastal water. Even

these purely oceanic stations were usually dominated by a few species as shown below for Cruise

2:

Special Stations

Percent of sample 12345678 9

Calanus minor 28 14 26 33 8 32 5 10 10

Clausocalanus furcatus 15 31 11 22 4 13 3 2 2

Lucicutia flavicornis 16 1 — 5 21 2 17 29 13

Grice and Hart (1962) reported that C. furcatus

was the most abundant calanoid in their Gulf

Stream and Sargasso Sea samples. Lucicutia flaxricornis was also numerically significant, but the importance of C. minor was less than in the Gill

samples.

A number of theories have been proposed to explain the sort of dominance diversity found in the

Gill samples. Most of these are highly mathematical

and are based on simplified assumptions that are

not yet fully proved. New and revised theories appear at a greater rate than the observations and

experiments needed to supply a firm factual basis

for them. It is impossible for a mathematical amateur to evaluate the merits of these theories, and I

retreat to the company of those who hold ". . . the

conviction that synecological and ecosystem approaches are too complicated for meaningful results

as long as we do not understand enough about the

individual species and factors in nature." (Hedgpeth 1967b.)

The Stability-Time Hypothesis and the

Gill Samples

To explain the increase in species diversity from

coastal to oceanic waters, Sanders' (1968) stabilitytime hypothesis, proposed to account for variations

in benthic diversity, may be applied to the pelagic

realm. Sanders defined two contrasting types of

communities:

1. The physically controlled community, where

physical conditions fluctuate widely and the animals

are exposed to severe physiological stress. Adaptations are primarily to the physical environment.

The species forming such communities are few in

number and eurytopic.

2. The biologically accommodated community,

where physical conditions are stable for long periods

of time. Stress is from biological rather than physical forces. Such communities are composed of many

species, which are stenotopic.

Neither type of community exists in pure form;

all communities in nature fall somewhere between

the two extreme types. Applied to the pelagic realm,

the inhabitants of coastal waters constitute essentially a physically controlled community, whereas

those of oceanic waters compose a biologically accommodated community.

Figures 11-12 show the ranges in surface temperature and salinity during Gill Cruises 1-4, and indicate that stress from these factors increases toward

the coast. Nearshore surface-living copepods must

endure an annual temperature range of about

15°C and a salinity change of more than 2%«.

Along the axis of the Florida Current they are subjected to annual variations of only about 5°C and

less than 0.5%o.

We know little about the ability of copepods to

withstand salinity changes, and nothing about the
16

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

1

:

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RANGE IN T (*C)

CRUISES 1-4

75" 74-

35*

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CRUISES 1-4

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81" 80' 79' 7 ' 1 • 76" 75- 74" 73"

FIGURE 11.—Variation in surface temperature during Cruises FIGURE 12.—Variation in surface salinity during Cruises 1-4.

mechanisms involved. Some preliminary experiments were carried out by Hopper (1960). Working

aboard ship in the Caribbean and South Atlantic,

he subjected eight species of oceanic calanoids, including Undinula vulgaris, to reduced salinities. He

found that diluting sea water by up to about 7%,

or decreasing the salinity to 33.50%,,, had no effect

on survival. This dilution amounts to a reduction

in salinity of 2.52%o, greater than that endured by

species of the Gill oceanic association and most

members of the shelf association. The salinity tolerance of Hopper's copepods was greater than would

be expected from distributional data, but his experiments were necessarily too limited in duration

and in number of specimens to warrant definite conclusions as to the role of salinity as a limiting factor

in distribution.

More extensive experiments on tolerance to salinity reductions have been performed with coastal

species. Lance (1963) found the order of salinity

tolerance in three species of Acartia from Southampton Water to be A. tonsa > A. bifilosa > A.

discaudata, and later (1964) added more copepod

species to give an expanded order (for adult females) A. tonsa > A. bifilosa > A. discaudata > A.

clausi > Centropages hamatus > Temora longicornis. Tundisi and Tundisi (1968) carried out experiments on tolerance to reduced salinity in planktonic crustaceans in the vicinity of Cananeia, Brazil (about 25°S). The order of tolerance of the

four calanoid species was Pseudodiaptomus acutus

> Acartia lilljeborgii > Centropages furcatus >

Temora stylifera.

Information on relative tolerance to reduced

salinity is available from distributional as well as

experimental data. Cronin, Daiber, and Hulbert

(1962) analyzed the distribution of calanoids along

the axis of the Delaware River estuary with salinities decreasing from about 30%o at the mouth to

fresh-water conditions upstream. The order of tolerance indicated by their analysis was Eurytemora

spp. > Acartia tonsa > Pseudodiaptomus coronatus

> Centropages hamatus -\- typicus (not distin-
NUMBER 96

guished) = Labidocera aestiva > Temora longicornis _ Paracalanus parvus.

From studies of the copepods in bays and coastal

waters outside of the bays of Puerto Rico by Coker

and Gonzalez (1960) and Gonzalez and Bowman

(1965). the order of tolerance of calanoids to bay

water (not necessarily to low salinity) is approximately Acartia tonsa > Paracalanus crassirostris >

Paracalanus "parvus" > Temora turbinata > Centropages furcatus.

Applying the above experimental and distributional data to the Gill calanoids, we would expect

to find an order of tolerance about as follows: Acartia tonsa > Pseudodiaptomus coronatus = Paracalanus crassirostris > Labidocera aestiva > Paracalanus "parvus" > Temora turbinata > Centropages furcatus > Temora stylifera. This order fits

reasonably well the distributional patterns of these

species on the four Gill cruises.

Acartia tonsa thrives under hypersaline conditions as well as in estuaries. In the Laguna Madre

of Texas, a hypersaline lagoon, it is the most abundant zooplankter and occurs at salinities as high as

80%, (Simmons 1957); Hedgpeth 1967a). Carpelin

(1967) emphasized the fact that organisms capable

of tolerating increases in salinity can also tolerate

reductions in salinity relative to marine water and

points out that this was observed and commented

upon by Ferronniere (1901) many years ago.

Coastal and estuarine copepods should not be

looked upon simply as animals adapted to withstand reductions in salinity, but, from a broader

viewpoint, as eurytopic animals adapted to withstand fluctuations in various physical conditions,

including but not necessarily limited to temperature and salinity. Eurytopic species must maintain

a high degree of genetic variability and cannot be

closely adapted to narrow ecological niches. Physiological efficiency must be sacrificed for adaptability.

In contrast, oceanic copepods are stenotopic and

can tolerate only limited fluctuations in environmental conditions. If the relatively stable conditions

of the environment persist long enough, interspecific competition leads to greater specialization and

increased efficiency. The niches occupied become

narrower and more numerous. The end result is

Sanders' (1968) biologically accommodated community. That a seemingly uniform layer of the

17

ocean can support as many as 40 species of calanoids, each with a distinct niche, challenges the

imagination, especially when it is realized that all

samples contained also a number of noncalanoid

zooplankton species. A high degree of specialization in feeding habits of oceanic calanoids would

not be a surprising find. Until now investigations

of feeding and nutrition in calanoids have been

carried out largely with the more accessible coastal

and shelf species, and it will be interesting to see

whether oceanic species have more restricted diets.

A greater efficiency in feeding compared with inshore species is also to be expected. There is evidence that Acartia is a relatively inefficient feeder

compared to more oceanic copepods (Conover

1956).

In addition to feeding specializations, coexistence

could be achieved by vertical segregation and seasonal separation. To what extent these factors operate in marine calanoids is poorly known (Mullin

1967), but all three mechanisms have been shown

to function in enabling several species of Diaptomus

to coexist in a Canadian lake (Sandercock 1967).

Distribution of the Individual Species of Calanoids

The quantitative distributions of the individual

species are shown on a series of maps on which the

number/100 m3 at each station is indicated by one

of a series of the symbols in Figure 13.

Numbers/100 M

<IO

10-99

100 - 999

1,000 - 9,999

10,000 - 99,999

> 100,000

o

O

o

o

O

o

A

A

A

A •

FIGURE 13.—Symbols used on maps (Figures 14-50) to indicate

presence and numerical abundance of calanoids on Gill

cruises.
18

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

For some species that occurred rarely or in small

numbers, only the qualitative distribution is shown,

and in some cases the distribution on all four

cruises is combined on one map.

Calanidae

Undinula vulgaris and Calanus minor were among

the most abundant and widespread of the oceanic

calanoids (Figures 14-15). The large species, Calanus gracilis and Calanus robustior, occurred in

many of the samples collected at night in oceanic

waters but were absent from most of the samples

collected during the day. Calanus tenuicornis occurred in small numbers at some oceanic stations

and appeared to be more restricted to oceanic

waters than the other Calanidae.

Eucalanidae

Eucalanus pileatus was a widespead and abundant

member of the shelf association (Figure 16). The

other species of Eucalanus (attenuatus, crassus,

elongatus, monachus, subtenuis) occurred less frequently and in much smaller numbers, in oceanic

waters (Figures 16-17), as did Rhincalanus cornutus. Mecynocera clausi was strictly limited to oceanic waters (Figure 18).

The specimens of Rhincalanus all belonged to

forma atlantica Schmaus (1917), distinguished

from Schmaus' forma typica by the female 5th legs

(Figures I9a,c). Schmaus' forma have been ignored

by most authors, and some confusion could arise

from the fact that the leading monographs on western Atlantic calanoids (Wilson 1932; Owre and

Foyo 1967) illustrate their accounts of R. cornutus

with figures copied from Giesbrecht (1892). Giesbrecht's illustrations are of f. typica, which occurs

in the Indopacific but not in the Atlantic.

A further complication is Schmaus' decision to

designate as f. typica the Indopacific variety, although the type-locality for R. cornutus given by

Dana (1852) is in the Atlantic (1°N, 18°W).

Schmaus was aware that on the same page and preceding the original diagnosis of R. cornutus was

Dana's diagnosis of a very similar species, Rhincalanus rostrifrons, from the Sulu Sea. The two

species were combined by Giesbrecht (1892), since

the only differences between them could be explained by the fact that R. cornutus was based on

adult females and R. rostrifrons on immature

males.

Although the differences between them are slight,

I believe the two forms merit recognition as full

species. In addition to the differences between the

female 5th legs, the Indopacific form has relatively

longer 1st antennae, about 1.5 times as long as the

body (only 1.3 times as long in the Atlantic form).

Figures \9b,d show the distal segments of the 1st

antennae of specimens of the two forms with nearly

identical body lengths. The longer segments of the

Indopacific form are evident.

A detailed comparison of the appendages and a

study of body proportions, which I have not attempted, might reveal other differences. The two

forms appear to be completely separated geographically, and no intergrades have been reported.

Hence I propose to recognize an Indopacific species,

R. rostrifrons Dana (=R. cornutus f. typica

Schmaus), and an Atlantic species, R. cornutus

Dana (=i?. cornutus f. atlantica Schmaus).

Paracalanidae

Acrocalanus andersoni and A. longicornis, as reported previously (Bowman 1958), are both limited

to oceanic waters. Neither species occurs in large

numbers, although A. longicornis was collected

much more commonly than A. andersoni.

In the genus Paracalanus the most common species presented unexpected taxonomic problems, and

it is necessary to discuss its systematics in detail.

Sewell (1929) divided the species of Paracalanus

into two groups, the Parvus group and the Aculeatus group. Characters that Sewell used to distinguish

the two groups were the form of the spermatheca,

the armature of the swimming legs, the length and

segmentation of antenna 1, and the proportionate

lengths of the prosome and urosome. Sewell included P. crassirostris in the Parvus group, but this

species and its close relatives (summarized by Wellershaus 1969) form a third distinct and coherent

group. The characteristics of the Crassirostris group

include the small size, thick and blunt rostral setae,

and short terminal setae of the 5th legs.

In the Gill samples there are two species of the

Parvus group, one a prominent member of the shelf
NUMBER 96 19

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FIGURE 14.—^Distribution of Calanus minor, Cruises 1-4.
20

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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75" 74- IJFIGURE 15.—^Distribution of Undinula vulgaris, Cruises 1-4.
NUMBER 96 21

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FIGURE 16.—Distribution of Eucalanus pileatus and £. elongatus, Cruises 1—4.
22

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

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FICURE 17.—Distribution of Eucalanus attenuatus, E. crassus, and E. subtenuis, Cruises 1-4.
NUMBER % 23

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FIGURE 18.—Distribution of Rhincalanus cornutus and Mecynocera clausi, Cruises 1—4.
24

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 19.—Rhincalanus rostrifrons, $: a, 5th leg; b, distal

segments of 1st antenna, dorsal. Rhincalanus cornutus, $ : c,

5th legs; d, distal segments of 1st antenna, dorsal.

association, the other also a constituent of the shelf

association but much less common. The two species were not distinguished at first, and both were

enumerated as P. parvus in the counts of Cruises

1-3. When I realized that I was lumping two species

I examined them in detail and concluded that the

less common species is identical with the P. parvus

of Giesbrecht, which I consider to be P. indicus

Wolfenden (see under P. indicus) and the common species is an undescribed species which I propose to name Paracalanus quasimodo.

Paracalanus quasimodo, new species

FIGURES 20-21, 22a

SYNONYMY.—Probably many references to western

Atlantic specimens of "Paracalanus parvus" summarized by Gonzalez and Bowman (1965), are attributable to P. quasimodo.

DIAGNOSIS.—Female. In Parvus group. Body rather

stocky for a Paracalanus, about 1.0 mm in length.

Prosome about 3 times as long as urosome, with

characteristic dorsal hump similar to those in some

species of Acrocalanus but less strongly developed.

Forehead not vaulted. Head fused with 1st pedigerous somite; 4th and 5th pedigerous somites separated by indistinct suture. Genital segment rather

broad in relation to length; lateral part of posterior margin sometimes armed with row of minute

spinules; lateral surface with cluster of spinules on

either side, anterior and dorsal to spermatheca.

Spermatheca obovate, distal half often narrower

than proximal half. Remaining urosomites relatively broader and shorter than those of P. indicus.

Antenna 1, 25-merous, often broken at suture

between segments 8 and 9, reaching to about posterior margin of caudal ramus.

Legs 1-4 with surface armature as shown in Figures 20h-k; pattern very similar to that of P. indicus; basipod conspicuously spinose. Leg 5, terminal

spine longer than 2nd segment.

Male. Genital segment with cluster of spinules

on either side, otherwise identical with P. indicus.

The name is derived from the protagonist of

Victor Hugo's classic novel, The Hunchback of

Notre Dame, and alludes to the distinctive shape

of the prosome.

TYPES.—Holotype $ (USNM 134484) and allotype $ (USNM 134485) from Cruise 4, Station 57,

27 October 1953, off Florida, 33°34'N, 78°24'W.

Paracalanus indicus Wolfenden, new rank

FIGURES 22b-m, 23a

Paracalanus parvus (Claus) .—Giesbrecht, 1892:164-199, pis.

1, 6, 9.—Sewell, 1929:68-71, figs. 24-25.

Paracalanus parvus var. indicus Wolfenden, 1905:998, pi. 96:

figs. 7, 9-11.

DIAGNOSIS.—Female. Body more slender and

slightly shorter than P. quasimodo, length about

0.9 mm. Prosome about 3.2 times as long as urosome; dorsal hump only slightly or not at all developed, hence prosome not so high in relation to its

length as in P. indicus. Forehead not vaulted. Genital segment, viewed dorsally, narrower than in P.

quasimodo, lateral parts of posterior margin with

row of minute spinules, without cluster of spinules

above spermatheca. Spermatheca subelliptical, not

narrowing distally.

Antenna 1 reaching about to posterior margin

of anal segment. Armature of legs very similar to

that of P. quasimodo but slightly less strongly developed.

Male. Identical to P. quasimodo except for the

lack of spinules on the genital segment.
NUMBER 96

25

FIGURE 20.—Paracalanus quasimodo, new species, $ : a, lateral view; b, dorsal view; c, 5th pedigerous and genital segments, lateral; d, same, dorsal; e—f, right and left sides of genital segment;

g, anal segment and caudal rami, dorsal; h—k, legs 1—4.
26

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FICURE 21.—Paracalanus quasimodo, new species: a, mandibular blade, 2 '• b-h, $ : b, lateral

view; c, head and base of antenna 1, lateral; d, dorsal view; e, anal segment and caudal rami,

dorsal; f. distal segments of antenna 1; g, leg 5, anterior; h, left leg 5, lateral.
NUMBER 96 27

FIGURE 22.—Paracalanus quasimodo, new species, $ : a, posterior prosome and genital segment,

dorsal. Paracalanus indicus, $ : b—j, from Gill Cruise 4, Station 35: b, dorsal view; c, lateral view;

d, posterior prosome and genital segment, lateral; e, same, dorsal; /, anal segment and caudal

rami, dorsal; g—j, legs 2-5. k—l, from Gulf of Naples: k, lateral; /, posterior prosome and genital

segment, lateral, m, from Martinique, West Indies; urosome and spermatophore, lateral.
28

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

The Gill specimens are very similar to and perhaps conspecific with specimens from the Gulf of

Naples collected for the Smithsonian Institution by

Dr. L. S. Kornicker; a few illustrations of Dr. Kornicker's specimens are given for comparison (Figures 22k-l).

Wolfenden (1905) proposed his varieties borealis

and indicus after comparing specimens from the Indian Ocean (Maldive Archipelago) and the Faroe

Channel with each other and with the descriptions

and illustrations of Sars (1901, Norwegian specimens) and those of Giesbrecht (1892) and Scott

(1894) from the Gulf of Naples and Gulf of Guinea

respectively. If further study should show that the

Indian Ocean and Mediterranean-Atlantic forms

that Wolfenden considered identical are specifically

distinct, the specific name indicus must be restricted

to the Indian Ocean form. My use of the name

indicus for the Gill species is tentative.

Paracalanus parvus (Claus)

FIGURES 2$b-p

Calanus parvus Claus 1963:173, pi. 26: figs. 10-14; pi. 27:

figs. 1-4.

Paracalanus parvus (Claus).—Boeck 1865:233q.—Sars 1901:

17-18, pis. 8-9.

In a plankton sample from the Gulf of Maine

(Station 20056, south of Mt. Desert Island, 3 March

1920) are P. parvus group specimens that closely

resemble those described by Sars. I have compared

the Gulf of Maine specimens with specimens collected from the type-locality, Helgoland, kindly sent

to me by Dr. Erik Hagmeir of the Meersesstation

Helgoland, and there is close agreement. A few

illustrations of the Helgoland specimens are given

(Figures 23n-p) to show the similarity with Gulf

of Maine P. parvus. This species was not found in

the Gill collections, but for comparative purposes

a brief diagnosis and some illustrations are given

herein. It would be of considerable interest to know

how far south its range extends before it is replaced by the two other Parvus group species.

DIAGNOSIS.—Female. Body slender, length 0.85-

0.90 mm. Prosome about 3.3-3.4 times as long as

urosome, without dorsal hump. Forehead distinctly

vaulted. Genital segment without spinules. Antenna

1 reaching to midlength of caudal ramus. Surface

armature of legs rather sparse, absent from 1st basal

segment.

Male. Distinguished from the other two western

Atlantic males in the Parvus group by the absence

of spinules on the basal segments of the legs.

DISTRIBUTION OF Gill Paracalanus SPECIES.—Paracalanus quasimodo and P. indicus were not enumerated separately for Cruises 1-3 but were counted

together as Paracalanus parvus. On Cruise 4 separate counts were made of the two species, and the

result is shown in Figure 24. Although there is a

slight indication that P. indicus is more likely to

be found in the more oceanic stations, it is obvious

that the two species usually occur together. The

Fager-McGowan index of affinity for Cruise 4 is

0.821, higher than that of the combined species,

Paracalanus "parvus" with any other species. The

relative abundance of the two species varied

markedly from station to station, but over the whole

cruise area P. quasimodo was on the average about

3 times as numerous as P. indicus.

In view of the close association of the two species,

I did not feel that the possible refinement of results

justified my spending the considerable time that

would be required to separate the species in Cruises

1-3 counts and to recalculate the affinity indices and

to reconstruct the trellis diagrams.

Paracalanus "parvus" is a prominent member of

the shelf association. In the cruise area it did not

show much seasonal variation either in the extent

of distribution or in abundance (Figure 24).

Paracalanus aculeatus is a common and abundant

constituent of the oceanic association, but appears

to be rather tolerant of shelf waters, for it may be

found at all but the innermost stations of any

cruise (Figure 25) .

Paracalanus crassirostris is uncommon in the Gill

samples, occurring at only a few inshore stations

of each cruise (Figure 25). Its rarity may be due in

part to its passing through the net because of its

small size, but the distribution is in keeping with its

known abundance in estuaries (references in Gonzalez and Bowman 1965). Its abundance off the

Florida coast during Cruise 3 and especially during

Cruise 4 reflects the reduced salinity caused there

by high runoff.

The species of Calocalanus are all oceanic. C.

pavo is relatively common but never very abundant.

C. pavoninus is much less common; it occurred at
NUMBER 96 29

FIGURE 23.—Paracalanus indicus, $ : a, leg 5. Paracalanus parvus, from Gulf of Maine, b—j, $:

b, lateral view; c, dorsal view; d, anal segment and caudal rami, dorsal; e, distal segments of

antenna 1; f—i, legs 2—5; ;', spermathecae from different specimens; k—m; $ : k, lateral view; /,

left leg 5, lateral; m, leg 5. Paracalanus parvus from Helgoland, $ : n, lateral view; o, spermathecae from different specimens; p, leg 3.
30

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

]

,,-

i : -

25"

8

WL\ ^-h\.

IT

WE

} * *

\

o

—

J •

1

CRUISE 1

PARACALANUS

8 1 " SO' 79" 78"

"PARVUS"_O

3"

3*>-

31'

301

7 4 - 73 "

j

• • •

27-

a^afz-C-N^^

IP

r ti •

1

• •

• •)* •

1

' I

1

o

• ••

• •

o

o

•

•

X——^ I

CRUISE 3

PARACALANUS

•PARVUS*_O

«•

S4-

3 3 '

12-

! ! •

wt

me

- • •

y

*3- « • ao- 79- 78' 77" 7

. - •

M-

.1

111

if

V

7Kft

•

Roo

" 81* K

wT

0 .

t

j*i •

• •

•

Wa.

f 75' 74-

•

>

m

CRUISE 2

PARACALANUS

•PARVUS*_O

It 7

3-

)5-

34-

33-

37-

31-

» •

?Bif

w

w

•

35-

:

waaar^^/ri

L ' i

Kioo

|

i

1

1

o

•• 75" 74"

-

CRUISE 4

PARACALANUS

OUASIMO 00.^^ 3

INOI

75" 74 '

r

ar

28"

2 6 -

2 5 '

3-

FIGURE 24.—Distribution of Paracalanus "paruus" (P. quasimodo + P. indicus) , Cruises 1—4.

Counts of the two species are combined on Cruises 1—3, separated on Cruise 4.
NUMBER 96 31

82" 11* « • 79' 71* 77" 76- 75"

:

:

:

)••• •

:

:

w

is8

I

Irf-c

* 81TM

f

I

r

o

r^

^—

9

o

A,

r

4* 7

CRUISE 1

PARACALANUS

ACULEATUS O

CRASSIROSTRISA

75* 74 " J

35"

33"

32-

W

3-

•

I

Booc

ft

' v Mi

)QO

oo

Oo

)o •

)

w

D

°

V

FT

l

o

4

CRUISE 3

PARACALANUS

ACULEATUS O

CRASSIROSTRIS A

7

PARACALANUS

ACULEATUS O

CRASSIROSTRtsA

82- 81* » • 79" 78-

:

•

W

1

HP

* 81 * K

1

)

Oo

'o

o

1

 ^

o

o

O

{• 75" 74-

CRUISE 4

PARACALANUS

ACULEATUS O

CRASSIROSTRIS A

3 -

3 « -

»<•

3 ; -

H"

i- •

?=•

: • •

' • 75' If 73-

FIGURE 25.—Distribution of Paracalanus aculeatus and P. crawmwfrij-, Cruises 1-4.
32 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

only slightly more than half as many stations and

the average number per station was less than half

that of C. pavo. The other four species were only

rarely encountered. The distribution of all six species during Cruise 4 is shown in Figure 26 (qualitative only).

Pseudocalanidae

When the Gill calanoids were being enumerated,

Frost and Fleminger's (1968) revision of Clausocalanus had not appeared, and I was unable to

identify with confidence any species of this genus

except the distinctive C. furcatus. The following

other species could occur in the Gill region, according to Frost and Fleminger: C. arcuicornis, C. jobei,

C. lividus, C. mastigophorus, C. parapergens, C.

paululus, and C. pergens.

Clausocalanus furcatus is one of the dominant

species in the oceanic plankton. It occurs in large

CAI OCALANUS

»AVO Q

»AVONINUS A

SRACIUS ^

'LUMULOSUS D

eOWTtMCTUSSTYURI MIS

FIGURE 26.—Distribution of Calocalanus species, Cruise 4

(nonquantitative).

numbers in oceanic waters and is found not infrequently in shelf waters (Figure 27) .

Ctenocalanus vanus occurred sporadically in

small numbers, generally in oceanic waters.

Aetididae

Euaetidius giesbrechti occurred occasionally and in

small numbers, always in oceanic waters (Figure

28).

The large-sized species of Euchirella and Undeuchaeta occur mainly at depths greater than those

sampled by the Gill nets and are uncommon in the

samples. As shown in Figure 29, the most frequently

collected species of Euchirella was E. amoena, which

was recorded from 16 stations in Cruises 1-4. Each

of the other species of Euchirella and the two species of Undeuchaeta were found in only one to

three samples. Both genera were strictly limited to

oceanic waters.

Euchaetidae

Euchaeta marina occurred in moderate to large

numbers at most oceanic stations of all four cruises

(Figure 30) and, because of its common occurrence

and abundance, was selected as one of four indicator

species for oceanic waters.

Phaennidae

Phaenna spinifera occurred in small numbers at a

few of the oceanic stations of each cruise (Figure

31).

Xanthocalanus agilis was found twice, at Station

27 of Cruise 2 and Station 7 of Cruise 4, both oceanic stations.

Scolecithridae

Lophothrix latipes was found once, at Station 27 of

Cruise 4.

Scaphocalanus curtus was found at three oceanic

stations: Special Station 1 of Cruise 2 and Stations

52 and 53 of Cruise 4. Scaphocalanus echinatus did

not occur in the Cruise 3 samples but was present at a total of 11 stations, all oceanic, during the

other three cruises.
NUMBER 96

;

. : •

.•« •

:•; •

M*

8

w

i

1

i

)OO

|

V

I

•

O

, j

b,

r

CRUISE 1

CLAUSOCALANUS

FURCATUS

34-

33-

11-

ir

vj29'

2«-

J."

26 •

« •

76" 75" 74- 73"

FIGURE 27.—Distribution of Clausocalanus furcatus, Cruises 1-4.
34 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

1

1 - r • •

m

mk

12'

w:

•o<

C •

i

• • — • •fq

. •

P

w

\

7 ' 1

i- IT

"o

, i

V

o#

y

f

•

CRUISES 1-4

EUCH1RELLA

AMOFNA O

MESSINENSIS A

PULCHRA A

ROSTRATA D

7 7. '3

FIGURE 28.—Distribution of Euaetidius giesbrechti, Cruises

1-4 (nonquantitative).

FIGURE 29.—Distribution of Euchirella species, Cruises 1-4

combined (nonquantitative).

Scolecithrix danae was a common and sometimes

fairly abundant constituent of the oceanic plankton on all cruises. Scolecithrix bradyi was a much

rarer and less abundant oceanic species (Figure 32).

The three species of Scolecithricella occurred

sporadically and in small numbers, always at oceanic stations. S. ctenopus was the rarest of the three;

it was not present in the Cruise 2 samples and was

present at only four stations on each of the other

cruises. S. dentata was somewhat more common and

was taken on all four cruises. S. tenuiserrata occurred much more frequently than S. dentata. The

occurrence of the three species on Cruise 4 is shown

in Figure 33.

Scottocalanus securifrons was found once, on Special Station 5 of Cruise 2.

Temoridae

Temora stylifera and T. turbinata were widespread

and abundant on all cruises (Figure 34). As shown

in the dendrograms and distribution charts, T.

turbinata usually was more prevalent at inshore

stations, whereas T. stylifera was more commonly

found at the oceanic stations. T. turbinata might

be classified as a shelf species that frequently occurs

in oceanic waters, and T. stylifera as an oceanic

species that frequently occurs in shelf waters. The

two species differ in their seasonal abundance

(Figure 35) : T. stylifera occurred in greatest numbers in the winter and spring (Cruises 1 and 2);

whereas T. turbinata was most abundant in the

summer and fall (Cruises 3 and 4).

Temoropia mayumbaensis occurred at a very few

stations, all in oceanic waters.

Metridiidae

Members of the genus Pleuromamma are noted for

their vertical diurnal migrations (Moore and

O'Berry 1957) and are usually found in samples

collected at night. The occurrence of the four spe-
NUMBER 96 35

1

w

34-

••

:,• •

W

W

1 '

I

V

*0

Da,

>oo

©n

e i 80 •"? 741

>«• 77" 76' 75' 4- 3-

0

V

') i

(

b

'

CRUISE 1

Euchaeta

mar na D

!V

W

76* 75- 74" 73"

1

34-

:

• : •

. • •

r

i " 81" «O- 79- 7S* IT •

In

8 1 " 8C

Q O (

•©o

_

J

O

o

V 75- 74"

CRUISE 4

manna O

w

w

w

w

w

w

r

74- 73"

FIGURE 30.—Distribution of Euchaeta marina, Cruises 1-4.
36 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 1.—Comparative abundance and sex ratios of

Pleuromamma gracilis and P. piseki

Cruise

I

II

III

IV

Station

1

6

7

48

50

62

18

27

Spec. 1

Spec. 5

Spec. 9

5

16

17

50

6

7

27

40

60

61

No. of

P. gracilis

No. of

P. piseki

4.3

3.5

2.8

1.5

2.3

11.7

2.8

2.0

1.5

3.6

3.0

2.4

3.3

5.5

3.6

2.7

6.3

6.3

2.9

5.0

4.6

Females/ m a it's

P. gracilis

5.0

6.0

4.5

5.0

3.5

4.0

7.5

5.0

7.0

3.5

5.0

11.0

No d

33.0

3.8

5.0

1.0

5.3

5.7

2.9

2.3

P. piseki

2.5

1.0

1.7

1.0

3.0

2.0

2.0

5.0

1.1

1.5

5.0

1.5

2.3

Nod"

0.7

8.0

0.4

2.0

2.5

1.3

4.0

FIGURE 31.—Distribution of Phaenna spinifera, Cruises 1-4

(nonquantitative).

cies during Cruises 1-4 in relation to time of day

and the percent of oceanic indicator species is

shown graphically in Figure 36. It is apparent that

most of the occurrences were at oceanic stations,

largely between 6 P.M. and 9 A.M. The few scattered occurrences during the day and at nonoceanic

stations were P. Abdominalis and P. gracilis. Of the

two large species, P. abdominalis occurred much

more frequently and in larger numbers than P.

xiphias (Figure 37).

Pleuromamma gracilis was much more common

than the closely related P. piseki. The two species

showed a marked difference in the proportion of

males and females. In P. gracilis the females were

always much more abundant than the males,

whereas in P. piseki the sexes were much more

nearly equal in number, with the females usually

slightly more numerous (Table 1). The reason for

the difference in sex ratio is not obvious. Owre and

Foyo's (1967) data indicate that the two species

live at similar depths, so that Mednikov's (1961)

evidence that the prevalence of females increases

with the depth at which a calanoid species dwells

cannot easily be applied. It is possible that in P.

gracilis the sex ratio is similar to that of P. piseki,

but most of the males remain below the upper 70 m

sampled by the Gill. Moore and O'Berry's (1957)

data show that the majority of the P. gracilis population is always below the Gill sampling depth, but

provides no information on the proportion of males

and females at different depths.

Difference in the male 1st antennae in the two

species might be related to the difference in sex

ratios. In P. gracilis, which has relatively fewer

males, the esthetes are noticably larger, perhaps

because the P. gracilis males must do more searching for females than the P. piseki males. Other noteworthy differences in the geniculate 1st antennae

are the more robust spines on fused segments 19-21,

the coarser teeth in the spine-row of segments 18

and 19-21, and the much broader segments 14, 15,

and 16 in P. piseki (Figure 38).

Because the two species have not always been distinguished by plankton workers, illustrations are

given here of some of the structures that are useful

in separating P. gracilis and P. piseki. In the male,

in addition to the characters of the grasping antennae, the larger spermatophore in P. piseki is
NUMBER 96

37

I

I

i

1

• •

. o 4

L

•®

j

®@

* •

°O

f

) o '

o

Wa

(

O/

i

CRUISE 1

SCOLECITHRIX

OANAE O

BRAOYI A

ej- Hi- m' »•• 71" " "

 7

"i

!H

• •

29-

W

!!•

If

25-

1

rf i

• •

•

pFT*

•

•

• G

O O

Qo

If*

|

•

o

i

i

o

' o

o

, — •

•r

5 o O '

75- 7 • .. J

> .

0

CRUISE 3

SCOLECITHRIX

DANAE O

BRAOYI A

W 7*'

IP

w

3 3 "

J 2 -

3 1 "

HP

V

28"

w

1w

> . a

• o i

B

•

i

o

oo(

OO

so

OO

o©

°o

D

o

1

r C

•v *

Q

b

O

CRUISE 2

SCOLECITHRIX

DANAE

BRAOYI

_O

- A

IP

itTM

1

* o

•o

SO

o o

• ©o

1

—i

b

o

o

'oo

o

D

•

CRUISE 4

SCOLECITHRI)

OANAE

BRAOYI

•

OO

_ A

-

FIGURE 32.—Distribution of Scolecithrix danae and S. bradyi, Cruises 1-4.
38 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

12* 8

1

1

Ha:-1'

P

1F

» • «

• ^ r

II

•

r

a

•

1

i

i

1* 77'

•

b

o

\

J

I

•

b

r|

o

sec

0

e

•

CRUISE 4

LECITHRICf

ENTATA

TENOPI

7

IS

•

LL

•

io

A

n

7

FIGURE 33.—Distribution of Scolecithricella species, Cruise 4

(nonquantitative).

helpful (Figures 38c,g). In P. piseki the spermatophore extends anteriad beyond the anterior margin of the 3rd pedigerous somite, whereas in P.

gracilis the spermatophore does not quite reach this

margin. In the female the more divergent lateral

margins of the anal somite in P. gracilis are usually

emphasized. Males exhibit a similar but smaller

difference (Figures 38d,/i). The female 5th legs of

the two species are similar, but differ in the relative

lengths of the 3 terminal spines (Figures $9d,h). In

P. gracilis the central spine extends beyond the

others; in P. piseki the medial spine is the longest.

Most useful for quick identification of the female

is the genital somite. In P. piseki the dark pigment

knob is usually apparent, and in profile the posterior margin of the genital swelling is more vertical.

Viewed dorsally or ventrally, the shape of the

spermatheca differs in the two species. In P. gracilis

it is kidney-shaped (Figure $9e); in P. piseki it is

asymmetrical, with a broad lobe on the right side in

the posterior half (Figure 396).

As Steuer (1932) clearly showed, the numerical

dominance of P. gracilis over P. piseki in the area

sampled by the Gill does not hold in all regions

where the two species occur together. For example,

Deevey (1964), in her study of variations in length

of calanoids sampled near Bermuda, used P. piseki,

but not P. gracilis.

Centropagidae

Centropages typicus occurred at a few of the northernmost stations, near Cape Hatteras, in Cruises 1,

2, and 4 (Figure 40). It is not a normal inhabitant

of Carolinian Coastal water, but is one of the

dominant species of Virginian Coastal water,

especially during the winter and spring (Bigelow

and Sears 1939; Van Engel and Tan 1965). Its

presence is an indication of the movement of coastal

water from the north around Cape Hatteras, which

normally serves as a natural barrier between the two

coastal plankton faunas.

Centropages hamatus occurred only at ten inshore

stations of Cruise 1. The calanoid fauna at these

stations was dominated by Paracalanus "parvus" or

Acartia tonsa, or both. As pointed out by Deevey

(1960), Centropages hamatus has an unusally wide

latitudinal range, and its seasonal occurrence varies

with latitude. In the Gulf of Maine it occurs primarily from late summer to winter (Bigelow 1926),

but south of Cape Cod it is a winter-spring species

(Deevey 1960; Van Engel and Tan 1965; Grice

1956; Jacobs 1969), and in the Gill samples it was

not found at other seasons.

Centropages furcatus was one of the most common and abundant shelf species.

Centropages violaceous was limited to oceanic

water. It was fairly common but always occurred in

small numbers.

Pseudodiaptomidae

Pseudodiaptomus coronatus was found only once,

at Station 56 of Cruise 1, a station close to shore in

Long Bay, South Carolina, occupied just after midnight. P. coronatus is a typical estuarine species

(Cronin et al. 1962; Jacobs 1961, 1969) and is not

fully planktonic, since it is capable of clinging

firmly to the substrate and often does in laboratory

culture (Jacobs 1961). It tends to remain near or
NUMBER 96

39

••• ]

H

;•<" •

28-

IT

M*

><t> O

•

*

i?

• /

Timora

ttyliOro

lurtowK

j - 74* 731

CRUISE 1

O

A

5- 74-

3 5 -

H'

:f

i-

:•••

r

»2" 81* 80" 79* 78» 76* 75* 74" 73"

-•H

• . i

.'•

W

? ' •

H-

. - •

IF

Op

5©

wG

4

1

k

• ,- •

{

• —

3 ;!

CHWSC 3

M O T

n

A

3 3 "

3 ? '

» •

^ » -

r

W

•

m

1

0,®

) •

©

1

.-• ©

O

4 .

USC 4

•

A

w

79-

FIGURE 34.—Distribution of Temora stylifera and T. turbinata, Cruises 1-4.
40

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

fe a

o

o: O

It!

NUMBER OF SAMPLES

FICURE 35.—Relative abundance of Tempora stylifera (black) and T. turbinata (white), Cruises

1_4. Width of bar represent number of samples in which a species formed a particular percentage, in steps of 10%, of the sample.

on the bottom during the day and is taken in surface collections mainly at night.

Lucicutiidae

Both species of Lucicutia encountered had oceanic

distributions, but L. flavicornis was far more abundant than L. gaussae and occurred at many more

stations (Figure 41). Because of its abundance

L. flavicornis was one of the species for which affinity indices were computed. It was clearly a member

of the oceanic association but, as can be seen in the

trellis diagrams (Figures 5-6), consistently had the

lowest affinity indices with other oceanic species of

any member of the association. A rather striking

suctorian was attached to the urosome of a number

of specimens of L. gaussae but was found only once

on L. flavicornis.

Heterorhabdidae

Heterorhabdus papilliger was fairly common but

never abundant at the oceanic stations of all four

cruises (Figure 42). As suggested by Owre and Foyo

(1967), the bulk of the population of this species

lives below the depth sampled by the Gill and

moves toward the surface at night.

Owre and Foyo (1967) found that H. spinifrons

(Claus) was about as abundant as H. papilliger at

their "40 mile station" (about 40 miles east of

Miami, Florida, in the Florida Current), but I have

not found H. spinifrons in the Gill samples. Specimens that I originally thought were H. spinifrons

proved upon close examination to be specimens of

H. papilliger in which ihe rostrum was sharply

pointed rather than bluntly rounded. Specimens

with blunt rostrums and with sharp rostrums occurred together in the same sample and agreed in

all characters except the rostrum. (Figure 43& shows

the exopod of the right 5th leg of a male with

pointed rostrum; this leg is typical for H. papilliger) . This is a rather disturbing discovery, since

the keys to the species of Heterorhabdus in many

widely used works on calanoids are so constructed

that the sharp-rostrum individuals of H. papilliger

will key out to H. spinifrons. Hence persons making

routine identifications of planktonic copepods and

using such keys could easily be misled. Works containing such keys are those of Giesbrecht and

Schmeil (1898), Esterly (1905), Wilson (1932),

Rose (1933), Brodsky (1950), and Owre and Foyo

(1967). A more reliable separation of the two species can be based on the relative lengths of the setae

on the distal segments of the 2nd maxillae. In H.

papilliger the 2 large setae of the penultimate lobe

are subequal, and the more distal seta, like that of

the terminal segment, is armed with rather coarse

spinules. In H. spinifrons the distal seta of the
NUMBER 96 41

80

CO

UJ

o

LU

fc60

o

240

o

o

20

0

E | 1 1

B

P

•

B °

• a

6 8 10 12 14 16 18 20 22 24

HOURS

FIGURE 36.—Occurrence of Pleuromamma species, Cruises 1-4, in relation to time of day and percent of oceanic indicator species. Each square represents a station; occurrence of a species at a

station is shown by solid black in its fourth of the square, G = P. gracilis, p = P. piseki, x =

P. xiphias, A = P. abdominalis.
42

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

.-•*•

••

, ,

1

r.\

'a

i

*

Q.

3 •

•

r

t *

W 2

K |

CRUISE 1

Pleuromamma

gracilis O

piseki A

at

xi

dominc

phias

ilis.D

)5

33

1

! •

"

CRUISE 2

Plleurornamma

gracilis O

piseki A

abdominalis •

xiphias X

CRUISE A

Ffleuromamma

gracilis O

piseki A

abdominalis a

xiphias X

FIGURE 37.—Distribution of Pleuromamma species, Cruises 1-4.
NUMBER 96 43

FIGURE $8.—Pleuromamma piseki, $ : a, distal segments of left antenna 1; b, segments 15-16 of

left antenna 1; c, posterior segments of prosome, lateral, showing position of spennatophore; d,

anal segment and caudal ramus, dorsal. Pleuromamma gracilis, $ : e, distal segments of left

antenna 1; /, segments 13—16 of left antenna 1; g, posterior segments of prosome, lateral, showing

position of spermatophore; h, anal segment and caudal ramus, dorsal; i, mandibular blade.
44 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 39.—Pleuromamma piseki, $ : a, urosome, lateral; b,

urosome, dorsal; c, leg 5; d, leg 5, terminal spines. Pleuromamma gracilis, J : e, urosome, dorsal; /, urosome, lateral; g,

leg 5; h, leg 5, terminal spines.

penultimate lobe is noticeably longer than the proximal seta, and it is armed with much finer and more

closely set spinules than the seta of the terminal

segment. On the antepenultimate lobe the medial

seta is more than half as long as the other two setae

in H. papilliger, but much less than a fourth as long

in H. spinifrons. These features are shown in Figures 43c-cJ in which the setae are drawn more

widely separated than in their natural position so

that their relative sizes can be easily compared.

Park's (1970) Heterorhabdus spinifer appears to

be identical with the pointed rostrum form of H.

papilliger. Park states that, in addition to the

pointed rostrum, H. spinifer is distinguished by the

absence of an inner seta on the 1st segment of the

endopod of the female 5th leg, and by the "characteristic internal projection on the second exopodal

segment of the [male] right leg." A comparison of

Giesbrecht's (1892) Plate 20: figures 33-35 of H.

papilliger and Park's (1970) Figure 237 of H. spinifer does not reveal any significant difference in the

male 5th legs, and the absence of a single seta on

the female 5th leg is of questionable significance at

the species level. Despite my respect for Park's

accuracy and taxonomic judgment I must question

the validity of H. spinifer until more convincing

evidence can be presented.

Augaptilidae

Three species of Haloptilus occurred in the Gill

samples, all strictly limited to oceanic water (Figure 44). H. longicornis, the most common, was

found in small numbers at a moderate number of

stations on each cruise. The bulk of the population

probably lives below the depth sampled by the Gill

(Roehr and Moore 1965) . H. spiniceps occurred at

a few stations of Cruises 2, 3, and 4 but was not

found in the Cruise 1 samples. Only a single specimen of H. oxycephalus was identified, from Cruise

2, Station 8.

Arietellidae

One specimen of Arietellus setosus was found, at

Station 7 of Cruise 2.
NUMBER 96 45

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violaceous A

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hamatus D

fypicus ^O

34-

33"

31-

w

29"

w

75- 74- TV

FIGURE 40.—Distribution of Centropages species. Cruises 1-4.
46

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

CRUISi

-ucicutia

flavicornis—O

gaussae A

CRUISE 2

icutia

flavicornis O

A

7 0 - 7« - 77- 7

>:•

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CRUISE 4

ucicutia

flavicornis O

gaussae A

75* 7f

35"

If

33"

• : •

3 1 -

rw

me

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tr

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FIGURE 41.—Distribution of Lucicutia flcnricornis and L. gaussae, Cruises 1-4.
NUMBER 96 47

CRUISES 1-4

HETERORHABDUS

PAPILLIGER

75" 74- 73"

FIGURE 42.—Distribution of Heterorhabdus papilliger, Cruises

1-4 combined (nonquantitative) .

Candaciidae

A brief discussion of species of Candacia in the area

sampled by the Gill is given by Fleminger and

Bowman (1956), but these remarks were based on

only Cruise 1.

All seven of the species of Candacia in the Gill

samples were limited to oceanic water (Figure 45).

C. curta and C. pachydactyla were encountered

fairly frequently, always in small numbers; the

other species were usually found at not more than

three stations of any cruise.

Both species of Paracandacia also were found

only at the oceanic stations (Figure 46) ; P. bispinosa occurred slightly more frequently than P.

simplex, but the difference may not be significant,

since I did not distinguish the very similar immature stages of the two species.

FIGURE 43.—Heterorhabdus papilliger: a, head of $ with

pointed rostrum, lateral; b, exopod of right leg 5 from same

specimen; c, distal end of $ maxilla 2. Heterorhabdus spinifrons, $, from Bache Station 10209 (near Gill special Station

8): d, distal end of maxilla 2.

Pontellidae

Anomalocera ornata was collected at six stations of

Cruise 1 and three stations of Cruise 3, all of them

coastal stations with bottom depths not greater than

36 m (Figure 47). It is probably more abundant

and widespread than is apparent from the Gill collections, since A. ornata presumably lives close to

the surface like its northern relative, A. patersoni

(Bigelow 1926), and is not adequately sampled by

oblique tows.

Calanopia americana had a rather unusual distribution (Figure 47). In the summer and fall

(Cruises 3 and 4) the largest populations were at

inshore stations, with smaller numbers farther out

on the shelf and even at some of the oceanic stations. In the winter and spring (Cruises 1 and 2)

it was less common overall and occurred mainly

well out on the shelf. The overall distribution of
48

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 44.—Distribution of Haloptilus species, Cruises 1-4

combined (nonquantitative).

C. americana, summarized by Gonzalez and Bowman (1965) and by Owre and Foyo (1967), shows

it to be a tropical and subtropical species, ranging

from Cape Hatteras to southern Brazil, principally

in coastal waters but sometimes offshore. It could

be postulated that along the United States coast

south of Cape Hatteras it moves offshore into

warmer water as the temperature drops seasonally.

Such a migration by a planktonic copepod only

about 1.5 mm long and supposedly at the mercy

of ocean currents is not very likely. In St. George's

Harbor, Bermuda, C. americana stays on the bottom

during the day and probably burrows into the mud

(Clarke 1934). Just before sunset it begins an u p

ward migration and occurs in the plankton throughout the night. In Puerto Rico and the Lesser Antilles, Gonzalez and Bowman (1965) reported that

C. americana was collected in nets towed at night

but not during the day.

Figure 48 shows the distribution of stations at

which C. americana was found in relation to the

time of day when the stations were occupied. In

this graph the data of Cruises 1-4 are combined

and the day is divided into 2-hour intervals. In general, C. americana occurred most frequently around

the middle of the night but, in contrast to its behavior at Bermuda, was present in the plankton at

all hours. Owre and Foyo (1967) also found it in

their Florida Current, 40-mile station during the

day, although in smaller numbers than at night. No

explanation for the difference in behavior is offered

here, but I might point out that the energy required

for Calanopia to swim to the bottom and back daily

at the Gill stations and the 40-mile station (depth

at the latter about 738 m) is much greater than in

St. George's Harbor (12.5-14 m) and at the West

Indian localities reported by Gonzalez and Bowman

(1965).

Labidocera aestiva was abundant at many inshore

stations (Figure 49) and, as stated earlier, was one

of two species that formed the "coastal association."

Of the common calanoids, only Acartia tonsa, the

other member of the coastal association, was more

severely restricted to coastal waters. L. aestiva was

most widespread in the winter and spring, when

it occurred at a number of the stations on the shelf,

although the greatest numbers were at coastal stations. In the summer and fall (Cruises 3 and 4) its

distribution was more restricted to the coast. Large

numbers along the coast of Florida during Cruise 4

resulted from the flood conditions discussed earlier

in this paper.

The other species of Labidocera were quite uncommon. Labidocera acutifrons occurred at a few

oceanic stations. Fleminger (1957) has already documented the oceanic distribution of this species in

the Gulf of Mexico, and Sherman and Schaner

(1968) associated its presence over George's Bank

with an incursion of Gulf Stream water. L. nerii

was found at two oceanic stations (Cruise 1, Station

49; Cruise 3, Station 31). Finally, L. scotti was collected at Cruise 1, Station 49, and Cruise 4, Station 5.

Pontella meadi (including P. pennata Wilson,

considered by Fleminger [1957] to be synonymous)

occurred at six stations of Cruise 2 and three stations of Cruise 3, all in coastal and shelf waters.

This distribution agrees with the findings of Fleminger (1957) and Sherman and Schaner (1968),

who characterized P. meadii as a coastal species.
NUMBER 96 49

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CRUSE 3

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FIGURE 45.—Distribution of Candacia species, Cruises 1-4.
50

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

82-

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iFIGURE 46.—Distribution of Paracandacia bispinosa and P. simplex, Cruises 1-4.
NUMBER 96 51

CRUISE I Anomakxefo

ornafa

Calanop.a

americona

RsnrelNng

pturnora

• •

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w

34-

r

%• t f 76- 75- 74- 73-

CRUISE 3

Anomalocera

ornata

C<*3nopia

americono

PonreHna

pfumata

FIGURE 47.—Distribution of Anomalocera ornata, Calanopia amcricana, and Pontellina plumata,

Cruises 1-4.
52

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

1 J

CO

z MBER OF STATIC

Z i I i

14 16 18 20 22 24 2 4 6 8 10 12

HOURS

FIGURE 48.—Occurrence of Calanopia americana, Cruises 1-4

combined, in relation to time of day.

Pontella securifer, on the other hand, was found at

six oceanic stations of Cruise 3. In the Gulf of

Mexico, Fleminger (1957) found P. securifer in

slope and oceanic waters; other authors (summarized by Sherman and Schaner 1968) have shown

it to be associated with high oceanic waters.

Pontella plumata occurred at a moderate number of oceanic stations on all four cruises.

The three species of Pontellopsis were taken at

only one or two oceanic stations each.

Acartiidae

Acartia tonsa was strictly limited to coastal waters,

as is to be expected of a copepod known to be a

typical estuarine species (Figure 50). During the

winter (Cruise 1) it was abundant at stations along

the coast of South Carolina, but at other seasons it

was confined mainly to the coasts of Georgia and

Florida, where more stations were close to shore

than to the north. Its abundance at the Florida

stations in the fall (Cruise 4) is associated with

the strong salinity gradient along the coast that

resulted from the flood conditions discussed previously.

Acartia danae and A. negligens are both characteristic of oceanic water. Acartia danae was the more

common of the two species and was somewhat less

restricted to oceanic water. It occurred occasionally

in shelf water, whereas A. negligens never did. Figure 51, a T-S-P diagram (Bary 1959) for Cruise 4,

with occurrences of the two species plotted on a

surface temperature-salinity graph, shows the narrower range of conditions under which A. negligens

exists.

Comparison of Carolinian and Virginian

Calanoid Faunas

It is instructive to compare the calanoid fauna

south of Cape Hatteras, sampled by the Gill, with

that north of Cape Hatteras, sampled by Bigelow

and Sears (1939), Deevey (1952a, 1952b, 1960),

Grice and Hart (1962), and Van Engel and Tan

(1965).

THE SHELF ASSOCIATION.—During the wanner

months Van Engel found that the coastal waters off

the mouth of Chesapeake Bay are dominated by

Labidocera aestiva, Centropages furcatus, and Eucalanus pileatus. Candacia armata and Temora

stylifera were less important. Except for Candacia

armata, these are important species in Carolinian

water. Conspicuous for its absence was the other

dominant member of the shelf association south of

Cape Hatteras, Paracalanus "parvus."

Farther north, off the mouth of Delaware Bay,

Deevey (1960) recorded the year-round presence

of Paracalanus parvus, with minimal numbers in

the spring. It is not known which of the three East

Coast species of the Paracalanus parvus group Deevey had. Eucalanus pileatus appeared in the Delaware Bay samples from July—December, and Deevey

lists it as one of the most consistent warm water or

southern forms. Centropages furcatus was much less

in evidence; during the sampling period (May

1929-July 1933) it was collected only during September-November 1930.

Neither Centropages furcatus nor Eucalanus pileatus occurs in Block Island Soutid, but Deevey

(1952a, 1952b) reports the presence of Paracalanus

parvus, with maximum numbers in August. Again,

it is not known whether this is the true P. parvus

or one of the species of the Parvus group that occurred in the Gill samples.

Whereas the species composition of the calanoid

shelf association south of Cape Hatteras remains

rather constant throughout the year, seasonal

changes take place north of Cape Hatteras. Pseudocalanus minutus and Centropages typicus are the

dominant species during the colder months off

Chesapeake Bay (Van Engel and Tan 1965), Delaware Bay (Deevey 1960), and Block Island Sound

(Deevey 1952a, 1952b).

In summary, the species that throughout the year

dominate the shelf association south of Cape Hat-
NUMBER 96 53

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:

i

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•

it

•

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Si

(j

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i

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2 ^

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CROISC 4

Lobidocero

oesi

nefi

(va O

3V

3V

1 0

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 ?5* ?4" 73'

FIGURE 49.—Distribution of Labidocera species, Cruises 1-4.
54

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

•»• »i- «o- r

• • 1

i

i

1

k

k 1

» A

•

• D

, .

81 80 7<

5P"

^_

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•

CRtWSE 1

Acar tia

done

neg(

fons

f A

g«K n

a O

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FIGURE 50.—Distribution of Acartia species, Cruises 1-4.
NUMBER 96 55

25

20

, r . . i , i

Acartia

— danaeA

negligens

A

A £

, , I , , , ,

35

Salinity

36

FIGURE 51.—Temperature-Salinity-Plankton diagram for Acartia danae and Acartia negligens.

teras appear in significant numbers north of Cape

Hatteras only during the warmer months. As we go

farther north they tend to diminish in numbers and

to disappear, at first during the colder months,

later year-round, and to be replaced by northern

species, especially Pseudocalanus minutus and Centropages typicus.

T HE OCEANIC ASSOCIATION.—The calanoid species

forming the oceanic association are essentially the

same on both sides of Cape Hatteras. To the north

this association moves farther offshore, since its

western boundary follows the Gulf Stream and a

region of slope water, consisting of mixed oceanic

and coastal water is present, containing, as might

be expected, a mixture of shelf and oceanic calanoid

species. This slope water is not present south of

Cape Hatteras.

In Grice and Hart's (1962) study of the zooplankton from stations in a New York-Bermuda

transect, the calanoid species in their stations II

(Gulf Stream) and JJ, KK, LL, and NN (Sargasso

Sea) are by and large those that occurred at the

oceanic stations sampled by the Gill. Grice and

Hart's oceanic samples were collected from a depth

of 200 m, hence they contained a few more species

than the Gill samples, collected from about 70 m.

T HE COASTAL ASSOCIATION.—Both Acartia tonsa

and Labidocera aestiva occur in coastal waters abundantly as far north as Cape Cod. Going north from

Cape Hatteras the seasonal occurrence of Acartia

tonsa becomes increasingly more limited to the

warmer months, and it is gradually replaced by its

northern relative, Acartia clausi. North of Cape Hatteras Labidocera aestiva occurs from early summer

to early winter, in contrast to its year-round occurrence in the Gill samples.

Paracalanus crassirostris and Pseudodiaptomus

coronatus, coastal species that were inadequately

sampled by the Gill, are abundant in coastal waters

north of Cape Hatteras, but the northern extent of

their occurrence in significant numbers is uncertain,

since ordinary net tows do not collect representative

numbers of either the tiny P. crassirostris or the

nocturnally benthic P. coronatus.

The fact that oceanic and coastal calanoid species of the Gill collections occur both north and

south of Cape Hatteras, whereas the shelf species

are replaced by other species, requires an explanation. The conditions of temperature and salinity

for the oceanic species do not change significantly in

the oceanic water of the Florida Current as it passes

Cape Hatteras and heads away from the continent.

Oceanic species will enjoy stable conditions of high

temperatures and salinities, regardless of whether

they are in the Florida Current, the Gulf Stream, or

the Sargasso Sea. In contrast, coastal species must

be able to withstand severe fluctuations in temperature and salinity. The acquisition of a high degree
56

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

of tolerance in the coastal species enables them to

thrive over a considerable latitudinal range.

The shelf species have neither the tolerance to

environmental changes of the coastal species nor the

constant conditions surrounding the oceanic species.

Hence they cannot survive in environmental

changes as great as those occurring north of Cape

Hatteras in the colder months and are replaced by

species with similar tolerances but adapted to lower

temperatures.

Literature Cited

Anderson, William W., and Jack W. Gehringer

1957a. Physical Oceanographic, Biological, and Chemical

Data—South Atlantic Coast of the United States,

Theodore N. Gill Cruise 3. United States Fish and

Wildlife Service, Special Scientific Report—Fisheries 210:1-208.

1957b. Physical Oceanographic, Biological, and Chemical

Data—South Atlantic Coast of the United States,

M/V Theodore N. Gill Cruise 4. United States Fish

and Wildlife Service, Special Scientific Report—

Fisheries 234:1-192.

Anderson, William W., Jack W. Gehringer, and Edward

Cohen

1956a. Physical Oceanographic, Biological, and Chemical

Data—South Atlantic Coast of the United States,

M/V Theodore N. Gill Cruise 1. United States Fish

and Wildlife Service, Special Scientific ReportFisheries 178:1-160.

1956b. Physical Oceanographic, Biological, and Chemical

Data—South Atlantic Coast of the United States,

Theodore N. Gill Cruise 2. United States Fish and

Wildlife Service, Special Scientific Report—Fisheries 198:1-270.

Arnold, Edgar L., Jr., and Jack W. Gehringer

1952. High Speed Plankton Samplers. United States Fish

and Wildlife Service, Special Scientific Report—

Fisheries 88:1-12.

Bary, Brian Mck.

1959. Species of Zooplankton as a Means of Identifying

Surface Waters and Demonstrating Their Movements and Mixing. Pacific Science, 13(1): 14-34.

Bigelow, Henry B.

1926. Plankton of the Offshore Waters of the Gulf of

Maine. Bulletin of the United States Bureau of

Fisheries, 40(2): 1-509.

Bigelow, Henry B., and Mary Sears

1939. Studies of the Waters of the Continental Shelf, Cape

Cod to Chesapeake Bay. III. A Volumetric Study of

the Zooplankton. Memoirs of the Museum of Comparative Zoology at Harvard College, 54(4): 183-378.

Boeck, Axel

1865. Oversigt over de ved Norges kyster lagtaggne Copepoder henhjSrende tie Calanidemes, Cyclopidemes

og Harpactidemes Famalier. Forhandlinger VidenskSelskabs, Christiania, for 1864:266-281.

Bowman, Thomas E.

1958. A New Species of Acrocalanus (Copepoda: Calanoida) from off the Southeastern Coast of the

United States. Bulletin of Marine Science of the

Gulf and Caribbean, 8(2) :118-124.

Brodsky, K. A.

1950. Calanoida of the Far Eastern Seas and Polar Basin

of the USSR. Keys to the Fauna of the USSR.

Published by the Zoological Institute of the Academy of Sciences of the USSR, 35:1-442 [In Russian;

English translation by Israel Program for Scientific

Translations published in 1967].

Bumpus, Dean F.

1955. The Circulation over the Continental Shelf South

of Cape Hatteras. Transactions of the American

Geophysical Union, 36(4) :601-611.

Bumpus, Dean F., and E. Lowe Pierce

1955. The Hydrography and the Distribution of Chaetognaths over the Continental Shelf off North Carolina.

Papers in Marine Biology and Oceanography, DeepSea Research, 3 (Supplement) :92-109.

Carpelan, Lars H.

1967. Invertebrates in Relation to Hypersaline Habitats.

Contributions to Marine Science, University of

Texas, 12:219-228.

Chen, Chin, and Norman S. Hillman

1970. Shell-Bearing Pteropods as Indicators of Water

Masses off Cape Hatteras, North Carolina. Bulletin

of Marine Science, 20(2) :35O-367.

Clarke, George L.

1934. The Diurnal Migration of Copepods in St. Georges

Harbor, Bermuda. Biological Bulletin, 67 (3) :456-

460.

Claus, Carl

1863. Die freilebenden Copepoden tnit besonderer Berucksichtigung der Fauna Deutschlands, der Nordsee und

des Mittelmeeres. x+230 pages, 37 plates. Leipzig.

Coker, Robert E., and Juan G. Gonzalez

1960. Limnetic Copepod Populations of Bahfa Fosforescente and Adjacent Waters, Puerto Rico. Journal

of the Elisha Mitchell Scientific Society, 76 (1) :8-28.

Conover, Robert J.

1956. Oceanography of Long Island Sound, 1952-1954:

VI. Biology of Acartia clausi and A. tonsa. Bulletin

of the Bingham Oceanographic Collection, 15:156-

233.

Cronin, L. Eugene, Joanne C. Daiber, and E. M. Hulbert

1962. Quantitative Seasonal Aspects of Zooplankton in the

Delaware River Estuary. Chesapeake Science, 3 (2):

63-93.

Dana, James D.

1853. Crustacea, Part II, In United States Exploring Expedition . . . During the Years 1838, 18)9, 1840,

1841, 1842 . . . Under the Command of Charles

Wilkes, I/.SJV., 14:689-1618.
NUMBER 96 57

Deevey, Georgiana B.

1952a. A Survey of the Zooplankton of Block Island

Sound, 1943-1946. Bulletin of the Bingham Oceanographic Collection, 13(3).-65-119.

1952b. Quantity and Composition of the Zooplankton of

Block Island Sound, 1949. Bulletin of the Bingham

Oceanographic Collection, 13(3) : 120-164.

1960. The Zooplankton of the Surface Waters of the Delaware Bay Region. Bulletin of the Bingham Oceanographic Collection, 17 (2) :5-53.

1964. Annual Variations in Length of Copepods in the

Sargasso Sea off Bermuda. Journal of the Marine

Biological Association of the United Kingdom, 44:

589-600.

Esterly, Calvin O.

1905. The Pelagic Copepoda of the San Diego Region.

University of California Publications in Zoology,

2(4): 113-233.

Fager, E. W., and J. A. McGowan

1963. Zooplankton Species Groups in the North Pacific.

Science, 140(3566) :453-460.

Ferronniere, G.

1901. Etudes Biologiques sur les Zones Supralittorales de

la Loire-Inferieure. Bulletin de la Sociiti des Sciences Naturelles de VOuest de la France, series 2,

1:1-451.

Fleminger, Abraham

1957. New Calanoid Copepods of Pontella Dana and Labidocera Lubbock with Notes on the Distribution of

the Genera in the Gulf of Mexico. Tulane Studies in

Zoology, 5 (2): 19-34.

Fleminger, Abraham, and Thomas E. Bowman

1956. A New Species of Candacia (Copepoda: Calanoida)

from the Western North Atlantic Ocean. Proceedings of the United States National Museum, 106

(3370) :331-3S7.

Frost, Bruce, and Abraham Fleminger

1968. A Revision of the Genus Clausocalanus (Copepoda:

Calanoida) with Remarks on Distributional Patterns in Diagnostic Characters. Bulletin of the

Scripps Institution of Oceanography. University of

California, San Diego, 12:1-235.

Giesbrecht, Wilhelm

1892. Systematik und Faunistik der pelagischen Copepoden

des Golfes von Neapel und der angrenzenden

Meeresabschnitte. Fauna und Flora des Golfes von

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