Calanoid Copepods of the

Family Euchaetidae from

the Gulf of Mexico and

Western Caribbean Sea

TAISOO PARK

m

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 196
SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION

The emphasis upon publications as a means of diffusing knowledge was expressed

by the first Secretary of the Smithsonian Institution. In his formal plan for the Institution, Joseph Henry articulated a program that included the following statement:

"It is proposed to publish a series of reports, giving an account of the new discoveries

in science, and of the changes made from year to year in all branches of knowledge."

This keynote of basic research has been adhered to over the years in the issuance

of thousands of titles in serial publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with

the following active series:

Smithsonian Annals of Flight

Smithsonian Contributions to Anthropology

Smithsonian Contributions to Astrophysics

Smithsonian Contributions to Botany

Smithsonian Contributions to the Earth Sciences

Smithsonian Contributions to Paleobiology

Smithsonian Contributions to Zoology

Smithsonian Studies in History and Technology

In these series, the Institution publishes original articles and monographs dealing

with the research and collections of its several museums and offices and of professional

colleagues at other institutions of learning. These papers report newly acquired facts,

synoptic interpretations of data, or original theory in specialized fields. These publications are distributed by mailing lists to libraries, laboratories, and other interested

institutions and specialists throughout the world. Individual copies may be obtained

from the Smithsonian Institution Press as long as stocks are available.

S. DILLON RIPLEY

Secretary

Smithsonian Institution
SMITHSONIA N CONTRIBUTION S T O ZOOLOG Y • NUMBE R 19 6

Galanoid Gopepods of the

Family Euchaetidae from

the Gulf of Mexico and

Western Caribbean Sea

Taisoo Park

71AY 3 9 1S75-

SMITHSONIAN INSTITUTION PRESS

City of Washington

1975
ABSTRACT

Park, Taisoo. Calanoid Copepods of the Family Euchaetidae from the Gulf of

Mexico and Western Caribbean Sea. Smithsonian Contributions to Zoology,

number 196, 26 pages, 20 figures, 1975.—The study is based on zooplankton

samples taken from various depth ranges between the surface and a depth of

about 3000 m in the Gulf of Mexico and western Caribbean Sea. Twenty species

of Euchaeta were found, including the following eight new records and a new

species: E. aequatorialis (Tanaka), E. calva (Tanaka), E. comosa (Tanaka), E.

confusa (Tanaka), E. gracilicauda (A. Scott), E. sarsi Farran, E. scotti Farran,

E. vorax Grice and Hulsemann, and E. alaminae, new species. Euchaeta calva

(Tanaka) and E. comosa (Tanaka) are restored from synonymy; E. withi

(Sewell) is recognized as synonymous with E. hansenii With. The males of E.

pubera, E. calva, E. comosa, E. gracilicauda, E. incisa, and E. vorax are described

for the first time. The relative abundance and bathymetrical distribution of each

species are briefly discussed. A key to the species is given.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 5270. SERIES COVER DESIGN:

The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Park, Taisoo

Calanoid Copepods of the Family Euchaetidae from the Gulf of Mexico and Western Caribbean

Sea.

(Smithsonian contributions to zoology, no. 196)

Supt. of Docs, no.: SI 127:196

1. Euchaeta. 2. Crustacea—Mexico, Gulf of. 3. Crustacea—Caribbean sea. I. Title. II. Series:

Smithsonian Institution. Smithsonian contributions to zoology, no. 196

QL1.S54 no. 196 [QL444.C72] 591'.08s [595'.34] 74-26956
Contents

Page

Introduction 1

Key to the Species of Euchaeta Found in the Gulf of Mexico and

Western Caribbean Sea 2

Shallow-Living Species 5

Euchaeta marina (Prestandrea, 1833) .. 5

Euchaeta media Giesbrecht, 1888 5

Euchaeta paraconcinna Fleminger, 1957 6

Euchaeta pubera Sars, 1907 6

Euchaeta spinosa Giesbrecht, 1892 8

Deep-Living Species 8

Euchaeta aequatorialis (Tanaka, 1958) 8

Eucaeta barbata Brady, 1883 9

Euchaeta bisinuata Sars, 1907 9

Euchaeta calva (Tanaka, 1958) 10

Euchaeta comosa (Tanaka, 1958) . . 12

Euchaeta confusa (Tanaka, 1958) 13

Euchaeta gracilicauda (A. Scott, 1909) 13

Euchaeta gracilis Sars, 1905 16

Euchaeta hansenii With, 1915 17

Euchaeta incisa Sars, 1905 17

Euchaeta pseudotonsa Fontaine, 1967 19

Euchaeta sarsi Farran, 1908 19

Euchaeta scotti, Farran, 1908 19

Euchaeta vorax Grice and Hulsemann, 1968 21

Euchaeta alaminae, new species 23

General Remarks . 24

Literature Cited 25

111

Calanoid Copepods of the

Family Euchaetidae from

the Gulf of Mexico and

Western Caribbean Sea

Taisoo Park

Introduction

The family Euchaetidae comprises medium to

large-sized marine planktonic copepods, which are

primarily carnivorous and numerically important

in the oceanic zooplankton communities from the

surface down to the bathypelagic realm. The family has often been classified into two genera—Euchaeta, consisting mostly of shallow-living forms,

and Paraeuchaeta of bathypelagic species. In this

study, all species are placed under a single genus,

Euchaeta, since the splitting of the family into two

genera seems unjustifiable from a morphological

point of view (Vervoort, 1957). However, in the

systematic account following (as a matter of convenience), they are arranged into two groups according to their bathymetrical distribution.

Over 50 species of Euchaeta have so far been described. Except for a relatively small number of

common species, the euchaetids are among the

most poorly known marine copepods. Most of them

are deep living, and most of the deep-living species

are so rare that their original descriptions are often

based on a single specimen and many have never

been recaptured. Adult males are even more

scarce and thus remain unknown for many species.

Furthermore, the sexual dimorphism is so much

Taisoo Park, Department of Marine Sciences, Texas A & M

University, Galveston, Texas 77500.

greater than the differences between species that

the female and male of the same species are often

described as separate species or misidentified with

different species.

In the Gulf of Mexico and Caribbean Sea, the

following 15 species of Euchaeta have been known

to occur (Fleminger, 1957; Owre and Foyo, 1967;

Grice, 1969; Park, 1970): E. acuta Giesbrecht, E.

barbata Brady, E. bisinuata Sars, E. gracilis Sars,

E. hansenii With, E. incisa Sars, E. malayensis (Sewell), E. marina (Prestandrea), E. media Giesbrecht, E. paraconcinna Fleminger, E. pseudotonsa

Fontaine, E. pubera Sars, E. spinosa Giesbrecht, E.

tonsa Giesbrecht, and E. withi (Sewell). According

to Fontaine (1967), E. tonsa reported by Owre and

Foyo (1967) from the Florida Current should be

referred to E. pseudotonsa.

In order to discover all euchaetid species of the

Gulf of Mexiceo and western Caribbean Sea and

to determine their relative abundance, I have examined over 200 zooplankton samples taken on the

R/V Alaminos in 1971-1973 from various depth

ranges between the surface and a depth of about

3000 m over these areas. The samples were collected mainly with Bongo nets originally designed

by McGowan and Brown (1966). The original

opening-dosing mechanism was replaced with a

new and more reliable one operated by messengers.

The tows were made horizontally at various depths

from half an hour to as long as three hours, depend1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ing on the depths of sampling, in order to obtain

samples large enough to contain sufficient numbers

of specimens of the rare species. In addition, a

number of samples were collected obliquely with

standard plankton nets of two different sizes (1

and 2 m, respectively, in mouth diameter). The

2-m net tows down to depths exceeding 1000 m

proved to be extremely useful in this study.

During this study, all the previously known

species have been found except E. acuta and E.

malayensis. Also found are the following eight new

records and a new species: E. aequatorialis

(Tanaka), E. calva (Tanaka), E. comosa (Tanaka),

E. confusa (Tanaka), E. gracilicauda (A. Scott),

E. sarsi Farran, E. scotti Farran, E. vorax Grice and

Hulsemann, and E. alaminae, new species. The

males of E. pubera, E. calva, E. comosa, E. gracilicauda, E. incisa, and E. vorax are described here

for the first time. The male known as E. wit hi is

recognized in this study as belonging to E. hansenii,

known from the female only. Euchaeta calva

(Tanaka) and E. comosa (Tanaka) are restored

from synonymy.

Euchaeta malayensis (Sewell) seems to be an

Indo-Pacific species and its record by Owre and

Foyo (1967) from the Florida Current, which is

based on a single specimen much larger (9.7 mm

in body length) than the size range known for the

species (6.0-7.5 mm) (Sewell, 1929; Tanaka, 1958;

Tanaka and Omori, 1968) needs to be confirmed.

Euchaeta acuta has been known to have a wide

range of distribution (Vervoort, 1957) but seems

to be more common in the temperate regions. Roe

(1972) found E. acuta as a very common euchaetid

species in the Canary Islands area, while Grice

(1962) and Vervoort (1963) have failed to find the

species in their extensive studies in the equatorial

Pacific and Atlantic, respectively. In the Gulf of

Mexico and Caribbean Sea, E. acuta has been

recorded from the Florida Current (Owre and Foyo,

1967), but no specimens referable to this species

have been found in the present study.

The present paper is intended to make contributions to the systematics of the euchaetid species

in the Gulf of Mexico and western Caribbean Sea,

providing descriptions and figures of the characters useful in the species identification, together

with notes on the abundance and bathymetrical distribution of each species. The body length given

for each species was measured from the tip of the

forehead to the end of the caudal ramus, and the

prosome length from the tip of the forehead to the

end of the posterolateral corner of the metasome.

When the posterolateral corners are asymmetrically produced, as in the male of many species, the

prosome length was determined from the side with

the longer projection. Although only the body

length is customarily given in the literature, the

prosome length is found to be very useful, for in

most specimens the urosome is flexed to a various

extent and thus the total length of the body is

difficult to measure accurately.

ACKNOWLEDGMENTS.—This study was supported

by National Science Foundation Grant GA-27485.

The identification of several species reported herein was possible by comparing them with specimens

of closely related species from the other geographical areas. I am particularly grateful to the following

persons who provided specimens for such comparisons: Thomas E. Bowman of the National Museum

of National History, Abraham Fleminger of Scripps

Institution of Oceanography, George D. Grice of

Woods Hole Oceanographic Institution, and Makoto Omori of Tokyo University.

Key to the Species of Euchaeta Found in the

Gulf of Mexico and Western Caribbean Sea

FEMALE

1. One or 2 of 6 apical setae of maxilla armed with long, widely separated spines in addition

to usual fine and short spinules. Appendicular caudal setae straight and parallel to and

much thicker than other caudal setae 2

None of 6 apical setae of maxilla provided with long, widely separated spines in addition

to usual fine and short spinules. Appendicular caudal setae geniculated or turned outward

and not thicker than other caudal setae 7

2. Two of 6 apical setae of maxilla armed with long, widely separated spines E. marina

One of 6 apical setae of maxilla armed with long, widely separated spines 3
NUMBER 196

3. Dorsally or ventrally, genital segment nearly symmetrical (Figures 46,d) E. pubera

Dorsally or ventrally, genital segment distinctly asymmetrical 4

4. Right side of genital segment with a sharply pointed toothlike process (Figure 3c). Frontal

eminence (fe) projected forward into a hornlike process (Figure 3a) E. paraconcinna

Right side of genital segment without such a toothlike process. Frontal eminence not

projected forward into such a process 5

5. Genital field elongated across genital segment and produced on left side into a large

protuberance (Figure 5b) E. spinosa

Genital field differently shaped 6

6. Viewed dorsally or ventrally, right side of genital segment forming a step posterior to

middle of segment (Figure 2b). Outer coxal lobe of maxillule with 7 setae JS. media

Right side of genital segment not forming such a step. Outer coxal lobe of maxillule with

5 setae E. acuta

7. Viewed laterally, genital prominence divided into 2 (Figures 156,c) or 3 lobes (Figure 86) ... 8

Viewed laterally, genital prominence not divided into lobes 9

8. Viewed laterally, genital prominence with 3 lobes formed by 2-lobed genital flange together

with a large protuberance posterior to genital aperture (Figure 86) E. bisinuata

Viewed laterally, genital prominence divided into 2 lobes, anterior lobe being genital flange

(Figures 15b,c) E. btcisa

9. Genital prominence extraordinarily large and similar in shape to a molar tooth (Figure

13a) E. gracilis

Genital prominence differently formed 10

10. Viewed laterally, genital prominence more or less triangular in shape. Genital flanges not

prominent (Figure 166) E. pseudotonsa

Viewed laterally, genital prominence not triangularly shaped. Genital flanges (gf) prominent

(Figure 146) 11

11. Genital segment with a process on left side posterior to genital field (Figures 76, 19c) ...12

Genital segment without such a process 14

12. Process of genital segment toothlike; genital prominence with straight posterior side clearly

distinct from ventral wall of segment (Figure 76) E. barbata

Process of genital segment not toothlike but composed of several ridges; genital prominence

without a distinct posterior side (Figures 126, 19c) 13

13. Rostrum relatively short, pointing straight forward in parallel to dorsal margin of forehead

(Figure 19a). Ventral wall of genital segment posterior to genital field strongly curved

(Figure 19c) E. vorax

Rostrum relatively long, pointing obliquely forward (Figure 12a). Ventral wall of genital

segment posterior to genital field only slightly curved Figure 126) E. graciticauda

14. Outer coxal lobe of maxillule with 9 setae (Figure 11/) 15

Outer coxal lobe of maxillule with 5 to 7 setae 16

15. Viewed laterally, genital flange (gf) produced posteriorly into a large triangular lobe

extending beyond genital field (Figure 146) E. hansenii

Genital flange not produced posteriorly into such a lobe (Figure 116,c) E. conjusa

16. In third exopodal segment of second leg, incision posterior to second external spine

unusually deep, extending higher than incision posterior to first external spine (Figure

10c) E. cotnosa

In third exopodal segment of second leg, incision posterior to second external spine not

unusually deep 17

17. Laterally, genital prominence without a posterior side separate from posterior ridge of

genital field (Figure 126) E. gracilicauda

Laterally, genital prominence with a distinct posterior side meeting ventral wall of segment

at an angle (Figures 186, 206) or in a continuous curve (Figure 66) 18

18. External spine of second exopodal segment of first leg short of reaching middle of third

exopodal segment (Figure 20/). Laterally, genital prominence with high posterior side

almost perpendicular to ventral wall of segment (Figures 206,d) ... E. alaminoe, new species

External spine of second exopodal segment of first leg reaching about to distal end of

third exopodal segment. Genital prominence appearing differently in lateral view 19

19. Laterally, posterior ridge (pr) of genital field produced posteriorly into a distinct lobe

similar in size to posterior lobe of genital flange (Figures 66, 186) 20
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Laterally posterior ridge of genital field not visible or only slightly produced (Figures 9b,

lie) • 21

20. Laterally, dorsal wall of genital segment with a hump about middle of segment (Figure 18&).

Posterior side of genital prominence meeting ventral wall of segment at an angle E. scotti

Laterally, dorsal wall of genital segment smoothly curved outward without such a hump

(Figure 6ft). Posterior side of genital prominence merging into ventral wall of segment

forming a smooth curve

 E

- aequatorialis

21. Viewed laterally, length of genital flange (fl) 80-95/100 length of genital segment (si) posterior to genital flange (Figure lie). Rostrum small (Figure 17a) E. sarsi

Viewed laterally, length of genital flange (fl) 55-65/100 length of genital segment (si) posterior to genital flange (Figure 96). Rostrum large (Figure 9a) E. calva

MALE

1. Third exopodal segment of left fifth leg prolonged into a spiniform process (Figure 46) 2

Third exopodal segment of left fifth leg not prolonged into a spiniform process (Figure

9A) 7

2. Third exopodal segment of left fifth leg less than two times the length of preceding segment

(Figure 5d) E. spinosa

Third exopodal segment of left fifth leg more than five times length of preceding segment

(Figure 46) 3

3. Serrated lamella of second exopodal segment of left fifth leg extending beyond tuft of

spinules of third exopodal segment (Figures Id, ie) 4

Serrated lamella far short of reaching tuft of spinules of third exopodal segment (Figures

2c, 4p) 5

4. Rostrum and frontal eminence closely contiguous (Figure \c) E. marina

Rostrum and frontal eminence widely apart (Figure 3d) E. paraconcinna

5. Serrated lamella of second exopodal segment of left fifth leg divided into 2 lobes (Figure

2c) E. media

Serrated lamella single lobed (Figure 4p) 6

6. Digitiform process of second exopodal segment of left fifth leg tapering into a sharp point

(Figure 4q) E. pubera

Digitiform process terminating with a blunt end JS. acuta

7. Digitiform process very small, much shorter than haired tubercle of third exopodal segment

(Figure 8<r) E. bidnuata

Digitiform process long 8

8. Digitiform process (dp) with distal half distinctly bent outward and considerably narrower

than proximal half (Figures 14d,/) E. hansemi

Digitiform process more or less uniform in thickness and relatively straight except distal

end 9

9. Digitiform process with distal end pointed (Figures *le, 11/, 18e, 19/) 10

Digitiform process with distal end rounded (Figures 9n, 13/) 13

10. Serrated lamella in form of an elongated triangle with fine marginal teeth (Figure 19A)

E. vorax

Serrated lamella in different form with relatively coarse marginal teeth 11

11. Serrated lamella of second exopodal segment of left fifth leg with 4 large teeth on medial

edge in addition to many small teeth (Figure llm) E. confusa

Serrated lamella with 2 or no large teeth on medial edge in addition to small teeth 12

12. Serrated lamella with 2 large teeth on medial edge in addition to many small teeth, and its

distal third slightly narrower than the rest (Figure Id) E. barbata

Serrated lamella with only small teeth, and its distal half considerably narrower than the

rest (Figure 18d) E. scotti

13. Serrated lamella terminating with a large tooth (Figures 13/, 16d) 14

Serrated lamella not terminating with a large tooth 15

14. Serrated lamella with large distal tooth and medially, with strongly curved toothed edge

(Figure 13/) E. gracilis

Serrated lamella with small distal tooth and medially, with slightly curved toothed edge

(Figure 16*) E . pseudotonsa
NUMBER 196

15. Viewed medially, serrated lamella with a sigmoidally curved toothed edge (Figure 15n)

E. incisa

Serrated lamella with teeth along only its margins, without a sigmoidally curved toothed

edge 16

16. Serrated lamella dagger shaped, with fine marginal teeth (Figure 17g) E. tarsi

Serrated lamella differently shaped 17

17. Serrated lamella more or less rectangular with distal projection along external margin

(Figure 9/) E. calva

Serrated lamella gradually narrowed distally, terminating in a round end 18

18. Serrated lamella with large teeth on distal margin and very fine teeth on medial and lateral

margins (Figure 10/) E. comma

All marginal teeth of serrated lamella more or less uniform in size 19

19. Digitiform process of second exopodal segment of left fifth leg relatively long, with distal

end sharply bent (Figure 12m) E. gracilicauda

Digitiform process relatively short, with straight distal end (Vervoort, 1963:174, fig. 20/)

E. aequatorialis

Shallow-Living Species

(Species usually found in upper 500 m)

Euchaeta marina (Prestandrea, 1833)

FIGURE 1

This is a common epiplanktonic species known

to occur widely in the tropical, subtropical, and

temperate zones of the World Ocean. In the Gulf

of Mexico and western Caribbean Sea, it is the

most common euchaetid species. in the epipelagic

zone. Although its bathymetrical distribution extends occasionally down to a depth of about 500

m, its main concentration usually appears between

depths of 25 and 100 m.

According to 200 randomly selected specimens

for each sex, the female measured 2.84-3.44 mm

in body length and 2.08-2.48 mm in prosome

length; the male 2.88-3.40 mm in body length and

2.12-2.36 mm in prosome length.

Euchaeta media Giesbrecht, 1888

FIGURE 2

In geographical distribution this species almost

coincides with, but usually occupies a deeper bathymetrical range than, E. marina. In the Gulf of

Mexico and western Caribbean Sea, E. media

usually occurs within a depth range of 100 to 1000

m, with a highest concentration between depths of

200 and 500 m, where it is the most common euchaetid species.

According to more than 200 randomly selected

FIGURE 1.—Euchaeta marina. Female: a, forehead, lateral; b,

genital segment, ventral. Male: c, forehead, lateral; d, exopod

of left fifth leg, anterior.

specimens for each sex, the female measured 3.60-

4.24 mm in body length and 2.48-2.80 mm in pro-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 2.—Euchaeta media. Female: a, forehead, lateral; b,

genital segment, ventral. Male: c, exopod of left fifth leg,

anterior.

FIGURE 3.—Euchaeta paraconcinna. Female: a, forehead, lateral; b, genital segment, lateral; c, genital segment, ventral.

Male: d, forehead, lateral; e, exopod of left fifth leg, anterior;

/, exopod of left fifth leg, medial, (fe = frontal eminence.)

some length; the male, 3.42-3.74 mm in body

length and 2.45-2.66 mm in prosome length.

Euchaeta paraconcinna Fleminger, 1957

FIGURE 3

This species was originally described from the

Gulf of Mexico and off North Carolina in the

northwestern Atlantic. Vervoort (1963) recorded

the species from the Gulf of Guinea. In the present

study, the species was found to be very common

in the upper 100 m throughout the area under consideration, with its bathymetrical distribution ranging down to a depth of about 200 m. The body

length of the specimens was 2.32-2.80 mm in the

female and 2.36-2.65 mm in the male, according

to about 200 randomly selected individuals for

each sex. The prosome length was 1.60-2.00 mm

in the female and 1.72-1.92 mm in the male.

Euchaeta pubera Sars, 1907

FIGURE 4

MALE.—Body and prosome lengths based on 45

specimens, 2.92-3.52 mm and 2.16-2.64 mm. respectively. Body slender. Dorsally, frontal eminence of

forehead produced into a triangular form (Figure

4/). Rostrum well developed (Figure Ah), pointing downward. Posterolateral corners of metasome

nearly symmetrical. Urosome about two-fifths

length of prosome and covered with hair. Appendicular caudal setae geniculated and smaller than

other caudal setae.

Antennule reaching about distal end of second

urosomal segment. Antenna with reduced setae on

-coxa, basis, and first endopodal segment (Figure

4t). Feeding apparatus of oral appendanges (Figure 4;,ft) reduced as usual in the genus. Coxa of

maxilliped with three distal setae only (Figure 4/).

Exopod of first leg (Figure 4m) three segmented;
NUMBER 1%

FIGURE 4.—Euchaeta pubera. Female: a, forehead, lateral; b, genital segment, ventral; c, genital

segment, left side; d, genital segment, dorsal; e, genital segment, right side. Male: /, habitus,

dorsal; g, habitus, lateral; h, forehead, lateral; i, antenna; /, mandible; k, maxillule; /, maxilliped;

m, first leg, anterior; n, second leg, anterior; o, fifth pair of legs, anterior; p, exopod of left fifth

leg, anterior; q, exopod of left fifth leg, medial, (dp = digitiform process.)
8

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

last two segments each with an external spine.

Endopod of second leg (Figure An) with a short

line representing a fused joint. Exopod with external spines of similar size. Third and fourth legs

with three-segmented endopods and exopods. Distal

exopodal segment of each fifth leg tapering in a

long spiniform process (Figure 4o). Serrated lamella of second exopodal segment of left fifth leg

nearly triangular in shape, with uniformly small

teeth along most of internal margin and only middle portion of external margin (Figure Ap). DigitiFIGUKE 5.—Euchaeta spinosa. Female: a, forehead, lateral; b,

genital segment, ventral. Male: c, forehead, lateral; d, exopod

of left fifth leg, medial.

form process tapering into a slightly curved spiniform process (Figure Aq).

REMARKS.—Wilson (1950) described a male as

belonging to E. pubera. According to the description and figure of the fifth pair of legs, however,

his male seems to be referable to E. marina. The

male described here therefore represents the hitherto unknown male of E. pubera.

The female specimens obtained in the present

study were 3.28-4.12 mm in body length and 2.48-

3.12 mm in prosome length.

DISTRIBUTION.—Euchaeta pubera was originally

described by Sars (1907) from the North Atlantic

and has been known to occur, usually in small numbers, in the tropical, subtropical, and temperate

zones of the Atlantic and Pacific oceans. Grice

(1969) recorded the species in the Gulf of Mexico.

In the present study, the species was represented

by 214 females and 45 males, most of which were

found in samples from depths of 100 to 200 m in

the Gulf of Mexico and western Caribbean Sea.

Euchaeta spinosa Giesbrecht, 1892

FIGURE 5

This is a mesopelagic species with a wide range

of geographical distribution over the tropical, subtropical, and temperate zones of the World Ocean.

In the present study, the species was found to be

quite common in the Gulf of Mexico and western

Caribbean Sea, and seemed to occupy mainly a

bathymetrical range of 200 to 500 m. According to

about 100 randomly selected individuals for each

sex, the female measured 5.83-6.83 mm in body

length and 4.33-4.92 mm in prosome length, and

the male 5.75-6.17 mm in body length and 4.28-

4.67 mm in prosome length.

Deep-Living Species

(Species usually found below 500 m)

Euchaeta aequatoriaUs (Tanaka, 1958)

FIGURE 6

This species has so far been known to occur in

the tropical Atlantic and off the Pacific coast of

Middle Japan (Tanaka, 1958; Vervoort, 1963). In

the present study, only three female specimens referable to this species were found in three separate

tows down to depths of 1650 to 2000 m in the Gulf

of Mexico, and these findings are the first record

of the species from this area. The specimens measured 4.16-4.24 mm in body length and 3.04-3.24
NUMBER 196

FIGURE 6.—Euchaeta aequatorialis, female: a, forehead, lateral; b, genital segment, lateral; c, genital segment, ventral;

d, outer lobe of maxillule; e, exopod of second leg, anterior.

mm in prosome length, and were in good agreement in morphological details with the description

given by Vervoort (1963).

Euchaeta barbata Brady, 1883

FIGURE 7

This species was originally described from the

southwestern Atlantic and has been known to occur

widely over the tropical, subtropical, and temperate zones of the World Ocean. With (1915) distinguished a large form of E. barbata in the Norwegian Sea as a separate species, E. farrani, which

was subsequently also found in the Antarctic seas

by Farran (1929) and Vervoort (1957). This bipolar species shows no morphological differences

from E. barbata except for the body size and appears to be only a geographical race rather than

a separate species.

In the present study, E. barbata was found rather

consistently, although in small numbers, in tows

down to depths of 1000 to 3000 m. Altogether 82

females and 23 males have been identified from the

FICURE 7.—Euchaeta barbata. Female: a, forehead, lateral; b,

genital segment, lateral. Male: c, exopod of left fifth leg,

lateral; d, exopod of left fifth leg, anterior; e, exopod of left

fifth leg, medial.

Gulf of Mexico and western Caribbean Sea. The

body length varied between 7.58 and 8.42 mm in

the female and between 6.58 and 7.25 mm in the

male. The prosome length of the female and male

was 5.42-6.08 mm and 4.45-5.25 mm, respectively.

Euchaeta bisinuata Sars, 1907

FIGURE 8

This is one of the more common bathypelagic

euchaetid species throughout the tropical, subtropical, and temperate zones of the World Ocean. In

the Gulf of Mexico and western Caribbean Sea, it

was found to be the most common euchaetid species

in the bathypelagial zone. Altogether, 234 females
FIGURE 8.—Euchaeta bisimiata. Female: a, forehead, lateral;

b, genital segment, lateral. Male: c, forehead, lateral; d, exopod of left fifth leg, anterior; e, exopod of left fifth leg,

medial; /, exopod of left fifth leg, lateral, (ht = haired

tubercle.)

and 42 males were identified in the present study,

most of which were found from a depth range below 1000 m. The female measured 5.17-5.58 mm

in body length and 3.67-4.04 mm in prosome

length, and the male 4.48-4.75 mm in body length

and 3.32-3.60 mm in prosome length.

Euchaeta calva (Tanaka, 1958)

FIGURE 9

Pareuchaeta calva Tanaka. 1958:347-548, fig. 71.

Pareuchaeta comosa Tanaka, 1958:363-365, fig. 79A-; [male

only].

Euchaeta dudia.—Vervoort, 1963:176-181, figs. 21-23.

Pareuchaeta dubia.—Tanaka and Omori, 1967:245 [male only];

1968:234 [male only].

Pareuchaeta californica —Tanaka and Omori, 1968:231-232,

figs. 3E, 4E, 7A-C.

Pareuchaeta polita Tanaka and Omori, 1968-247, figs. So,

4o, 15A-D.

Pareuchaeta simulantis Tanaka and Omori, 1968:253-255, figs.

Sw, 4w, 19A-F.

FEMALE.—Body length based on 86 specimens,

7.25-7.91 mm. Prosome length, 5.33-5.66 mm. RosSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

trum large, pointing obliquely forward (Figure

9a). Viewed laterally, genital prominence high and

relatively narrow (Figure 9b). Length of genital

flange (fl) 55-65/100 length of genital segment

posterior to genital flange (si). Posterior lobe of

genital flange large, usually pointing posteroventrad. Antennule a little short of reaching distal

end of prosome. Outer coxal lobe of maxillule with

five large setae of similar size and a small seta of

variable size in addition to 2 or 3 minute setae

proximally (Figure 9e).

MALE.—Body length based on 11 specimens, 6.66-

7.25 mm. Prosome length, 4.75-5.25 mm. Rostrum

elongated, pointing downward (Figure 9h). Posterolateral corners asymmetrical, each with a toothlike process dorsally. Antennule reaching middle

of second urosomal segment. Serrated lamella of

second exopodal segment of left fifth leg rectangular, with a projection along external margin (Figure 9/). Uniformly small teeth bordering entire

length of internal margin and distal portion of

external margin. Digitiform process straight and

shorter than serrated lamella, with a uniform

thickness and round distal end (Figure 9n).

REMARKS.—Euchaeta calva was originally described by Tanaka (1958) on the basis of six female

specimens taken in the Izu region of Middle Japan.

Tanaka and Omori (1968) redescribed the species

from a female specimen obtained from the same

locality and considered it synonymous with Euchaeta californica Esterly. Through loan I have reexamined Tanaka and Omori's specimen by comparing it with Esterly's original specimen of E.

californica and found that they are distinctly different species. Euchaeta californica will be redescribed elsewhere from Esterly's original specimen

and some additional material from the type-locality.

The female specimens of E. calva found in the

present study were carefully compared with Tanaka and Omori's (1968) specimen and were found

to be identical. The male described herein undoubtedly belongs to this species because of its

close similarity to the female in body size, distribution, and relative abundance.

Tanaka (1958) has described an identical male

from the Izu region, which he ascribed to Euchaeta comosa. Assuming that the male referred to E.

comosa by Tanaka (1958) is identical with Euchaeta dubia Esterly (known exclusively from the

male), Vervoort (1963) synonymized the two
NUMBER 196

11

FIGURE 9.—Euchaeta calva. Female: a, forehead, lateral; b, genital segment, lateral; c, genital

segment, dorsal; d, genital field; e, outer lobe of maxillule; /, exopod of first leg, anterior; g,

exopod of second leg, anterior. Male: h, forehead, lateral; t, exopod of first leg, anterior;

;, exopod of second leg, anterior; k, fifth pair of legs; /, exopod of left fifth leg, anterior; m,

exopod of left fifth leg, lateral; n, exopod of left fifth leg, medial, (fl = length of genital flange;

si = length of genital segment posterior to genital flange.)
12

species. In the present study, E. dubia was reexamined on the basis of a specimen from the typelocality provided by Abraham Fleminger, and

found to be distinctly different. As suggested by

A. Fleminger (pers. comm.), E. dubia seems to represent the male sex of E. californica Esterly.

Euchaeta comosa Tanaka is therefore restored

from synonymy in this study. However, the female

and male of E. comosa as originally described by

Tanaka (1958) cannot be considered as conspecific because they are significantly different in

shape of the second leg. The male, which has been

redescribed in detail (under the name of E. dubia)

by Vervoort (1963) from specimens obtained in

the Gulf of Guinea, is identical with the male of

E. calva described here. The female is properly

referable to E. comosa and a male attributable to

it has been found in the present study.

Tanaka and Omori (1968) described two species

(Pareuchaeta polita and P. simulantis) that show

no significant differences from their description of

E. calva (as P. californica). All of these three

species were said to be closely allied to E. sarsi and

distinguishable from it only by the rostrum and

genital segment, but no account was given as to

how they are different from one another. In the

present study, their specimens of P. polita and P.

simulantis were also reexamined through help by

Makoto Omori, and it was found that they are all

identical with their specimen of E. calm (referred

to P. californica).

The female of E. calva as described here is very

similar to that of Euchaeta regalis Grice and Hulsemann, 1968, which will be redescribed elsewhere

from specimens from the type-locality. The male

referred to E. regalis by Grice and Hulsemann

(1968) is here identified with E. comosa Tanaka.

DISTRIBUTION.—Euchaeta calva has so far been

known to occur in the Izu region, Middle Japan

(Tanaka, 1958; Tanaka and Omori, 1967, 1968, as

P. dubia), and in the Gulf of Guinea (Vervoort,

1963, as E. dubia). The records of E. dubia by

DeDecker and Mombeck (1965) and Grice and

Hulsemann (1967, 1968) from the Indian Ocean

and the southeastern Pacific may also be referable

to this species. In the present study, the species was

represented by 86 females and 11 males, most of

which were found in tows down to depths exceeding 1000 m. These findings constitute the first recSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ord of the species in the Gulf of Mexico and Caribbean Sea.

Euchaeta comosa (Tanaka, 1958)

FIGURE 10

Pareuchaeta comosa Tanaka, 1958:363, fig. 79a-g [female

only].

Pareuchaeta dubia.—Tanaka and Omori, 1968:234, figs. 3c, 4c,

[female only].

Pareuchaeta hanseni.—Tanaka, 1958:362, fig. 78g-/i [male

only].

Euchaeta regalis Grice and Hulsemann, 1968:331, figs. 41-48

[male only].

Not Pareuchaeta comosa Tanaka, 1958:123, fig. 79/J-; [male

only] [=P. calva Tanaka, 1958].

MALE.—Body length based on 4 specimens, 7.75-

8.08 mm. Prosome length, 5.41-5.75 mm. Frontal

eminence of forehead inconspicuous. Rostrum

FIGURE 10.—Euchaeta comosa. Female: a, forehead, lateral; b,

genital segment, lateral; c, third exopodal segment of second

leg, anterior. Male: d, forehead, lateral; e, third exopodal

segment of second leg, anterior; /, exopod of left fifth leg,

anterior.
NUMBER 196 13

elongated, pointing downward (Figure 10d). Posterolateral corners asymmetrical, each with a low

toothlike process dorsally. Antennule reaching

about distal end of second urosomal segment. Exopod of first leg 3-segmented, with external spines of

reduced size. Endopod of second leg 1-segmented.

Third exopodal segment (Figure lOe) with an

unusually deep incision posterior to second external spine as in the female. Serrated lamella gradually narrowed distally, terminating in a blunt end

armed with several large teeth (Figure 10/). Internal margin finely serrated. External margin naked.

Digitiform process large, with somewhat swollen,

round distal end reaching close to distal end of

serrated lamella.

REMARKS.—Tanaka's (1958) original description

of E. comosa is based on female and male specimens obtained in the Izu region, Middle Japan.

As the male of E. comosa described by Tanaka is

similar to E. dubia Esterly, 1906, exclusively based

on the male, Vervoort (1963) considered the two

species synonymous. As discussed under E. calva,

it has been found in the present study that the

male referred to E. comosa by Tanaka is not identical with E. dubia Esterly but attributable to E.

calva, and the female of E. comosa is a separate

valid species.

The female specimens found in the present

study are in good agreement with Tanaka's (1958)

original description, and they are readily distinguished by the characteristic genital segment (Figure 106) and unusually deep incision posterior to

the second external spine of the third exopodal

segment of the second leg (Figure 10c). The body

lengths of the 24 specimens found in the study

varied from 8.16 to 9.00 mm and the prosome

lengths from 6.08 to 6.66 mm.

The male described above is believed to belong

to E. comosa because of its close similarity to the

female in size, distribution, and, particularly, form

of the second leg. The exceptionally deep incision present in the third exopodal segment of the

second leg in both the female and male of this

species is not found in any other euchaetid species

observed in the present study.

The male referred to E. hansenii by Tanaka

(1958) and that described as belonging to E. regalis by Grice and Hulsemann (1968) seem to be

identical with the male of E. comosa described

above.

DISTRIBUTION.—Euchaeta comosa has so far been

known to occur off the Pacific coast of Middle

Japan by Tanaka (1958) and Tanaka and Omori

(1968, as Par euchaeta dubia) and in the southeastern Pacific (as the male of E. regalis) by Grice

and Hulsemann (1968). In the present study, the

species was represented by 24 females and 4 males,

all of which were found in tows down to depths

exceeding 1000 m in the Gulf of Mexico and western Caribbean Sea, and these findings constitute

the first record of the species in the Atlantic Ocean.

Euchaeta confusa (Tanaka, 1958)

FIGURE 11

This species was originally described from the

Izu region, Middle Japan, by Tanaka (1958) and

has been recorded from the Kurile-Kamchatka

Trench by Heptner (1971).

The female is characteristic in having a singlelobed genital flange and pronounced posterior edge

of the genital field followed by a biconvexed posterior side of the genital prominence (Figure lib/).

The male is easily recognized by the serrated lamella of the left fifth leg (Figure 11 Z,m), which is

unique in having four large serrated teeth along

the internal margin.

In the present study, the species was represented

by four females and two males found in two tows

down to depths of 1000 and 2000 m, respectively,

in the Bartlett Deep of the western Caribbean Sea.

These findings are the first record of the species

in the Atlantic Ocean. The females measured

6.50-7.08 mm in body length and 4.83-5.00 mm in

prosome length, and the males 5.83-5.91 mm in

body length and 4.16 mm in prosome length.

Euchaeta gracilicauda (A. Scott, 1909)

FIGURE 12

FEMALE.—Body length based on 28 specimens,

6.00-6.41 mm. Prosome length, 4.08-4.50 mm. Rostrum (Figure 12a) long, pointing obliquely forward,

often slightly curved backward, Laterally, frontal

eminence of forehead distinct. Genital segment

(Figure \2b) elongated, with relatively low genital

prominence. On left side of genital segment posterior to genital prominence a small, low tubercle
14

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 11.—Euchaeta confusa. Female: a, forehead, lateral; b, genital segment, left side; c, genital segment, right side; d, genital segment, dorsal; e, genital field; /, outer lobe of maxillule;

g, first leg, anterior; h, second leg, anterior. Male: i, forehead, lateral; /, exopod of first leg,

anterior; k, exopod of second leg, anterior; I, exopod of left fifth leg, medial; m, exopod of left

fifth leg, anterior.

is present, clearly visible when the genital segment

is tilted left (Figure 12c). Viewed laterally, genital

flange well developed, with distinct posterior lobe,

but flanking only proximal two-thirds of genital

field. Genital field only slightly produced distally.

Genital prominence without a distinct posterior

side. Posterior to genital field, ventral surface of

genital segment forming a single broad arch

(Figure 126).

Antennule reaching about middle of genital segment. Outer coxal lobe of maxillule (Figure 12/)

with 5 large setae of similar size in addition to two

or three minute setae proximally. First two exopodal segments of first leg (Figure 12g) fused, but a

faint line of joint visible. First segment with a minute external spine. Second and third segments

each with a well-developed external spine. Endopod of second leg (Figure 12h) 1-segmented.

External spines of exopod moderately developed,

that of second segment being the largest. Incision

posterior to second external spine of third segment

not unusually deep.
FIGURE 12.—Euchaeta gracilicauda. Female: a, forehead, lateral; b, genital segment, lateral; c, left

side of genital segment viewed obliquely; d, genital segment, dorsal; e, genital segment, ventral;

/, outer coxal lobe of maxillule; g, first leg, anterior; h, second leg, anterior. Male: i, forehead,

lateral; /, first leg, anterior; k, second leg, anterior; /, fifth pair of legs, anterior; m, exopod of

left fifth leg, anterior; n, exopod of left fifth leg, medial.
16

MALE.—Body length based on 3 specimens, 6.35-

6.41 mm. Prosome length, 4.41-4.50 mm. Frontal

eminence of forehead (Figure 12») not pronounced.

Rostrum well developed, pointing straight downward. Posterolateral corners of metasome asymmetrical. Antennule reaching middle of third

urosomal segment. Exopod of first leg (Figure 12;)

3-segmented. Distal 2 segments each with an external spine of reduced size. Second (Figure 12A) to

fourth legs similar to those of the female but external spines smaller. Serrated lamella of left fifth leg

scooplike, with uniform marginal teeth (Figure

12m,n). Digitiform process elongate, with distal

end sharply bent outward.

REMARKS.—Euchaeta gracilicauda was originally

described by A. Scott (1909) from 3 female specimens 7 mm long captured in 2 plankton tows down

to 750 m and 2000 m, respectively, in the Malay

Archipelago. The specimens described herein are

believed to be identical with A. Scott's species

because they seem to show a perfect agreement in

details of the genital segment and appendages.

The rostrum also shows a close similarity between

them, although it appears to be somewhat larger

and less curved in the present specimens.

Euchaeta gracilicauda has been recorded from

the Indian Ocean by Sewell (1929), but according

to his figure of the genital segment, his specimen

seems to be not referable to this species. Grice and

Hulsemann (1969) have recorded E. gracilicauda

from the eastern South Pacific. When reexamined

through loan by George D. Grice, their specimens

were not in agreement with E. gracilicauda in form

of the rostrum and appeared to be referable to a

new species I have found recently in sub-Antarctic

waters.

Sars (1925) described Euchaeta scotti from the

North Atlantic but his description is, however, obviously different in the form of genital segment

from the original species description by Farran

(1908). Although clearly distinguishable in the

form of rostrum, Sars' E. scotti is rather closely

related to E. gracilicauda.

The male of E. gracilicauda is described here for

the first time. It is also similar to the male of E.

scotti described by Sars (1925) except for the digitiform process of the left fifth leg, which in Sars'

species is almost straight.

DISTRIBUTION.—Since the records by Sewell (1929)

and Grice and Hulsemann (1968) are believed to

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

be not referable to this species, as stated above,

the present findings seem to constitute the first record of the species since its original discovery from

the Malay Archipelago by A. Scott (1909). The

species was represented in the present study by 28

females and 3 males, all taken in tows down to

depths exceeding 1000 m.

Euchaeta gracilis Sars, 1905

FIGURE 13

This is a common euchaetid species in deep

waters of the North Atlantic from the tropical to

boreal region (Vervoort, 1963). It has also been

recorded from the Indian Ocean by De Decker and

Mombeck (1965) and Grice and Hulsemann (1967)

and from the Pacific by Wilson (1950).

In the Gulf of Mexico and Caribbean Sea, E.

FIGURE IS.—Euchaeta gracilis. Female: a, genital segment,

lateral; b, forehead, lateral. Male: c, forehead, lateral; d,

exopod of left fifth leg, anterior; e, exopod of left fifth leg,

lateral; /, exopod of left fifth leg, medial.
NUMBER 196 17

gracilis has been recorded by Grice (1969). In the

present study, the species was represented by 32

females and 8 males, most of which were found in

the samples obtained from a depth range of 500 to

1000 m. The female measured 6.00-6.66 mm in

body length and 4.20-4.75 mm in prosome length,

and the male 5.08-5.58 mm in body length and

3.66-4.00 mm in prosome length.

Euchaeta hansenii With, 1915

FIGURE 14

Paraeuchaeta withi Sewell, 1947:131, fig. 30.

Euchaeta sarsi.—With, 1915:178, pi. 6: fig. 76 [male only].

Not Pareuchaeta hanseni.—Tanaka, 1958:362, fig. 78g-/i [male

only] [=Pareuchaeta comosa Tanaka].

MALE.—Body length based on 11 specimens,

8.08-8.58 mm. Prosome length, 5.75-6.08 mm.

Frontal eminence of forehead inconspicuous (FigFICURE 14.—Euchaeta hansenii. Female: a, forehead, lateral;

b, genital segment, lateral. Male: c, forehead, lateral; d,

exopod of left fifth leg, anterior; e, exopod of left fifth leg,

lateral; /, exopod of left fifth leg, medial, (dp = digitiform

process; gf = genital flange.)

ure 14c). Rostrum rather short but relatively

heavy, pointing downward. Posterolateral corners

of metasome asymmetrical, each with a small toothlike process dorsally. Antennule reaching about

distal end of second urosomal segment. Exopod of

first leg 3-segmented, with external spines of

reduced size. Endopod of second leg 1-segmented. Exopod with external spines of reduced

size. Serrated lamella of left fifth leg (Figure

\Ad-f) elongated into a narrow scooplike structure,

with small marginal teeth, all pointing medially.

Distal half of digitiform process distinctly bent

outward and much narrower than proximal half.

REMARKS.—The male described above is believed

to represent the hitherto unknown male of £.

hansenii, for it is usually found along with the

female of that species and is the closest to it in

body size. Euchaeta withi (Sewell, 1947), known

exclusively from the male, seems to be identical

with the male of E. hansenii described above. Euchaeta withi has been recorded from the North

Atlantic by With (1915, as E. sarsi), the Arabian

Sea by Sewell (1947), the Florida Current by Owre

and Foyo (1967), and the western North Pacific by

Tanaka and Omori (1968), and in all these areas

the female of E. hansenii has also been found by

the same authors.

The female specimens obtained in the present

study show no anatomical differences from the

original description by With (1915). Their body

length ranged from 8.41 to 9.25 mm and their prosome length from 6.08 to 6.83 mm according to

79 specimens.

DISTRIBUTION.—Euchaeta hansenii has been

known to occur widely in deep waters of the Atlantic, Pacific, and Indian oceans (Tanaka and

Omori, 1968). In the present study, the species was

represented by 79 females and 12 males, practically

all of which were found in tows down to depths

exceeding 1000 m.

Euchaeta incisa Sars, 1905

FIGURE 15

MALE.—Body length based on 20 specimens, 4.83-

5.75 mm. Prosome length, 3.50-4.08 mm. Frontal

eminence of forehead (Figure \5h) relatively low.

Rostrum powerful, pointing straight downward.

Posterolateral corners of metasome asymmetrical,
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 15.—Euchaeta incisa. Female: a, forehead, lateral; b, genital segment, left side; c, genital

segment, right side; d, genital segment, ventral; e, outer lobe of maxillule; /, first leg, anterior;

g, second leg, anterior. Male: h, forehead, lateral; i, exopod of first leg, anterior; j , exopod of

second leg, anterior; A, fifth pair of legs, anterior; I, exopod of left fifth leg, anterior; m, exopod

of left fifth leg, lateral; n, exopod of left fifth leg, medial.

each with a small toothlike process dorsally. Antennule reaching about middle of second urosomal

segment. Exopod of first leg (Figure 15i) 3-

segmented, last two segments each with a welldeveloped external spine. Endopod of second leg

1-segmented. Exopod (Figure 15;) with external

spine of medium size. Incision posterior to second

external spine of third exopodal segment moderately deep. Serrated lamella of left fifth leg relatively short. Viewed medially (Figure I5n), toothed

edge sigmoidally curved, with four to five large

teeth on distal end. Digitiform process of a nearly

uniform thickness, with round distal end, and

slightly longer than serrated lamella.

REMARKS.—The male of E. incisa, described here

for the first time, is readily recognized by its characteristic serrated lamella of the left fifth leg, as in

the other euchaetid species. The female specimens
NUMBER 196 19

found in the present study were identical in every

detail with the description given by Sars (1925).

They measured 5.41-5.75 mm in body length and

4.00-4.25 mm in prosome length.

DISTRIBUTION.—Euchaeta incisa was originally described from the North Atlantic by Sars (1905)

and has been recaptured in the western North Atlantic and the Gulf of Mexico by Grice (1963,

1969). In the present study, a total of 80 females

and 20 males were found, mainly in tows down to

depths over 1000 m.

Euchaeta pseudotonsa Fontaine, 1967

FIGURE 16

This Atlantic bathypelagic species had been

known to be conspecific with E. tonsa of the Pacific

until Fontaine (1967) recognized it as a separate

species. In the present study, the species was found

to be one of the most common bathypelagic euchaetid species. Altogether, 172 females and 26 males

were found in tows down to a depth range of 500

to 2000 m. The females measured 5.83-6.50 mm in

FIGURE 16.—Euchaeta pseudotonsa. Female: a, forehead, lateral; b, genital segment, lateral. Male: c, forehead, lateral;

d, exopod of left fifth leg, anterior; e, exopod of left fifth

leg, medial.

body length and 4.16-4.83 mm in prosome length,

and the males 5.50-5.91 mm in body length and

3.91-4.25 mm in prosome length.

Euchaeta sarsi Farran, 1908

FIGURE 17

Not Euchaeta sarsi.—With, 1915:178, pi. 6: fig. 1b [male only]

[=Euchaeta hansenii].

Not Paraeuchaeta sarsi.—A. Scott, 1909:75, pi. 21: figs. 9-15

[male only] [=Euchaeta barbata].

Euchaeta sarsi is a deep-living species known

to occur widely over the tropical, subtropical, and

temperate zones of the World Ocean (Vervoort,

1963; Tanaka and Omori, 1968). In the present

study, the species was represented by 35 females

and 5 males found in tows down to depths exceeding 1000 m. These finding are the first record of

the species in the Gulf of Mexico and Caribbean

Sea. The females ranged from 8.50 to 9.41 mm in

body length and from 6.25 to 6.75 mm in prosome

length, and the males measured 7.00-7.41 mm in

body length and 5.16-5.41 mm in prosome length.

The female of E. sarsi is closely related to that

of E. calva but can be distinguished from it by the

large body size and long genital flanges as compared with the length of the genital segment posterior to the flanges (Figure 17c). The male of E.

sarsi was correctly described for the first time by

Sars (1925) and redescribed by Tanaka (1958),

and can be readily recognized, as in the other

species of the genus, by its characteristic serrated

lamella of the left fifth leg (Figure 17g-t.)

Euchaeta scolti Farran, 1908

FIGURE 18

This rather rare bathypelagic species was originally described by Farran (1908) from female

specimens obtained from off Ireland. The male

was correctly described for the first time by With

(1915) from the Norwegian Sea. In the present

study, the species was represented by 62 females

and 9 males found in tows down to depths of more

than 1000 m. These findings constitute the first

record of the species from the Gulf of Mexico and

Caribbean Sea. The females measured 5.91-6.16

mm in body length and 4.16-4.48 mm in prosome
20 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

length, and the males 5.33-5.58 mm in body length

and 3.75-4.00 mm in prosome length.

The female is characteristic in having a humped

dorsal wall of the genital segment and a straightly

sloping posterior side of the genital prominence

(Figure 186). In the male the hollow scoop-shaped

serrated lamella and pointed digitiform process

serve as distinguishing characters (Figure \Sd-f).

FICUM 17.—Euchaeta sarsi. Female: a, forehead, lateral; b, genital segment, ventral; c, genital

segment, lateral. Male: d, forehead, lateral; e, first leg, anterior; /, exopod of second leg, anterior;

g, exopod of left fifth kg, anterior, h, exopod of left fifth leg. lateral; i, exopod of left fifth leg,

medial, (ft = length of genital flange; si = length of genital segment posterior to genital flange.)
NUMBER 196

21

FIGURE 18.—Euchaeta scotti. Female: a, forehead, lateral; b,

genital segment, lateral. Male: c, forehead, lateral; d, exopod

of left fifth leg, anterior; e, exopod of left fifth leg, lateral;

/„ exopod of left fifth leg, medial, (pr = posterior ridge of

genital field.)

Euchaeta vorax Grice and Hulsemann, 1968

FIGURE 19

Pareuchaeta striata Tanaka and Omori, 1968:257-258, figs.

3x, 4x, 21A-D.

FEMALE.—Body length based on 14 specimens,

6.41-6.75 mm. Prosome length, 4.58-4.91 mm.

Viewed laterally, forehead (Figure 19a) with a

pronounced frontal eminence. Rostrum well developed, straight in parallel to dorsal margin of forehead. Genital segment (Figure 19c) elongated,

with a small, low tubercle composed of several

closely contiguous ridges on left side posterior to

genital prominence. Laterally, genital flange undivided along ventral edge and produced posteiorly into a lobe. Posterior ridge (pr) of genital

field produced posteriorly, forming a conspicuous

lobe extending far beyond distal end of genital

flange. Posterior side of genital prominence merging into ventral wall of segment, forming a single

smooth arch (Figure 19c).

Antennule reaching middle of genital segment.

Outer coxal lobe of maxillule with 5 large setae

of equal size in addition to 2 or 3 minute setae

proximally. First 2 exopodal segments of first leg

(Figure \2e) incompletely fused, with a faint line

of joint. First segment with a minute external

spine; second and third segments each with a welldeveloped external spine. Second leg (Figure 19/)

with 1-segmented endopod and 3-segmented exopod.

External spines of exopod moderately developed,

that of second segment being the largest. Incision

posterior to second external spine of third segment not unusually deep.

MALE.—Body and prosome length of specimen

6.66 mm and 4.66 mm, respectively. Forehead (Figure 19g) with a low frontal eminence. Rostrum

arising from a broad base, pointing straight downward. Posterolateral corners of metasome asymmetrical. Antennule reaching distal end of second

urosomal segment. Exopod of first leg (Figure 19/»)

3-segmented; external spine of second segment

small, turned inward. Second (Figure 19i) to

fourth legs similar to those of female except that

external spines are smaller. Serrated lamella of left

fifth leg (Figure 19ft) in form of an elongated triangle with uniformly fine marginal teeth. Medially,

lateral toothed margin approximating medial

toothed margin toward distal end (Figure 19/).

Digitiform process slightly longer than serrated lamella, with distal portion tapering into a curved

process.

REMARKS.—Euchaeta vorax was originally described by Grice and Hulsemann (1968) from a

single female specimen captured in the eastern

South Pacific. It was characterized mainly by the

relative length of the genital segment and the presence of a knob on the dorsal side and another on

the left side. When reexamined through loan by

Thomas E. Bowman of the National Museum of

Natural History, the holotype of E. vorax, without

a distinct knob on the dorsal side of the genital

segment, was practically identical with the specimens obtained in the present study. Euchaeta

vorax resembles closely E. gracilicauda but may be

readily distinguished from it by the relatively short
FIGURE 19.—Euchaeta vorax. Female: a, forehead, lateral; b, genital segment, dorsal; c, genital

segment, lateral; d, genital segment, ventral; e, first leg, anterior; /, second leg, anterior. Male:

g, forehead, lateral; h, first leg, anterior; i, second leg, anterior; ;, fifth pair of legs, anterior;

A, exopod of left fifth leg. anterior; /, exopod of left fifth leg, medial, (pr = posterior ridge of

genital field.)
NUMBER 196 23

rostrum, the strong curvature of the ventral surface of the genital segment as viewed laterally, and

the relatively large ridged tubercle on the left side

of the genital segment.

Tanaka and Omori (1968) described an identical

species, Pareuchaeta striata, from the Izu region of

Middle Japan only a few months after the publication of E. vorax. I have examined a paratype of

P. striata through loan by Makoto Omori to verify

its identity with E. vorax.

The male of E. vorax is described here for the

first time. It is readily distinguished from the males

of the other species by its characteristic serrated

lamella of the left fifth leg.

DISTRIBUTION.—The species was represented in

the present study by 14 females and a single male,

which are found in samples taken from depths

exceeding 1000 m in the Gulf of Mexico and western Caribbean Sea. These findings are the first

record of the species since its discovery in the

eastern South Pacific and western North Pacific

almost simultaneously by Grice and Hulsemann

(1968) and Tanaka and Omori (1968), respectively.

Euchaeta alaminae, new species

FIGURE 20

MATERIAL.—A female from the R/V Alaminos

cruise 73-A-7, station 6, 20°41'N and 84° 17 ^ in

the western Caribbean Sea, 2900-0 m, deposited as

holotype in the National Museum of Natural

History, Smithsonian Institution, under the catalog

number of the United States National Museum

(USNM 150969).

FEMALE.—Body length, 6.35 mm. Prosome length,

4.58 mm. Forehead (Figure 20a) with a distinct

frontal eminence bearing suprafrontal sensilla.

Rostrum large, pointing obliquely forward. LatFICURF. 20.—Euchaeta alaminae, new species, female: a, forehead, lateral; b, genital segment, left

side; c, genital segment, ventral; d, genital segment, right side; e, outer lobe of maxillule; /, first

leg, anterior; g, exopod of second leg, anterior.
24

erally, posterolateral corners of metasome smoothly

rounded but somewhat squarish when viewed dorsally or ventrally. Dorsally, genital segment symmetrical, with lateral sides moderately swollen at

the middle. Laterally, dorsal side of genital segment markedly convex dose to proximal end

(Figure 2Qb,d). Genital prominence high, occupying about middle of segment. Anterior side of genital prominence highly convex and posterior side

nearly perpendicular to ventral wall of segment.

Laterally, genital flange appearing like a threelobed structure. Ventrally (Figure 20c), genital

flange with a large posterior lobe extending medially. Viewed laterally, posterior edge of genital

field produced posteriorly to form a low ridge midway on posterior side of genital prominence. Appendicular caudal setae glniculated, not thicker

than other caudal setae.

Antennule reaching distal end of prosome.

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

Outer coxal lobe (Figure 20e) of maxillule with

5 long setae. None of six apical setae of maxilla

provided with long, widely separated spines in

addition to fine spinules. First two exopodal segments of first leg fused (Figure 20/). External spine

of first segment minute, that of second segment

short of reaching middle of third segment. Endopod of second leg 1-segmented. External spines of

exopodal segments (Figure 20g) well developed,

that joi second segment being the largest. Incision

posterior to second external spine of third segment

not unusually deep.

REMARKS.—Although the observation is based on

a single specimen, the genital segment is so distinct

from those of all other euchaetid species so far described that the specimen is considered as representing a valid new species. The species is named

after the R/V Alaminos, the ship from which the

specimen was collected.

General Remarks

There seemed to be no significant difference in

the distribution of the euchaetid copepods between

the western Caribbean Sea and the Gulf of Mexico. Except for three rare species (E. aequatorialis,

E. confusa, and E. alaminae, new species), all the

species showed similar patterns of abundance and

bathymetrical distribution in both areas. All three

specimens of E. aequatorialis were found in the

Gulf of Mexico, and all six specimens of E. confusa

and one specimen of E. alaminae, new species,

were found in the Caribbean Sea.

Euchaeta marina and E. paraconcinna were

found mainly in the upper 100 m, and the former

was much more abundant than the latter. Occupying slightly deeper depths than these species were

E. pubera and E. media, whose main concentrations occurred at depths of 100-200 m and 200-500

m, respectively. Euchaeta media was much more

abundant than E. pubera. Euchaeta spinosa showed

high concentrations in a similar depth range to E.

media, but its bathymetrical range seemed to extend down to a depth of about 1000 m and therefore could be considered a mesopelagic species.

The remaining 15 species all belonged to the

bathypelagial zone and seemed to have a wide

range of vertical distribution. The most common

bathypelagic species was E. bisinuata, followed in

order by E. pseudotonsa, E. barbata, E. incisa, E.

calva, E. hansenii, and E. scotti. Euchaeta gracilis,

E. sarsi, E. gracilicauda, E. comosa, and E. vorax

were among the less common species, although

their populations in the area seemed to be well

established.

Since there are no comparable studies available,

it is not possible to show in detail to what extent

the euchaetid fauna in the Gulf of Mexico and

western Caribbean Sea is different from that of the

Atlantic. According to Vervoort (1963), the tropical Atlantic seems to show no significant difference

from the Gulf of Mexico and western Caribbean

Sea as far as the common species are concerned.

However, Roe (1972) reported euchaetid populations near the Canary Islands that are significantly

different from what have been found in the present

study from the Gulf of Mexico and western Caribbean Sea, in that E. acuia is as abundant in the

same depth range as E. media, E. pseudotonsa and

E. sarsi are the dominant bathypelagic species, and

E. bisinuata is absent.
NUMBER 196 25

Literature Cited

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.]

De Decker, A., and F. J. Mombeck

1965. South African Contribution to the International

Indian Ocean Expedition, 4: A Preliminary Report

on the Planktonic Copepoda. Republic of South

Africa Department of Commerce and Industries,

Division of Sea Fisheries, Investigational Report,

51:10-67.

Esterly, C. O.

1906. Additions to the Copepod Fauna of the San Diego

Region. University of California Publications in

Zoology, 3(5):53-92.

Farran, G. P.

1908. Second Report on the Copepoda of the Irish Atlantic Slope. Number 2 in Department of Agriculture and Technical Instruction for Ireland, Fisheries

Branch, Scientific Investigations 1906. 104 pages, 11

plates.

1929. Crustacea, Part X: Copepoda. In British Antarctic

{Terra Nova) Expedition, 1910, Natural History

Report, Zoology, 8 (3):203-306.

Fleminger, A.

1957. New Calanoid Copepods of the Families Aetideidae,

Euchaetidae, and Stephidae from the Gulf of

Mexico. United States Fish and Wildlife Service,

Fishery Bulletin 117, 57:355-363.

Fontaine, M.

1967. Two New Species of Euchaeta (Copepoda, Calanoida). Crustaceana, 12 (2): 193-213.

Grice, G. D.

1962. Calanoid Copepods from Equatorial Waters of the

Pacific Ocean. United States Fish and Wildlife

Service, Fishery Bulletin 186, 61:171-246.

1963. Deep Water Copepods from the Western North

Atlantic with Notes on Five Species. Bulletin of

Marine Science of the Gulf and Caribbean, 13(4):

493-501.

1969. Calanoid Copepods from the Caribbean Sea and

Gulf of Mexico, 1: New Species and New Records

from Midwater Trawl Samples. Bulletin of Marine

Science, 19 (2):446-455.

Grice, G. D., and K. Hulsemann

1967. Bathypelagic Calanoid Copepods of the Western

Indian Ocean. Proceedings of the United States

National Museum, 122 (3583): 1-67.

1968. Calanoid Copepods from Midwater Trawl Collections Made in the Southeastern Pacific Ocean. Pacific Science, 22 (3): 322-335.

Heptner, M. V.

1971. To the Copepod Fauna of the Kurile-Kamchatka

Trench: The Families Euchaetidae, Lucicutiidae,

Heterorhabdidae. Akademiya Nauk SSSR, Trudy

Instituta Okeanologii, 92:73-161. [In Russian.]

McGowan, J. A., and D. M. Brown

1966. A New Opening-Closing Paired Zooplankton Net.

Manuscript, Scripps Institution of Oceanography

Reference, number 66-23, 56 pages.

Owre, H. B., and M. Foyo

1967. Copepods of the Florida Current. In Copepoda,

part 1 of Crustacea, in Fauna Caribaea, 1:1-137.

Park, T.

1970. Calanoid Copepods from the Caribbean Sea and

Gulf of Mexico, 2: New Species and New Records

from Plankton Samples. Bulletin of Marine Science,

20(2):472-546.

Roe, H. S. J.

1972. The Vertical Distributions and Diurnal Migrations

of Calanoid Copepods Collected on the Sond cruise,

1965, III: Systematic Account: Families Euchaetidae

up to and Including the Metridiidae. Journal of

the Marine Biological Association of the United

Kingdom, 52:525-552.

Sars, G. O.

1905. Liste preliminaire des Calanoides recueillis pendant

les Campagnes de S.A.S. le Prince Albert de Monaco,

avec diagnoses des genres et des especes nouvelles

(Ire partie). Bulletin du Muse"e Ocianographique

de Monaco, 26:1-22.

1907. Notes supplementaires sur les Calanoides de la

Princesse-Alice (corrections et additions). Bulletin

de I'Institut Oceanographique de Monaco, 101:1-27.

1924-1925. Copepodes particulierement bathypelagiques

provenant des campagnes scientifiques du Prince

Albert ler de Monaco. In Resultats des Campagnes

Scientifiques text (1925), 69: 408 pages; atlas (1924),

127 plates.

Scott, A.

1909. The Copepoda of the Siboga Expedition, Part 1:

Free-Swimming, Littoral and Semi-parasitic Copepoda. Monographe 29a in Siboga-Expeditie. 323

pages, 69 plates.

Sewell, R. B. S.

1929. The Copepoda of Indian Seas. Calanoida. Memoire

of the Indian Museum, 10:1-221.

1947. The Free-Swimming Planktonic Copepoda: Systematic Account. In John Murray Expedition, 1933-

34, Scientific Reports, 8(1): 1-303.

Tanaka, O.

1958. The Pelagic Copepods of the Izu Region, Middle

Japan, Systematic Account, V: Family Euchaetidae.

Publication of the Seto Marine Biological Laboratory, 6(3):327-367.
26

Tanaka, O., and M. Omori

1967. Large-Sized Pelagic Copepods in the Northwestern

Pacific Ocean Adjacent to Japan. Pages 239-260 in

Information Bulletin on Planktology in Japan, Commemoration Number of Dr. Y. Matsue's Sixtieth

Birthday.

1968. Additional Report on Calanoid Copepods from the

Izu Region, Part 1: Euchaeta and Pareuchaeta.

Publication of the Seto Marine Biological Laboratory, 16(4):219-261.

Vervoort, W.

1957. Copepods from Antarctc and Sub-Antactic Plankton

Samples. In British Australian New Zealand AntSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

arctic Research Expedition, 1929-1931, Report Series B, 3:1-160.

1963. Pelagic Copepoda, Part 1: Copepoda Calanoida of

the Families Calanidae up to and Including Euchaetidae. Atlantic Report, 7:77-194.

Wilson, C. B.

1950. Copepods Gathered by the United States Fisheries

Steamer Albatross from 1887 to 1909, Chiefly in the

Pacific Ocean. United States National Museum

Bulletin 100, 14 (4): 141-441, plates 2-36.

With, C.

1915. Copepoda, 1: Calanoida, Amphascandria. In The

Danish Ingolf-Expedition, 3 (4): 1-260, plates 1-8.

U.S. GOVERNMENT PRINTING OFFICE I»7S 84«-S6«/l«


Publication in Smithsonian Contributions to Zoology

Manuscripts for serial publications are accepted by the Smithsonian Institution Press, subject to substantive review, only through departments of the various Smithsonian museums. NonSmithsonian authors should address inquiries to the appropriate department. If submission is

invited, the following format requirements of the Press will govern the preparation of copy.

Copy must be typewritten, double-spaced, on one side of standard white bond paper, with

W2" top and left margins, submitted in ribbon copy with a carbon or duplicate, and accompanied by the original artwork. Duplicate copies of all material, including illustrations, should be

retained by the author. There may be several paragraphs to a page, but each page should begin

with a new paragraph. Number consecutively all pages, including title page, abstract, text, literature cited, legends, and tables. The minimum length is 30 pages, including typescript and illustrations.

The title should be complete and clear for easy indexing by abstracting services. Taxonomic

titles will carry a final line indicating the higher categories to which the taxon is referable:

"(Hymenoptera: Sphecidae)." Include an abstract as an introductory part of the text. Identify

the author on the first page of text with an unnumbered footnote that includes his professional

mailing address. A table of contents is optional. An index, if required, may be supplied by the

author when he returns page proof.

Two headings are used: (1) text heads (boldface in print) for major sections and chapters and (2) paragraph sideheads (caps and small caps in print) for subdivisions. Further

headings may be worked out with the editor.

In taxonomic keys, number only the first item of each couplet; if there is only one couplet,

omit the number. For easy reference, number also the taxa and their corresponding headings

throughout the text; do not incorporate page references in the key.

In synonymy, use the short form (taxon, author, date:page) with a full reference at the

end of the paper under "Literature Cited." Begin each taxon at the left margin with subsequent lines indented about three spaces. Within an entry, use a period-dash (.—) to separate

each reference. Enclose with square brackets any annotation in, or at the end of, the entry.

For references within the text, use the author-date system: "(Jones, 1910)" and "Jones

(1910)." If the reference is expanded, abbreviate the data: "Jones (1910:122, pi. 20: fig. 1)."

Simple tabulations in the text (e.g., columns of data) may carry headings or not, but they

should not contain rules. Formal tables must be submitted as pages separate from the text, and

each table, no matter how large, should be pasted up as a single sheet of copy.

Use the metric system instead of, or in addition to, the English system.

Illustrations (line drawings, maps, photographs, shaded drawings) can be intermixed

throughout the printed text. They will be termed Figures and should be numbered consecutively; however, if a group of figures is treated as a single figure, the components should be

indicated by lowercase italic letters on the illustration, in the legend, and in text references:

"Figure 9b." If illustrations (usually tone photographs) are printed separately from the text as

full pages on a different stock of paper, they will be termed Plates, and individual components

should be lettered (Plate 96) but may be numbered (Plate 9: figure 2). Never combine the

numbering system of text illustrations with that of plate illustrations. Submit all legends on

pages separate from the text and not attached to the artwork. An instruction booklet for the

preparation of illustrations is available from the Press on request.

In the bibliography (usually called "Literature Cited"), spell out book, journal, and

article titles, using initial caps with all words except minor terms such as "and, of, the." For

capitalization of titles in foreign languages, follow the national practice of each language.

Underscore (for italics) book and journal titles. Use the colon-parentheses system for volume,

number, and page citations: "10(2) :5-9." Spell out such words as "figures," "plates," "pages."

For free copies of his own paper, a Smithsonian author should indicate his requirements

on "Form 36" (submitted to the Press with the manuscript). A non-Smithsonian author will

receive 50 free copies; order forms for quantities above this amount with instructions for payment will be supplied when page proof is forwarded.
i