ROBERT II. ii. GIBBS, GIBBS, JR. Taxonomy, Sexual

^m Dimorphism, Vertical

Distribution, and

Evolutionary Zoogeography

of the Bathypelagic

Fish Genus Stomias *

(Stomiatidae)

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1969 NUMBER 31
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SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 31

Robert H. abbs, jr. Taxonomy, Sexual

Dimorphism, Vertical

Distribution, and

Evolutionary

Zoogeography

of the JBathypelagic

Fish Genus Stomias

(Stomiatidae)

ISSUED

DEC-2W9

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

1969
ABSTRACT

Gibbs, Robert H. Jr. Taxonomy, Sexual Dimorphism, Vertical Distribution, and

Evolutionary Zoogeography of the Bathypelagic Fish Genus Stomias (Stomiatidae).

Smithsonian Contributions to Zoology, 31:1-25. 1969.—New information on the

characters and geographic distribution and a key for identification are presented for

the ten recognized species and subspecies of Stomias, of which one, the eastern Atlantic

subspecies S. colubrinus orientalis Blache, is considered a full species and is redescribed.

The name orientalis, a junior homonym, is replaced by lampropeltis. External sexual

dimorphism is demonstrated for all species in three characters: males are smaller

than females and have larger eyes and larger postorbital photophores. The magnitude

of the dimorphism varies among the species, the most extreme differences in eye

and postorbital organ occurring in species in which males attain the least maximum

size. Vertical distributions of all except S. danae are estimated by comparing numbers

of specimens caught in nonclosing nets with the number of meter-hours of trawling

at depth in the known geographic range of each form. All appear to migrate from

deeper to shallower depths at night. Most species for which data approach adequacy

occur in the greatest abundance between 500-1000 meters during daylight and in

the upper 200 meters at night, although concentrations of S. gracilis are deeper than

200 meters at night. In S. colubrinus, however, greatest daytime catches are below

1000 meters and at night below 600 meters. The apparent phylogenetic trends of

morphological characters, together with present geographical distributions, suggest

that S. brevibarbatus and S. danae represent the earliest evolved stock of Stomias, from

which, perhaps simultaneously, the colubrinus-lampropeltis group and S. nebulosus

arose. The S. boa group probably arose from nebulosus-like ancestors, with the almost

circumtropical S. affinis the earliest and giving rise to S. atriventer in the eastern

Pacific and S. boa boa in the Subtropical Convergence, and the latter giving rise to

5". gracilis in subantarctic and Antarctic waters and, most recently, to S. boa ferox

in the North Atlantic as well as a Mediterranean population that has retained boa boa

characteristics.

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in the Institution's annual report, Smithsonian Year

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

Washington, D.C. 20402 - Price 40 cents (paper cover)
Robert H. Gibbs, Jr Taxonomy, Sexual

Dimorphism, Vertical

Distribution, and

Evolutionary

Zoogeography

of the Bathypelagic

Fish Genus Stomias

(Stomiatidae)

Introduction

The genus Stomias includes elongate stomiatoid fishes

with five to six rows of closely spaced hexagons on the

sides (each hexagon apparently occupied by a scale),

with the dorsal and anal fins set far back toward the

caudal fin, with a barbel that is shorter to slightly

longer than the head, and rarely with more than 100

photophores in the ventral series. The only other

species in the family Stomiatidae is Macrostomias

longibarbatus, which is much more attenuate than any

Stomias species, has a barbel several times as long as

the head, and has about 150 or more photophores in

the ventral series. Macrostomias, relatively rare in collections although it has been reported from the Atlantic, Pacific, and Indian oceans, is not treated in this

study.

The studies of Ege (1918, 1933, 1934) provided

a solid foundation for the systematics, of the genus

Stomias. Based on specimens collected by several Danish oceanographic expeditions, Ege recognized all but

one of the taxonomic entities that are currently recognized and reduced many nominal forms to synonRobert H. Gibbs, Jr., Division of Fishes, Smithsonian Institution, Washington, D.C. 20560

ymy. The rank of some of Ege's taxa was questioned

by Morrow (1964a), who considered some of the

subspecies as deserving species status, and I concur.

The only valid new entity described since 1934 is S.

colubrinus orientalis Blache (1964) which I consider

a full species. Fowler (1934) described two new genera

and species, Microdontostomias orientalis and Pseudeustomias myersi, which are synonyms of Stomias

nebulosus and S. affinis, respectively (Morrow,

1964a). Fowler's use of the name orientalis necessitates

the renaming of the entity described by Blache.

Ege's studies and all that followed were hampered

by a lack of specimens of several species and by gaps

in geographic coverage. In recent years, while engaged primarily in revisionary studies of other stomiatoid families, I have examined numerous specimens

of Stomias in or from many collections around the

world. This paper presents data on the meristic characters of all species that indicate ranges of variation,

for the first time in those species formerly considered

rare (danae, atriventer, and gracilis), and redescribes

and renames the form that was inadequately described

by Blache. Sexual dimorphism is described for the

first time in this genus. Geographic and vertical distributions are determined and analyzed, and from these

and the morphological information a hypothesis is

1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

derived that explains the evolutionary zoogeography

of Stomias species.

METHODS.—In those species for which adequate

data are already published (S. affinis, S. nebulosus, S.

boa ferox, S. brevibarbatus) most counts and measurements were taken on only a few specimens. For S.

atriventer, S. boa boa, S. colubrinus, S. lampropeltis,

S. danae, and S. gracilis, data were taken on many

specimens.

In the dorsal and anal fins, the last two rays almost

invariably are separated by a considerable gap. Examination of cleared and stained material indicates

that each of these rays has its own pterygiophore, so

these are counted separately, not as one. Pectoral and

pelvic rays in most species deviate only rarely from

a count of six and five, respectively, and are not considered further except in S. danae and S. brevibarbatus, where the pectoral rays are seven to nine.

Counts of the large photophores in the ventral and

lateral series are expressed in the terminology recently

modified slightly from that customarily used for

stomiatoids, omitting the hyphen and more clearly

designating the sections between pelvic and anal fins

(see Morrow, 1964b, p. 276).

In the vental row:

IP, from anterior isthmus to before pectoral

insertion.

PV, from between pectoral insertions to before

pelvic (ventral) insertions.

VAV, from between pelvic insertions to before

anal origin.

AC, from above anal origin to end of row on

posterior caudal peduncle.

IC, the entire row.

In the lateral row:

OV, from behind operculum to before pelvic

(ventral) insertion.

VAL, from above pelvic insertion to end of row,

usually before anal origin, but occasionally

slightly behind it.

OA, the entire row.

Vertebral counts were made from radiographs or

from cleared and stained specimens and comprise all

ossified centra including the urostylar; the small unossified space between the first vertebra and the skull,

however, is not included.

Sex determination was made by gross microscopic

examination of gonads or by use of squash preparations of gonad material stained with aceto-orcein.

MATERIALS.—The following colleagues and institutions have very generously extended to me the use of

their collections and facilities or loaned me specimens

used in this study: Dana Collection (Dr. E. Bertelsen,

Miss Esther Hansen); Universitetets Zoologiske Museum, Copenhagen (Dr. Jergen Nielsen); Centre

de Recherches Oceanographiques, Abidjan, Cote

d'lvoire, R/V Reine Pokou (Dr. P. Rancurel); South

African Museum, Cape Town, (Michael J. Penrith);

Victoria University of Wellington, New Zealand (Dr.

J. A. F. Garrick) ; New Zealand Oceanographic Institution (Dr. E. W. Dawson); Zoologisches Museum

der Humboldt Universitat, Berlin (Dr. KurtDeckert);

Institut fur Seefischerei, Hamburg, R/V Walther Herwig (Dr. Gerhard Krefft) ; Shimonoseki College of

Fisheries (Dr. Reizo Ishiyama) ; University of Southern California (Dr. Hugh H. DeWitt, Dr. John R.

Paxton, Robert J. Lavenberg, Richard F. McGinnis);

Scripps Institution of Oceanography (Dr. Carl L.

Hubbs, Dr. Richard H. Rosenblatt, Joseph Copp),

Stanford University (Dr. Warren C. Freihofer); Museum of Comparative Zoology, Harvard University

(Dr. Giles W. Mead, Mrs. Myvanwy M. Dick); Institute of Marine Science, University of Miami (Dr. C.

Richard Robins); Bureau of Commercial Fisheries

Biological Laboratory, Honolulu (John C. Marr, Dr.

Donald W. Strasburg) ; Bureau of Commercial Fisheries, Tropical Atlantic Biological Laboratory, Miami

(Frederick H. Berry, Dr. William J. Richards); Bureau of Commercial Fisheries, Exploratory Fishing and

Gear Research Base, Pascagoula, Mississippi (Harvey

R. Bullis) ; Naval Oceanographic Office, Washington,

D.C. (Bernard Zahuranec) ; General Motors Defense

Research Laboratory, Santa Barbara, California (Dr.

William Aron); Smithsonian Oceanographic Sorting

Center (Dr. Leslie W. Knapp).

The only abbreviations used for institutions at which

collections are housed are the following: SIO, Scripps

Institution of Oceanography; SU Stanford University;

USNM, United States National Museum.

Stomias affinis Giinther, 1887

Most of my counts fall within the range recorded by

Ege (1934), with the exception of VAV, OV, and IC,

where some slightly higher counts were found.

Ege had no records of S. affinis between the longitudes of New Caledonia (about 178°E) and 116°W.
NUMBER 31

Key to the Species and Subspecies of Stomias

1. A single tooth on anterior end of each palatine 2

Two teeth on anterior end of each palatine 3

2. Premaxillary teeth on one side 7 or fewer (rarely 8); mandibular teeth on one side 15 or

fewer (rarely 16); combined number of premaxillary and maxillary teeth 21 or fewer

(rarely to 23) on each side; no teeth on posterior end of palatine (east tropical Pacific)

S. colubrinus Garman

Premaxillary teeth usually 8 or more (6-7 not unusual); mandibular teeth almost always

16 or more (rarely 14—15); combined number of premaxillary and mandibular teeth 22 or

more (rarely to 20) on each side; a tooth on posterior end of each palatine (east

tropical Atlantic) S. lampropeltis, new name

3. Most mandibular teeth longer than longest premaxillary teeth; mandibular teeth fewer (9—16)

than premaxillary teeth (16-25) (tropical Indo-Pacific) S. nebulosus Alcock

Longest mandibular tooth shorter than longest premaxillary teeth; mandibular teeth more

numerous (7-18) than premaxillary teeth (4—12) 4

4. Five rows of hexagonal areas dorsal to lateral series of photophores; barbel length (without

terminal filaments) 75 percent of head length or less; premaxillary teeth usually 10 or more;

pectoral rays 7 or more 5

Six rows of hexagonal areas dorsal to lateral series of photophores; barbel length (without

terminal filaments) usually about equal to head length, rarely less than 67 percent of

head length; premaxillary teeth 8 or fewer; pectoral rays 6 6

5. Bulb of barbel without filaments; 2 slender filaments at base of barbel stem; 6 or fewer

photophores in any hexagonal area in the 3 rows above lateral series of photophores;

vertebrae fewer than 64 (Indo-Pacific and South Atlantic central waters) S. danae Ege

Bulb of barbel with 4 filaments; no filaments at base of barbel stem; 7 or more photophores

in any hexagonal area in the 3 rows above lateral series of photophores; vertebrae 64 or

more (North Atlantic between about 20°-40°N) S. brevibarbatus Ege

6. Total photophores in ventral series (IC) more than 90 (94—102); in lateral series (OA) 65 or

more; PV 53 or more; OV 52 or more; vertebrae 86 or more (subantarctic and Antarctic

waters) S. gracilis Garman

Total photophores in ventral series (IC) 90 or fewer (73-90); lateral series (OA) 64 or

fewer; PV 51 or fewer; OV 50 or fewer; vertebrae 83 or fewer 7

7. VAV photophores 5-8 (rarely 9); VAL 4-8 (circumglobal in warmer waters)

S. affinis Gunther

VAV photophores 10-14 (rarely 9); VAL 10-15 8

8. OV photophores 39-43; OA photophores 52-55; IC photophores 77-82; vertebrae 69-74

(east Pacific) S. atriventer Garman

OV photophores 43-50; OA photophores 57-64; IC photophores 79-90, usually 83 or more;

vertebrae 74-83 S. boa 9

9. IC photophores 79-88, usually 83-86; vertebrae 74-80 (Mediterranean Sea, northwest

African waters, southwest African waters, Subtropical Convergence) S. boa boa (Risso)

IC photophores 85-90, usually 87-89; vertebrae 77-83 (north Atlantic north of about 30°N)

S. boa ferox Reinhardt

The present material fills a portion of this distributional

gap in equatorial waters between 160°W and 120°W.

There is only one record for the entire area of the

western Pacific occupied by the Polynesian and Micronesian island groups—a small specimen taken in the

Samoan region on Eltanin cruise 31. Norman (1939)

reports of S. affinis from the southern Red Sea, and

Aron and Goodyear (1969) now record it from the

Gulf of Eilat (Aqaba) and adjacent northern Red

Sea.

Stomias atriventer Garman, 1899

Until recently, the holotype and eight additional specimens (Parr, 1931) of this species had been recorded.

Ege (1934) regarded it as a subspecies, S. boa atriventer, but, as Morrow (1964a) indicated, there is little

or no overlap in certain meristic characters between

this and any other form closely related to S. boa.

Counts of OA photophores so far afford complete

separation of S. atriventer from S. boa boa, the most

similar species, and OV, PV, and IC photophore
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

counts and vertebral counts show very slight overlap.

Thus S. atriventer should be regarded as a full

species.

The geographic range of S. atriventer comprises two

separate areas (Figure 5). One comprises the lower

Gulf of California and the California Current off

southern California and Baja California (Lavenberg

and Fitch, 1966; Lavenberg and Ebeling, 1967; Berry

and Perkins, 1967). A single specimen was taken in a

deep haul by Scripps Institution's Tethys expedition at

13°N, 127°W, indicating possible occasional westward transport by the extension of the California

Current.

The second portion of the range is at or below the

equator from the Galapagos Islands south to 23 °S

in the influence of the Humboldt Current.

In both areas frequency distributions of most meristic characters are quite similar, but in the southern portion numbers of dorsal and anal rays and vertebrae

average higher than in the northern portion. Differentiation has thus been slight, in spite of the wide

separation between the geographical ranges.

Ege (1934) records a single small transitional specimen from west of the Galapagos as S. boa boa. I have

not seen this specimen, but it is almost certainly S.

atriventer.

Stomias boa boa (Risso), 1810

The geographic range of S. boa boa is divided into two

disjunct parts. One part includes the Mediterranean

Sea (including the Sea of Marmora; Demir, 1958) and

waters under the influence of its outflow off northwestern Africa. The other part is the Subtropical Convergence and southern Humboldt and Benguela currents.

Ege (1934) found no noteworthy differences between samples from various parts of the range, but

the present data offer some suggestions that invite future study. In vertebral numbers and in photophores

of the PV, IA, IC, and OA groups, specimens from

the vicinity of New Zealand have the lowest counts,

while those from the central South Pacific (mostly

from Eltanin cruise 24) have the highest. Specimens

from the western Indian Ocean and from the southeastern Pacific are intermediate, but tend to approach

the New Zealand and central South Pacific samples,

respectively, in their counts. These trends are illustrated by the PV counts in Table 1. The probability

that southern S. boa boa consists of more than a single

subpopulation is indicated also by the flatness of the

combined frequency distributions and the wide ranges

of meristic characters, especially when compared with

the strongly modal distributions of the same data from

the Mediterranean population taken from Ege (1934)

and included in Tables 8-11.

TABLE 1.—Stomias boa boa : frequency distribution of

PV photophores in the southern population

Region

Western Indian Ocean

New Zealand

Central South Pacific

Southeast Pacific

44

_

1

-

1

Number of PV photophorti

45

_

4

-

—

46

5

5

-

1

47

9

5

1

5

48

3

1

3

6

49

2

-

4

3

50

-

2

1

Stomias gracilis Gar man, 1899

Five specimens of this species have been reported previously (Giinther, 1887; Ege, 1934). Several recent

expeditions, especially those of the Eltanin, have found

S. gracilis abundant in Antarctic and subantarctic

waters.

In numbers of vertebrae and some photophore

counts (PV, OV, IC, OA), S. gracilis is widely separated from its congeners, justifying Morrow's (1964a)

contention that it should be regarded as a full species.

Stomias lampropeltis, new name

FIGURES 1, 2

Stomias colubrinus orientalis Blache, 1964 [no holotype

designated; syntypes in Museum National d'Histoire Naturelle, Paris].

This species has been called S. colubrinus by previous

authors (Brauer, 1906; Ege 1934). Blache (1964), for

the first time, compared southeastern Atlantic specimens with Ege's (1934) data for eastern Pacific specimens. Using a statistical test of the differences between means, he found that his sample differed significantly from that from the eastern Pacific in numbers of dorsal rays, anal rays, and PV photophores,

although in each case the modes were the same. On

this basis he described the eastern Atlantic population

as a new subspecies, Stomias colubrinus orientalis.

If the differences between two nominal subspecies

are so slight that they cannot be determined by inspection of specimens or data, then I do not accept the

validity of the subspecies. The use of a statistical test
NUMBER 31

FIGURE 1.—Stomias lampropeltis. Top: female, 233 mm, Dana station 4003(1). Bottom: male,

95.8 mm, Reine Pokou station 540. Drawn by Howard E. Hamman.

of significance between means, when it is the only

criterion for naming a subspecies, is unacceptable, to

me at least. In the case of Blache's new subspecies,

not only were such tests the only criterion, but the

basic assumption of a normal distribution was not

present in the frequencies of some characters. To indicate the impropriety of using such criteria, I employed

Blache's statistical tests using two different samples of

the same form, S. colubrinus from the eastern Pacific.

My own data were tested against those of Ege (1934)

that had been used by Blache. The two samples from

the eastern Pacific were just as significantly different

as were those tested by Blache from the Pacific and

Atlantic.

Despite the fact that the characters and criteria used

by Blache were inadequate to show that two subspecies

should be recognized, comparison of the dentition of

the two populations (Figure 2) convinced me that they

are, indeed, separate entities. I choose, furthermore, to

recognize them as full species.

The name orientalis, applied by Blache, is not available for this species, because it is a homonym of

Microdontostomias orientalis Fowler, 1934, which is a

synonym of Stomias nebulosus Alcock (Morrow,

1964a). I propose the new specific name lampropeltis

for the eastern Atlantic species of Stomias related to

S. colubrinus of the eastern Pacific. The name is a

noun in apposition, Lamppropeltis being a genus of

colubrid snakes.

COMPARATIVE DIAGNOSIS.—Stomias lampropeltis is

closely related to S. colubrinus and distinct from all

other species in the genus in the following combination of characters: a single tooth on the head of each

palatine; premaxillary teeth fewer and longer than

mandibular teeth; barbel, exclusive of end filaments, at

least two-thirds of head length; six rows of hexagonal

(scale) areas on each side of body; in the space ventral to each photophore in the lateral row, an arcuate

group of 20 to 30 small diffuse photophores.

Compared with S. colubrinus, S. lampropeltis has

more and generally shorter teeth (Figure 2; Table 2).

The longest premaxillary tooth of S. lampropeltis goes

4.6-7.2 times into the length of the premaxilla, in S.

colubrinus 3.8-6.0 times. The number of premaxillary

teeth in S. lampropeltis is 6-14, in S. colubrinus 5-8.

There are 14-26 mandibular teeth in S. lampropeltis,

8-16 in S. colubrinus. The total tooth count (both premaxillary and mandibular teeth) is 20-37 in S. lampropeltis, 13-23 in S. colubrinus. In S. lampropeltis,

there is a small tooth on the posterior end of each

palatine; such a tooth has not been observed in S.

colubrinus.

Meristic characters show only minor differences. S.

lampropeltis has, on the average, more vertebrae and

fewer photophores in both ventral and lateral rows

(Tables 8-10), but overlap is almost complete in every

case.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

FIGURE 2.—Heads of male Stomias lampropeltis, 95.8 mm (left) and S. colubrinus, 144.4- mm

(right), showing differences in size and number of jaw teeth. Drawn by Howard E. Hamman.

TABLE 2.—Stomias colubrinus (count in italics) and S. lampropeltis: frequency

distribution of premaxillary and mandibular teeth

Number of

premaxillary

teeth

5

6

7

8

9

10

11

12

13

14

8 9 10 11

1 2 3 4

--3 4

4

- - - 1

_ _ _

_

_ _ _

_

_

12

3

3

2

-

-

-

-

-

-

13

5

6

1

-

-

-

-

-

-

14 15

4

2,1 2,\

1

i

-

1

-

-

-

Number of mandibular teeth

16

/

-

A 2

2

2

2

-

-

-

17

-

-

3

2

5

-

-

-

18

1

2

4

3

2

1

-

-

19

1

7

3

4

2

1

-

20

2

4

3

2

3

-

1

21

-

4

5

2

1

-

-

22

-

1

2

1

-

1

-

1

23

1

2

_

2

1

1

3

24

1

1

-

1

25 26 27 28

1

1

1

1

DESCRIPTION.—Meristic characters given in Tables

8-15. Morphometic characters, as percent of standard

length unless otherwise stated, as follows:

Predorsallength: 80.7-86.0.

Preanal length: 78.7-84.7.

Prepelvic length: 66.6-72.6.

Depth behind head: 5.6-9.8.

Head length: 10.2-13.9.

Barbel length (excluding filaments) : females:

5:5-12.0 (60-192 percent of head length); males:

10.2-17.1 (77-165 percent of head length).

Fleshy orbit length: females: 1.5-2.8 (15-29 percent of head length) ; males: 2.1-4.1 (21-34 percent

of head length).

Postorbital organ length: females: 21-47 percent

of fleshy orbit; males: 40-91 percent of fleshy orbitUpper jaw length: 9.1-11.2.

Premaxillalengh: 7.3-9.3.

Longest premaxillary tooth: 13.8-21.5 percent of

premaxilla length.

Snout to bony orbit: 1.3-2.6.

Premaxillary and mandibular tooth counts shown

in Table 2. Vomerine teeth: 1 on each side. Palatine

teeth: 1 on anterior end, 1 on posterior end. Replacement teeth often present and contiguous to vomerine

and palatine teeth. Three widely spaced groups of basibranchial teeth, each composed of 1 to 3 teeth, on each

side of midline. Pharyngobranchial teeth in two groups
NUMBER 31

on each side of roof of mouth. Groups of short teeth

present on 1st 4 gill arches, eight to ten groups on 1st

arch; none on last, attached arch.

DISTRIBUTION.—S. lampropeltis has been taken only

in the eastern Atlantic Ocean off the west coast of Africa from 21°40'N {Dana station 4008) to 14°55'S

(Ombango station 350).

Stomias colubrinus Garman, 1899

Stomias colubrinus was formerly known from the Gulf

of Panama and adjacent waters in the eastern Pacific.

The collections reported here extend the known geographic range of the species farther to the west and

south than Ege (1934) reported, and Bussing (1965)

has published the southernmost locality at about 32°S,

73°W. Meristic and morphometric characters either

fall within the ranges given by Ege or extend these

ranges slightly.

The record of S. colubrinus from Hudson Canyon

(Beebe, 1929) is almost certainly in error. This specimen (SU 43286) has been reexamined, and is definitely

referable to eastern Pacific S. colubrinus, not to S.

lampropeltis from the eastern South Atlantic. Two

other bathypelagic species found in the eastern Pacific

but not in the Atlantic were misidentified and recorded

by Beebe (1929) among the Hudson Canyon fauna.

One is Idiacanthus antrostomus (SU 57328, listed by

Beebe as /. fasciola); the other is an undescribed species

of Astronesthes (SU 57460, listed by Beebe as

Astronesthes martensi). All three questioned species

were labeled as taken at Arcturus station 113, which

was the last station following an expedition that made

several midwater collections in the eastern tropical

Pacific. I strongly suspect that a mixup in labeling

occurred, either during or after the Arcturus

expedition.

Borodin (1931, p. 65) recorded S. hexagonatus, a

synonym of S. colubrinus, from 47°40'N, 37°20/W in

the North Atlantic. These specimens (MCZ 31606,

3 specimens, 100, 200, 230 mm) were reexamined and

proved to be S. boa ferox.

Stomias nebulosus Alcock, 1889

Counts were made on only four central Pacific specimens of this distinctive species. Numbers of dorsal and

anal rays were at the low extreme of the ranges given

by Ege (1934). Other counts are nearer the center of

356-599 O—69 2

these ranges. Ege noted differences in VAV and IC

photophores in populations of S. nebulosus. The few

central Pacific specimens agree most closely in VAV

counts with Ege's South China Sea specimens

(modally eight).

Two specimens taken off southeast Africa at

Galathea station 203 (25°36'S, 35°21'E, 21 February

1951, maximum depth 730 m) were far south of the

otherwise known range of the species. Possibly this

extension is due to the warm Agulhas Current.

Stomias danae Ege, 1933

This species was described by Ege from a single South

Pacific specimen, and no others have since been reported. I have examined four additional specimens, two

from near Hawaii (SIO 60-249; USNM 201739) and

two from the western Indian Ocean (USNM 201829,

USNM 201830). Another specimen was taken in the

South Atlantic by the Walther Herwig (Dr. Gerhard

Krefft, in litteris, see Figure 6). Meristic and morphometric data for five of the six known specimens are

given in Table 3.

The new specimens confirm the characters used by

Ege (1933, 1934) to distinguish S. danae from the

closely related but allopatric S. brevibarbatus. In S.

danae no filaments arise from the end of the bulb of the

barbel; two long filaments arise from the base of the

barbel stem. The small photophores in the three ventralmost rows of hexagonal areas are few; usually two

to three in the third row from the dorsum; usually three

to five in the fourth row; usually three to five in the

fifth row (the upper two rows have one photophore per

hexagon). The number of vertebrae, reported here for

the first time, is less than in any other Stomias except

nebulosus. The postorbital organ is apparently smaller

in S. danae than in S. brevibarbatus. In two male S.

danae this organ is about 39 percent of the fleshy orbit

diameter, and in one of undetermined sex it is

50 percent. In two small female S. brevibarbatus the

organ is 62-75 percent of the eye diameter, and in a

110-mm male, it is 84 percent.

The characters that set S. danae and S. brevibarbatus apart from all other species of Stomias are also

confirmed. There are five, rather than six, rows of

hexagons. The numbers of premaxillary and mandibular teeth in both species are similar and high for

Stomias. The barbel is shorter than in other Stomias

at any given size. In S. brevibarbatus it is about one-
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 3.—Stomias danae counts and measurements 1

Character

Dorsal rays

Anal rays

IP

PV

VAV

OV

VAL

AC

Vertebrae

Premaxillary teeth

Mandibular teeth

Gill-raker patches

Branchiostegal photophores

Standard length

Predorsal length

Preanal length

Prepelvic length

Head length

Barbel length*

Barbel bulb length**

Snout to bony orbit*

Fleshy orbit*

Postorbital organ**

Upper jaw length

Premaxilla length

Longest premaxillary tooth***

Longest mandibular tooth***

Depth at pectoral insertion

Greatest depth (distorted)

Caudal peduncle depth

Length dorsal base

Length anal base

18

20

11

31

13

30

13

13

60

10

11 +

3 + 7

18

48.9

41.2

41.0

30. 1

5.5

1.5

0.7

1.6

1.0

0.5

4 . 9

4 . 5

0.8

0.4

3.6

3.6

1.0

4 . 5

5. 1

USNM

201829

84.3

83.8

61.6

11.2

27.3

70.0

29. 1

18.2

50.5

10.0

9.2

17.8

8.9

7.4

7.4

2.0

9.2

10.4

DANA

3583

18

21

11

32

13

32

12-13

15

-

12

17

-

-

68.0

58.5

58.0

42.0

8.2

4 . 0

—

»2. 5

1.5

—

—

—

—

—

—

4.7

1.6

5.7

8.3

86.0

85.3

61. 8

12.1

48.8

—

30.5

18.3

—

—

—

—

—

—

6.9

2.4

8.4

12.2

Specimen

USNM

201739{<?)

16

20

11

31

14

31

14

14

62

10

16-17

-

17

139. 1

118.5

117.3

84.2

16.2

10.6

1.4

3.9

2.8

1. 1

16. 1

12.5

2.4

1.5

11. 1

12.8

3. 1

12.0

16. 1

85.2

84.3

60. 5

11.6

65.4

50.0

24. 1

17.3

39.3

11.6

9.0

26.7

12.0

8.0

9.2

2.2

8.6

11.6

SIO

60-249

17

20

-

30

12

30

12

14

61

10

15

3 + 7

-

145.2

122.3

123.2

92.5

16.6

12.0

1.6

2.5

2 . 4

—

14.7

12. 1

—

—

11.2

14.6

—

—

—

84.2

84.8

63. 7

11.4

72.3

66. 7

15. 1

14.5

—

10.2

8.3

—

—

7. 7

10. 0

—

—

—

USNM

201830((?)

18

21

11

31

13

31

13

15

62

11

20

3 + 7

15

155.9

134.2

132.6

97.9

18.0

11.9

1.3

3 . 9

3 . 8

1.5

16.5

14. 1

2. 1

1.5

11.3

13.4

3 . 4

15. 1

20. 7

84.6

83. 7

61.8

11.4

66. 1

34.2

21.7

21.1

39.5

10.6

9.0

14.9

10.6

7.2

8.6

2. 2

9.5

13.1

1

 Proportions in italics are in percent of standard length except where the character is marked with asterisks: *percent of

head length; **percent of fleshy orbit diameter; ***perccnt of premaxilla length.

2

 Ege probably measured snout to fleshy orbit.

third of the head length (Ege, 1934), although in two

small specimens that I examined it was approximately

40 percent. In S. danae the barbel appears to increase

in relative length, from 27 percent to 72 percent

(Table 3). The pelvic fins are inserted more anteriorly

than in other Stomias: prepelvic length in S. brevibarbatus is 59-63 percent of standard length (Ege, 1934),

in S. danae 60-64 percent; other species of Stomias

range from 65-76 percent.

Sexual Dimorphism

Sexual dimorphism in the genus Stomias is manifested

externally in at least three ways: (1) males are smaller

than females; (2) males tend to have larger eyes;

(3) males have larger postorbital organs. The sexes

have not been determined in previous accounts of the

genus, and the literature is useful only for the maximum size of females. The data presented here for S.
NUMBER 3 1

nebulosus, S. brevibarbatus, and S. danae are inadequate and need further amplification.

The maximum size attained by females varies

greatly among the species (Table 4). Largest of all

are the closely related species S. colubrinus and S.

lampropeltis. Next in order is the group of species related to S. boa, in which maximum size is correlated

roughly with numbers of serial photophores and vertebrae. Data from Ege (1934) and Morrow (1964a)

are sufficient to establish that S. nebulosus and S. brevibarbatus are small species, the former less than 200

mm, the latter less than 150 mm. No females of S.

danae have yet been recognized, but if the size of the

largest male is taken as an indication, females probably become larger than 200 mm.

TABLE 4.—Maximum known standard length of Stomias

species

Species

colubrinus

lampropeltis

gracilis

boa fcrox

boa boa

atriventer

affinis

nebulosus

brevibarbatus

danae

Maximum standard

9

309

1297

» 290

3 289

298

238

»204

176

» 150

?

length (mm)

<?

191

116

257

256

239

144

130

93

111

159

1

 Information from Norman (1939).

2

 Information from Ege (1934).

3

 Information from Morrow (1964a).

Males in the S. boa group parallel the females in

maximum size. Those of S. gracilis, S. boa ferox, and

S. boa boa reach a length that is only about 10-20 percent shorter than the largest females. The largest male

S. atriventer, however, is almost 100 mm (40 percent)

shorter than the largest female. Not only do the smaller

species apparently show this trend of the males being

smaller in size than the females, but also the males of

the largest species, S. colubrinus and S. lampropeltis,

are much smaller than the females, markedly so in

S. lampropeltis.

Data on eye size are inadequate for S. nebulosus, S.

brevibarbatus, S. danae, and S. boa ferox. In the other

six forms there is overlap between males and females,

but males, on the average, have larger eyes than females of the same species at any given size. Fleshy orbit

diameter relative to head length is given in Table 5.

Relative to standard length, the eyes of females are

not greatly different among the species. Because head

length differs, however, the eye size is inversely correlated with head length, those species with the longest

heads having the smallest relative eye size. In males,

the head length-eye size relationship does not follow

that of the females, although the relative head lengths

are similar. These relationships are shown graphically

in Figure 3, for S. lampropeltis, in which species the

dimorphism is most extreme.

TABL E 5.—Fleshy orbit diameter as percent of head length

of Stomias species, showing that males have relatively

larger eyes than females 1

Species

colubrinus

lampropeltis

gracilis

boa ferox

boa boa

atriventer

affinis

nebulosus

brevibarbatus

danae

Flesh}i orbit percent of head length

9 o*

11. 9-22. 1

15.0-29.4

23. 7-28. 9

24. 0-27. 1

21. 6-26. 5

11.8-26.3

14. 9-28. 6

20. 5-24. 5

. 15. 2-19. 2

—

9. 8-31. 4

20. 5-34. 1

24. 6-35. 0

-

21.3-36.6

19.4-28. 5

19. 1-28. 6

24. 5-29. 3

19. 1

17. 3-21. 1

1

 Original data only.

As in many stomiatoids, the postorbital organ is the

most striking sexually dimorphic character, always

larger in males. Its size relative to eye size is shown in

Figures 3 and 4. Because the eyes are larger in males

than females of each species, the differences in postorbital organ size are even more obvious than indicated

by this relationship. In those species in which males become almost as large as females, the postorbital organ

is relatively small in both males and females, and the

distinction between males and females is not as pronounced. This is shown in Figure 4 for S. gracilis, and

S. boa is quite similar. In 5". atriventer and S. nebulosus,

the organ in females is about the same relative size as

in S. gracilis and S. boa, but in males it is relatively

larger and hardly overlaps the female size range. This

trend is continued in S. affinis, in which the female
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

• • o

:

* * •

°o°

. V*

°° •* V*

g °o

°e

*& ° <xP o O 0

° ^j,°° 8° ° °

o Q>

0 Oo ° o

° °° ^8° o 0°

8o

o°

O ° o ° o * cp ° °o °

FIGURE 3.—Stomias lampropeltis. Graphs showing relationships of head length, fleshy orbit diameter, and postorbital

organ. Open circles=females. Dots=males.

postorbital organ becomes somewhat larger, and that of

the males is still larger and does not impinge upon the

female size range. In females of S. colubrinus the postorbital organ is relatively larger than in females of the

preceding five species. Males of S. colubrinus, however, reach an intermediate size, and the organ is similar in relative size to that of S. affinis, still considerably

larger than in females. Females of the related species,

S. lampropeltis, have a postorbital organ that is similar

in size, but the males, which do not become as large as

those of S. colubrinus, have an organ that may be al-

-

00

a.

o

j «

o

o

in

o

0 .

6 0

5 0

4 0

3 0

2 0

10

6 0

5 0

4 0

3 0

2 0

10

5 0

4 0

3 0

2 0

1 0

5 0

4 0

3 0

2 0

10

•

•

O

_

| | |

".."•' •

* * • * •

_ ' *

• •

• •

• * #

m *

• •

o °

o n o oo 9O

TD O

a °°

• )

i . ' •

- *

O° 0

• o 0*0° o o

CO

1

o o o ($>

o \ ^ .Pa?

8

o 9

o

• • •

x ° o oo, o o ° §

y

o8o °o oe

°

o o°o o

0

 ^ o °°

0

1 1

cjb°

 <Bt

o

 o<p °

°

tolubrmui

„,,,„..

mbulotut

FIGURE 4. Graphs showing relative size of postorbital organ in

five species of Stomias (see Figure 3 for S. lampropeltis).

Open circles=females. Dots=males.

most as large as the eye. Two male S. danae (Table 3)

have postorbital organs about 40 percent of fleshy orbit,

while in one small specimen of undetermined sex the

organ is 50 percent. This suggests that, in postorbital

organ size, S. danae may prove similar to S. atriventer

or S. nebulosus. The largest postorbital organ appears
NUMBER 3 1 11

to be that of S. brevibarbatus. In two females, 60-70

mm SL, its is 62-75 percent of fleshy orbit; in a single

male, 111 mm SL, it is 84 percent. The general rule

within Stomias, then, is that a larger postorbital organ

is associated with males that attain the least maximum

size. In those species in which the size attained by males

and females differs the most, the separation in size of

male and female postorbital organs is the greatest.

Vertical Distribution

METHODS.—Because all available collections of

Stomias were made with nonclosing nets, an analytic

procedure was devised, similar to that used by William

H. Krueger (unpublished manuscript), for determining depths of capture of Idiacanthus. Each species was

considered separately. Data were used from expeditions

from which all specimens of any species were examined.

Only those stations within the geographic range of a

species were used. Daylight (0700-1700 hours) and

night (1900-0500 hours) tows were used, but those that

included the usual periods of vertical migration (0500-

0700, 1700-1900) were not considered. Collections

made by the Dana using 100, 200, and 300 cm nets

with circular openings were analyzed separately from

Isaacs-Kidd midwater trawl (IKMT) collections.

Dana depths were considered to be one-half the meters

of wire out.

For each tow, the number of hours at depth (excluding up-down time) was multiplied by the area

encompassed by the mouth of the net. For ring trawls

of 100, 200, and 300 cm, the areas are 0.785, 1.766, and

7.065 square meters, respectively; for 3-foot, 6-foot,

and 10-foot IKMT's, areas of 1, 4, and 9 square meters

were used. The number of meter-hours for each depth

interval, and the number of specimens caught at each

depth interval were tabulated and reduced to percent

of total for comparison (Tables 6 and 7). Much of the

calculation was done on a time-share computer, using

a program devised by Richard H. Goodyear.

In addition to providing the shallowest depth of

capture during day or night, the reduced data remove

some of the influence of the up-down component, and,

therefore, indicate the depths at which concentrations

of a species occur. When the percentage of specimens

caught at any depth is considerably greater than the

percentage of meter-hours at that depth, it may be assumed that this represents a real region of concentration. The reverse indicates that specimens recorded for

that depth probably were caught while the net was

bing lowered or raised.

GENERAL OBSERVATIONS.—When Dana data are

used, results usually are biased by the paucity of shallow tows during daylight and of deep tows at night.

Furthermore, the number of meter-hours logged by

the Dana at night within various species ranges is two

to eight times the number during daylight. Thus

while interpretations of night distributions may be fairly reliable, daytime distributions are seldom so. The

IKMT data that combine numerous Scripps Institution or USNS Eltanin collections provide the most reliable estimates.

No specimen of any species was taken above 300 m

during daylight, and the data suggest that the bulk of

most species populations occur between 400 and 1000

m. Two species, S. colubrinus and S. lampropeltis, appear to inhabit mainly depths below 1000 m during

the day. Most species apparently migrate to the upper

100 or 200 m at night; S. gracilis remains mostly deeper than 200 m and S. colubrinus mostly below 600 m.

These generalized vertical distributions place most

species in the intermediate water masses during the

day, and in subsurface water masses during the night.

Some species have apparent peaks of night distribution, in addition to the upper concentration, at depths

at which they occur in daytime. This suggests either

that a part of the population does not migrate vertically, or that deeper populations become concentrated

at somewhat shallower levels at night (see S. atriventer,

S. gracilis, Tables 6 and 7).

Stomias atriventer. IKMT station data for the

northern population are from Clarke (1963). Trawling time is relatively equally distributed among depth

categories both day and night. During daylight, S. atriventer is most abundant at 500-600 m, with lesser

peaks at 800-900 and 1250-1500 m. At night populations are concentrated in the upper 100 m, with lesser

peaks at 500-600 and 700-800 m. Lavenberg and Ebeling (1967) indicate a vertical distribution between

500-700 m in the San Pedro basin. Data for the southern population do not allow speculation.

Stomias boa boa. Only the southern population has

been analyzed. IKMT station data are from my own

records for Anton Bruun cruise 14; from Humes

(1967) and field notes of Leslie W. Knapp for Anton

Bruun cruise 18; from the original data sheets for Eltanin cruise 21; and from Savage and Caldwell (1965,

1966, 1967) for Eltanin cruises 4-6, 9-11, 13-16, 19,
12 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 6.—Daytime vertical distributions of Stomias species, based on midwater trawls

(IKMT) and ring trawls (Dana)1

Depth (m)

0-100

101-200

201-300

301-400

401-500

501-600

601-700

701-800

801-900

901-1000

1001-1250

1251-1500

1501-2000

2001-3000

>3000

Number of specimens

Number of meter-hrs.

Number of nets

0-100

101-200

201-300

301-400

401-500

501-600

601-700

701-800

801-900

901-1000

1001-1250

1251-1500

1501-2000

2001-3000

>3000

Number of specimens

Number of meter-hrs.

Number of nets

gracilis

IKMT

M-hr.

8.5

1.3

8.5

8. 1

3.0

4. 7

3.3

6. 1

5.0

3.9

8.5

4.5

12.5

16.3

5.9

2445

140

Spec.

0

0

0

0

4.7

14.2

29.3

31. 1

0

0.9

4.7

3.8

4.7

5.6

0.9

106

lampTopdtis

DANA

M-hr.

0

0

0

0

11. 1

0

0

0

0

11. 1

8.3

11.1

44.5

13.9

0

127

24

Spec.

-

-

-

0

-

-

-

-

southern

boa boa

IKMT

M-hr.

0

0

5.2

2 . 4

6.3

4 . 8

3 . 6

4 . 8

8.3

2 . 4

7.4

2.4

2. 7

20.4

29.3

746

40

15.4

15.

0

61.

7.

-

13

4

5

7

Spec.

-

0

0

0

10

10

0

10

10

10

0

0

20

30

10

M-hr.

0

0

0

0

6.2

0

1.6

0

0

17.3

9.8

23.4

25.9

15.8

0

685

57

DANA

M-hr.

2.5

0

0

0

13.7

0

3 . 4

0

0

12.6

6.8

23.2

11.9

25.9

0

313

48

nebulosus

DANA

Spec.

-

-

-

0

-

0

_

-

80

0

15

5

0

-

20

Spec.

0

-

-

-

0

-

0

-

-

14.2

42.9

42.9

0

0

-

7

northern

atriventer

IKMT

M-hr.

0.9

13.5

2. 1

9.7

0.8

11.8

3.2

7. 1

5. 1

7.7

7.9

7.9

12.2

10.2

0

1199

59

affinis

DANA

Spec.

-

-

-

4 . 8

_

0

_

-

61.9

4.8

23.8

0

4 . 8

-

21

Spec.

0

0

0

0

0

62.5

0

7.5

10.0

0

0

15.0

0

5.0

0

40

colubrinus

IKMT DANA

M-hr.

27. 1

0

0

33.9

35.6

0

/. 7

0

0

0

1.7

0

0

0

0

53

6

brevibarbatus

DANA

M-hr.

18.9

16.0

15.0

9.4

13.6

0.4

1.5

0.9

0.8

3. 1

2. 1

0.4

6.3

11.5

0

842

207

Spec.

0

0

0

0

0

0

0

0

0

0

0

100

0

0

-

1

Spec. M-hr.

0 3.9

0

0

22.2 0

22. 2 12. 2

0

44. 4 2. 0

0

0

11.0

22. 2 15. 5

11.1

44. 3

0

0

9

159

21

boaferox

DANA

Spec.

0

-

-

-

0

-

3 . 8

-

-

10.0

21.2

20.0

45.0

-

-

80

M-hr. Spec.

14.1

6.7

4. 1

3.2

7.9

0

2 . 4

0

0

8.0

0

8 . 0

8 . 0

37.6

0

221

44

0

0

0

0

0

-

0

-

50

-

50

0

0

-

2

Methods of calculation given in text (page 11). Meter-hours (M-hr.) and specimens (Spec.) expressed as percent of total.
NUMBER 31 13

TABLE 7.—Night vertical distributions of Stomias species

Depth (m)

0-100

101-200

201-300

301-400

401-500

501-600

601-700

701-800

801-900

901-1000

1001-1250

1251-1500

1501-2000

2001-3000

>3000

Number of specimens

Number of meter-hours

Number of nets

0-100

101-200

201-300

301-^00

401-500

501-600

601-700

701-800

801-900

901-1000

1001-1250

1251-1500

1501-2000

2001-3000

>3000

Number of specimens

Number of meter-hours

Number of nets

gracilis

IKMT

M-hr.

13.4

4 . 9

3. 8

6.2

3.5

4.2

6. 1

8.3

1.5

4. 7

5.9

6.6

11.7

11.8

7.5

2743

163

lamp

Spec.

4.7

0

10.6

4 . 7

4.7

17.6

3.5

4 . 7

1.2

9.4

16.5

2.3

9 . 4

9.4

1.2

85

robeltis

DANA

M-hr.

32.9

15.8

15.8

0

35.5

0

0

0

0

0

0

0

0

0

0

278

36

Spec.

0

71.

14.

-

14.

-

-

-

-

-

-

-

-

-

-

6

southern

boa boa

IKMT

M-hr.

10.2

3. 1

3 . 4

5.6

8.3

2.7

6. 7

3 . 4

3.7

1.4

3 . 4

9.2

12.3

18.0

8 . 7

1335

76

4

3

3

Spec.

35.7

2 . 4

2 . 4

4 . 8

26.2

0

7. 1

0

4 . 8

2 .4

0

2 . 4

0

4 . 8

7. 1

42

M-hr.

38.4

27.9

14.4

0.7

15.7

0

0.6

0

0

0.7

0.2

0.7

0.7

0

0

2963

500

DANA

M-hr.

32.7

14.2

12.0

0 . 9

39.8

0

0

0

0

0 .4

0

0

0

0

0

799

99

nebulosus

DANA

Spec.

27.3

46. 5

16.8

0.6

8.2

-

0.6

-

-

0

0

0

0

-

-

333

Spec.

84

4

0

0

12

-

-

-

-

0

-

-

-

-

-

25

northern

atriventer

IKMT

M-hr.

4.6

17.2

1.3

8 . 8

3 . 5

7.6

2 . 6

1.2

9.9

7.2

8.2

6. 1

3 .6

13.9

4 . 3

1261

58

aJRnis

DANA

Spec.

50.6

35.7

7.0

0.8

5.5

-

0

-

-

0

0

0 . 4

0

-

-

253

Spec.

51.6

0

0

6.3

6.3

14.1

0

4.7

3. 1

0

1.6

4.7

3. 1

3. 1

1.6

64

colubrinus

IKMT DANA

M-hr.

0

6 .4

4.7

12.7

21.6

23.5

22. 1

0

0.5

0

0

0

0

6.0

2 . 4

671

31

brcvibarbatus

DANA

M-hr.

58.2

19.2

5.3

1.9

11.2

1. 1

0.9

0. 1

0

0. 1

0.5

0.3

0.6

0 .4

0.3

7021

1318

Spec.

15.0

65.0

10.0

2.5

7.5

0

0

0

-

0

0

0

0

0

0

40

Spec. M-hr.

24.9

0 10.7

1.4 14.5

8. 1 2. 5

10. 8 29. 6

6. 8 5. 5

55.4 1.4

0

10.8 0

2.7

2.7

5.5

0

1.4 0

5.4 0

74

256

49

boa ferox

DANA

Spec.

2 . 4

7. 1

4 . 8

0

35.7

0

2.4

-

-

7. 1

28.6

11.9

-

-

-

42

M-hr. Spec.

61.5

20.3

4 . 4

1.4

10.2

0

0

0

0

0.2

0 .4

0 .4

0.2

0.4

0.6

3361

537

75.0

22.0

1.5

0.9

0.6

-

-

-

-

0

0

0

0

0

0

545

1

 See explanations to Table 6.
14

24, and 26. Data for Dana stations from Carlsberg

Foundation (1934).

The meager daytime IKMT catches suggest that S.

boa boa lives below 500 m, but allow no further limitation of its vertical range. At night this species shows

concentrations in the upper 100 m and at 400-500 m.

Dana collections tentatively indicate daytime concentrations at 900-1500 m, and confirm the night

range by IKMT data.

Stomias boa ferox. Dana station data are from

Schmidt (1929) and Carlsberg Foundation (1934),

catch records are from Ege (1934). Despite reasonable

daytime sampling, only two specimens are recorded,

between 900-1500 m. The only real conclusion to be

drawn is that this species seems to occur below 500 m

during daylight hours. At night, it is abundant in the

upper 200 m but sampling below 500 m is inadequate

to indicate possible deeper concentrations.

Stomias gracilis. Data are from Savage and Caldwell (1965, 1966, 1967) for the same Eltanin cruises

used for S. boa boa, and from Fisher (1964) for Scripps

Institution's Expedition "Monsoon."

Although it occurs between 400-500 m in daytime,

S. gracilis is clearly concentrated between 500-800 m.

It occurs in the upper 100 m at night, but the peaks

of abundance are found at 200-300 m, 500-600 m,

and 900-1250 m. This species remains throughout its

vertical migration almost entirely in intermediate

water of Antarctic origin (see Reid, 1965).

Stomias affinis and Stomias nebulosus. Depth relations of these two species have been analyzed only in

the broad area where they occur sympatrically. This

includes a relatively narrow band from off southeastern

Africa, curving northward to Ceylon, and south of

the Indonesian Islands, the South China Sea, Celebes

Sea, and closely adjacent areas. Data are from the

1928-30 Dana expedition (Carlsberg Foundation,

1934). These data are strongly biased toward night

collections, and toward deep daytime and shallow

night collections. All daytime stations were used in the

calculations, but only every second night station.

A primary objective was to seek some difference

in the vertical distribution of these two geographically

sympatric species that might explain their apparent

coexistence. None was found. The data suggest that,

in a general way, S. affinis tends to occur at shallower

depths than S. nebulosus, but the overlap is great.

Both species were taken together commonly in the

same net by the Dana.

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

At the shallowest daytime depths sampled, 400-

500 m, S. affinis was taken, but not S. nebulosus. Both

species appear most abundant at 900-1000 m but this

is probably an artifact due to collecting bias and small

sample size. At night both species clearly are most

abundant in the upper 200 m, with S. affinis concentrated in the upper 100 m and S. nebulosus at 100-

200 m.

In contrast to the sympatry exhibited by these two

species throughout the entire range of S. nebulosus in

the Indian Ocean and Southeast Asian seas, their geographic ranges in the only other region of S. nebulosus

occurrence, the Central Pacific, are almost completely

separated (Figures 5 and 6). Most of these captures

were made in the upper 400 m at night (specimens

examined by me at the Bureau of Commercial Fisheries Biological Laboratory, Honolulu, and reported,

in part, by King and Iversen, 1962).

Stomias colubrinus. Dana data are from Schmidt

(1929), the stations being in or near the Gulf of

Panama. IKMT data, all from cruises of the Anton

Bruun, are from my own records for cruise 14, from

Chin (1966) for cruise 16, and from Humes (1967)

and field notes of Leslie W. Knapp for cruise 18. These

stations are all between 2°N and 32°S in the eastern

Pacific.

Little collecting has been done in the upper 400 m

during daylight, and no catches are recorded in this

upper stratum. The vast majority of specimens were

caught in nets fished between 900-2000 m, which is

where the Dana placed most of its nets. Night captures have been made in the upper 100 m, with peaks

at 500-600 m (Dana), 600-700 m (IKMT), and

1000-1500 m (Dana). It seems probable, then, that

S. colubrinus remains largely at considerable depths,

both day and night, perhaps avoiding the oxygen-poor

layer. The southern population of S. atriventer, on the

other hand, may be associated with the oxygen-poor

water, if depth data for the northern population can

be extrapolated.

Stomias lampropeltis. Data from Dana stations

3999-4009 were used, and these are too few to allow

reasonable conclusions. They suggest that, like S. colubrinus, S. lampropeltis may inhabit depths from 900-

2000 m during the day, and at night are found up to

100-200 m, but not in the upper 100 m. In the numerous collections of the Reine Pokou, most of them

made at night, S. lampropeltis was taken at 375-750

m (750-1500 m of wire out), shallower than Dana
NUMBER 31 15

o aff mis

* b. boa

•b.ferox

• atriventer

o gracilis

FIGURE 5.—Distributions of the five members of the Stomias boa species group. Original data

and records from the literature (Ege, 1934; Demir, 1958; Berry and Perkins, 1967; Norman,

1939; Aron and Goodyear, 1969; Blache, 1964).

• brevibarbatu s

D danae

o lampropelti s

• colubrinus

* nebulosus

FIGURE 6.—Distributions of species in the Stomias brevibarbatus, colubrinus, and nebulosus

species groups. Original data and records from the literature (Ege, 1934; Blache, 1964; Pieper,

1967; Bussing, 1965).
16

data suggest. Unfortunately, these were virtually the

only depths sampled.

Stomias brevibarbatus. The abundant Dana collections in the North Atlantic (Schmidt, 1929; Carlsberg Foundation, 1934) were used in conjunction with

specimen data reported by Ege (1934). Despite reasonable effort during the day between 0-500 m and

1500-3000 m, only one specimen was caught. This

suggests that the daytime occurrence of S. brevibarbatus is between 500-1500 m, where relatively little

effort was expended.

A tremendous amount of fishing was done at night

from the surface to 500 m but little deeper than 500

m. This clearly shows the greatest night concentrations

at 100-200 m.

Stomias danae. Only six specimens are known. The

Dana specimen from the South Pacific was taken in

a trawl fished at 300 m during twilight. One of the

two specimens from near Hawaii was taken in a

discrete-depth sampler at 317-451 m during daytime

(Pieper, 1967); the other was taken in a long trawl

at 2671 m covering both night and day hours. One

of the two Indian Ocean captures was in a similarly

inconclusive night and day trawl to 2500 m; it was,

however, in the deep fraction of a Foxton catch divider,

and was probably taken below about 250 m. The

other was taken in a shallow Foxton fraction during

a day-night tow.

Zoogeography and Evolution

Four species groups are apparent within the genus

Stomias. Group one (the brevibarbatus group), comprising S. brevibarbatus and S. danae, has only five

lateral rows of hexagonal areas, the hyoid barbel

shorter than the head, seven or more pectoral rays, and

the pelvic fins inserted anteriorly, at 59-65 percent of

standard length. Group two (the colubrinus group),

including S. colubrinus and S. lampropeltis, has only

a single tooth at the anterior end of each palatine.

Group three, including only S. nebulosus, has 16-25

premaxillary teeth, all of which are short, and 9-16

mandibular teeth, most of which are longer than any

of the premaxillary teeth. Group four (the boa group)

contains the four remaining species—S. atriventer, S.

boa (with two subspecies), S. gracilis, and S. affinis.

All usually have five fanglike premaxillary teeth and

eight to ten mandibular teeth, of which the first two

or three are short, the posterior ones fanglike and gradSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ing from long to moderate toward the rictus. All four

groups are distinguished by combinations of other

characters, as may be seen in the key to species.

Many morphological characters of the species and

species-groups show trends that I interpret as evolutionary trends. The brevibarbatus group has many

characters, some of them different in the two species of

that group, that are changed and stabilized in all the

other species-groups. For example, the barbel is short

in the brevibarbatus group, with either no filaments

arising from its tip or with four filaments. In all other

groups the barbel is longer, quite similar in length in all

species, and has three terminal filaments. There are

seven to nine, usually eight pectoral rays in the brevibarbatus group, six in all others. The number of lateral

rows of hexagons is five in the brevibarbatus group,

six in all others. I regard this as evidence that the

brevibarbatus group is phylogenetically the oldest, its

species being the survivors of a stock that was considerably more variable in its morphology than are the

more recently evolved groups.

The colubrinus and nebulosus groups are next in

order of phylogenetic age, and I believe that the former

evolved earliest. About the only primitive character

that they retain is a relatively large number of fairly

small teeth, and S. colubrinus shows signs of reduction

in number and enlargement of individual teeth.

Most recently evolved is the boa group, with four

species that have stable morphological characters, with

the exception of somite and photophore numbers.

The trend among and within all groups is toward

elongation of the body and higher numbers of vertebrae, somites, and photophores. The lowest counts

are seen in the brevibarbatus and nebulosus groups,

followed by the colubrinus group. Within the boa

group, S. affinis is quite similar to the colubrinus group,

followed by S. antriventer, S. boa boa, S. boa ferox, and

S. gracilis, in that order.

Another such trend is seen in postorbital organ size

in males. This light organ is largest in S. brevibarbatus

and the colubrinus group, while in S. nebulosus it is

intermediate in size and resembles some of the boa

group. Within the boa group, the reduction in size of

the postorbital organ follows the increase in photophore

counts from S. affinis, with the largest postorbital

organ, to S. gracilis with the smallest.

The number of small photophores in the hexagonal

areas and in the interspace between the lateral and

ventral rows of large photophores show apparent evolu-
NUMBER 31 17

tionary trends toward reduction. In S. brevibarbatus

there are 14-20 photophores in the hexagons of the

ventralmost (fifth) row, 12-18 in the fourth row, and

7-10 in the third. These numbers in S. danae are 4-6,

4-5, and 2-4, respectively. The three lower hexagon

rows in the two species of the colubrinus group have

5-9 in the sixth, 4-6 in the fifth, and 4-6 in the fourth

rows. The boa group has 3-5, 3-4, and 2-4 photophores

in these rows, except for S. affinis, which has 3, 2-3, and

2, respectively. The greatest reduction is seen in S.

nebulosus, with 1-3, 1, and 1. The uppermost rows

(two in the brevibarbatus group, three in all others)

have 1 photophore per hexagon. The small photophores between the lateral and ventral rows of serial

photophores form a concave arc below each lateral

photophore in the series. In the brevibarbatus and

colubrinus groups, these arcs are composed of wide

bands of very small photophores. In S. nebulosus the

arcs are irregular and composed of about 6, somewhat

larger photophores, and in the boa group the arcs are

quite regular and formed primarily by 3-5 larger

photophores.

The geographic distribution patterns of the species

support the contention that the boa group is the most

recently evolved. The species of that group occupy

complementary ranges in the more productive waters

of the world (Figure 5). Stomias affinis is found in

equatorial or adjacent tropical waters of the Atlantic,

Indian, and Pacific oceans, except for the eastern tropical Pacific. It apparently occupies the areas of the cenTABLE 8.—Stomias species: frequency distribution of photophores in ventral row (IC)1

Species

Number of photophores in ventral row (IC)

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

------------23971 -

-----------356332 -

________________ 2 12 34

-------------1-31 9 13

------ - 2 5 24 53 74 45 13 5 1 1 -

------- - 1 3 22 49 40 23 52- -

-------2 6 22 32 31 20 52-- -

------2 7 15 51------ -

--111------------ -

X 2 9 19 35 44 13 2--------- -

Number of photophores in ventral row (IC)

85 86 87 88 89 90 91 94 95 96 97 98 99 100 101 102 N

54

25

1

29

19

8

6

6

27

2

6

37 24 X ---- - -

- - - - 4 6 10 10

22

22

139

83

100

45

223

145

120

30

3

124

80.

79.

84.

85.

87.

96.

76.

77.

76.

73.

69.

70.

1

2

9

0

8

9

9

5

5

9

0

3

1

 In additition to original observations, data are included from Ege (1934), Morrow (1964a), and Blache (1964). Where

frequency distributions were not given in the literature, the extensions are indicated by an X.
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

tral water masses in the South Atlantic and Indian

oceans, but large areas in these oceans have not been

adequately sampled. The two subspecies of S. boa

meet the northern boundary of S. affinis range in the

Atlantic, with S. boa boa found only in the Mediterranean and its outflow off the northwest coast of Africa and S. boa ferox throughout practically the entire

North Atlantic. The southern population of S. boa boa,

in the Subtropical Convergence around the world and

northward in the Benguela and Humboldt current

regions, abuts the southern boundary of the range of

S. affinis. In turn, S. gracilis occupies subantarctic and

Antarctic waters south of the S. boa boa range. Two

populations of S. atriventer are found in the northeastern Pacific and southeastern Pacific, with a wide

gap between them. The southern population meets the

northward extension of S. boa boa along the coast of

Chile south of Antofagasta. The only region that has

been well collected and where the boa group is not

represented is the central North Pacific. Whether or

not the group is represented in the central South Pacific is still open to question.

The remaining three species groups, in contrast to

the boa group, have relatively limited ranges, all of

them at least partly confluent with members of the

boa group. This fact alone suggests that the boa group

has superimposed itself on the others. In most cases,

the older groups show evidence of retracted distributions and limitation to relatively unfavorable or specialized environments. The most extreme example is the

TABLE 9.—Stomias species: frequency distribution of photophores in lateral rows (OA)l

Species

Number of photophores in lateral rows (OA)

40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

------------397 4

------------466 5

--------XX I 1 X 2 - -

------2 9 13 71---- -

- - - - - 4 14 40 22 13 2 1 -

----- - 1X X IX---- -

- - 1 1 2 (1) --------- -

xxxxxx--------- -

Number of photophores in lateral rows (OA)

57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 N

------------- - -2 3 53.5

----------- - ---2 1 53.6

xxxxx----------- -

1 1 0 1 7 6 3 1 ---____ _ - 3 8 59 . 1

xxxxxxxx-------- -

------- - 1 1 6 16 11 7 3 45 68.5

---------- - ----3 2 47.9

------------ - --9 6 47.4

----------- - --- 4 43.3

1

 In addition to original observations, data are included from Ege (1934), Morrow (1964a), and Blache (1964). Where frequency distributions were net given in the literature, the extensions are indicated by an X.
NUMBER 31 19

colubrinus group, of which S. colubrinus inhabits the

eastern tropical Pacific, with its apparent center of

abundance between the equator and 10°N, and S.

lampropeltis inhabits the eastern tropical Atlantic, also

apparently most abundant between 0° and 10°N.

There is no question that these two species

are closely related and that they are distinct

from all others. Their present geographic distributions could only have resulted from reduction of a

much wider range that included, at one time, at least

the eastern Pacific and the width of the Atlantic. In

all probability S. affinis displaced the representative of

this group in the tropical Atlantic, and S. lampropeltis

now occupies only the region off west Africa that is

characterized by seasonal upwelling, high productivity,

and the presence of an oxygen-poor layer (Bubnov,

1966). These two species coincide in the west African

area and are able to coexist, presumably, by virtue of

having different vertical distribution patterns, although the available data are not sufficient to establish

this. In the eastern tropical Pacific, S. colubrinus occupies an area that is largely separate from the southern population of S. atriventer, but the two occur

together in abundance at the Galapagos Islands and

along the coasts of Ecuador and Peru, areas within

which an oxygen-poor layer occurs. In this case, the

vertical distribution data suggest that S. colubrinus

tends to remain below the oxygen-minimum layer,

while S. atriventer inhabits this layer (about 100-700

m according to Wooster and Cromwell, 1958), and verTABLE 10.—Vertebral counts of Stomias species: frequency distribution

Species

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

59

-

76

10

7

60

-

— — I I I I

77

26

11

1

61

-

1 1 1 1 — 00

78

9

7

16

62

_

2

17

79

7

9

49

63

_

i i I I

16

80

1

4

70

64

-

X

8

81

1

56

65

_

1

X

1

82

1

17

Number of vertebrae

66 67 68

_

3

1

2

X

-

_

19

1

9

X

-

39

14

15

X

-

Number of vertebrae

83 86 87

3

1 1 1 CM

7

69

1

1

35

33

12

-

88

9

70

4

8

19

29

5

-

89

7

71

6

18

4

14

-

90

5

72

12

5

X

3

-

91

- i i I

73 74

7 2

1 1

1

i I I iI I I I

-

92 N

34

- 54

- 47

- 212

1 32

119

44

14

75

1

6

1 I I I -

X

71.8

71.0

77.3

77.5

80. 1

88.4

68.2

69.5

68.1

61.3

62.5

1

 In addition to original data, counts are included from Ege (1934); where Ege did not give frequencies, his data are represented

by an X.
20 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

tically migrates within it. Even the northern population of S. atriventer, which does not occur together

with S. colubrinus, apparently has its main vertical distribution (see Tables 6 and 7) within the oxygen-poor

layer (about 300-800 m according to Reid, 1965).

The two species of the brevibarbatus group are restricted to the North Atlantic (S. brevibarbatus) and

the central waters of the Indo-Pacific and South Atlantic (S. danae). These are regions of low productivity, and the populations of both species are relatively

sparse, as indicated by trawling success. More day or

night meter-hours of trawling are recorded within

the distributional limits (mainly the Sargasso Sea) of

S. brevibarbatus than for any other species, yet only

41 specimens were caught during these hours (this

does not include trawls during dawn, twilight, or

both night and day). This is an average of only one

fish per 176 meter-hours at night, a figure not approached by any of the other species that were computed for Tables 6 and 7. The rarity of S. danae is

attested to by the existence of only six known specimens. The species is known to occupy waters that are

inhabited by S. affinis (Indian Ocean) and S. nebulosus (South Pacific), and it also occurs in the North

Pacific near the Hawaiian Islands, where it is the only

recorded species of Stomias. Probably it was formerly

more abundant throughout a large part of the IndoPacific, but has diminished in numbers through competition with S. affinis. It seems that S. danae may

even be on the verge of extinction.

TABLE 11.—Stomias species: frequency distribution of photophores in PV portion of ventral row

 1

Species

30 31 32

Number of photophores in PV portion of ventral row

33 34 35 36 37 38 39 40 41 42 43 44

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

-

2

1

-

15

3

-

42

20

-

65

59

-

29

38

1

3

17

3

1

5

11 10

45 46 47

Number of photophores in PV portion of ventral row

48 49 50 51 52 53 54 55 56 57

1

X

6

X

10

X

X

10

X

X

8

X

X

6

X

2

X

16 13

N

6

3

X

1

25

24

43

45

19

157

144

28

5

42.7

42.3

47.0

54.9

43.9

38.7

39.4

33.4

31.0

1

 In addition to original observations, data are included from Ege (1934), Blache (1964), and Morrow (1964a). Where

frequency distributions were not given in the literature, the extensions are indicated by an X.
NUMBER 3 1

The distribution pattern of S. nebulosus is interesting. Across the Indian Ocean, it occurs in a narrow

band, which apparently is not owing to the fact that

most collections were made by the Dana. Two northsouth transects made by the Anton Bruun along 60°

and 65° (cruises 3 and 6, 1963 and 1964) took S.

affinis at ten stations from 12°N to 23°S, but S. nebulosus was captured only at three stations, all within a

few degrees of the equator (Gibbs, manuscript unpublished). Among the islands of southeast Asia, S.

nebulosus is common in the Celebes, Sulu, Flores, and

South China seas and adjacent waters of the western

Pacific, in which areas it is also found together with

S. affinis, the two species having been taken commonly

in the same net (see Ege, 1934 for data). The vertical

21

distribution computations (Tables 6 and 7) suggest

that S. affinis tends to concentrate at somewhat shallower depths, both day and night, than S. nebulosus,

but the difference is not striking. The Dana data (Ege,

1934) indicate that, in the region of mutual occurrence,

S. nebulosus is generally more abundant than S. affinis (see Tables 6 and 7). Apparently, then, S. nebulosus is holding its own against S. affinis, but within a

limited range. In the central Pacific, a different situation is evident. There, S. affinis inhabits the equatorial

waters, while S. nebulosus occurs separately in a band

between about 8° and 18°S (Figures 5 and 6). One

factor appears to clarify the situation. Virtually all collections of S. nebulosus have been made in the vicinity

of land masses or islands. Thus, again, this more primiTABLE 12.—Stomias species: frequency distribution of photophores in OVportion of lateral row

 x

Species

atrivcnter (S)

atriventer (N)

boa boa (Mcd)

boa boa (S)

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atrivcnter (N)

boa boa (Mcd)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

30

_

_

-

-

-

2

—

45

-

X

7

X

-

X

-

-

-

31

_

_

-

-

-

2

—

46

-

X

7

X

-

X

_

-

-

_

-

32 33

_ _

-

-

X X

1

X X

47

-

X

12

X

-

-

_

-

-

-

-

Number of photophores in OV portion of lateral row

34 35

_ _

_ _

-

-

X X

_ _

X X

36 37

_ _

_ _

X 6

1 8

_ _

_

X X

38

_

_

25

36

-

_

X

39

1

_

6

35

-

_

-

40

3

X

3

14

-

_

—

Number of photophores in OV portion of lateral row

48 49

-

X

3 2

X X

-

_ _

_

-

-

- -

50 51

-

- -

_ _

X

_

-

_

-

-

-

— -

52

-

-

-

_

5

-

-

-

-

-

-

53

-

-

-

_

19

-

-

-

-

-

-

54

_

-

-

-

-

12

-

-

-

-

-

—

41

1 0

9

X

X

4

-

_

—

55

_

-

-

-

-

7

-

-

-

-

-

—

42

c

4

1

-

-

-

_

—

56

_

-

-

-

-

2

-

-

-

-

-

-

43

7

5

2

-

-

-

_

—

N

23

22

-

32

-

45

-

40

98

-

5

-

44

_

X

1

2

-

-

-

—

X

41.9

41.4

-

46.5

-

53.6

-

38.2

38.7

-

30.8

—

1

 In addition to original observations, data are included from Ege (1934), Blache (1964), and Morrow (1964a). Where frequency

distributions were not given in the literature, the extensions are indicated by an X.
22 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

tive species is surviving in a relatively specialized habitat, while S. affinis inhabits the open seas as well.

The conjectural zoogeographic-evolutionary picture

that emerges, then, starts with a species resembling one

of the brevibarbatus group that eventually occupied

the Atlantic and the Indo-Pacific, probably via tropical

waters of the former Tethys Sea. This species was separated, perhaps by the closing off of Tethys connections, and diverged in the two regions to give rise to

S. brevibarbatus in the Atlantic and S. danae in the

Indo-Pacific. Next, perhaps essentially simultaneously,

the precursors of the colubrinus and nebulosus groups

developed, the former probably in the Atlantic, the

latter probably in the Indian Ocean or the southeast

Asian area, and both proceeded to occupy the richer

equatorial waters, excluding therefrom the original

occupants of the brevibarbatus group. The ancestral

form of the S. boa group was S. affinis or something

similar to it, since this species is at the base of the

morphological trends previously described for the

group. The ancestral form probably arose from S.

nebulosus in the Indo-Pacific for they are quite similar in most respects except tooth structure, and spread

to the Atlantic, probably around South Africa. From

S. affinis, two species apparently were generated. A

stock became isolated in the eastern Pacific to give rise

to S. atriventer. At one time S. atriventer probably occupied most of the eastern Pacific between about 33°N

TABLE 13.—Stomias species: frequency distribution of photophores in VAVportion of ventral row and

VAL portion of lateral row

 1

Species

Number of photophores in VAV portion of ventral row

8 9 10 11 12 13 14 15 16 N

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus.

lampropeltis

brevibarbatus

danae

nebulosus

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

13 146

—

-

-

-

-

-

94

1

1

-

_

-

-

-

-

-

-

18

11

17

-

_

-

X

-

-

-

-

1

77

72

-

_

3

3

3

3

11

-

-

57

51

-

_

16

8

29

19

47

-

-

8

7

-

_

8

12

52

14

36

1

-

1

1

1

1

-

4

13

8

6

13

-

-

-

5

3

-

-

3

1

-

13

-

-

_

17

1

15

35 52 43

27

27

100

45

100

45

272

155

149

28

5

136

11.2

11.6

11.8

11.7

11.4

14. 1

6.4

9.4

9.3

14.0

13.0

7. 1

Number of photophores in VAL portion of later val row

7 8 9 10 11 12 13 14 15 16 17 N

-

-

-

-

-

-

43

X

9

-

_

-

-

-

-

-

-

90

7

23

-

_

-

-

-

-

-

-

13

26

52

-

_

-

1

-

-

-

-

-

6

14

-

_

10

7

X

2

X

-

-

3

-

X

_

13

6

X

10

X

-

_

_

_

X

2

1

8

X

14

X

6

-

-

_

X

2

-

1

X

1

-

11

-

-

_

X

1

-

-

X

1

-

15

-

-

_

X

_

13

24

23

28

47

148

42

98

11.

12.

12.

14.

7.

9.

8.

6

0

6

9

8

1

7

5 12.8

- X

1

 In addition to original observations, data included from Ege (1934), Blache (1964), and Morrow (1964a). Where frequency distributions were not given in the literature, the extensions are indicated by an X.
NUMBER 31 23

and 24°S, but the closing of the Central American

isthmus, setting up the present set of oceanic conditions, may have made the habitat more favorable for

S. colubrinus, but unfavorable for S. atriventer. It is

well established that the permanent thermocline becomes very shallow in this region. Combined with

the upwelling that occurs, this might be expected to

make suitable habitat for S. colubrinus, which lives at

greater depths in adjacent areas, leaving no niche for

S. atriventer.

To the southward, populations of S. affinis occupied

the Subtropical Convergence and gave rise to S. boa

boa. In turn, S. boa boa derivatives populated the subantarctic and Antarctic intermediate waters and

reached species status there as S. gracilis.

Probably during one of the Pleistocene glacial periods, S. boa boa was able to extend its range through

the tropical Atlantic into the North Atlantic and

Mediterranean Sea. Fluctuations of up to 9°C have

been postulated for the surface waters of the Atlantic

TABLE 14.—Stomias species: frequency distribution of photophores on isthmus (IP) and in AC portion of ventral row *

Species

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

Number of photophores on

9

-

-

1

-

-

X

-

3

X

-

10

1

X

2

X

2

3

9

42

-

-

X

11

20

20

X

31

X

41

11

109

47

16

4

X

12 13

5

3

-

4

X X

1

2

38

2

12

-

X

Number of photophores in AC portion of ventral row

13 14

3

5 8

X

2 4

-

1

2

-

-

3

1 2

X

15

16

7

X

20

X

3

3

11

2

18

2

X

16

5

1

X

10

X

14

6

15

31

7

-

2

17

-

X

1

X

17

3

26

33

-

-

X

18

-

X

-

X

6

3

59

17

-

-

X

19

-

_

-

X

3

-

25

1

-

-

20

_

-

-

-

X

2

-

5

-

-

-

N

24

21

-

37

-

46

17

141

84

28

5

*~

X

15. 1

14.2

-

15. 1

-

16.9

16.1

17.6

16.8

15.1

14.2

1

 In addition to original observations, data are included from Ege (1934) and Morrow (1964a). Where frequency distributions

were not given in the literature, the extensions are indicated by an X.

Species

atriventer (S)

atriventer (N)

boa boa (Med)

boa boa (S)

boa ferox

gracilis

affinis

colubrinus

lampropeltis

brevibarbatus

danae

nebulosus

TABLE

15 16

1

- 6

-

-

-

- -

- 1

_ _

-

- X

- 1

4 X

15.—Stomias

17

4

16

X

6

X

2

21

6

14

-

1

X

species: frequency distribution of dorsal and anal fin-ray counts

Number of dorsal rays

18

12

4

X

13

X

6

92

24

46

X

3

X

19

4

1

X

7

X

7

87

66

49

X

-

X

20

2

-

X

3

X

14

18

44

32

X

_

X

21

_

-

-

-

X

5

1

14

7

-

-

—

22 23

- -

- -

1 -

- -

2 1

- -

3 -

2 -

- -

- -

— —

N

23

27

-

30

-

37

220

157

150

-

5

—

X

18. 1

17.0

-

18.4

-

19.6

18.5

19.3

18.9

-

17.4

• •

16 17

1 2

- -

- -

- -

- 2

- -

- -

- -

- -

- -

— —

18

2

12

X

5

-

6

X

-

-

-

-

1

19

5

9

X

3

X

7

1

-

-

X

-

2

20

6

2

X

9

X

14

6

-

7

X

3

1

Number of anal rays

21

8

1

X

6

X

5

36

9

26

X

2

X

22

3

-

X

6

X

2

88

33

51

X

-

X

23

_

-

-

-

X

1

84

55

51

-

-

X

24

_

-

-

-

-

-

22

41

17

-

-

X

l

25

_

-

-

-

-

-

2

16

2

-

-

X

26 N

- 24

- 27

-

- 29

-

- 37

- 239

- 154

- 154

-

5

X

X

20.

18.

20.

19.

22.

23.

22.

20.

2

4

-

2

-

6

3

1

3

-

4

1

 In addition to original observations, data are included from Ege (1934), Blache (1964), and Morrow (1964a). Where frequency

distributions were not given in the literature, the extensions are indicated by an X.
24 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

(see Briggs, 1966). If this cooling extended to the midwaters, this should have been sufficient to create temperature conditions similar to those in the areas now

occupied by S. boa boa. This same cooling would have

restricted the range of S. affinis, which is a tropical

species, preventing competitive exclusion. The relative recency of the invasion of North Atlantic waters

by S. boa boa is indicated by the development in cooler

North Atlantic waters of the subspecies, S. boa ferox.

At the same time, the stock of S. boa boa in the Mediterranean has undergone no apparent change.

Acknowledgments

I wish to thank the numerous individuals and institutions that provided materials for this study. Many

counts, measurements, x-radiographs, and sex determinations were made by Miss Barbara Hurwitz. Radiographs were made for me by Keith W. Radford

(Scripps Institution), Edward F. Sweeney (Boston

University), William Witt (Bureau of Commercial

Fisheries Systematics Laboratory), Edgar N. Gramblin

and Hans-Joachim Bahr (United States National

Museum), and Mrs. Edith Neil (Stanford University).

This study has been supported by National Science

Foundation grants G-18001 and GB 3906 and by

Smithsonian Research Awards 3309 and 3362. Much

pertinent material was collected from the R/V

Anton Bruun as part of the United States Program

in Biology of the International Indian Ocean Expedition and of the Southeast Pacific Biological Oceanographic Program, and from the USNS Eltanin as

part of the United States Antarctic Research Program,

all of which were sponsored and supported by the National Science Foundation.

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