Spinacopia variabilis Kornicker 1969

“Spinacopia variabilis, new species

FIGURES 5-9; PLATES 1d, 3e, f

ETYMOLOGY — The specific name is derived from the Latin "variabilis" = changeable, in reference to the variability of appendages among specimens in the species.

HOLOTYPE — USNM 122191, female with eggs in brood chamber, carapace length 1.92 mm; carapace and some appendage in alcohol, remaining appendages on slides; sta. V-15-131, specimen no. 4.

PARATYPES — USNM 122192, female from sta. V-18-13; USNM 122193, female, specimen no. 5 from sta. V-15-131; USNM 122195, juvenile male, instar IV, specimen no. 1 from sta. V-15-131; USNM 122196, juvenile male, instar IV, specimen no. 204 from sta. V-15-131; USNM 122194, femake with eggs, specimen no. 8 from sta. V-15-131; USNM 122547, female with eggs, specimen no. 3 from sta. V-15-131; USNM 122548, female , specimen no. 2, sta. V-15-131; USNM 122549, female specimen no. 6, sta. V-15-131; USNM 122550, 67 adult females and juvenile females and males, sta. V-15-131; USNM 122691, adult female carapace figured on Plate Id, sta. V-15-131.

MATERIAL — Adult females: 27 inflated, 13 noninflated; instar IV, 36; instar II, 1.

TYPE-LOCALITY — Lamont Geological Observatory Sta. V-15-131, South Atlantic along western slope of Argentine Basin, lat. 40°14.6'S, long. 55°24.7'W, 1475 meters; collected in small bottom trawl on bottom 45 minutes, 3 April 1959.

OTHER LOCALITIES — LGO Sta. V-18-13, South Atlantic on Falkland Rise north of Falkland Islands, lat 47°10'S, long. 61°02'W, 135 meters; collected in small bottom trawl 17 February 1962.

DISTRIBUTION — South Atlantic on Falkland Rise north of Falkland Islands and along western margin of the Argentine Basin between latitudes 40°14.6'S and 47°10'S, and longitudes 55°24.7/W and 61°02'W, at depths of 135 to 1475 meters.

DISCUSSION OF VARIATION WITHIN THE SPECIES — This species includes specimens collected at station V-15—131 on the western margin of the Argentine Basin at a depth of 1475 m, and 1 specimen from station V-18-13 from the Falkland Rise at a depth of 135 m. The latter specimen differs somewhat from those collected at greater depth in having a carapace with a slightly greater height-to-length ratio and in having a different distribution and number of claws on one lamella of the caudal furca, but is tentatively considered herein to be conspecific with the deeper water specimens.

The species contains many individual variants, and it is difficult to be certain that the collection does not contain more than one species. The presence of 2 bristles on the end joint of the endopodites on the second antennae of specimen number 4 from station V-15-131 suggests that it might belong to a different species than the many specimens with only 1 bristle; however, 2 specimens in the collection with 1 bristle on one end joint of the endopodite and 2 on the endopodite of the opposite limb seem to be intermediate forms. Therefore, this presence of 2 bristles is considered to be due to individual variation within the species. The 6th limb of specimen 4 also differs from other specimens in having 5 bristles on the 4th endite of one limb and 4 bristles on the other. Other specimens in the species have 3 bristles on this endite with the exception of one specimen which has 3 bristles on the endite of one limb and 4 on the other. The linkage of this difference with differences on the 2nd antennae noted above strengthens the possibility of specimen 4 being another species. However, the 2 specimens having "intermediate" endopodites on the 2nd antennae have "normal" 6th limbs. Therefore, the 4th endite of the 6th limb of specimen 4 is considered herein to be an individual variant.

Specimens 3 and 6a, both from station V-15-131, have 3 posterior bristles on the end joints of the 6^th limbs, whereas 5 specimens (and all specimens of the other 3 species of the genus) have only 2. This also suggests that 2 species are in the sample; however, 2 specimens have 3 posterior bristles on one limb and 2 on the other. Therefore, the presence of 3 posterior bristles on the end joint of the 6th limb is considered herein to be the result of individual variation.

Specimen 3 in addition to having 3 posterior bristles on the end joint of the 6th limb also has 2 bristles on the outer lobe of the 3rd joint on the 5th limb; other specimens have only 1. This linkage strengthens the possibility of specimen 3 being another species; however, specimen 6a, which also had 3 posterior bristles on the end joint of the 6th limb, has the "normal" number of bristles on the outer lobe of the 3rd joint of the 5th limb. Therefore, the presence of 2 bristles on the outer lobe of the 3rd joint is considered herein to be an individual variant.

Considerable variability was also noted in the frontal organ: some have a pointed tip, some a rounded tip, and others have a rounded tip with small protuberances. Most are 1-jointed, but on one specimen the frontal organ is 2-jointed. The frontal organ of specimen 4 is bifurcate. All these are considered here to be individual variants.

The number of bristles in the proximal group on the 7th limb varies from 4 to 7, but as differences could not be linked to differences on other appendages, this, too, is considered herein to be, due to individual variation.

The sample from station V-15-131 is from a trawl which was dragged on the bottom for 45 minutes. It is possible that specimens from many different habitats and populations are included in the sample. Additional collections from the area sampling smaller areas may elucidate whether more than one species or population is included in S. variabilis.

DESCRIPTION OF FEMALE (adult male unknown) — Shape (Figures 5a-g; Plate 1d), ornamentation, selvage, muscle scars, and pore canals: Similar to S. menziesi.

Infold: Infold below incisur with single bristle near inner margin as in S. menziesi; infold in front of caudal process with 5 spinous bristles forming row in middle near dorsal margin of process (Figures 5h-l); 4 to 8 small spinous bristles present below the 5 larger bristles; numerous minute bristles present along inner margin of infold in front of and dorsal to caudal process. The distribution of spinous bristles forming row on infold in front of caudal process of six adult females is tabulated below:

Left valve

Right valve

Station (specimen no.)

Large bristles

Small bristles

Large bristles

Small Bristles

V-18-13

5

5

5

5

V-15-131 (5)

5

4

5

4

V-15-131 (4)

5

4

5

5

V-15-131 (6a)

5

6

5

7

V-15-131 (10)

5

5

5

4

V-15-131 (11)

5

8

5

5

Size: Length of adult females 1.76-1.92 mm, average 1.84 mm. Dimensions of twelve adult females are tabulated below:

Station (specimen no.)

Length mm (includes caudal process)

Height mm

Height as percent of length

V-18-13

1.90

1.57

82.6

V-15-131 (5)

1.81

1.59

87.8

V-15-131 (4)

1.92

1.64

85.4

V-15-131 (6a)

1.85

1.74

94.1

V-15-131 (6)

1.81

1.62

89.5

V-15-131 (3)

1.90

1.71

90.0

V-15-131 (2)

1.76

1.50

85.2

V-15-131 (8)

1.83

1.63

89.1

V-15-131 (9)

1.83

1.55

84.7

V-15-131 (10)

1.79

1.60

89.4

V-15-131 (11)

1.85

1.58

85.4

V-15-131 (12)

1.84

1.55

84.2

First antenna: Bristles of joints 1-3 similar to S. menziesi; joint 4 with single dorsal bristle and 2 ventral bristles, 1 long, 1 medium; sensory bristle of 5th joint with 2 short filaments; 6^th joint without bristle or with minute medial bristle; 7th joint with a-, b-, and c-bristles: a-bristle with spines distally and one-half length of sensory bristle of 5th joint; b-bristle longer than a-bristle and with short filament near middle; c-bristle about same length as sensory bristle and with 3 short filaments near middle; bristles of 8th joint shorter than sensory bristle of 5^th joint; d- and e-bristles bare, f- and g-bristles each with 3 short filaments near middle.

Second antenna: Exopodite similar to S. menziesi except comb of short spines present on distal margins of joints 2-8. Endopodite distinctly 2-jointed: 1st joint with 2-4 (generally 3) short bristles; 2nd joint with 1 or 2 (usually 1) long bristles. Distribution of bristles on endopodite of fourteen adult females is tabulated below:

1^st joint

2^nd joint

Station (specimen no.)

Left limb

Right limb

Left limb

Right limb

V-18-13

3*

3

1

1

V-15-131 (5)

4

3

2

1

V-15-131 (4)

3

3

2

2

V-15-131 (6a)

3

3

1

1

V-15-131 (6)

3

3

1

1

V-15-131 (3)

3

3

1

1

V-15-131 (2)

3

2

1

1

V-15-131 (8)

3

3

1

1

V-15-131 (203)

3

3

1

1

V-15-131 (9)

3

3

1

2

V-15-131 (10)

3

3

1

1

V-15-131 (11)

3

3

1

1

V-15-131 (12)

3

3

1

1

V-15-131 (203)

3

3

1

1

* 1 of the bristles bifurcate (see Figure 5r)

Mandible: Similar to S. menziesi with following exceptions: 3 short bristles form row on lateral surface near ventral margin of basale on both limbs; bristle of exopodite only about one-fourth length of ventral margin of 1st endopodite joint.

Maxilla: Similar to S. menziesi.

Fifth limb: Epipodial appendage with 40-42 hirsute bristles; single endite with bristle. Expodite: 1^st joint with 3 bristles; 2^nd joint with 6 bristles; 3^rd joint with bristles on inner lobe and 1 or 2 bristles on outer lobe; 4^th and 5^th joints with 4 or 5 bristles; surface of exopodite joints hirsute. The distribution of bristles on limbs of ten adult females is tabulated below:

Endopodite

3^rd joint

Station (specimen no.)

Endite

1^st joint

2^nd joint

Inner lobe

Outer lobe

4^th + 5^th

Endopodite

V-18-13

1

3

6

3

1

4

Frag.

1

3

6

3

1

5

Frag.

V-15-131 (4)

1

3

6

3

0

4

40

1

3

6

3

1

4

42

V-15-131 (3)

1

3

6

3

2

4

Frag.

Frag.

3

6

3

2

4

42

V-15-131 (6a)

1

3

6

3

1

5

42

1

3

6

3

1

5

42

V-15-131 (203)

1

3

6

3

1

4

Frag.

1

3

6

3

1

4

42

V-15-131 (2)

1

4

6

3

1

5

Frag.

1

3

5

3

1

4

Frag.

V-15-131 (5)

1

3

6

3

1

4

Frag.

V-15-131 (8)

Frag.

3

6

3

1

4

Frag.

1

4

5

3

1

4

Frag.

V-15-131 (9)

1

3

6

3

1

4

Frag.

V-15-131 (6)

1

3

6

3

1

4

Frag.

1

3

6

3

1

4

Frag.

Sixth limb: 4 endites present, but on some specimens 3rd endite only slightly separated from end joint: 1st endite with 3 bristles, 2 short and 1 medium; 2nd endite with 2 long terminal bristles; 3rd endite with 4 bristles; 4th endite with 3-5 bristles. End joint with 3 or 4 anterior bristles, 1 or 2 bristles near middle, and 2 or 3 hirsute posterior bristles; medial surface of limb with clusters of hairs. The distribution of bristles on limbs of ten adult females is tabulated below:

Endite I

Endite II

Endite III

Endite IV

End Joint

Station (Specimen no.)

Short

Medium

Anterior

Middle

posterior

V-18-13

2

1

2

4

3

3

2

2

2

1

2

4

3

4

2

2

V-15-131 (4)

1

1

2

4

5

4

2

2

2

1

2

4

4

4

2

2

V-15-131 (6)

2

2

2

4

3

4

Frag.

3

3

1

3

-

3

4

2

2

V-15-131 (3)

2

1

2

4

3

4

1

3

2

1

2

4

3

4

1

3

V-15-131 (6a)

2

1

2

4

3

4

1

3

2

1

2

3

3

3

2

3

V-15-131 (203)

2

1

2

4

3

4

1

2

3

1

2

4

3

5

1

2

V-15-131 (2)

2

1

2

4

3

5

1

2

2

1

2

4

3

4

1

2

V-15-131 (5)

2

1

2

4

3

4

2

2

2

1

Frag.

Frag.

3

4

2

Frag.

V-15-131 (8)

2

1

2

4

3

4

2

3

2

0

3

3

4

4

1

2

V-15-131 (9)

2

1

2

4

3

4

1

2

2

1

2

4

3

3

1

2

Seventh limb: Proximal group with 4-7 bristles (usually 4-6); distal group with 6 bristles, 3 on each side; each bristle with 2-6 bells, and with long marginal spines distally; terminus with opposing combs, each with 9-12 teeth. Numbers of bristles in proximal group on left and right limbs of seven adult females are tabulated below:

Station (specimen no.)

Left limb

Right limb

V-18-13

Frag.

5

V-15-131 (5)

6

6

V-15-131 (4)

4

5

V-15-131 (6a)

4

4

V-15-131 (6)

6

6

V-15-131 (3)

5

5

V-15-131 (2)

7

5

Furca: Each lamella with 7-9 claws (usually 8): claw 1 continuous with lamella, remaining claws separated by suture; claw 3 more slender and shorter than claw 4, remaining claws decreasing gradually in length proximally on lamella (an exception is left lamella of specimen from station V-18-13 on which both claws 3 and 5 are smaller than claw 4, apparently an aberrant form); spines and hairs as in S. menziesi, but with some variation between specimens. The number of claws on each lamella of eight adult females is tabulated below:

Station (specimen no.)

Left lamella

Right lamella

V-18-13

9*

7

V-15-131 (5)

7

8

V-15-131 (4)

8

8

V-15-131 (6a)

8

8

V-15-131 (6)

8

7

V-15-131 (3)

8

8

V-15-131 (2)

8

7

V-15-131 (203)

8

8

* Claw 3 smaller than claw 4, claw 5 smaller than claw 6.

Eyes: Lateral eyes absent. Medial eye similar to S. menziesi.

Rod-shaped organ: Generally 1-jointed with pointed tip adjacent to rounded flap; sclerotized pit present at end of tip. Variations observed included a 2-jointed organ, one with 2 branches, and some with rounded tip, or with rounded tip and protuberances. The number of joints and shape of tip of eight adult females are given in tabular form below:

Station (specimen no.)

Number of joints

Shape of tip

V-18-13

1

Pointed

V-15-131 (5)

1

Pointed

V-15-131 (4)

Bifurcate with both branches 1-jointed

Pointed

V-15-131 (6a)

1

With protuberance

V-15-131 (6)

1

With protuberance

V-15-131 (3)

2

Rounded with protuberances

V-15-131 (12)

1

Pointed

V-15-131 (8)

1

Pointed with protuberances

Genitalia: Oval amber-colored spermatophore present on each side over genital pore.

Brush-like organ: Consisting of about 8 minute ringed bristles posterior to and above genitalia.

Posterior: Clusters of long hairs present on posterior margin of thorax above furca.

Upper lip: Similar to S. menziesi.

Eggs: Gravid females contain 2-6 eggs in the marsupium. Some specimens with eggs in the marsupium also have as many as 7 eggs in the ovaries. The number of eggs in the marsupium and ovaries of twelve adult females is tabulated below (eggs in ovaries obscure in some specimens):

Station (specimen no.)

In brood chamber

In ovaries

V-18-13

6

7

V-15-131 (5)

3

4

V-15-131 (4)

3

0

V-15-131 (6a)

0

0

V-15-131 (6)

3

0?

V-15-131 (3)

2

7

V-15-131 (2)

0

1?

V-15-131 (8)

4

0

V-15-131 (9)

3

5

V-15-131 (10)

4

0

V-15-131 (11)

4

5

V-15-131 (12)

0

0

Food: Gut of specimen 4 from station V-15-131 contained remains of 3 harpacticoid copepods, 1 nematode, and 3 pellets. Two of the pellets are oval and dark brown and are probably fecal pellets, 1 is rectangular and yellowish. Their position in the gut suggests that they were ingested. The gut of specimen 28, an adult female from station V-15-131, contained a polycopid ostracod and copepod fragments. The polycopid carapace was closed and contained undisturbed appendages which appeared cleaned of protoplasm.

DISCUSSION OF DIMORPHISM IN SHELLS OF ADULT FEMALES — Thirteen of the adult females in the collection are not inflated in the posterodorsal region, but instead are evenly rounded as in juveniles. The dimensions of three carapaces are as follows:

Station (specimen no.)

Length mm (includes caudal process)

Height mm

Height as percent of length

V-15-131 (15)

1.86

1.60

86.0

V-15-131 (16)

1.75

1.55

88.6

V-15-131 (24)

1.81

1.50

82.9

The appendages of the 3 specimens are similar to specimens with inflated posterodorsal regions with the exception that specimens 15 and 16 have 3 ventral bristles on the 4th joint of the 1st antenna; this number was present only rarely on inflated forms. All inflated forms examined have attached spermatophores, whereas only specimen 24 of the noninflated forms has them. The above 3 specimens do not contain eggs in either the ovaries or carapace. All specimens contained harpacticoid copepods in their gut, and in addition specimen 24 had 1 free living nematode, showing that the diet of the inflated and noninflated forms are similar.

The reason for the observed dimorphism is not clear. The similarity in lengths and heights of both types make it unlikely that the noninflated forms are juveniles, although it is a possibility; for example, when preadult males of some sarsiellids molt to form adults, the resulting carapace has a different shape than the preadult, but has about the same length and height. Another possibility is that the preadult female molted to form adults not having all characters of mature females. The absence of eggs in the few specimens examined supports either hypothesis.

DESCRIPTION OF INSTAR II (sex undetermined) — Shell: Shell similar in lateral outline to adult female but without inflated posterodorsal region; infold below shallow sinus with single bristle; infold in front of caudal process with 2 long spinous bristles and 1 shorter bristle. Dimensions of single specimen (no. 20) in collection is as follows: length 1.11 mm, height 0.94 mm, height as percent of length 84.6.

First antenna: Similar to adult female except for having on 2nd and 4th joints only 1 dorsal bristle and no ventral bristles.

Second antenna: Protopodite and exopodite similar to adult; endopodite 2-join ted; 1st joint with short bristle; 2nd joint with long distal bristle.

Mandible, maxilla, 5th limb: All well developed and similar in general morphology to adult female.

Sixth limb: Outer margin divided into 2 hirsute lobes; 1 long bristle present anterior to middle.

Seventh limb: Short, bare.

Furca: Each lamella with 4 claws decreasing in length posteriorly; claw 1 continuous with lamella; spines present posterior to claw 4.

Rod-shaped organ: Elongate, with restriction about one-third distance from terminal end.

DESCRIPTION OF FEMALE INSTAR IV — Shell: Shape of carapace similar to adult female but not globose in posterodorsal region. Infold below shallow sinus with single bristle; infold in front of caudal process with 3 or 4 large and 3 small spinous bristles forming row near middle and additional bare bristles along inner margin. Dimensions of specimen 23, station V-15-131, are as follows: length 1.59 mm, height 1.29 mm, height as percent of length 81.1.

First antenna, mandible, maxilla, 5th and 6th limbs: Well developed, similar in general morphology to adult female.

Second antenna: Protopodite and exopodite similar to adult female; endopodite 2-jointed: 1^st joint with 2 or 3 short bristles; 2nd joint with 2 bristles, 1 long and 1 medium.

Seventh limb: Proximal group with 5 bristles; distal group with 4 bristles; bristles tapering distally, each with 2-5 bells; terminus with opposing combs, each having about 10 teeth.

Furca: Each lamella with 7 claws; claw 1 continuous with lamella; claw 3 shorter than claw 4, clusters of hairs medially at base of claw 1.

Rod-shaped organ: Elongate, single jointed with rounded tip.

Genitalia: Undeveloped.

DESCRIPTION OF MALE INSTAR IV — Shell: Shape of carapace in lateral view similar to adult female but not globose in posterodorsal region. Infold below shallow sinus with single bristle; infold in front of caudal process with 4 or 5 large spinous bristles and several smaller spinous bristles forming row near middle of infold and about 12 bare slender bristles along inner margin. Distribution of spinous bristles is listed below:

Left valve

Right valve

Station (specimen no.)

Large bristles

Short bristles

Large bristles

Short bristles

V-15-131 (1)

4

5

5

4

V-15-131 (2)

4

4

4

4

V-15-131 (21)

4

3

4

3

V-15-131 (204)

4

5

4

4

V-15-131 (22)

4

3

4

3

Dimensions of measured specimens are listed as follows:

Station (specimen no.)

Lenth mm (includes caudal process)

Hight mm

Height as percent of length

V-15-131 (1)

1.72

1.56

90.7

V-15-131 (2)

1.65

1.28

75.6

V-15-131 (21)

1.56

1.32

84.6

V-15-131 (204)

1.48

1.24

83.8

V-15-131 (22)

1.58

1.27

80.4

First antenna, mandible, maxilla, 5th and 6th limbs, rod-shaped organ, posterior: Well developed, similar in general morphology to adult female.

Second antenna: Protopodite and exopodite similar to adult female. Endopodite quite variable, 2- or 3- jointed; number of joints and bristles per joint are listed below for specimens studied:

1^st joint

2^nd joint

3^rd joint

Station (specimen no.)

Left

Right

Left

Right

Left

Right

V-15-131 (1)

3

2

2Pa, 1Tb

2P, 1T

No third joint

V-15-131 (2)

3

3

3P

3P

2T

2T

V-15-131 (21)

3

3

2P, 1T

1P, 1T

No third joint

V-15-131 (204)

3

3

3P

3P

2T

2T

V-15-131 (22)

3

3

3P

3P

1T

2T

a. Proximal bristles

b. Terminal bristles

Seventh limb: Proximal group with 3-5 bristles, distal group with 4-6, each with 2-5 bells distally; terminus with opposing combs with few to many teeth. The number of bristles on proximal and distal groups of specimens studied is as follows:

Proximal group

Distal group

Station (specimen no.)

Left

Right

Left

Right

Remarks

V-15-131 (6a)

4

5

6

5

(not tapered)

V-15-131 (6a)

4

4

4

4

Tapered

V-15-131 (6a)

6

5

4

4

“

V-15-131 (6a)

5

4

4

4

“

V-15-131 (6a)

4

4

4

4

“

Furca: Each lamella with 7 or 8 claws; claw 1 continuous with lamella; claw 3 shorter than claw 4. The number of claws on each lamella of specimens studied is listed below:

Station (specimen no.)

Left lamella

Right lamella

V-15-131 (1)

8

8

V-15-131 (2)

7

7

V-15-131 (21)

7

7

V-15-131 (204)

7

7

V-15-131 (22)

7

7

Copulatory organ: Very weakly developed.

Brush-like organ: Consisting of about 6 annulated bristles above copulatory organ (observed only on specimen no. 1).

DISCUSSION OF SPECIMEN NUMBER I — Although this specimen has been included in the description of instar IV, it differs from other specimens in this group in many respects. In carapace size, number of furcal claws, and absence of tapering bristles on the 7th limb, the speciment resembles an adult. In shape of carapace, development of the 1st antenna, mandible, endopodite of the 2nd antenna, and copulatory organ, the specimen resembles instar IV.

COMPARISONS — The adult female of Spinacopia variabilis is much smaller than S. menziesi; the former 1.76 — 1.92 mm long compared to 2.75 mm for the latter. Another difference is that the 4th joint of the female 1st antenna of S. menziesi has 3 ventral bristles, whereas the 4th joint of S. variabilis rarely has more than 2. Each 7th limb of S. variabilis has 4-7 bristles in the proximal group compared to 8-10 for S. menziesi. The epipodial appendage of the 5th limb of S. variabilis has 40-42 hirsute bristles compared to 45 or 46 for S. menziesi.” (Kornicker 1969, 13-21)

Spinacopia variabilis

ETYMOLOGY.—The specific name is derived from the Latin “variabilis” = changeable, in reference to the variability of appendages among specimens in the species.

HOLOTYPE.—USNM 122191, with eggs in brood chamber, carapace length 1.92 mm; carapace and some appendage in alcohol, remaining appendages on slides; sta. V–15–131, specimen no. 4.

PARATYPES.—USNM 122192, from sta. V–18–13; USNM 122193, , specimen no.5 from sta. V–15–131; USNM 122195, juvenile , instar IV, specimen no.1 from sta. V–15–131; USNM 122196, juvenile , instar IV, specimen no.204 from sta. V–15–131; USNM 122194, with eggs, specimen no. from sta. V–15–131; USNM 122547, 9 with eggs, specimen no. 3 from sta. V–15–131; USNM 122548, , specimen no. 2, sta. V–15–131; USNM 122549, specimen no. 6, sta. V–15–131; USNM 122550, 67 adult and juvenile and , sta. V–15–131; USNM 122691, adult female carapace figured on Plate 1d, sta. V–15–131.

MATERIAL.—Adult females: 27 inflated, 13 noninflated; instar IV, 36; instar II, 1.

TYPE-LOCALITY.—Lamont Geological Observatory Sta. V–15–131, South Atlantic along western slope of Argentine Basin, lat. 40°14.6′S, long. 55°24.7′W, 1475 meters; collected in small bottom trawl on bottom 45 minutes, 3 April 1959.

OTHER LOCALITIES.—LGO Sta. V–18–13, South Atlantic on Falkland Rise north of Falkland Islands, lat 47°10′S, long. 61°02′W, 135 meters; collected in small bottom trawl 17 February 1962.

DISTRIBUTION.—South Atlantic on Falkland Rise north of Falkland Islands and along western margin of the Argentine Basin between latitudes 40°14.6′S and 47°10′S, and longitudes 55°24.7′W and 61°02′W, at depths of 135 to 1475 meters.

DISCUSSION OF VARIATION WITHIN THE SPECIES.—This species includes specimens collected at station V–15–131 on the western margin of the Argentine Basin at a depth of 1475 m, and 1 specimen from station V–18–13 from the Falkland Rise at a depth of 135 m. The latter specimen differs somewhat from those collected at greater depth in having a carapace with a slightly greater height-to-length ratio and in having a different distribution and number of claws on one lamella of the caudal furca, but is tentatively considered herein to be conspecific with the deeper water specimens.

The species contains many individual variants, and it is difficult to be certain that the collection does not contain more than one species. The presence of 2 bristles on the end joint of the endopodites on the second antennae of specimen number 4 from station V–15–131 suggests that it might belong to a different species than the many specimens with only 1 bristle; however, 2 specimens in the collection with 1 bristle on one end joint of the endopodite and 2 on the endopodite of the opposite limb seem to be intermediate forms. Therefore, this presence of 2 bristles is considered to be due to individual variation within the species. The 6th limb of specimen 4 also differs from other specimens in having 5 bristles on the 4th endite of one limb and 4 bristles on the other. Other specimens in the species have 3 bristles on this endite with the exception of one specimen which has 3 bristles on the endite of one limb and 4 on the other. The linkage of this difference with differences on the 2nd antennae noted above strengthens the possibility of specimen 4 being another species. However, the 2 specimens having “intermediate” endopodites on the 2nd antennae have “normal” 6th limbs. Therefore, the 4th endite of the 6th limb of specimen 4 is considered herein to be an individual variant

Specimens 3 and 6a, both from station V–15–131, have 3 posterior bristles on the end joints of the 6th limbs, whereas 5 specimens (and all specimens of the other 3 species of the genus) have only 2. This also suggests that 2 species are in the sample; however, 2 specimens have 3 posterior bristles on one limb and 2 on the other. Therefore, the presence of 3 posterior bristles on the end joint of the 6th limb is considered herein to be the result of individual variation.

Specimen 3 in addition to having 3 posterior bristles on the end joint of the 6th limb also has 2 bristles on the outer lobe of the 3rd joint on the 5th limb; other specimens have only 1. This linkage strengthens the possibility of specimen 3 being another species; however, specimen 6a, which also had 3 posterior bristles on the end joint of the 6th limb, has the “normal” number of bristles on the outer lobe of the 3rd joint of the 5th limb. Therefore, the presence of 2 bristles on the outer lobe of the 3rd joint is considered herein to be an individual variant.

Considerable variability was also noted in the frontal organ: some have a pointed tip, some a rounded tip, and others have a rounded tip with small protuberances. Most are 1-jointed, but on one specimen the frontal organ is 2-jointed. The frontal organ of specimen 4 is bifurcate. All these are considered here to be individual variants.

The number of bristles in the proximal group on the 7th limb varies from 4 to 7, but as differences could not be linked to differences on other appendages, this, too, is considered herein to be. due to individual variation.

The sample from station V–15–131 is from a trawl which was dragged on the bottom for 45 minutes. It is possible that specimens from many different habitats and populations are included in the sample. Additional collections from the area sampling smaller areas may elucidate whether more than one species or population is included in S. variabilis.

DESCRIPTION OF FEMALE (adult male unknown).—Shape (Figures 5a–g; Plate 1d), ornamentation, selvage, muscle scars, and pore canals: Similar to S. menziesi.

Infold: Infold below incisur with single bristle near inner margin as in S. menziesi; infold in front of caudal process with 5 spinous bristles forming row in middle near dorsal margin of process (Figures 5h–l); 4 to 8 small spinous bristles present below the 5 larger bristles; numerous minute bristles present along inner margin of infold in front of and dorsal to caudal process. The distribution of spinous bristles forming row on infold in front of caudal process of six adult females is tabulated below:

Left valve

Right valve

Station (specimen no.)

Large bristles

Small bristles

Large bristles

Small bristles

V–18–13

5

5

5

5

V–15–131

(5)

5

4

5

4

“

(4)

5

4

5

5

“

(6a)

5

6

5

7

“

(10)

5

5

5

4

“

(11)

5

8

5

5

Size: Length of adult females 1.76–1.92 mm, average 1.84 mm. Dimensions of twelve adult females are tabulated below:

Station (specimen no.)

Length mm (includes caudal process)

Height mm

Height as percent of length

V–18–13

1.90

1.57

82.6

V–15–131

(5)

1.81

1.59

87.8

“

(4)

1.92

1.64

85.4

“

(6a)

1.85

1.74

94. 1

“

(6)

1.81

1.62

89. 5

“

(3)

1.90

1.71

90.0

“

(2)

1.76

1.50

85.2

“

(8)

1.83

1.63

89. 1

“

(9)

1.83

1.55

84. 7

“

(10)

1.79

1.60

89.4

“

(10)

1.85

1.58

85.4

“

(12)

1.84

1.55

84.2

First antenna (Figures 5m–o): Bristles of joints 1–3 similar to S. menziesi; joint 4 with single dorsal bristle and 2 ventral bristles, 1 long, 1 medium; sensory bristle of 5th joint with 2 short filaments; 6th joint without bristle or with minute medial bristle; 7th joint with a-, b-, and c-bristles: a-bristle with spines distally and one-half length of sensory bristle of 5th joint; b-bristle longer than a-bristle and with short filament near middle; c-bristle about same length as sensory bristle and with 3 short filaments near middle; bristles of 8th joint shorter than sensory bristle of 5th joint; d- and e-bristles bare, f- and g-bristles each with 3 short filaments near middle.

Second antenna (Figures 5p–t; Plate 3e, f): Exopodite similar to S. menziesi except comb of short spines present on distal margins of joints 2–8. Endopodite distinctly 2-jointed: 1st joint with 2–4 (generally 3) short bristles; 2nd joint with 1 or 2 (usually 1) long bristles. Distribution of bristles on endopodite of fourteen adult females is tabulated below:

Station (specimen no.)

1st joint

2nd joint

Left limb

Right limb

Left limb

Right limb

V–18–13

3a

3

1

1

V–15–131

(5)

4

3

2

1

“

(4)

3

3

2

2

“

(6a)

3

3

1

1

“

(6)

3

3

1

1

“

(3)

3

3

1

1

“

(2)

3

2

1

1

“

(8)

3

3

1

1

“

(203)

3

3

1

1

“

(9)

3

3

1

2

“

(10)

3

3

1

I

“

(11)

3

3

1

1

“

(12)

3

3

1

1

“

(203)

3

3

1

1

*1 of the bristles bifurcate (see Figure 5r).

Mandible (Figures 6a–c): Similar to S. menziesi with following exceptions: 3 short bristles form row on lateral surface near ventral margin of basale on both limbs; bristle of exopodite only about one-fourth length of ventral margin of 1st endopodite joint.

Maxilla: Similar to S. menziesi.

Fifth limb: Epipodial appendage with 40–42 hirsute bristles; single endite with bristle. Expodite: 1st joint with 3 bristles; 2nd joint with 6 bristles; 3rd joint with bristles on inner lobe and 1 or 2 bristles on outer lobe; 4th and 5th joints with 4 or 5 bristles; surface of exopodite joints hirsute. The distribution of bristles on limbs of ten adult females is tabulated below:

Sixth limb (Figures 6d–f): 4 endites present, but on some specimens 3rd endite only slightly separated from end joint: 1st endite with 3 bristles, 2 short and 1 medium; 2nd endite with 2 long terminal bristles; 3rd endite with 4 bristles; 4th endite with 3–5 bristles. End joint with 3 or 4 anterior bristles, 1 or 2 bristles near middle, and 2 or 3 hirsute posterior bristles; medial surface of limb with clusters of hairs. The distribution of bristles on limbs of ten adult females is tabulated below:

Seventh limb: Proximal group with 4–7 bristles (usually 4–6); distal group with 6 bristles, 3 on each side; each bristle with 2–6 bells, and with long marginal spines distally; terminus with opposing combs, each with 9–12 teeth. Numbers of bristles in proximal group on left and right limbs of seven adult females are tabulated below:

Station (specimen no.)

Left limb

Right limb

V–18–13

frag.

5

V–15–131

(5)

6

6

“

(4)

4

5

“

(6a)

4

4

“

(6)

6

6

“

(3)

5

5

“

(2)

7

5

Furca (Figures 6g, h): Each lamella with 7–9 claws (usually 8): claw 1 continuous with lamella, remaining claws separated by suture; claw 3 more slender and shorter than claw 4, remaining claws decreasing gradually in length proximally on lamella (an exception is left lamella of specimen from station V–18–13 on which both claws 3 and 5 are smaller than claw 4, apparently an aberrant form (Figure 6g)); spines and hairs as in S. menziesi , but with some variation between specimens. The number of claws on each lamella of eight adult females is tabulated below:

Station (specimen no.)

Left lamella

Right lamella

V–18–13

9a

7

V–15–131

(5)

7

8

“

(4)

8

8

“

(6a)

8

8

“

(6)

8

7

“

(3)

8

8

“

(2)

8

7

“

(203)

8

8

a Claw 3 smaller than claw 4, claw 5 smaller than claw 6.

Eyes: Lateral eyes absent. Medial eye similar to S. menziesi.

Rod-shaped organ: Generally 1-jointed with pointed tip adjacent to rounded flap (Figure 6k); sclerotized pit present at end of tip. Variations observed included a 2-jointed organ (Figure 6i), one with 2 branches (Figure 6l), and some with rounded tip, or with rounded tip and protuberances (Figures 6j, m). The number of joints and shape of tip of eight adult females are given in tabular form below:

Station (specimen no.)

Number of joints

Shape of tip

V–18–13

1

pointed

V–15–131

(5)

1

pointed

“

(4)

bifurcate with both branches 1-jointed

pointed

“

(6a)

1

with protuberance

“

(6)

1

with protuberance

“

(3)

2

rounded with protuberances

“

(12)

1

pointed

“

(8)

1

pointed with protuberances

Genitalia (Figure 6n): Oval amber-colored spermatophore present on each side over genital pore.

Brush-like organ (Figure 6n): Consisting of about 8 minute ringed bristles posterior to and above genitalia.

Posterior: Clusters of long hairs present on posterior margin of thorax above furca.

Upper lip: Similar to S. menziesi.

Eggs (Figure 6o): Gravid females contain 2–6 eggs in the marsupium. Some specimens with eggs in the marsupium also have as many as 7 eggs in the ovaries. The number of eggs in the marsupium and ovaries of twelve adult females is tabulated below (eggs in ovaries obscure in some specimens):

Station (specimen no.)

In brood chamber

In ovaries

V–18–13

6

7

V–15–131

(5)

3

4

“

(4)

3

0

“

(6a)

0

0

“

(6)

3

0?

“

(3)

2

7

“

(2)

0

1?

“

(8)

4

0

“

(9)

3

5

“

(10)

4

0

“

(11)

4

5

“

(12)

0

0

Food (Plate 2e): Gut of specimen 4 from station V–15–131 contained remains of 3 harpacticoid copepods, 1 nematode, and 3 pellets. Two of the pellets are oval and dark brown and are probably fecal pellets, 1 is rectangular and yellowish. Their position in the gut suggests that they were ingested. The gut of specimen 28, an adult female from station V–15–131, contained a polycopid ostracod and copepod fragments. The polycopid carapace was closed and contained undisturbed appendages which appeared cleaned of protoplasm.

DISCUSSION OF DIMORPHISM IN SHELLS OF ADULT FEMALES.—Thirteen of the adult females in the collection are not inflated in the posterodorsal region, but instead are evenly rounded as in juveniles (Figures 5a–c). The dimensions of three carapaces are as follows:

Station (specimen no.)

Length mm (includes caudal process)

Height mm

Height as percent of length

V–15–131

(15)

1.86

1.60

86.0

“

(16)

1.75

1.55

88.6

“

(24)

1.81

1.50

82.9

The appendages of the 3 specimens are similar to specimens with inflated posterodorsal regions (Figures 5d–f) with the exception that specimens 15 and 16 have 3 ventral bristles on the 4th joint of the 1st antenna; this number was present only rarely on inflated forms. All inflated forms examined have attached spermatophores, whereas only specimen 24 of the noninflated forms has them. The above 3 specimens do not contain eggs in either the ovaries or carapace. All specimens contained harpacticoid copepods in their gut, and in addition specimen 24 had 1 free living nematode, showing that the diet of the inflated and noninflated forms are similar.

The reason for the observed dimorphism is not clear. The similarity in lengths and heights of both types make it unlikely that the noninflated forms are juveniles, although it is a possibility; for example, when preadult males of some sarsiellids molt to form adults, the resulting carapace has a different shape than the preadult, but has about the same length and height. Another possibility is that the preadult female molted to form adults not having all characters of mature females. The absence of eggs in the few specimens examined supports either hypothesis.

DESCRIPTION OF INSTAR II (sex undetermined) (Figure 7).—Shell (Figure 7a): Shell similar in lateral outline to adult female but without inflated posterodorsal region; infold below shallow sinus with single bristle; infold in front of caudal process with 2 long spinous bristles and 1 shorter bristle. Dimensions of single specimen (no. 20) in collection is as follows: length 1.11 mm, height 0.94 mm, height as percent of length 84.6.

First antenna: Similar to adult female except for having on 2nd and 4th joints only 1 dorsal bristle and no ventral bristles.

Second antenna (Figure 7b): Protopodite and exopodite similar to adult; endopodite 2-jointed; 1st joint with short bristle; 2nd joint with long distal bristle.

Mandible, maxilla, 5th limb: All well developed and similar in general morphology to adult female.

Sixth limb (Figure 7c): Outer margin divided into 2 hirsute lobes; 1 long bristle present anterior to middle.

Seventh limb (Figure 7f): Short, bare.

Furca (Figure 7d): Each lamella with 4 claws decreasing in length posteriorly; claw 1 continuous with lamella; spines present posterior to claw 4.

Rod-shaped organ (Figure 7e): Elongate, with restriction about one-third distance from terminal end.

DESCRIPTION OF FEMALE INSTAR IV (Figure 8).—Shell (Figure 8a): Shape of carapace similar to adult female but not globose in posterodorsal region. Infold below shallow sinus with single bristle; infold in front of caudal process with 3 or 4 large and 3 small spinous bristles forming row near middle and additional bare bristles along inner margin. Dimensions of specimen 23, station V–15–131, are as follows: length 1.59 mm, height 1.29 mm, height as percent of length 81.1.

First antenna, mandible, maxilla, 5th and 6th limbs: Well developed, similar in general morphology to adult female.

Second antenna: Protopodite and exopodite similar to adult female; endopodite 2-jointed (Figure 8b): 1st joint with 2 or 3 short bristles; 2nd joint with 2 bristles, 1 long and 1 medium.

Seventh limb: Proximal group with 5 bristles; distal group with 4 bristles; bristles tapering distally, each with 2–5 bells; terminus with opposing combs, each having about 10 teeth.

Furca: Each lamella with 7 claws; claw 1 continuous with lamella; claw 3 shorter than claw 4, clusters of hairs medially at base of claw 1.

Rod-shaped organ: Elongate, single jointed with rounded tip.

Genitalia: Undeveloped.

DESCRIPTION OF MALE INSTAR IV (Figure 9).—Shell (Figures 9a, b): Shape of carapace in lateral view similar to adult female but not globose in posterodorsal region. Infold below shallow sinus with single bristle; infold in front of caudal process with 4 or 5 large spinous bristles and several smaller spinous bristles forming row near middle of infold and about 12 bare slender bristles along inner margin. Distribution of spinous bristles is listed below:

Station (specimen no.)

Left valve

Right valve

Large bristles

Short bristles

Large bristles

Short bristles

V–15–131

(1)

4

5

5

4

“

(2)

4

4

4

4

“

(21)

4

3

4

3

“

(204)

4

5

4

4

“

(22)

4

3

4

3

Dimensions of measured specimens are listed as follows:

Station (specimen no.)

Length mm (includes caudal process)

Height mm

Height as percent of length

V–15–131

(1)

1.72

1.56

90.7

“

(2)

1.65

1.28

75.6

“

(21)

1.56

1.32

84.6

“

(204)

1.48

1.24

83.8

“

(22)

1.58

1.27

80.4

First antenna, mandible, maxilla, 5th and 6th limbs, rod-shaped organ, posterior: Well developed, similar in general morphology to adult female.

Second antenna: Protopodite and exopodite similar to adult female. Endopodite quite variable, 2- or 3- jointed (Figures 9c–e); number of joints and bristles per joint are listed below for specimens studied:

Seventh limb (Figures 9f, g): Proximal group with 3–5 bristles, distal group with 4–6, each with 2–5 bells distally; terminus with opposing combs with few to many teeth. The number of bristles on proximal and distal groups of specimens studied is as follows:

Furca: Each lamella with 7 or 8 claws; claw 1 continuous with lamella; claw 3 shorter than claw 4. The number of claws on each lamella of specimens studied is listed below:

Station (specimen no.)

Left lamella

Right lamella

V–15–131

(1)

8

8

“

(2)

7

7

“

(21)

7

7

“

(204)

7

7

“

(22)

7

7

Copulatory organ: Very weakly developed (Figure 9i).

Brush-like organ (Figure 9h): Consisting of about 6 annulated bristles above copulatory organ (observed only on specimen no. 1).

DISCUSSION OF SPECIMEN NUMBER 1.—Although this specimen has been included in the description of instar IV, it differs from other specimens in this group in many respects. In carapace size, number of furcal claws, and absence of tapering bristles on the 7th limb, the speciment resembles an adult. In shape of carapace,

development of the 1st antenna, mandible, endopodite of the 2nd antenna, and copulatory organ, the specimen resembles instar IV.

COMPARISONS.—The adult of Spinacopia variabilis is much smaller than menziesi; the former 1.761.92 mm long compared to 2.75 mm for the latter. Another difference is that the 4th joint of the female 1st antenna of S. menziesi has 3 ventral bristles, whereas the 4th joint of S. variabilis rarely has more than 2. Each 7th limb of S. variabilis has 4–7 bristles in the proximal group compared to 8–10 for S. menziesi. The epipodial appendage of the 5th limb of S. variabilis has 40–42 hirsute bristles compared to 45 or 46 for S. menziesi.

BENTHIC