Spinacopia sandersi Kornicker 1969

Spinacopia sandersi

HOLOTYPE.—USNM 122551, with eggs in brood chamber, carapace length 1. 77; carapace and some appendages in alcohol, remaining appendages on slides; station 118A, specimen no. 1. Allotype: USNM 122558, adult specimen no. 3, carapace length 1.59 mm.

PARATYPES.—USNM 122557, specimen no. 2; USNM 122559, 12 adult ; USNM 122560, specimen no. 6, figured on Plate 1b; USNM 122561, adult ; USNM 122562, 5 specimens instar I, 12 specimens instar II and 12 of instar III; USNM 122563, 18 and 19 instar IV; USNM 122564, 260 whole specimens. USNM 122692, adult no. 45, figured on Plate 1a.

MATERIAL.—Adult females with eggs, 75; adult females without eggs, 48; instar IV, 112; instar III, 39; instar II, 26; instar I, 21; adult males, 32.

TYPE-LOCALITY.—Station 118A, RV Atlantis II, cruise 24, near Bermuda, lat. 32°19.4′N, long. 64°34.9′ W to lat. 32°19.0′N, long. 64°38.8′W; dredge sample, 18 August 1966, depth 1135–1153 m. Collected by H. Sanders and R. Hessler. All specimens from same epibenthic trawl.

Etymology.-—The species is named in honor of Dr. Howard Sanders, Woods Hole Oceanographic Laboratory, under whose direction the sample containing the species was collected.

DESCRIPTION OF ADULT FEMALE (Figures 2l–n, 11; Plates 1b, 4a).—Shape (Figure 11a; Plates 1b, 4a): Similar to S. menziesi.

Ornamentation (Figures 11d, e; Plate 1b): Surface with shallow punctations and scattered normal pores; punctae with inwardly pointing spines in vicinity of periphery; surface with scattered spines and hairs, the latter especially abundant around margins.

Infold: Infold below incisur with single bristle near inner margin as in S. menziesi; infold in front of caudal process with 5 (rarely 4 or 6) spinous bristles forming row in middle near dorsal margin of process; (Figures 11f–i); 3 (rarely 2) small spinous bristles present below the larger bristle; minute bristles present along inner margin of infold in front of and dorsal to caudal process. The distribution of large and small spinous bristles forming row on infold of caudal process of seven adult females is tabulated below:

Left valve

Right valve

Specimen number

Large bristles

Small bristles

Large bristles

Small bristles

1

6

3

5

3

2

5

2

5

3

4

5

3

5

3

6

5

2

3

3

7

5

3

4

2

8

5

3

5

3

21

5

3

4

2

Selvage: Similar to S. menziesi.

Muscle scars (Figures 11b, c): Central muscle scars consisting of about 14 individual scars.

Pore canals: Normal pore canals scattered over valve surface (Figure 11d). Radial pore canals numerous around anterior, ventral, and posterior margins.

Size: Dimensions of holotype: length 1.77 mm, height 1.42 mm, height as percent of length 80.2. Average dimensions of 7 specimens: length 1.77 mm, height 1.45 mm, height as percent of length 82.0. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

1

1.77

1.42

80.2

2

1.74

1.41

81.0

4

1.71

1.45

84.8

6

1.79

1.46

81.6

7

1.79

1.48

82. 7

8

1.80

1.45

80.6

21

1.79

1.49

83.2

First antenna (Figures 11j, k), mandible, maxilla: Similar to S. bisetula.

Second antenna (Figures 11l–n): Exopodite similar to S. bisetula. Endopodite weakly 2-jointed: 1st joint with 2 (rarely 1) bristles, 2nd joint with 1 long bristle. The distribution of bristles on the endopodites of six adult females is tabulated below:

Bristles on 1st joint

Specimen number

Left limb

Right limb

1

1

1

2

2

2

4

2

2

6

2

2

7

1

2

8

2

2

Mandible, maxilla Figure 11o: Similar to S. bisetula.

Fifth limb (Figures 11p, q): Endite with 1 bristle. Exopodite: 1st joint with 3 bristles; 2nd joint with 6 (rarely 5) bristles; 3nd joint with 3 (rarely 4) bristles on the inner lobe and 1 on outer lobe; 4th + 5th joints with total of 6 (rarely 3, 4, 5) bristles. Epipodite with 38–42 bristles. The distribution of bristles on six adult females is tabulated below:

Sixth limb (Figures 11r, s): Endites not sharply defined from each other or from end joint except by spaces between them; 1st endite with 3 (rarely 4) bristles; 2nd endite with 2 or 3 bristles; 3nd endite with 3 or 4 bristles; 4th endite with 3 (rarely 2, 4) bristles; end joint with 2–4 (rarely 5) anterior bristles, 1 or 3 (rarely 3) middle bristles, and 2 posterior bristles; surface and margin in vicinity of posterior bristles of end joint hirsute. The distribution of bristles on six adult females is tabulated below:

Seventh limb (Figures 11t, u): Proximal group with 4 (rarely 3) bristles; distal group with 6 bristles, 3 on each side; each bristle with 2–4 bells and marginal spines distally; terminus with opposing combs, each with about 10 teeth. Number of bristles in proximal group on left and right limbs of six adult females is tabulated below:

Specimen number

Number of bristles in proximal group

1

4

3

2

4

4

4

4

4

6

4

7

4

4

8

4

3

Furca: Each lamella with 7 or 8 claws; 3rd claw smaller than 4th; only claw 1 continuous with lamella. (A single specimen has 7 claws on 1 lamella and 9 on the other; on the latter, the 5th as well as the 3rd claw is smaller than the following claw.) The distribution of claws on seven specimens is as follows:

Specimen number

Left lamella

Right lamella

1

7

8

2

8

7

4

8

8

6

8

7

7

8

8

8

8

8

21

7

7

Rod-shaped organ (Figures 11v, w): Elongate, 1-jointed (rarely weakly 2-jointed), tip acuminate or rounded. The number of joints and shape of tip of six adult females are tabulated below:

Specimen number

Number of joints

Shape of tip

1

1

pointed

2

1

rounded

4

1

pointed

6

1

rounded

7

faintly 2-jointed

pointed

8

2

pointed

Eyes, brush-like organ, posterior, upper lip: Similar to S. menziesi.

Genitalia (Figures 2l–n): Not observed on whole mount. In section, genital opening observed to be covered laterally by thin flap; opening in spermatophore facing outward abutting against genital opening; tubular oviduct passing upward into body.

Discussion of reproduction: Only distal portion of oviduct could be clearly observed in sections studied. Sperm present in duct only in vicinity of genital opening suggesting that eggs are fertilized as they leave oviduct. Eggs are present both in the ovaries and marsupium of some adult females having attached spermatophores. It seems probable that part of the genital opening is sufficiently free from the spermatophore to permit passage of eggs.

Eggs: Gravid females contain 2–4 eggs in the marsupium; some specimens also contain 3 or 4 eggs in the ovaries. Generally, when 4 eggs were observed in the brood chamber 2 were in the right valve and 2 in the left. The distribution of eggs in thirteen adult females is tabulated below:

Specimen number

In brood chamber

In ovaries

1

3

0

2

4

0

4

4

4

6

3

3

7

0

4

8

2

0

21

3

0

29

3

0

66

4

3

67

3

1

68

4

3

69

3

?

71

3

3

COMPARISONS.—The adult of S. sandersi differs from previously described species in having large, but shallow, punctations. The endopodite of the 2nd antenna on the 9 differs from that of S. menziesi and S. variabilis in having only 2 bristles on the 1st joint. The 5th limb of S. sandersi differs from that of described species in having a total of 6 bristles on the 4th + 5th joints of at least 1 limb; all other species have a maximum of 5 bristles. The carapace of S. sandersi is much smaller than those of S. menziesi and S. bisetosa, and slightly smaller than that of S. variabilis (see Figure 12).

DESCRIPTION OF ADULT MALE (Figures 2a–k, 13; Plates 1a, 4e–f, 5).—Shape (Figure 13a; Plate 1a): More elongate than female and with prominent rostum and caudal process; carapace highest posterior to middle.

Ornamentation, selvage, pore canals: Similar to female.

Infold: Infold below rostrum with single bristle (Figure 13e); infold in front of caudal process with 4 or 5 spinous bristles near posterior margin and 2 or 3 smaller spinous bristles ventral to them (Figures 13b, c); minute bristle present along inner margin of infold anterior to caudal process.

Muscle scars: Central muscle scars consisting of about 18 individual scars (Figure 13d).

Size: Length of allotype 1.70 mm, height 1.18 mm, height as percent of length 69.4. Average dimensions of 10 specimens: length 1.56 mm, height 1.08 mm, height as percent of length 77.1. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

3

1.59

1.17

73.6

5

1.60

1.09

68.1

38

1.62

1.08

66.7

39

1.54

1.07

69.5

40

1.53

1.06

69.3

42

1.52

1.08

71.1

43

1.48

1.02

68.9

45

1.54

1.08

70.1

48

1.54

1.12

72.7

49

1.46

1.05

71.9

First antenna (Figure 13f; Plate 5b): 2nd joint with 1 dorsal bristle and clusters of surface spines; 3rd joint not separated from 4th and with a ventral and dorsal bristle; 4th joint with 2 ventral and 1 dorsal bristle; 5th joint triangular and placed ventrally between 4th and 5th joints; sensory bristle with 3 filaments; filaments of basal part of sensory bristles numerous (not shown in Figure 13f) and about equal in length to bristles; 6th joint with short medial bristle. 7th joint: a-bristle with marginal spines distally; b-bristle with 2 filaments; c-bristle with 6 filaments. 8th joint: d- and e-bristles bare, slightly longer than b-bristle; f-bristle with 4 filaments; g-bristle with 6 filaments.

Second antenna (Figures 13g, h; Plate 5c): 1st joint with short recurved medial spine on distal margin; joints 2–8 with combs of short spines along distal margins; bristles of joints 2–8 with sparse natatory hairs; joint 9 with 1 long stout bristle with natatory hairs and 1 shorter and more slender bristle. Endopodite 3-jointed: 1st joint with 2 short proximal spines and clusters of surface hairs; 2nd joint with 3 medium bristles near proximal end; 3rd joint recurved, with 2 short bristles near terminal end.

Mandible (Figures 13i–k): Basale with 3 dorsal bristles with sparse marginal spines and 1 very long and 7 short ventral bristles; exopodite reaching about one-third length of 1st endopodite joint and with spinous ventral bristle with base near middle (Figure 13j). Endopodite: 1st joint with clusters of surface spines and 1 long and 2 short distoventral bristles; 2nd joint with clusters of surface spines, 2 dorsal bristles near middle of margin, 1 medial bristle on distal margin, and 1 long stout distoventral bristle; 3rd joint with short a-bristle, stout clawlike b-bristle with short spines on surface, short clawlike c-bristle with teeth along ventral margin, and long spinous d-bristle; dorsal margin of 1st endopodite joint indented in region of exopodite (Figure 13i).

Maxilla (Figure 13l): Appendage reduced; exopodite with 3 bristles; coxale with spinous dorsal bristle.

Fifth limb (Figure 13m): Reduced to about half size of female. Epipodite with about 39 bristles; single endite with short spinous bristles. Endopodite: 1st joint with 3 spinous bristles; 2nd joint with 1 short bare bristle and 5 longer spinous bristles; inner lobe of 3rd joint with 3 spinous bristles; outer lobe of 3rd joint with 1 long bristle; 4th + 5th joints with 5 spinous bristles.

Sixth limb (Figure 13n): 1st, 2nd, and 4th endites with 3 bristles; 3rd endite with 4 bristles; end joint with 4 anterior bristles, 2 middle bristles and 1 or 2 posterior bristles; 4th endite not differentiated from end joint except by narrow space; bristles of middle and anterior group of end joint not distinctly separated from each other.

Seventh joint (Figures 13o–q; Plate 5d): Well developed, 4 bristles in distal group, 3 or 4 in proximal group, each with 2–4 bells and marginal spines distally; terminus with opposing combs each containing 3 teeth; joint is shorter and more slender than that of adult female.

Furca (Figure 13r): Each lamella with 7 claws (rarely 8); claw 1 continuous with lamella; claw 3 about half length of claw 4; claw 1 with medial hairs near base; all claws with marginal spines; dorsal margin of right lamella with about 5 spines.

Rod-shaped organ: Elongate, 1-jointed.

Eyes: Lateral eyes absent, medial eye about same size as on female.

Posterior: Posterior differs from female in not having clusters of long hairs.

Genitalia (Figures 2a–k; Plates 4e, f, 5e–f): Two pear-shaped testes present, one on each side above penis, connected to seminal vesicle by tubular vas deferens. Seminal vesicle bilobed consisting of core (secretion) and sperm peripheral to core, sperm mainly restricted to ventral part; core of secretion consisting of 2 discrete masses either completely separated or fused at middle (vas deferens somewhat larger when secretion fused). Ductus ejaculatorius curved, apparently opening at side of penis. Complex clasping organs hanging down on each side of penis; each clasper consisting of 3 lobes, each with 3–5 bristles; main lobe terminating in sclerotized hook and with triangular tooth proximally; ridges and minute projections present on triangular tooth (Figures 2g, i).

Spermatophore (observed on adult female): Ovoid having amber color in transmitted light; consisting of sperm enclosed in sheath of secretion (Figures 2l–n).

Sperm: Numerous in testis (Figure 2j), seminal vesicle (Figure 2k) and spermatophore (Figures 2l, m). When stained with Mallory’s, head yellow, posterior blue; flagellum observed on some. When stained with aceto-carmine, head pink, posterior unstained (Plate 4e, f).

Gut content: Gut examined in three specimens and found empty.

DESCRIPTION OF INSTAR I (sex undetermined) (Figure 14).—Shell (Figure 14a): Oval with shallow sinus and short caudal process and similar in lateral outline to adult female, but not inflated in posterodorsal region; infold below sinus with single bristle as in adult female; infold in front of caudal process with single large spinous bristle near middle; in addition, several small bare bristles present along inner margin of infold in front of caudal process.

AVERAGE DIMENSIONS OF FIVE SPECIMENS.—Length 0.88 mm, height 0.64 mm, height as percent of length 72.4. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

16

0.89

0.68

76.4

24

0.86

0.62

72.1

26

0.89

0.65

73.0

27

0.91

0.64

70.3

30

0.84

0.60

71.4

First antenna: Similar to adult female but with no bristles on 2nd and 4th joints.

Second antenna (Figure 14b): Protopodite similar to adult female; medial spine on 1st joint of exopodite not recurved as on adult female; endopodite 1 or 2 jointed with single long terminal bristle.

Maxilla, mandible, 5th limb: Well developed, similar in general morphology to adult female.

Sixth limb (Figure 14c): Reduced, not divided into endites, without bristles but with abundant marginal and surface hairs.

Seventh limb: Absent.

Furca (Figure 14d): Each lamella with 2 claws similar to claws 1 and 2 of adult female followed by a single prong with long marginal hairs; prong continuous with lamella; clusters of hairs present on margin of lamellae posterior to prong and medially at base of claw 1.

Rod-shaped organ (Figure 14e): Elongate without joints or with 1–3 weak sutures.

Gut content: Specimen 26 contained in the gut 1 polycopid ostracod and 3 copepods.

DESCRIPTION OF INSTAR II (sex undetermined) (Figure 15; Plate 2c).—Shell (Figure 15a): Similar in shape to instar I; infold differs from instar I in having 2 long spinous bristles forming row in front of caudal process. Average dimensions of 3 specimens: length 1.02 mm, height 0.78 mm, height as percent of length 77.1. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

17

1.06

0.86

81.1

28

1.07

0.79

74.2

29

0.92

0.70

76.1

First antenna: Similar to instar I except for having 1 dorsal bristle on 2nd and 4th joints.

Second antenna: Protopodite similar to instar I. Exopodite similar to instar I except medial spine of 1st joint recurved. Endopodite 2-jointed (Figure 15b): 1st joint with 1 or 2 short proximal bristles; 2nd joint with 1 long terminal bristle.

Mandible, maxilla, 5th limb, rod-shaped organ: All well developed and similar in general morphology to instar I and adult female.

Sixth limb (Figure 15c): Similar to instar I except for having single bristle on anteroventral section of margin.

Seventh limb (Figure 15d): Very short and without bristles or terminal comb.

Furca (Figures 15e, f): Each lamella with 3 or 4 (usually 4) claws decreasing in length posteriorly; differs from adult female in having fewer claws and in 3rd claw not being shorter than 4th. The distribution of claws on each lamella of three specimens is as follows:

Specimen number

Left lamella

Right lamella

17

4

3

28

4

4

29

4

4

Gut content (Plate 2c, d): Specimen 28 contains within the gut a large complete copepod with its head toward the posterior part of the gut, indicating that it had been swallowed head first. The gut of specimen 29 contains a large podocopid ostracod; although the ingested specimen is toward the rear of the gut, it is still strongly calcified, and the shell fragmented when flattened under a cover glass. This suggests that the gut is not sufficiently acid to dissolve the calcium carbonate of the podocopid. The ingested ostracod contains its appendages in place, but they appear cleaned of internal muscles and cells.

DISCUSSION OF SPECIMEN 29.—The dimensions of the carapace of specimen 29 would suggest that the specimen is a stage I instar. However, the number of spinous bristles on the infold of the caudal process, the number of bristles on the 2nd and 4th joints of the 1st antenna, the recurved nature of the medial spine on the 1st joint of the exopodite of the 2nd antenna, the number of furcal claws, and especially the presence of a single bristle on the 6th limb indicate that specimen 29 is a stage II instar, and it has been considered so herein.

DESCRIPTION OF FEMALE INSTAR III (Figure 16; Plate 2a).—Shell (Figure 16a): Differs from instar II in having 2 or 3 (usually 3) large spinous bristles and 1 or 2 small spinous bristles forming row near middle of infold in front of caudal process. Average dimensions of 2 specimens: length 1.22 mm, height 0.92 mm, height as percent of length 75.5. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

19

1.18

0.91

77.1

34

1.26

0.93

73.8

First antenna: Differs from instar II in having a ventral bristle on the 4th joint.

Second antenna, maxilla, mandible, 5th limb, rod-shaped organ (Figure 16e): Similar in general morphology to instar II.

Sixth limb (Figure 16b, c): Well developed, similar in general morphology to adult instar, except having only 3 endites and fewer bristles, about 15.

Seventh limb (Figure 16d): Longer than on instar II but otherwise similar.

Furca: Each lamella with 6 claws; 3rd claw shorter than 4th, otherwise similar to instar II.

DESCRIPTION OF MALE INSTAR III (Figure 17; Plate 4b, d).—Shell (Figure 17a): Similar to female instar III. Average dimensions of 5 specimens are length 1.25 mm, height 0.92 mm, height as percent of length 73.7. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

10

1.21

0.92

76.0

18

1.28

0.93

72.7

25

1.21

0.88

72.7

32

1.28

0.94

73.4

33

1.29

0.95

73.6

First antenna (Plate 4b), mandible, maxilla, 5th, 6th, 7th limbs (Figure 17d), rod-shaped organ (Figure 17c), furca: Similar to female instar III.

Second antenna: Protopodite and exopodite similar to female instar III. Endopodite 2-jointed or weakly 3-jointed (Figure 17b; Plate 4d): 1st joint with 2 short proximal bristles; 2nd joint with 2 long proximal bristles; 3rd joint with 1 short terminal bristle (this bristle is on tip of 2nd joint when 3rd joint is absent).

DISCUSSION OF SPECIMEN 31 (Figure 18).—This specimen could not easily be placed in any particular stage. The shell dimensions are as follows: length 1.14 mm, height 1.04 mm, height as percent of length 91.2. The shell dimensions, the number of bristles on the infold of the caudal process (Figure 18a), the number of bristles on the 4th joint of the 1st antenna and the development of the 6 th limb, which has 15 bristles, and the length of the bare 7th limb (Figure 18c) indicate that it belongs in stage III. The endopodite of the 2nd antenna is 2-jointed (Figure 18b), the 1st joint has the usual 2 short bristles, but the end joint has 1 long terminal bristle and 1 longer proximal bristle

oriented anteriorly. This type endopodite is not present on either male or female instars. The endopodite would fit nicely as a developmental stage between male instars II and III. The 5 claws on the furca (Figure 18d) also fit between the number on the furcae of instar II (3 or 4 claws) and instar IV (6 claws). The dimensions of instars II and III, however, are such that it seems unlikely that another instar could fit between them. I have considered specimen 31 to be an aberrant male instar III on Figure 21 but have not included it in the description of male instar III above.

DESCRIPTION OF FEMALE INSTAR IV (Figure 19; Plates 2b, 4c).—Shell (Figures 19a, b): 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 4 (rarely 3) large and 2 or 3 small spinous bristles forming row

near middle of infold and about 10 bare slender bristles along inner margin. Average dimensions of twelve specimens: length 1.54 mm, height 1.23 mm, height as percent of length 80.3. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

13

1.54

1.21

78.6

15

1.54

1.21

78.6

22

1.54

1.24

80.5

51

1.56

1.27

81.4

53

1.53

1.25

81.7

55

1.53

1.26

82.4

58

1.51

1.24

82.1

59

1.50

1.18

78.7

60

1.49

1.17

78.5

62

1.51

1.28

84.8

64

1.58

1.22

77.2

65

1.59

1.26

79.2

First antenna: Similar to instar III except for having 2 ventral bristles on the 4th joint.

Second antenna (Figure 19c), mandible (Figures 19d, e; Plate 4c), maxilla, rod-shaped organ (Figure 19f): Similar in general morphology to instar III female and adult female.

Fifth limb: Similar to adult female. Distribution of bristles on 1 appendage is as follows: endite with single bristle. Exopodite: 1st joint with 3 bristles; 2nd joint with 6 bristles; inner lobe of 3rd joint with 3 bristles; outer lobe of 3rd joint with 1 bristle; 4th + 5th joints with 5 bristles; surface of exopodite hirsute; epipodial appendage with about 39 bristles.

Sixth limb: Similar to adult female. Distribution of bristles on 1 appendage is as follows: endite I with 3 bristles; 2nd endite with 3 bristles; 3rd endite with 4 bristles; 4th endite with 3 bristles; end joint with 2 or 3 anterior bristles, 2 middle bristles and 2 hirsute posterior bristles; all endites fairly well defined; surface and margin of end joint hirsute.

Seventh limb: Proximal group with 4 bristles; distal group with 4 or 5 (usually 4) bristles; bristles tapering distally, each with 2–5 bells; terminus with opposing closely spaced combs with few 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 and following claw 7.

Gut: Specimen 15 with complete specimen of the ostracod Polycope sp. present in rear portion of gut (Plate 2b). Measured length of polycopid shell 0.21 mm; height 0.20 mm (Figure 19h). (Apparently the esophagus [Figure 19g] of this specimen is capable of stretching to a diameter of about 0.2 mm.)

DESCRIPTION OF MALE INSTAR IV (Figure 20).—Shell (Figure 20a): Similar to female instar IV. Average dimensions of 13 specimens: length 1.51 mm, height 1.18 mm, height as percent of length 78.0. Dimensions of measured specimens are as follows:

Specimen number

Length mm (includes caudal process)

Height mm

Height as percent of length

9

1.43

1.19

83.2

11

1.54

1.18

76.6

12

1.55

1.21

78.1

14

1.51

1.24

82.1

20

1.56

1.20

76.9

23

1.53

1.18

77.1

35

1.42

1.09

76.8

52

1.55

1.22

78.7

54

1.51

1.15

76.2

56

1.57

1.20

76.4

57

1.49

1.12

75.2

61

1.50

1.19

79.3

63

1.53

1.18

77.1

First antenna, maxilla, mandible, 7th limb, furca, frontal organ, posterior: Similar to female instar IV.

Second antenna: Protopodite and exopodite similar to adult female; endopodite 3-jointed (Figure 20b): 1st joint with 2 small proximal bristles and clusters of surface hairs; 2nd joint elongate with 3 proximal bristles; 3rd joint elongate with 2 terminal bristles.

Fifth limb: Similar to female instar IV. Distribution of bristles on fifth limb of 1 specimen is as follows: endite with single bristle. Exopodite: 1st joint with 3 bristles; 2nd joint with 4 or 5 bristles; outer lobe of 3rd joint with 4 or 5 bristles; inner lobe of 3rd joint with 1 bristle; 4th + 5th joint with 5 bristles; surface of exopodite hirsute.

Sixth limb: Similar to female instar IV. Distribution of bristles of 1 appendage is as follows: endite I with 3 bristles; 2nd endite with 2 bristles; 3rd endite with 3 bristles; 4th endite with 4 bristles; end joint with 3 anterior bristles, 2 middle bristles, 2 hirsute posterior bristles; surface and margin of end joint hirsute.

Copulatory organ: 2 or 3 poorly developed lobes with few bristles (Figure 20c).

Gut content: Specimen 9 contained remains of a copepod.

SUMMARY OF DEVELOPMENT.—Shell: The overall shape of the instars are quite similar to the female adult except for not having the inflated posterodorsal region which serves as a brood pouch for eggs. As indicated in Table 4 below, the average adult female is also higher relative to length than juveniles of both sexes. The number of both large and small spinous bristles on the list of the infold in front of the caudal process increases fairly regularly in each succeeding developmental stage (Table 5; Figure 21A). The average growth factor of the shell excluding the growth factor between male instar V and the adult male is 1.216. This estimated factor was obtained by averaging both the length and height factors between male and female instars (see Tables 6 and 7). The growth factors between the preadult and adult male is quite low, 1.03 for the length growth factor and 0.92 for the height factor.

Sex not determined

Female

Male

Instar

72.4 (N = 5)

Instar II

77.1 (N = 3)

Instar III

75.5 (N = 2)

73.7 (N = 5)

Instar IV

80.3 (N= 12)

78.0 (N = 13)