Spinacopia antarctica Kornicker 1970

Spinacopia antarctica

HOLOTYPE.—USNM 123340, adult , length 1.92 mm, height 1.74mm.

ALLOTYPE.—USNM 123341, juvenile (?N–1), length 1.61 mm, height 1.30 mm.

PARATYPES.—USNM 123342, adult with 6 eggs in brood chamber, length 1.81 mm, height 1.65 mm. USNM 123343, adult with eggs in brood chamber, length 1.86 mm, height 1.70 mm. USNM 123344, adult with eggs, length 1.71 mm, height 1.67 mm. USNM 123345, 3 juveniles: length 1.01 mm, height 0.92 mm; length 1.01 mm, height 0.86 mm; length 0.89 mm, height 0.72 mm.

TYPE-LOCALITY.—Antarctic Ocean, lat. 62°41′S, long. 54°43′W; bottom depth 210–220 m; station 1003, cruise 12, RV Eltanin, 15 March 1964. Collected in 10-foot Blake trawl on bottom 15 minutes by University of Southern California. All specimens from same sample.

DESCRIPTION OF FEMALE.—Carapace oval in lateral view with greatest height near middle (Figure 11); anterior produced in area of rostrum and with shallow but distinct incisur; posterior with short caudal process below valve middle; carapace widest in posterodorsal part.

Ornamentation: Surface completely covered with short spines (Figure 12e); long hairs present along anterior and anteroventral margin of each valve; a few long hairs present on lateral surface; prominent rim present slightly within and parallel to valve edge; several distinct but vaguely defined nodes and ridges present on valve surface (Figure 11).

Infold: Infold below shallow incisur with minute bristle near inner margin (Figure 12d); infold in front of caudal process of right valve with 7 spinous bristles, 4 large above and 3 below (Figure 12b); left valve with 5 above and 4 below (Figure 12a); about 16 minute bristles present near inner margin of posteroventral section of infold.

Selvage: Lamella prolongation with smooth outer margin present along anterior, ventral and posterior margins of both valves; prolongation broad along anterior and caudal process, narrow elsewhere; prolongation continuous across incisur.

Muscle scars: Central muscle scars consisting of about 14 individual scars (Figure 12c). Posterodorsal and dorsal scars (Figure 12f) not visible through shell.

Pore canals: Radial pore canals numerous around anterior, ventral, and posterior margins (Figures 12e); canals along ventral margin terminating at minute spines at valve edge.

Size: The dimensions of four adult females are as follows:

Length

mm

Height

mm

Remarks

USNM 123340

1.92

1.74

holotype

USNM 123342

1.81

1.65

6 eggs in brood chamber

USNM 123343

1.86

1.70

eggs in brood chamber

USNM 123344

1.71

1.67

eggs in body or chamber

First antenna (Figures 12g, h): 2nd joint with spinous dorsal bristle and short spines in clusters along ventral and dorsal margins; 3rd joint with 2 spinous bristles, 1 ventral and 1 dorsal; 4th joint with 3 spinous bristles, 2 ventral, 1 dorsal; 3rd and 4th joints not separated by suture; sensory bristles of 5th joint with 2 short filaments near middle and 1 near tip; 6th joint with minute medial bristles on left limb, and with stump of bristle on right limb; 7th joint with a-, b-, and c-bristles: a-bristle spinous and about same length as b-bristle; b-bristle about half length of sensory bristle of 5th limb and with short filament near middle; c-bristle same length as sensory bristle and with 3 short filaments near middle and one near tip; 8th joint with d-, e-, f-, g-bristles: d- and e-bristles bare and of similar length; f-bristle with 1 short filament distally and 1 near tip; g-bristle with 3 short filaments near middle and 1 at tip.

Second antenna (Figures 12 i–l): Protopodite bare and without medial bristles. Endopodite 2-jointed: 1st joint with 2 or 3 short bare bristles, 2nd joint with 1 short bare bristle and 1 long terminal bristle. Exopodite: distal margin of 1st joint with short curved medial spine; bristle of 2nd joint with single ventral spine near middle and few distal natatory hairs; bristles of joints 3–8 with sparse natatory hairs; ninth joint with 1 short spinous bristle and 1 long bristle with sparse natatory hairs; distal margins of joints 2-8 with comb of short spines.

Mandible (Figure 12m): Ventral margin of coxale hirsute; coxale endite with bifurcate tip and spinous process near base (Figure 12p). Basale: dorsal margin with short spine near middle and 1 or 2 longer spines distally; ventral margin with total of 3 spines and bristles in proximal group and 4–6 in distal group: proximal group with 2 short medial spines and 1 longer marginal bristle; distal group with 1 short spine on medial surface, 1 very long spinous marginal bristle and 2–4 shorter lateral bristles forming row; a bilobed sclerotized glandular process present on lateral side between proximal and distal groups (Figure 12o). Exopodite blunt, short and with single ventral bristle (Figure 12n). Endopodite: 1st joint with spines forming row on distal dorsal margin, shorter spines in clusters distally on medial surface, and 2 medial spines near base of main ventral claw; 2nd joint with subterminal spine on dorsal margin, and small lateral spine at base of main claw; 3rd joint with 1 short medial spine dorsal to main claw and 1 or 2 somewhat longer spines ventral to base of main claw.

Maxilla (Figures 13a, b): Coxale with anterior bristle having 2 small subterminal spines; basale with 1 bristle with subterminal spine; exopodite with 1 short bare bristle and 2 long bristles with short spines distally; 1st and 3rd endites each with 6 bristles; 1st joint of endopodite with spinous α- and β-bristles, and a few short spines distally on anterior margin; 2nd joint of endopodite with 2 spinous a-bristles, 1 bare c-bristle, and usual 5 pectinate bristles.

Fifth limb (Figure 13c): Endite with 1 bare bristle. Exopodite: 1st joint with 3 spinous bristles, 1 long and 2 short; 2nd joint with 5 spinous bristles; short lobe between 2nd and 3rd joint (may be part of 2nd joint) with 1 small spinous bristle; 3rd joint with 3 spinous bristles on inner lobe and 1 on outer lobe; joints 4 + 5 with 3 bristles; surface of joints hirsute. Epipodial appendage with 43 hirsute bristles.

Sixth limb (Figures 13d, e): Four endites present: 1st endite with 2–4 bristles, 2nd with 2, 3rd with 4, 4th with 3, all bristles spinous. End joint with 3 or 4 spinous anterior bristles, 1 spinous bristle near middle, and 2 stout hirsute posterior bristles; clusters of hairs present on medial and lateral surfaces and along margin of end joint on each side of posterior bristles.

Seventh limb (Figure 13f): Proximal and distal groups each with 6 bristles, 3 on each side; each bristle with 2–5 bells and marginal spines distally; terminus with opposing combs.

Furca (Figure 13g): Each lamella with 8 claws: claw 1 continuous with lamella, remaining claws separated from lamella by suture; claw 3 more slender and shorter than claw 4; each claw with teeth along posterior margin; clusters of spines present along anterior margin of each lamella and at bases of claw 1 and claws 5–8.

Eyes: Lateral eyes absent. Medial eye fairly large, enlongate.

Rod-shaped organ (Figures 13h, l, m): Elongate, single jointed, with minute terminal process.

Genitalia: Oval, amber-colored spermatophore present on each side.

Brushlike organ (Figure 13j): Minute ringed bristles posterior to and above genitalia.

Upper lip (Figure 13k): Simple curvature with several clusters of hairs. Triangular process present on each side between lip and 1st antenna above mandible attachment.

Posterior (Figure 13i): Posterior margin of thorax above furca with clusters of long hairs.

Eggs: 6 eggs present in brood chamber and about the same number unextruded in specimen USNM 123342.

DESCRIPTION OF JUVENILE MALE USNM 123341 (?N–1).—Carapace more elongate than adult female but with similar ornamentation and surface spinosity (Figure 14a); length 1.61 mm, height 1.30 mm. Endopodite of 2nd antenna with 3 segments (Figure 14d): 1st segment with 3 short bristles and surface spines; 2nd segment elongate with 1 long and 2 shorter bristles; 3rd segment elongate with 2 short terminal bristles. Exopodite of 2nd antenna with 1 long and 2 short bristles on 9th segment (Figure 14b). Furca with 7 claws (Figure 14g): claw 1 united with lamella; claw 3 smaller than claw 4; main claws with teeth forming lateral and medial rows along posterior margin. Left 7th limb with 6 bristles in proximal group (Figure 14f), right limb with only 3; each limb with 4 bristles in terminal group and small indentation in place of terminal comb. Copulatory organ undeveloped, consisting of small lobes. Remaining appendages similar to those of adult female.

COMPARISONS.—The configuration and distribution of nodes and ridges of the shell distinguishes S. antarctica from previously described species.