Eusarsiella dispar Kornicker 1986

Eusarsiella dispar

ETYMOLOGY.—The specific name from the Latin dispar (different, unequal) in reference to dissimilarities between ornamentation of the left and right valves.

HOLOTYPE.—USNM 158033, adult female in alcohol and on slide.

TYPE-LOCALITY.—R/V Gyre cruise 11, station 9, Gulf of Mexico, 57.5 m.

PARATYPES.—Texas continental shelf: 1 adult female, USNM 158040, R/V Gyre cruise 11, sta 12. R/V Longhorn: 1 adult male, transect I, sta 6; 1 female, 1 early instar, transect III, sta 4; 2 adult females, + 2 stage IV females, USNM 193113, 2 juvenile males, 1 juvenile, transect IV, sta 1; 1 adult male, transect IV, sta 2; 1 ovigerous female, transect IV, sta 4. Corpus Christi ship channel: 1 adult female, sta SR 6.

DISTRIBUTION.—Texas continental shelf and Corpus Christi ship channel (Figure 1). Known depth range 3–100 m (Table 1).

DESCRIPTION OF ADULT FEMALE (Figures 74, 75).—Carapace oval in lateral view with long tapering caudal process, and without rostrum (Figure 74).

Ornamentation (Figures 74, 75a): Right valve: lateral alar process with 2 long backward oriented projections, 1 in vicinity of central adductor muscle attachment and 1 at posterior end extending well past posterior margin of valve; dorsal margin with 3 backward pointing processes: posterior margin with 2 backward pointing processes; ventral margin with 5 small processes. Left valve: similar to right valve except processes less well developed, especially anterior of these, which may be missing; ventral margin may have only 4 small processes; surfaces of processes with striped shingle-like microstructures. Long hairs present along outer margin of valve and sparsely distributed on valve surface. Gelatinous coating not present.

Infold (Figure 75a): Anterior infold with small bristle near middle. Infold of caudal process with 5 or 6 bristles; 2 bristles present on ventral infold just anterior to caudal process; posterior infold with 3 or 4 small bristles and 2 setiferous bristles.

Selvage: Wide lamellar prolongation with smooth outer cdge present along anterior, ventral, and posterior margins of valves.

Size: USNM 158033, length including spines 1.49 mm, length without spines, 1.34 mm, height with caudal process 1.32 mm, height without caudal process 1.10 mm; USNM 193112, length including processes 1.33 mm, height including processes 1.19 mm; USNM 158040, length including processes 1.34 mm; USNM 193113, length including processes 1.27 mm, height including processes 1.16 mm.

First Antenna (Figure 75b): First joint bare. Second joint with 1 dorsal bristle and dorsal spines. Third and fourth joints fused; third joint with 1 dorsal bristle; long fourth joint with 3 bristles (1 dorsal, 2 ventral). Sensory bristle of long fifth joint with 1 minute proximal filament and spine at tip. Fifth and sixth joints fused; medial bristle of sixth joint short, spinous. Seventh joint: a-bristle bare, about same length as bristle of sixth joint; bare b-bristle about 2 or 2 times length of a-bristle; c-bristle about same length as sensory bristle of fifth joint, with spine at tip. Eighth joint: d- and e-bristles bare with blunt tip, both bristles shorter than c-bristle, d- bristle longer than e-bristle; f-bristle slightly longer than d-bristle, with minute proximal filament and spine at tip; g-bristle about same length as c-bristle, with minute proximal filament and spine at tip.

Second Antenna (Figure 75d): Protopodite bare. Endopodite 1-jointed, with 2 proximal anterior bristles and ventral spine. Exopodite: first joint with long ventral hairs and minute, medial bristle on terminal margin; second joint about twice length of third joint; bristles of joints 2–8 long, with natatory hairs, no ventral spines; ninth joint with 2 bristles (1 long with natatory hairs, 1 short with short marginal hairs); joints 2–6 with 1–3 minute medial spines on distal margins.

Mandible (Figure 75e): Coxale endite consisting of single spine; ventral margin of coxale with short spines along ventral margin. Basale: dorsal margin with 3 short unringed bristles (1 distal, 2 terminal) with slender pointed tips; medial side near ventral margin with 4 bristles (3 proximal, 1 distal); lateral side with 1 short distal bristle near ventral margin. Endopodite: first joint with medial spines and ventral claw with few faint minute proximal spines on dorsal margin; dorsal margin of joint undulate proximally; second joint with minute dorsal bristle and stout ventral claw; third joint with stout terminal claw and 3 minute bristles (1 dorsal, 2 ventral).

Maxilla (Figure 75f): Three endites present, each with 4 or 5 bristles (some claw-like and pectinate). Precoxale and coxale with dorsal fringe of long hairs; coxale with short dorsal bristle. Basale with 1 short bristle near exopodite. Exopodite with 3 bristles (1 of these longer than others). Endopodite: first joint with 1 spinous alpha-bristle and 1 spnous beta-bristle; end joint with 2 bare a-bristles, 1 bare c-bristle, and 5 terminal claw-like bristles.

Fifth Limb (Figure 75g): Single endite with 1 short bare bristle. Exopodite: first joint with 2 spinous bristles; remaining joints fused, hirsute, with total of 7 bristles (1 of these minute).

Sixth Limb (Figure 75h): Single endite with 3 bristles. End joint with 9 spinous bristles followed by space and 2 long, stout, hirsute bristles.

Seventh Limb (Figure 75i): Four bristles in proximal group (2 on each side), 6 bristles in terminal group (3 on each side), each bristle with up to 5 bells. Terminus consisting of opposing combs, each with about 10 teeth.

Furca (Figure 75j): Each lamella with 5 slender claws; claw 1 fused to lamella, claws 2–5 separated from lamella by suture; claws 1–4 with posterior teeth of varying length; margin of lamella between claws 4 and 5 with 2 minute spines; margin of right lamella following claw 5 bare; margin of left lamella following claw 5 with about 8 spines forming 3 groups.

Bellonci Organ (Figure 75k): Elongate, broadening distally, with rounded tip.

Eyes (Figure 75k): Medial eye bare, with brown pigment. Lateral eye small, about same size as medial eye, with brown pigment and about 5 minute ommatidia.

Upper Lip (Figure 75k): Helmet shaped.

Comparisons: The appendages of the new species E. dispar are similar to those of E. disparalis, and the close relationship between the 2 species is further indicated by the dissimilarities between the left and right valves of specimens of both species. The carapace of the adult E. dispar differs from that of E. disparalis in not having a rib extending from near the middle of the valve to the ventral margin. The ornamental processes on the valves of E. dispar are longer than those of E. disparalis.