Harbansus thrix Kornicker 1992

Harbansus thrix

ETYMOLOGY.—From the Greek thrix (hair) in reference to wreath of spines on the bristle of the 2nd joint of the endopodite of the 2nd antenna of the female.

HOLOTYPE.—MNHN Os 448, A-1 female on slide and in alcohol.

TYPE LOCALITY.—Sta 75-R, 30 Mar 1977, N Dzaoudzi, Mayotte, 12°46′24″S, 45°15′18″E, depth 20 m.

PARATYPES.—Sta 75-R: 1 A-1 male (length 0.73 mm, height 0.38 mm) undissected and in alcohol. Sta 116-S: USNM 193691, 1 ovigerous female on slide and in alcohol.

DISTRIBUTION.—Sta 75-R, N Dzaoudzi, Mayotte, depth 20 m. Sta 116-S, Geyser Bank, southern part of lagoon, depth 13 m. Known depth range 13–20 m.

DESCRIPTION OF ADULT FEMALE (Figures 55, 56a–i).—Each valve with overhanging rostrum and well-developed caudal process (caudal process of right valve of USNM 193691 more rounded than that of left), and with poorly defined lateral ribs (Figure 55a,b,e). Rostrum with narrow ridge extending to anterior edge of rostrum. Anterior edge of rostrum with about 12 minute tubercles (Figure 55e,f). Surface of valves with well-developed fossae having crenulate inner edge (Figure 55a,b,e; crenulate edge not shown). Single and setose bristles sparsely distributed over valve surface (Figure 55a,d,e).

Infold: Infold of rostrum with 4 bristles forming row and paired bristles at inner end of incisur (Figure 55f); 1 small bristle ventral to inner end of incisur. Infold of caudal process with 5 setose bristles forming row along anterior edge of pocket (Figure 55g). Anteroventral infold with 6 or 7 ridges parallel to valve edge.

Selvage: Wide lamellar prolongation divided in vicinity of incisur.

Central Adductor Muscle Attachments (Figure 55a–c): Comprising many elongate and ovoid attachments.

Carapace Size: USNM 193691, length 1.03 mm, height 0.52 mm.

First Antenna (Figure 55h): 1st joint with few minute spines forming lateral rows near dorsal margin. 2nd joint: dorsal margin with long proximal spines and bare distal bristle; medial side with short spines forming rows near ventral margin (not shown on illustrated limb); medial side with minute spines along distal margin. 3rd joint short, with 3 bristles (2 dorsal, 1 medial near ventral margin). 4th joint elongate, with 5 or 6 bristles (2 or 3 dorsal, 3 ventral). Sensory bristle of 5th joint with 2 short proximal filaments, 3 longer subterminal filaments, and tip of stem with 2 minute papillae. 6th joint minute, fused to 5th, with short medial bristle near dorsal margin. Bristles of joints 2–6 with minute terminal spine. 7th joint: a-bristle about length of 5th joint; b-bristle shorter than sensory bristle of 5th joint, with a pair of short distal filaments, and tip with 2 minute papillae; c-bristle same length as sensory bristle, with 3 short proximal filaments, 3 longer subterminal filaments, and stem with 2 minute terminal papillae. 8th joint: d-and e-bristles same length as c-bristle, bare with blunt tips; f-bristle slightly shorter than c-bristle, with 2 short proximal filaments and 3 longer subterminal filaments (tip of stem missing on specimen examined); g-bristle same length as c-bristle, with 1 short proximal filament and 3 longer subterminal filaments (tip of stem missing on specimen examined).

Second Antenna (Figure 55i–k): Protopodite bare. Endopodite 2-jointed (Figure 55i): 1st joint with 2 short bristles; 2nd joint with broadly rounded bare tip and long ventral bristle with wreaths of long spines near midlength. Exopodite: 1st joint with minute bent medial bristle on distal margin; bristles of joints 2–8 with 7–9 stout proximal ventral spines and distal natatory hairs but no proximal hairs (Figure 55j). 9th joint with 2 bristles (Figure 55k); ventral bristle about length of bristle of 8th joint, with 7 small ventral spines followed by minute spines along both margins and long hairs near tip; dorsal bristle small, about same length as joints 6–9, with few minute spines. Joints 4–8 with short stout basal spines (Figure 55k). Joints 2–8 with minute spines forming row along distal edge.

Mandible (Figure 55l): Coxale endite spinous, bifurcate at tip. Basale: medial surface spinous, with 3 small bristles near ventral margin (2 proximal, 1 at midlength); lateral surface with 2 long spinous bristles and long hairs near ventral margin; ventral margin with 1 long spinous terminal bristle; dorsal margin with 3 bristles (1 at midlength, 2 terminal). Exopodite: about length of dorsal margin of 1st endopodial joint, hirsute near tip, with 2 bristles (terminal bristle about length proximal bristle). Endopodite: ventral margin of 1st joint with 3 bristles (2 long with wreaths of long spines, 1 short with short spines). Ventral margin of 2nd joint with bristles forming 2 distal groups, each with 2 spinous bristles (medial bristle in proximal pair longer than others); dorsal margin with 6 bristles near midlength (2 or 3 with bases on lateral side; proximal marginal bristle short). 3rd joint with 3 claws (dorsal claw small, larger claws with minute ventral spines) and 3 bristles.

Maxilla (Figure 55m–o): Endites I and II each with 6 bristles; endite III with 7 bristles plus 1 proximal lateral bristle (latter bristle observed only on left limb of specimen examined). Precoxale, coxale, and proximal part of basale with fringe of dorsal hairs. Coxale with spinous dorsal bristle. Basale with 3 long bristles along distal margin (not all shown). Exopodite short with 3 bristles (2 long spinous, 1 short bare) (Figure 55n). Endopodite: 1st joint with 1 spinous alpha-bristle, 3 beta-bristles (Figure 55o), and spines forming rows along dorsal margin. 2nd joint with 9 bristles including 3 claw-like bristles.

Fifth Limb (Figure 56a,b): Endites obscured (endite I with 1 bristle, others with more). Exopodite: 1st joint with 2 anterior bristles at midwidth of distal margin and 1 short bristle on hirsute lobe on outer corner; main tooth obscured but with 3 stout teeth, smaller pointed tooth, and proximal bristle (Figure 56b). 2nd joint with large squarish tooth with 2 posterior bristles (1 short slender, 1 long stout pectinate) (Figure 56a); anterior side of joint obscured. 3rd joint with 3 bristles on inner lobe and 2 on outer lobe. 4th and 5th joints fused, with total of 5 bristles.

Sixth Limb (Figure 56c): With 1 epipodial bristle. Endite I small, with 3 spinous bristles; endite II elongate, with 3 spinous bristles; endite III with 5 bristles; endite IV narrower than endite III, with 5 spinous bristles. End joint not prolonged posteriorly, with 7 bristles (5 spinous anterior and 2 hirsute posterior). Endites III and IV and end joint with hairs forming rows (not shown on illustrated limb).

Seventh Limb (Figure 56d): Each limb with 2 proximal bristles (1 on each side) with distal spines and 2 bells, and 4 terminal bristles (2 on each side) with distal spines and 3 or 4 bells (only proximal part of bristles shown on illustrated limb). Terminus with comb of 5 recurved teeth opposite 4 recurved pegs (not all pegs and teeth shown on illustrated limb).

Furca (Figure 56e): Each lamella with 6 claws: claws 1, 2, and 4 stout; claws 3, 5, and 6 shorter and more slender; all claws with short teeth along posterior margin; claw 1 with teeth forming 2 rows (distal medial tooth stout, others small); hairs present on lamellae following claws. Right lamella slightly anterior to left.

Bellonci Organ (Figure 56g,h): Elongate with about 5 sutures in middle part and short broader distal part.

Eyes (Figure 56f): Medial eye bare, unpigmented. Lateral eye smaller than medial eye, with 5 amber-color ommatidia.

Upper Lip (Figure 56i): With minute spines or processes at anterior tip.

Genitalia (Figure 56h): Oval ring on each side of body anterior to furca.

Posterior of Body (Figure 56h): Bare.

Y-Sclerite (Figure 56h): Branching distally.

Eggs: USNM 193691 with 3 eggs in marsupium and 3 much smaller unextruded eggs (Figure 55a).

DESCRIPTION OF A–1 FEMALE HOLOTYPE (MNHN Os 448) (Figures 56j–m, 57).—Carapace similar to that of adult female (Figures 56j, 57).

Carapace Size: Length 0.74 mm, height 0.34 mm.

First Antenna: 1st joint bare. 2nd joint with 1 dorsal bristle. 3rd joint with 3 bristles (1 ventral, 2 dorsal). 4th joint with 4 bristles (2 ventral, 2 dorsal). Joints 5–8 with same number of bristles as on adult female but bristles not examined in detail. (Right limb aberrant and with fewer bristles on joints 2–4.)

Second Antenna: Protopodite, endopodite, and exopodite similar to those of adult female. Exopodite with bristles of joints 2–8 and long bristle of 9th joint with proximal ventral spines and distal natatory hairs.

Mandible: Differs from adult female in having 3 instead of 2 proximal medial bristles on basale.

Maxilla and Fifth Limb (Figure 56k,l): Similar to those of adult female.

Sixth Limb: Similar to that of adult female except with 2 rather than 1 epipodial bristle.

Seventh Limb: Similar to that of adult female except bristles strongly tapering and with only 1 or 2 bells.

Furca, Bellonci Organ, Eyes, Upper Lip, and Posterior of Body: Similar to those of adult female.

Y-Sclerite (Figure 56m): Distal branches forming smaller angle than on adult female.

COMPARISONS.—In the key to species of Harbansus in Kornicker (1978:16) the new species H. thrix keys out to H. paucichelatus. However, the adult female of H. thrix differs from that of H. paucichelatus in having 5 or 6 rather than 3 bristles on the 4th joint of the 1st antenna, in having wreaths of long spines on the ventral bristle of the 2nd endopodial joint of the 2nd antenna, and having 2 rather than 1 proximal medial bristles on the basale of the mandible. The adult female of H. thrix differs from that of H. slatteryi Kornicker, 1983a:181 in having 5 or 6 rather than 3 bristles on the 4th joint of the 1st antenna, 3 rather than 2 claws on the 3rd endopodial joint of the mandible, and 5 rather than 2 ommatidia in the lateral eye.