Abasia pusilla Cressey & Cressey 1979

Abasia pusilla

MATERIAL EXAMINED.—Holotype (USNM 171333), allotype (USNM 171334) and 5 paratypes (USNM 171335), 2 , (1 prepared for SEM study) from the gills of 5 Synodus ulae from Wakanoura, Japan. Three from 1 Synodus ulae from Misaki, Japan; 1 from the gills of Synodus ulae from Kochi, Japan; 1 from the gills of Synodus ulae from Japan: and 1 from Okinawa.

Female: Body form as in Figures 30a and 30b. Total length 4.96 mm, greatest width 2.23 mm. Cephalon slightly longer than wide (1.77 × 1.58 mm) with lateral margins folded ventrally to encompass host gill filament. Thoracic segments indistinctly separated from cephalon. Genital segment wider than long (2.23 × 1.57 mm), globose. Abdomen unsegmented, somewhat longer than wide (0.62 × 0.51 mm), constricted in posterior third, probably indicating fused segmentation. Caudal rami (Figure 30c) longer than wide (118 × 71 μm) each bearing 6 plumose setae, longest 165 μm.

Rostrum projecting forward with indistinct frontal lunules (SEM photo. Figure 39a, indicates lunule is well developed but difficult to see with light microscope) and bearing a well-defined rugose area ventrally at mid point of anterior margin (Figure 39b). First antenna (Figure 30d) of usual caligid type, first segment with 24 sparsely plumose setae, second segment with 12 setae and 1 aesthete. Second antenna (Figure 30e) with robust basal segment and a short claw bearing 2 short setae. Tip of mandible (Figure 30f) bearing 12 teeth. First maxilla (Figure 30g) as in the figure. Second maxilla (Figure 30h) second segment with a prominent spine on inner distal corner (Figure 39c), terminal claw with rows of spinules as indicated in the figure and and Figure 39d. Maxilliped (Figure 30i) with stout base and short, recurved, terminal claw.

Leg 1 (Figure 30j) biramose; basipod with an inner and an outer seta; exopod 2–segmented, first segment with a short spine on outer distal corner, second segment with 4 terminal setae, outer 2 with lateral spinules, innermost with short plumosities, remaining seta naked; endopod reduced, bearing one, short, terminal seta. Leg 2 (Figure 31a) coxopod with broad hyaline membrane along outer edge; basipod with short seta on outer edge and broad hyaline membrane along inner margin; exopod 3–segmented, first segment with broad hyaline membrane on outer edge, a long finely spinose spine on outer distal corner, and an inner seta, second segment with a long finely spinose spine on outer distal corner (Figure 39e) and an inner seta, last segment with 2 outer spines and 6 setae; endopod 3–segmented, first segment with a row of spinules along outer distal third and an inner seta, second segment with a row of spinules along outer margin and 2 inner setae, last segment with a short row of spinules on outer margin and 6 setae; interpodal plate with a broad posterior hyaline membrane. Leg 3 (Figure 31b) coxopod and basipod forming a lamella, outer distal corner bearing a seta, inner margin bearing a plumose seta near exopod and a broad hyaline membrane to interpodal plate; exopod 2–segmented, first segment heavily sclerotized with stout spine on outer distal corner, second segment with 2 terminal setae; endopod represented by single seta. Leg 4 (Figure 31c) coxopod and basipod indistinctly divided with seta on outer distal corner; exopod 2–segmented, first segment with short, stout spine on outer distal corner, second segment with 2 terminal, short, stout spines; entire leg weakly developed. Legs 5 and 6 absent.

Male: Body form as in Figure 31d. Total length 2.10 mm, greatest width 0.88 mm. Cephalon slightly longer than wide (0.99 × 0.88 mm), lateral margins not folded ventrally; frontal lunules more developed than female. Genital segment (Figure 31e) about as long as wide (0.61 × 0.59 mm), rounded, widest near middle. Abdomen 2–segmented (see Figure 31e), first segment much wider than long (206 × 53 μm), second segment only slightly wider than long (248 × 230 μm). Caudal rami 118 μm long and 71 μm wide, each with 6 plumose setae, 2 short lateral, 3 terminal, 1 subterminal; longest seta 153 μm.

Appendages as in female except as follows. Second antenna with dactylate tip (Figure 31f). Maxilliped with claw longer than in female relative to basal segment. Legs 1–4 as in female. Legs 5 and 6 represented by 2 setae and 1 seta on lateral margins of genital segment as indicated in Figure 31e.

ETYMOLOGY.—The Latin pusilla (“small”) refers to the size of the abdomen when compared to the other species of the genus.

Japan: Wakanoura, Kochi, Misaki, and Okinawa