Acantholochus nudiusculus (Cressey & Cressey 1980)

Holobomolochus nudiusculus

MATERIAL EXAMINED.—Holotype (USNM 172247), allotype (USNM 172248), paratypes 33 1 (USNM 172249) from the nasal sinuses of Scomberomorus sierra from Buenaventura, Colombia (USNM 218565). In addition 13 collections containing 30 1 from the nasal sinuses of S. concolor from Baja California and Sonora, Mexico; 26 collections containing 105 7 from the nasal sinuses of S. sierra from Baja California, Sonora, Panama (Pacific), Colombia (Pacific), Peru.

FEMALE.—Body form as in Figure 5d. Total length 1.76 mm, greatest width 0.72 mm, Genital segment (see Figure 5e) wider than long (230 × 271 μm) with 3 naked setae at area of egg sac attachment. Abdomen (Figure 5e) 3-segmented segments measuring 171 × 206 μm, 118 × 177 μm, and 112 × 147 μm respectively, ventral surface of last segment with 2 patches of minute spinules (see Figure 6a). Caudal rami (Figure 6a) slightly longer than wide (59 × 53 μm) with 6 setae (longest 652 μm).

First antenna, second antenna, mandible, paragnath, first maxilla, second maxilla, and maxilliped similar to those of Holobomolochus divaricatus.

First leg similar to that of H. divaricatus. Legs 2–4 biramous, rami 3-segmented. Leg 2 (Figure 6b) similar to that of H. divaricatus except endopod third segment with row of blunt spinules at base, 2 outer spinulose spines, gradually tapering, with no terminal flagellum. Leg 3 (Figure 6c) coxopod, basipod, exopod similar to those of H. divaricatus except exopod spines relatively longer with distal spine longest; endopod similar to leg 2 except third segment with 2 rather than 3 setae and inner spine slightly longer than outer. Leg 4 similar to that of H. divaricatus. Leg 5 (Figure 6d) generally similar to that of H. divaricatus except free segment not as elongate, lateral and terminal spines relatively longer. Leg 6 represented by 3 setae at area of egg sac attachment.

MALE.—Body form as in Figure 6e. Total length 0.98 mm, greatest width 0.38 mm. Genital segment (Figure 7a) longer than wide (194 × 159 μm). Abdomen (see Figure 7a) 2-segmented, segments measuring 53 × 94 μm and 64 × 88 μm respectively, ventral surface of last segment with 2–3 irregular transverse rows of spinules near anterior edge and a small patch of spinules near insertion of each caudal ramus (see Figure 7b). Caudal rami (Figure 7b) longer than wide (47 × 29 μm), each with small ventral patch of slender spinules and 6 setae (longest 531 μm).

Cephalic appendages and legs 1–5 as in H. divaricatus male.

ETYMOLOGY.—The Latin nudiusculus (“somewhat naked”) refers to the small patches of minute hairs on the ventral surface of the last abdominal segment and the naked surface of the female caudal rami.

Mexico (Pacific side), Colombia (Pacific side), and Peru