Ctenascarophis lesteri n. sp. and Prospinitectus exiguus n. sp. (Nematoda: Cystidicolidae) from the skipjack tuna, Katsuwonus pelamis.

Two cystidicolid nematodes, Ctenascarophis lesteri n. sp. and Prospinitectus exiguus n. sp., are described from the skipjack tuna, Katsuwonus pelamis, from Fiji, New Caledonia, Marquesas Islands, New Zealand, Papua New Guinea, and Puerto Rico. The former species differs from Ctenascarophis gastricus, the only other member of the genus, by having comb rows extending farther posterior than two-thirds the body length, to the anus in the female; it also has differently distributed spines on each comb, with a maximum of 32 rather than 8. The male has 7 rows of precloacal longitudinal crests; 3 pairs of precloacal, 1 pair adanal, and 6 pairs postcloacal papillae; and a spicule ratio of 1:3.4-1:5.0. The latter species differs from Prospinitectus mollis, the only other species in the genus, by being less than one-half as long, 3.5-5.9 mm long; with a proportionally longer esophagus; fewer spines per spine ring, a maximum of 49 compared with 100; deirids that lack spinules; males with an unornamented precloacal cuticle as well as a different number and distribution of caudal papillae, 2 precloacal and 7 postcloacal; and a smaller spicule ratio, 1:4 rather than 1:5-1:7.