Two new species of Cucullanus Müller, 1777 (Nematoda: Cucullanidae) from marine fishes off Thailand.

Based on light and scanning electron microscopical observations, two new species of Cucullanus Müller, 1777 (Nematoda: Cucullanidae) are described from the intestine of marine perciform fishes in the coastal region of the Gulf of Thailand, Thailand: Cucullanus rastrelligeri n. sp. from the short mackerel Rastrelliger brachysoma (Bleeker) (Scombridae) and Cucullanus thaiensis n. sp. from the brownstripe red snapper Lutjanus vitta (Quoy & Gaimard) (Lutjanidae). The former species, C. rastrelligeri, is mainly characterised by an elongate pseudobuccal capsule, the presence of a ventral sucker, markedly short spicules (306-360 μm), a median papilla-like formation on the anterior anal lip and a distinctly elevated posterior anal lip, the location of the deirids and excretory pore, and by the distribution of genital papillae in the male. The latter species, C. thaiensis, is characterised by a broad pseudobuccal capsule, the presence of a ventral sucker and spicules 680 μm long. It is morphologically closest to C. pargi González-Solís, Tuz-Paredez & Quintal-Loria, 2007, but differs from it mainly in the distribution of the genital papillae in the male and apparently larger gravid females, and, whereas C. thaiensis occurs in the West Pacific (Gulf of Thailand), C. pargi was described from the West Atlantic (Caribbean Sea). C. rastrelligeri and C. thaiensis are the first nominal species of cucullanid nematodes reported from marine fishes in Thai waters. Indocucullanus thapari Gupta & Srivastava, 1984 is transferred to Cucullanus as C. thapari (Gupta & Srivastava, 1984) n. comb.