Observations on cucullanid nematodes from freshwater fishes in Mexico, including Dichelyne mexicans Sp n.

A new cucullanid nematode, Dichelyne mexicanus sp. n,, is described from th e intestine of three species of fishes, Agonostomus monticola (Bancroft) (M ugilidae, Perciformes) (type host), Ictalurus balsanus (Jordan et Snyder) ( Ictaluridae, Siluriformes) and Cichlasoma beani (Jordan) (Cichlidae, Percif ormes), from three rivers (La Maquina River, Veracruz; Chontalcoatlan River , Guerrero and Santiago River, Nayarit) in central Mexico. This species is characterised by the absence of a ventral sucker in the male (subgenus Dich elyne) and it differs from its congeners mainly in possessing very unequal and dissimilar spicules (left 0.465-0.768 mm and right 293-548 mm long), an asymmetrical gubernaculum, and two intestinal caeca. Another cucullanid ne matode, Cucullanus caballeroi Fetter, 1977, is reported from Dormitator mac ulatus (Bloch) (Eleotridae, Perciformes) from the La Palma and La Maquina R ivers and Balzapote stream, Veracruz, being briefly described and illustrat ed; this represents a new host record. Findings of D. mexicanus and C. caba lleroi represent a new record of cucullanid nematodes from fishes in Mexica n fresh waters.