Cucullanus mexicanus sp n. (Nematoda : Cucullanidae) from the intestine ofthe freshwater catfish Rhamdia guatemalensis (Pimelodidae) in Mexico

A new cucullanid nematode, Cucullanus mexicanus sp. n., is described from s pecimens recovered from the intestine of the freshwater catfish Rhamdia gua temalensis (Gunther) (Pisces, Pimelodidae) from three localities (brooks El Saltillo, Valle Nacional and San Juan Bautista) in the State of Oaxaca, ce ntral Mexico. The new species, belonging to the subgenus Cucullanus, distinctly differs f rom all its congeners in having an unusually large, conspicuously elongated precloacal sucker and only one pair of preanal papillae near it; it is fur ther characterized by almost equal spicules (length 330-356 mum), a small Y -shaped gubernaculum, and by the distribution of caudal papillae in the mal e. Cucullanus mexicanus sp. n. is the second freshwater species of the genu s reported from Mexico.