The taxonomic status of Choanoscolex lamothei, a proteocephalidean tapeworm described from the catfish Ictalurus meridionalis (= I. furcatus) from Oaxaca, Mexico, was evaluated on the basis of morphological examination of types and freshly collected specimens from the type host and partial sequences of the large subunit (28S) ribosomal DNA. This study revealed that C. lamothei is a species of Megathylacoides (Proteocephalidae: Corallobothriinae) because of the medullary position of the genitalia (entirely cortical in Choanoscolex), the presence of semispherical sphincters on the suckers, a follicular ovary, and the alternating position of the vagina. Megathylacoides lamothei n. comb. differs from congeneric species in lacking an apical organ and in the number (130-208) of testes. Molecular data confirm the position of M. lamothei within Megathylacoides, which contains species parasitizing ictalurid fishes in North America.

Institute of Parasitology Academy of Sciences of the Czech Republic Branisovská 31 370 05 Ceské Budejovice Czech Republic

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Caryophyllidean tapeworms (Cestoda), Nearctic parasites of fish in Mexico, including description of a new species of Isoglaridacris and the first report of Khawia japonensis, an invasive parasite of common carp (Cyprinus carpio)