A new nematode species, Atractis vidali sp. n., is described from the intestine of cichlid fishes, Vieja intermedia (Günther) (type host) and Cichlasoma pearsei (Hubbs), from specimens collected in three localities in the Mexican states of Campeche (Santa Gertrudis Creek) and Chiapas (Cedros and Lacanjá Rivers). It differs from the only other atractid species reported in fishes of Mexico, Atractis bravoae, mainly in possessing two very unequal spicules. In contrast to the 10 species parasitising amphibians and reptiles in America, the new species has a longer body, spicules and a gubernaculum, and a different distribution of the caudal papillae. This is the second species of the genus Atractis recorded from freshwater fishes.
A new nematode species, Spirophilometra pacifica sp. n. (Philometridae), is described from gravid female specimens collected from the mouth cavity (the upper palate) of the fish (yellow snook) Centropomus robalito (Centropomidae, Perciformes) from the Chantuto-Panzacola system, Chiapas, in the Pacific coast of Mexico. Its morphology is very similar to that of the species originally described as Philometra centropomi Caballero, 1974, but the gravid females of S. pacifica are about three times longer (body length 11.63-18.17 mm); host species and the geographical distribution of both these forms also differ. Scanning electron microscope (SEM) examination of S. pacifica, used for the first time for a Spirophilometra species, confirmed the presence of numerous minute cuticular spines on the body surface, 14 cephalic papillae arranged in two circlets, and two small lateral papilla-like caudal projections. It is evident that some features of P. centropomi were incorrectly described (its types are not available) and this species is now transferred to Spirophilometra as S. centropomi (Caballero, 1974) comb. n.
A new capillariid nematode, Capillostrongyloides morae sp. n., is described from specimens collected from the stomach and intestine of the common mora, Mora moro (Risso), and the Mediterranean codling, Lepidion lepidion (Risso) (both Gadiformes, Moridae), off the Mediterranean coasts of Spain. The new species shows similar morphological features as other congeneric species occurring in freshwater and marine fishes, but it differs in the length of the body and spicules, the size of the caudal bursa, and the presence of an elevated anterior vulvar lip. Capillostrongyloides morae sp. n. is the second species within the genus for which the presence of a stylet is reported, and the first one in which this structure along with the distribution of cephalic papillae and oral structures (e.g. lips and lobes) are clearly shown by using scanning electron microscopy.
A new nematode species, Cucullanus pargi sp. n., is described from the intestine and pyloric caeca of the grey snapper, Lutjanus griseus (Linnaeus), off the southern Quintana Roo coast, Mexico. This species shows similar morphological features as cucullanids occurring in marine and brackish-water fishes; however, it differs from all other species in the length of spicules, arrangement and number of caudal papillae, position of the excretory pore and deirids. Cucullanus pargi is the third species of this genus described from fishes in Mexico and the second one from Mexican marine fishes.
Two little-known species of Spinitectus (Nematoda: Cystidicolidae) were, for the first time, recorded from fishes of the Lacantún River (Usumacinta River basin) in the Lacandon rain forest, Chiapas, southern Mexico: S. tabascoensis Moravec, García-Magaña et Salgado-Maldonado, 2002 in intestines of Ictalurus furcatus (Valenciennes) (Ictaluridae) (adults and juveniles), Cathorops aguadulce (Meek) and Potamarius nelsoni (Evermann et Goldsborough) (both Ariidae) (in both only juveniles), and S. osorioi Choudhury et Pérez-Ponce de León, 2001 in Atherinella alvarezi (Díaz-Pardo) (Atherinopsidae) (adults in intestine) and Eugerres mexicanus (Steindachner) (Gerreidae) (adults and juveniles in stomach). Eugerres mexicanus, C. aguadulce and P. nelsoni represent new host records. Detailed light and electron microscopical studies of S. tabascoensis revealed some taxonomically important, previously not observed features, such as cuticular spines arranged in four sectors, the cephalic structure, the number (2) of ventral precloacal ridges or the structure of the male caudal end. Therefore, Spinitectus tabascoensis is redescribed. Spinitectus macrospinosus Choudhury et Perryman, 2003, described from ictalurids in Canada and the USA, is considered its junior synonym. Spinitectus tabascoensis seems to be a specific parasite of Ictalurus spp., whereas C. aguadulce and P. nelsoni, as well as some other fishes, serve only as its paratenic hosts. The definitive hosts of S. osorioi are atherinopsid fish (A. alvarezi, Chirostoma spp.), whereas the gerreid E. mexicanus probably serves only as its postcyclic host.
Scanning electron microscopy of the cystidicolid nematode Ascarophis mexicana Moravec, Salgado-Maldonado et Vivas-Rodríguez, 1995 enabled the first detailed study of its cephalic structure. In contrast to most Ascarophis species, its pseudolabia are highly reduced and sublabia are unlobed and weakly developed. Similascarophis is considered a synonym of Ascarophis, to which two its species are transferred as A. maulensis (Muñoz, González et George-Nascimento, 2004) comb. n. and A. chilensis (Muñoz, González et George-Nascimento, 2004) comb. n.