New species of Cosmocerca (Nematoda: Cosmocercidae), parasite of Leptodactylus melanonotus in Western Mexico, and new records for this species and Incilius marmoreus (Amphibia)

Specimens of the amphibian species Leptodactylus melanonotus and Incilius marmoreus were collected in several localities in Colima State, Mexico, from July to October 2021. An undescribed species of nematode of the genus Cosmocerca was found in the intestine of L. melanonotus. The new species differs from every other species assigned to this genus by the combination of the following characters: absence of lateral alae in males, 5 plectanes, spicules size, and gubernaculum size and shape. This is the 39th species included in the genus worldwide and it is the second described in Mexico. Six helminth species were collected during this study: Rauschiella poncedeleoni, Cosmocerca colimense n. sp., Oswaldocruzia subauricularis, and Rhabdias sp. of L. melanonotus; Aplectana incerta and Oswaldocruzia pipiens of I. marmoreus.