A new species of Cruzia (Nematoda: Cosmocercoidea, Kathlaniidae) parasitic in lizards from a threatened region of Argentina.

Cruzia Travassos, 1917 is a diverse genus of nematode parasites in amphibians, reptiles, and mammals. During a parasitological survey, specimens of Cruzia were found in the intestine of the lizards Ameiva ameiva (Linnaeus) and Teius teyou (Daudin) (Squamata: Teiidae) at the Chaco region, Formosa province, Argentina. A comparative analysis revealed that these nematodes represent a new species, named as Cruzia toba n. sp. The new species can be distinguished from the congeners based on the combination of the following features: presence 12-14 teeth per row in the pharynx, equatorial vulva in females, and number and arrangement of caudal papillae in males (11 pairs: 3 precloacal, 3 paracloacal, 5 postcloacal; plus a precloacal minute unpaired papilla). Cruzia toba n. sp. is closely related to C. lauroi Vieira, Gonçalves, Lima, Sousa, and Muniz-Pereira, 2020 a likewise parasite of lizards, regarding the length of spicules and the presence of an unpaired papilla in males, but differs from it in the position of the vulva, the size of the gubernaculum and in the number and arrangement of caudal papillae. This is the first report of a representative of Kathlaniidae parasitizing A. ameiva and T. teyou, and the first Cruzia infecting lizards from Argentina. The morphological affinities among species of Cruzia are mostly random, not allowing a morphological grouping of these parasites in relation to their host taxa, or geographic origin. Thus, the speciation process in Cruzia most likely occurred via host capture.