A new species of Travassos 1917 (Nematoda: Heligmonellidae) in small rodents (Cricetidae and Heteromyidae) from Mexico.

A new species of (Nematoda: Heligmonellidae) is described from the small rodents (Cricetidae: Tylomyinae) and (Heteromyidae: Heteromyinae) in the Yucatan Peninsula, Mexico, based on studies of light and scanning electron microscopy, and partial sequences of COI, ITS1 and 28S rRNA. n. sp. is characterized by a synlophe of 13 interrupted ridges (except those forming careen) in both sexes at midbody; males with a ventral cuticle inflation at anterior region of copulatory bursa, rays 9 and 10 long, comparable in length, and rays 9 strongly curved laterally at a right angle crossing ventrally rays 8; and females with a torsion of 180° to left of the posterior extremity. These characteristics were shared with nematodes reported previously from and (Cricetidae: Neotominae) also in the Yucatan Peninsula. The absence of intraspecific sequence variations in COI, and the low variation in D2-D3 expansion segments of 28S rRNA and ITS1 among the specimens obtained from the different hosts provided strong support that the worms found in the three rodent species belong to the same new species. The nine previously known species of have been reported from caviomorph rodents of the families Cuniculidae, Dasyproctidae, Echimyidae, and Erethizontidae from the Neotropics. The occurrence of in three phylogenetically distant rodent species suggests that this nematode species could have the ability to expand its host range by colonizing new hosts.