Camallanus sonaiensis sp.n. (Camallanidae), a new species of nematode from Heteropneustes fossilis collected from Assam, India.

During the study fishes of the species Channa striatus, Heteropneustes fossilis, Anabas testudineus, Channa punctata were collected and examined for ecto as well as endoparasites. However, a new species of parasitic nematode of the genus Camallanus Railliet and Henry (Rev Parasitol 39:117-129, 1915) is described only from intestinal region of Siluriformes fish Heteropneustes fossilis Bloch (1794). Buccal capsule of the new species is slightly longer than width marked internally by 9-10 beaded longitudinal ridges in lateral view, 1-2 dorsal and ventral ridges incomplete that differs from other related species. It also differs on the basis of body measurements, maximum width/length ratio of buccal capsule, number and length of spicule, tridents nature, number and arrangement of caudal papillae in the posterior end. Due to differences in many aspects from the related congeners, the present species is proposed as new to the science. The present study deals with the morphological and morphometric description of Camallanus sonaiensis sp.n. from Assam, India. © Indian Society for Parasitology 2021.