Morphological evidence for a new species of the Genus Cosmocercoides Wilkie, 1930 (Ascaridida: Cosmocercidae) from Iranian toads (Bufotes surdus)

Background/objective: There is little data on infections of the genus Cosmocercoides Wilkie, 1930 in toad populations in Iran. Hence, the present study aims to report the first morphological description of the new genus Cosmocercoides Wilkie, 1930 (Ascaridida: Cosmocercidae) in Iranian toads (Bufotes surdus).

Methods: During the helminthological survey from October 2023 to December 2023, 10 specimens of Bufotes surdus were collected. They were transferred to the parasitological laboratory of Ardakan University, where they were euthanized and necropsied, and parasites were isolated from the toad's large intestine. Nematodes were washed in physiological saline and then fixed and stored in 80% ethanol until studied. Moreover, for light microscopic studies, nematodes were washed in lactophenol, and the morphological and morphometric parameters of male and female nematodes, including total length, esophagus, spicule, and eggs, were evaluated.

Results: The results showed that the total length of male worms was 2.83 (2.45-3.17) mm on average, and the length of the esophagus was 632.67 (631.50-634) µm. Additionally, the spicule of the male nematode was 381 (354-426) µm on average, and the eggs of female worms were 72 (59-85) × 47 (42-53) µm on average. The morphometric parameters indicate the biological differences of worms in this region compared to other countries and indicate local biodiversity.

Conclusion: In conclusion, the morphological and morphometric parameters evidence reported in the present study supports identifying a new species within the genus Cosmocercoides, based on specimens collected from Bufotes surdus.