A new and a known species of Dorylaimoidea (Nematoda: Dorylaimida) from West Bengal, India with a key to the species of the subgenus Axonchium Cobb, 1920

Resumo

Axonchium (Axonchium) coomansi sp. n. was collected from soil around the roots of guava (Psidium guajava L.) and litchi (Litchi chinensis Sonn.) and a small population of Mesodorylaimus mesonyctius (Kreis, 1930) Andrássy, 1959 was collected from the rhizosphere of guava, in South 24-Parganas. Axonchium (Axonchium) coomansi sp. n. is characterized by its incompletely amalgamated lip region, long pharynx, long anterior uterine sac without sperm and posteriorly directed, unsclerotized vagina. It comes close to A. (A.) amplicolle Cobb, 1920, A. (A.) metobtusicaudatum (Sch. Stekhoven et Teunissen, 1938) Nair et Coomans 1973, A. (A.) parasaccatum Rahman, Jairajpuri et Ahmad, 1985, A. (A.) saccatum Jairajpuri, 1964 and A. (A.) transkeiense Nair,1973. Axonchium (A.) coomansi sp. n. can be separated from all other closely related species except A. (A.) amplicolle in having a longer pharynx and rounded to tongue-shaped cardia (length of pharynx = 514-723 μm and cardiform cardia in A. (A.) metobtusicaudatum, 695-768 μm and clavate cardia in A. (A.) parasaccatum, 644-675 μm and conoid cardia in A. (A.) saccatum, 616-670 μm and bulboid to oval cardia in A. (A.) transkeiense). Axonchium (A.) coomansi sp. n. can be distinguished from A. (A.) amplicolle in having a much longer anterior uterine sac, comparatively thinner cuticle on the tail and by differently shaped cardia. The present specimens of Mesodorylaimus mesonyctius show similarities with M. pizai Lordello, 1965 with reference to tail structure, whereas the body structure and measurements of both male and female specimens agree well with M. mesonyctius. This is the first report of M. mesonyctius from West Bengal, India.