Notes on the systematic position of the genus Nygellus Thorne, 1939. Ahmad Maqsood, Jairajpuri M. Shamim Section of Nematology, Department of Zoology, Aligarh Muslim University, Aligarh-202001. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract The genus Nygellus Thorne, 1939 is distinct among all dorlyaim nematodes as it shares the characters of the super-families Nygolaimoidea De Coninck, 1965 (possession of a mural tooth) and Belondiroidea Thorne, 1964 (possession of spiral muscle sheath). Thorne (1939) placed this genus under the family Belondiridae while Jairajpuri (1964) proposed a separate family Nygellidae for its reception. Since then, the position of this peculiar nematode has remained controversial. Thorne (1964), Siddiqi (1968), Ferris (1971) included Nygellus as well as the family Nygellidae under Belondiroidea while Heyns (1968) and Andrassy (1976) considered it under Nygolaimoidea. Recently, Jairajpuri & Ahmad (1980) did not include it under Belondiroidea. The genus at present includes only three species and all these possess a mural tooth, cardiac glands at base of oesephagus and spiral muscle sheath around the basal expanded portion of oesophagus. Study of a large number of specimens of Nygellus clavatus Thorne, 1939 collected from Jorhat (Assam) revealed the definite presence of a spiral muscle sheath around the expanded portion of oesophagus though the sheath is not very conspicuous. We, therefore, suggest that this genus be included under the superfamily Nygolaimoidea of the suborder Nygolaimina Ahmad & Jairajpuri, 1979 because of the presence of mural tooth and the cardiac glands, both of which are characters of fundamental importance in dorylaim systematics. The presence of spiral muscle sheath has already been reported in some other genera outside Belondiroidea as also pointed by Jairajpuri & Ahmad (1980). Top |