Taxonomic studies on the genus Tylencholaimus de Man, 1876 (Dorylaimoidea) with a key to the species

Abstract

The genus Tylencholaimus de Man, 1876 is removed from the Dorylaimidae and placed in the Leptonchidae. Consequently the subfamily Tylencholaiminae Filipjev, 1934 is also transferred to Leptonchidae; it is considered synonymous with Xiphinemellinae Jairajpuri, 1964, and contains the genera Tylencholaimus, Botalium, Discomyctus, Xenonchium and Xiphinemella. The genus Enchodelus remains in the Dorylaimidae. Tylencholaimus mirabilis (Butschli, 1873), the type species of Tylencholaimus, is redescribed from topotypes; T. brevicaudatus (Tarjan, 1953) is considered identical with it. A neotype is designated and the male, unknown so far, is described. Eight new species are described. T. pusillus has the same shape of lips as T. minimus de Man, but is much smaller and there are no radial striae in the cuticle. T. congestus and T. savaryi are characterized by didelphic gonads and by a number of large cells surrounding the vagina; in T. congestus the lip region is offset by a shallow constriction, the inner papillae do not project and the tail is hemispheroid; in T. savaryi the lips are offset by a deep constriction, the inner papillae project markedly and the tail is convex-conoid. T. crassus is also didelphic, but much stouter than T. congestus and T. savaryi, and there are no large cells around the vagina. T. formosus and T. airolensis are prodelphic, the rudiment of the posterior gonad is large and serves as receptaculum seminis; in T. formosus the oesophagus is expanded behind the middle, the two parts being separated by a marked constriction; in T. airolensis the two parts of the oesophagus are equal in length and not separated by a constriction. In T. maritus the rudiment of the posterior female gonad is very small, the tail is hemispheroid and males are numerous. T. paradoxus has a very fine spear and minute sclerotized pieces near the oral opening. In addition, a redescription is given of T. stecki Steiner, 1914. T. similis jairajpuri, 1965 is synonymized with T. lepionchoides Loof, 1964; T. macrurus Siddiqi, 1964 may also be identical with this species. A few additional details of T. viduus Jairajpuri, 1965 are given. A key to the species is presented.