Redescription of Diplogasteroides nasuensis Takaki, 1941 and D. magnus Völk, 1950 (Nematoda: Diplogastrina) associated with Scarabaeidae (Coleoptera)

Abstract

AbstractA detailed morphological description is presented of Diplogasteroides nasuensis Takaki, 1941 and D. magnus Völk, 1950, using light and scanning electron microscopy. Neoaplectana melolonthae Weiser, 1958 and Diplogasteroides (Rhabdontolaimus) berwigi Rühm, 1959 are synonymised with D. nasuensis. This gonochoristic species is distinguished from the hermaphroditic D. magnus by the dorsal metastomal decoration which consists of bristle-like protrusions instead of a more or less uniform tooth. The spermatocytes in D. nasuensis are twice as big as those in hermaphrodites of D. magnus. Dauer juveniles of D. nasuensis are considerably bigger than those of D. magnus. Dauer juveniles of both species are present on wood cockchafer (Melolontha hippocastani) larvae and adults but, on adult beetles, D. nasuensis dauer juveniles enter the genital pouch, whereas those of D. magnus are found under the hind coxae. In Germany, D. nasuensis is found only on M. hippocastani. D. magnus dauer juveniles are also found on a variety of other Scarabaeidae. Further small differences distinguish the two species. The genus Diplogasteroides is proposed to be taken in a broad sense. Several genera names are synonymised with Diplogasteroides.