Diplogaster (Diplogastrellus) Cerea Sp. N. From Saguaro Cactus Rot and a Revision of the Subgenus Diplogastrellus (Nematoda: Diplogastridae)

A new species of Diplogaster is described from decaying cactus in Arizona, USA. It is characterized by a single female gonad, a quite short postvulvar uterine sac with paired pouches, and a keel shaped gubernaculum, proximally notched, with an interrupted caudal margin. Its dauerlarvae are phoretic on beetles and Diptera from the same habitat. Characters of the ground pattern of Diplogaster sensu lato are reconstructed to discern apomorphies for the subgenus Diplogastrellus of Diplogaster. Within this subgenus three transformation series of the pattern of male caudal papillae are recognized. We comment on the phylogenetic relationships of the twelve species in this subgenus and provide male and female keys to species, as well as information on their habitats and geographic distribution. Our reexamination of type material revealed that Diplogaster microstoma Goodey, 1929 is conspecific with D. graciloides Skwarra, 1921. The new name Diplogaster heynsι nom. nov. is proposed for Metadiplogaster secundus Dassonville & Heyns, 1984. Diplogaster minor Cobb, 1893 is synonymous with D. parva Cobb, 1893. Acrostichus toledoi Rahm, 1928 is placed in the Nudicapitatus-group of Diplogaster. Diplogaster attenuatus Cobb in Banks & Snyder, 1920 is a nomen nudum.