Nematodes associated with Psychodidae: description of Rhabditis berolina sp. n. and redescription of R. dubia Bovien, 1937 (Nematoda: Rhabditidae), with biological and ecological notes, and a phylogenetic discussion

The association of saprobiotic nematodes from cow pats with species of Psychoda was investigated. Seven out of 10 species examined transported phoretic stages of 6 different nematode species. Predominantly Rhabditis (Choriorhabditis) dubia, followed by the recently discovered R. (Ch.) berolina sp.n. R. axei as well as R. elegans, R. helversenorum, and Hexatylus coprophagus were transported sporadically. The claim of Goodey (1943) that dauerlarvae of R. curvicaudata also wrap themselves round the abdomen of moth-flies is questioned. R. berolina sp.n. can easily be distinguished from the closely related R. dubia by its longer tail in dauerlarvae and adults, the conical (instead of dome-shaped) female tail, the open (instead of closed) bursa, and the shorter specules. Both species are recorded from dung samples taken in different places in Europe. In both species the dauerlarvae attached to the psychodids have cast the cuticle of the preceding stage. At least for R. dubia the transport by insects is physiologically absolutely necessary for further development of the J3 on fresh manure (proximate factor). A phylogenetic analysis reveals that R. berolina sp. n., R. dubia, R. cristata, R. dudichi and R. longipapillata form a monophyletic group. Their relationship is shown in a cladogram. As a nomenclatorial consequence Amphidirhabditis Andrassy, 1978 has to be treated as a junior synonym of Rhabditis.