DESCRIPTION OF A NEW SPECIES OF MICROSPORIDIA FROM MUSCIDIFURAX RAPTOR (HYMENOPTERA, PTEROMALIDAE), A PUPAL PARASITOID OF MUSCOID FLIES

A microsporidian parasite, Nosema muscidifuracis n. sp., has been foun d in Muscidifurax raptor, a parasitoid of muscoid flies. Stages of the parasite developed in direct contact with the host cell cytoplasm and were detected in midgut epithelium, Malpighian tubules, ovaries (incl uding oocytes) and fat body of larvae and adults. Spores were also det ected within eggs deposited on the host. Light and electron microscopy revealed a developmental cycle with diplokaryotic stages dividing by binary fission and disporous sporulation sequences producing diplokary otic spores of three morphological classes, differing significantly on ly in length of the polar filament. Two of the classes were found in l arvae, pupae and adults. One of these, with about five turns in the co iled polar filament, is presumed to be responsible for transmission fr om cell to cell within the host (autoinfection) and the other, with ab out 10 turns, responsible for transmission from host to host. A third class, with about 15 turns in the polar filament, was found in eggs of M. raptor. It is, presumably, either involved in initiation and sprea d of the infection at eclosion or is responsible for horizontal transm ission to a new host individual when eggs are cannibalized.