OCCURRENCE OF PSOROSPERMIUM SP IN SEVERAL NORTH-AMERICAN CRAYFISH SPECIES, WITH COMPARATIVE NOTES ON PSOROSPERMIUM-HAECKELI IN THE EUROPEANCRAYFISH, ASTACUS-ASTACUS

Psorospermium haeckeli is a thick-walled, unicellular organism widely reported in European astacid crayfish. Its taxonomic status and life c ycle have not been elucidated. It is often referred to as a ''parasite '', but conclusive evidence has yet to be found. Recent examination of two North American crayfish species, Procambarus clarkii and Procamba rus zonangulus, confirmed its presence in the south-central USA (Louis iana) with morphologies that differ from that of P. haeckeli. This for m had been previously reported from Orconectes virilis in southern Can ada. We report here the presence of this North American form of Psoros permium in additional North American crayfish including Orconectes imm unis and Orconectes rusticus from the northern USA (Minnesota and Wisc onsin), Procambarus alleni and Procambarus fallax from the southern US A (Florida), and Pacifastacus leniusculus from the western USA. We als o confirm this Psorospermium in O. rusticus from eastern Canada (Ontar io). It was not, however, confirmed in several additional southern cra yfish species including Cambarus diogenes, Cambarellus puer, Fallicamb arus fodiens, and Orconectes palmeri. We describe the morphological fo rms of this Psorospermium and conclude that it is present in many cray fish species in North America.