A comparison of the known life forms of Psorospermium spp in freshwater crayfish (Arthropoda, decapoda) with emphasis on Astacus astacus L (Astacidae) and Procambarus clarkii (Girard) (Cambaridae)

Psorospermium spp. are unicellular organisms of uncertain taxonomic status found in the tissues of crayfish from three crayfish families. We describe the various life forms that we have identified in astacid, cambarid, and parastacid crayfish. A small amoeboid form, 10 mu m, is described from juvenile North American Procambarus clarkii. A similar form had been described only once before in European Astacus astacus in the 1930s. Psorospermium spp. described to date are apparently otherwise immobile and often surrounded by a thick wall. Infection becomes apparent in 5th or 6th stage crayfish.