Couchia Circumplexa, A Water Mold Parasitic in Midge Eggs

SUMMARY

Couchia circumplexa is described as the type of a new genus of the Saprolegniaceae. The fungus parasitizes eggs of midges (Diptera, Chironomidae) producing appressorial complexes aiding in penetration of the egg chorion. The zoospores are dimorphic, the primary ones encysting near the zoosporangium orifice. The secondary zoosporangia proliferate internally. Three isolates of the new species differ primarily in the dimensions of their zoosporangia and gametangia and in the form of the appressorial complexes. Preliminary observations on the growth of one isolate in artificial and synthetic media are also reported.