EURYCHASMOPSIS-MULTISECUNDA GEN-ET-SP-NOV, A PARASITE OF THE SUCTORIAN CILIATE PODOPHRYA

The life-history of Eurychasmopsis multisecunda gen. nov., sp. nov. is described. This oomycete fungus parasitizes Podophrya sp., a suctoria n which feeds on Nassula aurea in Windermere, a lake in Cumbria, Engla nd. The unicellular thallus is holocarpic, becoming transformed into a sporangium with one or more exit tubes, which initially remain closed , Cytoplasmic cleavage takes place within the sporangium to produce mo tile biflagellate zoospores which encyst within the sporangium away fr om the exit tubes. The cysts form a honeycomb-like network adpressed a gainst the inner wall of the sporangium leaving a large central space confluent with the lumena of the exit tubes. The exit tubes of the spo rangia then become open. Each cyst produces an exit papilla centripeta lly, from which a single, principal-form zoospore emerges into the cen tral lumen of the sporangium. These zoospores swim out through the exi t tubes. Separate oogonial and antheridial thalli occur. The antheridi al thallus is divided into a number of small antheridial cells, each o f which is capable of producing a fertilization hypha which traverses any gap between the antheridial and oogonial thalli and penetrates the oogonium. One or two oospores develop, each with distinctive redistri bution of endogenous reserves. Earlier reports of other fungi which pa rasitize suctoria are reviewed.