Abstract
Saprolegniaceous fungi associated with the rainbow trout (Salmo gairdneri) were observed at Ma-ling Hatchery in Tai-Chung Prefecture, Taiwan during December, 1979 to February, 1980. One strain among the isolated fungi attached a male spawning fish was identified as Aphanomyces laevis. Another strain infected mainly on the peduncle and caudal fin of a female spawning fish was examined and identified as Saprolegnia diclina. The former was incubated at 10°C and gave well-developed sexual organs, and the latter was kept at 16°C and appeared both asexual and sexual structures. It may produce abundant of antheridia and oogonia either short after or after prolonged period of time when mycelium was removed from diseased fish. Oogonial wall of this fungus is usually pitted under point of attachment of antheridial cell and shows antheridia of diclinous form only. Some isolates of S. dicline were heavily affected by Woronina polycystis (in the Order Plasmodiophorales) which acts as an obligate parasite and eventual destruction of host hyphae.
