Characterization of the Aphanomyces Species Involved with Ulcerative Mycosis (UM) in Menhaden

Abstract

Aphanomyces and Saprolegnia were isolated from characteristic lesions of Ulcerative Mycosis (UM) on Atlantic menhaden and other fish. One of the Aphanomyces isolates was selected for cultural studies which revealed that the fungus was stimulated to increased vegetative growth and improved zoosporulation by low levels of NaCl. The salt tolerance exhibited by this fungus surpassed the known recorded limits for Oomycetes in regard to zoosporogenesis. The relationship of the fungal isolates to the lesions found on fish and the association of prevailing climatological conditions with the disease suggest a complex interaction between the fungus, possibly pre-stressed fish, and the salinity of the estuary systems of North Carolina.