Atkinsiella awabi sp. nov. isolated from stocked abalone, Haliotis sieboldii

Abstract

A fungal disease in the abalone,Haliotis sieboldii, stocked in Yamaguchi Prefecture, Japan, showed external signs of infection of tubercle-like swelling on the mantle and melanized lesions on the peduncle. The fungus responsible was isolated by inoculating materials taken from the lesions onto PYGS agar with streptomycin sulphate and ampicillin, and incubation at 20°C. For morphological observation and spore formation study, the fungus was transferred respectively into PYGS broth and sterilized artificial seawater and incubated at 20°C. Resulting, hyphae were stout, irregular, branched, 16–140µm diam, sporadically consisting of dense cytoplasmic swollen hyphae. Sporangia were formed through the formation of septa and lateral or terminal discharge tubes which were wavy or coiled. Zoospores were pyriform, biflagellate and diplanetic. The encysted spore generally developed a hairlike filament with globular enlarged tip in PYGS broth. Direct germination without filament formation also occurred occasionally. This fungus was identified as belonging to the genusAtkinsiella, and was designatedAtkinsiella awabi sp. nov. The fungus was exclusively a marine fungus and grew best in shrimp extract medium at 20°C. Five chemicals were tested for their effects against fungal zoospores.