Freshwater fungi isolated from eggs of the common carp (Cyprinus carpio) in Thailand

Abstract

Fungal infection in the eggs of freshwater fish is well known as a problematic disease. We had a chance to examine fungal infection in common carp (Cyprinus carpio) eggs at fish farms in Khon Kaen province, northeast Thailand, in February 2002, attempting to isolate fungi from eggs with fungal infection at three fish farms (A, B, and C). Nineteen stocks of fungi from farm A, 2 fungi from farm B, and 2 fungi from farm C were isolated and 3 of them were identified as Saprolegnia diclina, Achlya (A.) klebsiana, and Allomyces (Al.) arbuscula. S. diclina, A. klebsiana, and Al. arbuscula grew well at 25°–30°C and pH 6–7, at 30°–35°C and pH 6–7, and at 30°–40°C and pH 6–8, respectively. Saprolegnia diclina grew in a medium containing NaCl up to a concentration of 3.0%, whereas A. klebsiana and Al. arbuscula grew poorly in 1.0% NaCl. Artificial infection to platyfish (Xiphophorus maculatus) was also made using the 3 fungi selected, in which injured fish were exposed to 104 spores/ml of S. diclina and A. klebsiana and showed 100% of mortality, but none in the other experiments. This article includes the first description of Allomyces arbuscula from fish eggs in Thailand.