First report of Mucor circinelloides occurring on yellow catfish (Pelteobagrus fulvidraco) from China.

Infected yellow catfish (Pelteobagrus fulvidraco) were sent from Niushan Lake Fishery, Hubei Province, China, to our laboratory for diagnosis. Macroscopic daffodil yellow mold was observed on the heads and fins of the fish and one Mucor species was isolated. Based on the morphological and molecular analysis, the species was identified as Mucor circinelloides. Its optimum growth temperature was 30 degrees C and it could not grow at 40 degrees C. The infectivity results showed wound infection could cause 100% cumulative mortalities at all experimental CFU (10(6), 10(7) and 10(8)). The cumulative mortalities of the intraperitoneal infection increased along with the sporangiospore concentrations; the highest mortality was 90% with 10(8) CFU. Histopathological studies showed M. circinelloides could cause a series of pathological changes in the host tissues and they disseminated in different viscera, perhaps by the blood. This is the first report of M. circinelloides infection in yellow catfish.