IDENTIFICATION AND GENETIC-CHARACTERIZATION OF YEASTS ISOLATED FROM FRESH-WATER PRAWNS, MACROBRACHIUM-ROSENBERGII DE-MAN, IN TAIWAN

Since 1987, farmers in southern Taiwan have reported significant disea se-related mortalities in freshwater prawns. Most mortalities have occ urred during the winter, and usually almost all the adult prawns die w ithin 4-5 days after clinical signs appear. Histopathological studies show that cells in hepatopancreatic ducts and tubules are vacuolized a nd degenerated. Large numbers of membrane-bound yeast aggregates are o bserved in the affected tissues. Two hundred and seventeen yeast isola tes were obtained from diseased prawns, pond water and sediments from six areas. :DNA restriction fragment length polymorphism (RFLP) was us ed to analyse the yeast genomes and to categorize them into five group s. conventional biochemical and metabolic methods were then used to id entify the yeasts of each group. The results.showed that two strains o f Candida sake (I and II), Pichia anomala, Endomyces fibuliger and Can dida famata were present. In addition, the RAPD (random amplified poly morphic DNA) method was used to determine their genomic similarities. Two strains (I and II) of C. hike were the most similar (72%). C. sake I appears to be the primary causative agent of disease, based on freq uencies of occurrence of tile yeasts found in the diseased prawns.