Metschnikowiella zobellii sp.nov. and M. krissii sp.nov., two Yeasts from the Pacific Ocean Pathogenic for Daphnia magna

SUMMARY Metschnikowiella zobellii sp.nov. and M. krissii sp.nov. are described and Latin diagnoses given. Both species form on V8 agar (Wickerham, 1951) club-shaped asci containing a single needle-shaped ascospore and are capable of parasitizing Daphnia magna under experimental conditions. M. zobellii differs from M. krissii by its capacity to ferment glucose and to assimilate galactose, l-sorbose, d-xylose, d-glucosamine, adonitol, d-sorbitol and pyruvate. In infected daphnias the asci and cells of both yeasts resemble Metschnikoff's drawings of M. bicuspidata. As cultures of M. bicuspidata do not exist and its physiological properties are unknown, the possible identity of either M. zobellii or M. krissii with M. bicuspidata cannot be verified and M. bicuspidata (Metschnikoff 1884) Genkel 1913 is therefore considered a nomen dubium. Both yeasts were repeatedly isolated from marine substrata on and off the coast of La Jolla, California, U.S.A. Minimum numbers of viable organisms in positive samples varied for M. zobellii as follows: sea water, 2–58/100 ml.; fish gut contents (of Atherinopis affinis littoralis and Trachurus symmetricus), 25–5,730/ml.; surface of Giant Kelp (Macrocystis pyrifera), 520–39,200/g. M. krissii was isolated only from sea water, 1–57/100 ml.