DINOFLAGELLATE INFECTIONS OF FAVELLA-PANAMENSIS FROM 2 NORTH-AMERICANESTUARIES

Favella panamensis Kofoid and Campbell, 1929 is seasonally abundant in meso- to polyhaline waters of Chesapeake Bay and Indian River, Florid a, USA, where it reaches densities of 10(3) cells 1(-1). During the su mmers of 1986-1992, F: panamensis populations of the two estuaries wer e commonly infected by the parasitic dinoflagellate Duboscquella aspid a Cachon, 1964. The intracellular phase of the parasite reached maturi ty in similar to 21 h (30 degrees C) and consumed similar to 35% of th e host's biomass. Infections were not typically lethal to F: panamensi s, but sometimes forced the host from its lorica. Several D. aspida we re found in the cytoplasm of many hosts, and the number of parasites i nfection(-1) was directly related to infection level. Parasite prevale nce averaged 24.0 and 11.5% with mean number of parasites infection(-1 ) being 1.5 and 1.3 for Chesapeake Bay and Indian River samples, respe ctively. D. aspida was estimated to remove up to 68% of host standing stock d(-1) with a mean of similar to 10% for all samples. The average impact of parasitism on F: panamensis populations was somewhat less t han would be expected from copepod grazing.