DINOFLAGELLATE INFECTIONS OF FAVELLA-PANAMENSIS FROM 2 NORTH-AMERICAN ESTUARIES

Favella panamensis Kofoid and Campbell, 1929 is seasonally abundant in meso- to polyhaline waters of Chesapeake Bay and Indian River, Florida, USA, where it reaches densities of 10(3) cells 1(-1). During the summers of 1986-1992, F: panamensis populations of the two estuaries were commonly infected by the parasitic dinoflagellate Duboscquella aspida Cachon, 1964. The intracellular phase of the parasite reached maturity in similar to 21 h (30 degrees C) and consumed similar to 35% of the host's biomass. Infections were not typically lethal to F: panamensis, but sometimes forced the host from its lorica. Several D. aspida were found in the cytoplasm of many hosts, and the number of parasites infection(-1) was directly related to infection level. Parasite prevalence 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, respectively. 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 than would be expected from copepod grazing.