Field and laboratory studies on effects of salinity and temperature on Perkinsus marinus infection of oysters from the Gulf of Mexico

Hemolymph diagnosis for Perkinsus marinus was performed on laboratory-held oysters (Crassostrea virginica ) from the Gulf of Mexico to assess the influence of salinity and temperature. All experimental conditions exhibited 100% prevalence. Differences in incidence for low salinity/low temperature conditions and high salinity/high temperature conditions ranged from 10 super(0.02) to 10 super(0.37) hypnospores/mL hemolymph/wk. Temperature was the most important factor in oyster mortalities; oysters containing 10 super(3)-10 super(4) hypnospores/mL hemolymph survived at 18 degree C, but not at 27 degree C. Field studies were also performed to examine P. marinus) prevalence and infection intensity at four sites in the Gulf of Mexico: Lake Borgne (LA), Galveston Bay, San Antonio Bay and Padre Island (TX). Mantle tissue diagnosis displayed high prevalence at high salinity sites and low prevalence at low salinity sites. Hemolymph diagnosis was more sensitive, revealing high prevalence for all sites and collections. Infection intensity in hemolymph was relatively constant at high salinity sites throughout the year, but increased between fall and spring at low salinity sites