| Abstract: | Immunological probes were developed for the investigation of reproductive effort of oysters, Crassostrea virginica, and the effect of protozoan parasite Perkinsus marinus on reproduction of oysters in Galveston Bay. Number of P. marinus hypnospore present in FTM cultured oyster tissue was determined by dissolving the tissue in 2 M sodium hydroxide. Mackin's commonly used 0-5-point scale of infection intensity was proven to be exponential. From general relationships for oysters and protozoa, the impact of P. marinus at varying infection intensity on the oyster's energy budget was estimated. Mortality, decreased growth and decreased fecundity in infected oysters could be explained by a reduction in the oyster's available energy by P. marinus production and respiration. Polyclonal antiserum was produced from P. marinus hypnospores. Indirect immunofluorescence suggested that the antigenic material was a component of the cell wall. Cross-reactivity of the antiserum to other life stages of P. marinus present in oyster tissues could not be demonstrated by ELISA or immunofluorescence indicating that a substantial change in the antigenic properties of the cell wall occurs during spore formation. A quantitative gonadal index was developed for oysters using polyclonal antibodies from eggs and sperm. The quantity of eggs or sperm was measured using ELISA and a quantitative gonadal-somatic index (dry wt of egg or sperm-dry wt oyster^-1(GSI) was calculated. Maximum GSI observed during the study was 0.422 for female oysters and 0.446 for male oysters. Female oysters produce 3.7 to 65.4 million eggs, with an average of 21.1 million during each spawning. A positive correlation was observed between the number of eggs produced and oyster size; the number of eggs in the gonad increased as oyster size (i.e. total dry wt) increased (r^2=0.67). However the relationship was nonlinear; large oysters produce proportionally fewer eggs per biomass. Prevalence of Perkinsus marinus parasitism was high, 90 to 100%, during the study, as was weighted incidence, 1.33 to 2.67. No statistically significant correlation was observed between infection intensity and the percent weight of oyster eggs or egg number. |
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