Fle. Chu et Jf. Lapeyre, PERKINSUS-MARINUS SUSCEPTIBILITY AND DEFENSE-RELATED ACTIVITIES IN EASTERN OYSTERS CRASSOSTREA-VIRGINICA - TEMPERATURE EFFECTS, Diseases of aquatic organisms, 16(3), 1993, pp. 223-234
The relationship of potential defense-related cellular and humoral act
ivities and the susceptibility of eastern oysters Crassostrea virginic
a to the parasite Perkinsus marinus were examined at 10, 15, 20 and 25
-degrees-C. Oysters were acclimated at experimental temperatures for 2
0 d and then challenged with P. marinus. Total hemocyte counts (TC) an
d percentage of granulocytes (PG) 20 d after temperature acclimation w
ere higher in oysters dt high than at low acclimation temperature. Hig
her protein (P) and lysozyme (L) concentrations were found in oysters
at 10 and 15-degrees-C. No significant differences in hemagglutination
(H) titers due to temperature acclimation were observed. Infection pr
evalence 46 d after challenge by P marinus was 100, 91, 46 and 23% res
pectively, for oysters at 25, 20, 15 and 10-degrees-C. Disease intensi
ty increased with temperature. OysterS dt higher temperatures had grea
ter PG and TC and hemocyte phagocytic activity. No difference was foun
d in TC and PG between control and challenged oysters within each temp
erature treatment. Bleeding may to some extent reduce TC and PG in oys
ters. P did not vary much among temperatures. No reduction of P in oys
ters was found due to P. marinus challenge and infection. L tended to
be higher in oysters at lower than at higher treatment temperatures. T
he oysters at 10-degrees-C had the highest L concentration and lowest
P. marinus infection. But, it is not known whether the high extracellu
lar L in oysters at 10-degrees-C is attributable to the low P marinus
susceptibility in these oysters. There was no significant difference i
n condition index (CI) between control and challenged oysters and betw
een infected and uninfected oysters. However, CI decreased with increa
sing temperatures. The H titers were not associated with any measured
variables. The greater TC, PG, and phagocytic capability in oysters at
higher temperatures did not result in fewer or less intense P. marinu
s infections.