조석에 따른 열스트레스와 노출이 대서양산굴, Crassostrea virginica의 생존과 생리적 반응에 미치는 영향

Abstract

Environmental condition is a significant determinant of oyster survival. Few studies have examined the effects of sublethal heat shock and air exposure on progression of “Dermo” disease caused by the parasite, Perkinsus marinus (Dermo), on survival and physiological condition of the oysters, Crassostrea virginica. Oysters (n=180) were acclimated to experimental conditions for a week, and then their condition, survival and the progression of Dermo infection were assessed under different environmental conditions. There were four treatment groups: sublethal heat shock aerial exposure (HS+AE) and non-aerial exposure (HS-AE), non-sublethal heat shock aerial exposure (-HS+AE) and non-aerial exposure (-HS-AE). There were three replicate tanks (n=15 oysters/replicate tank) in each treatment group. Oysters were heat shocked at 40ºC for 1 h in a heated water bath, and then held in each replicate tank separated by plastic mesh. Percent survival rate was determined by direct counting of live and dead oysters in each tank. Condition index (CI) was determined as a ratio between tissue dry weight and shell dry weight. Fifteen oysters were also analyzed for prevalence and intensity of Dermo infection and expressed as total body burden analysis.The highest survival was recorded in the HS+AE treatment group and the lowest in the -HS-AE treatment, suggesting that sublethal heat shock and air exposure improve oyster survival. The CI of the -HS+AE treatment group was significantly lower than the initital CI. Dermo intensities in the aerial exposure treatments (HS+AE and -HS+AE) did not change significantly from the initial. Infection intensities in the non-aerial exposure (HS-AE and -HS-AE) group, however, significantly increased over time. Our results imply that air exposure (i.e. intertidal cultivation) may have the potential to reduce disease pressure from Dermo infection and enhance survival of C. virginica.