Pablo Piña-Valdez

Gender Differences and Short-Term Exposure to Mechanical, Thermic, and Mechanical—Thermic Stress Conditions on Hemocyte Functional Characteristics and Hsp70 Gene Expression in Oyster Crassostrea corteziensis (Hertlein, 1951)

ABSTRACT On sea farms, oysters are constantly submitted to mechanical manipulation through size sorting and cleaning of epibionts, and also are maintained out of seawater and exposed to air and sunlight radiation during cleaning and transport to marketplaces. Therefore, the aim of this work was to evaluate gender differences and short-term changes in the immune response, glucose plasma levels, and Hsp70 gene expression in oyster Crassostrea corteziensis exposed for 0 (control), 15, 30, 45, and 60 min to mechanical (agitated), thermic (sunlight), and a combination of both stressors. Variations in total hemocyte count (THC) and granulocyte count (GC), as well in functional characteristics [i.e., mortality of hemocytes, phagocytosis, and anion superoxide production (SOA)] of hemocytes, suggest that oysters seems well adapted to mechanical disturbance, because SOA values increased, phagocytic activity was not affected, and hemocyte counts and mortality were rapidly recovered. Contrary with prolonged exposure of oysters to thermic conditions, which exerted a constantly increase of THC, whereas both hemocyte mortality and phagocytic activity decreased, but oxidative capacity (i.e., SOA) decreased in male and increased in female oysters. Immune competence and Hsp70 gene expression were significantly diminished in oysters exposed for 30 min to a combination of both stressors (i.e., mechanical and thermic), indicating the most vulnerable stress conditions. Hsp70 gene expression showed that females were more susceptible than male oyster to short-term (i.e., 15–30 min) exposure to mechanical and thermic stresses, but prolonged (i.e., 60 min) exposure of combined stressors exerted a particular effect on male oysters. The immune responses assessed and glucose levels in plasma demonstrated that thermic and mechanical—thermic stress conditions were more stressful than mechanical disruption, and that females were more susceptible than male oysters to stress conditions assayed. These environmental and anthropogenic stressors should be considered for the cultivation of this oyster species, as well for further research related with immune response of C. corteziensis.