Modulation of the adrenocortical stress response in marine turtles (Cheloniidae): evidence for a hormonal tactic maximizing maternal reproductive investment

The relationships between reproductive condition, level of reproductive inv estment and adrenocortical modulation to capture stress in marine turtles f orm the basis of this study. When subjected to either capture or ecological stressors, nesting marine turtles have demonstrated adrenocortical respons es that are both small in magnitude, and slow in responsiveness. These obse rvations were further investigated to determine whether this minimal stress response was a physiological strategy to maximize reproductive investment in adult green Chelonia mydas and hawksbill Eretmochelys imbricata turtles. Female green and hawksbill turtles exhibited a decrease in adrenocortical responsiveness with progressive reproductive condition. Breeding turtles ex hibited most suppression of their adrenocortical response to capture compar ed to both non-breeding and pre-breeding female counterparts. Nesting green turtles maintained a suppressed adrenocortical response to capture through out the nesting season despite decreased reproductive investment. In contra st, male green and hawksbill turtles were less able to modulate their corti costerone (B) response to acute capture stress. During breeding, male turtl es possessed significantly greater adrenocortical responses to capture than females. These results could indicate that the large reproductive investme nt necessary for female marine turtle reproduction might underlie the marke d decrease in adrenocortical responsiveness. This hormonal mechanism could function as one strategy by which female marine turtles maximize their curr ent reproductive event, even though under certain situations this mechanism could entail costs to female survival.