Modulation of the adrenocortical stress response in marine turtles (Cheloniidae): evidence for a hormonal tactic maximizing maternal reproductive investment
Ts. Jessop, Modulation of the adrenocortical stress response in marine turtles (Cheloniidae): evidence for a hormonal tactic maximizing maternal reproductive investment, J ZOOL, 254, 2001, pp. 57-65
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.