Further characterization of adrenocortical and thyroid hormone concentrations of leatherback turtles (Dermochelys coriacea) under various stressors, including validation of a plasma aldosterone assay.

Abstract

Leatherback turtles (Dermochelys coriacea) are endangered by anthropogenic threats. Characterizing the physiologic response of leatherback turtles under various stressors may inform conservation strategies. In this study, a commercially available enzyme immunoassay for aldosterone was validated for leatherback turtle plasma, and it was used with previously validated assays for corticosterone and free thyroxine (fT4) to evaluate the physiologic status of leatherback turtles that were entangled in fishing gear, stranded on shore, nesting or intentionally captured at sea during ecologic studies. Mean aldosterone concentrations were significantly higher in entangled turtles (156 ± 102 pg/ml), stranded turtles (274 ± 165 pg/ml) and intentionally captured turtles (457 ± 464 pg/ml) than in nesting females (23 ± 16 pg/ml). In contrast, nesting females had higher fT4 (2.9 ± 0.6 pg/ml) compared to entangled turtles (0.8 ± 0.9 pg/ml), stranded turtles (0.7 ± 0.8 pg/ml) and intentionally captured turtles (0.3 ± 0.2 pg/ml). Corticosterone concentrations were significantly higher in stranded individuals (10.9 ± 6.6 ng/ml) compared with nesting (3.8 ± 2.0 ng/ml) and intentionally captured turtles (3.6 ± 2.5 ng/ml), with intermediate levels in entangled turtles (5.1 ± 2.8 ng/ml). This study provides additional insight into the variable physiologic status of leatherback turtles under the influence of different anthropogenic and natural stressors, and it provides an additional tool to evaluate the role of aldosterone in the acute stress response and health of endangered sea turtle species.