Abstract

Plasma corticosterone (B) and free thyroxine (fT4) concentrations were assessed in frozen (-80°C) archived samples from leatherback (Dermochelys coriacea) and Kemp’s ridley turtles (Lepidochelys kempii). Samples were obtained from leatherbacks that were entangled in fishing gear (n=8) or captured directly as part of an ecology and health study (n=10); and from Kemp’s ridleys hospitalized after natural cold-stunning events (n=87 samples, 57 turtles). Corticosterone was measured using a double-antibody 125-I radioimmunoassay kit, and fT4 with a coated-tube 125-I radioimmunoassay kit (MP Biomedicals, Orangeburg, NY). Parallelism and accuracy validation were successful. Entangled leatherbacks had higher B and fT4 than directly captured leatherbacks (entangled: B=10.2±6.6 ng/ml, fT4=1.67±0.68 pg/ml; captured: B=4.7±2.5 ng/ml, fT4=0.10±0.10 pg/ml; p=0.045 for B, p=0.01 for fT4, t-tests). Kemp’s ridleys sampled within 3 days of admission tended to have high B and low fT4, with no significant difference between turtles that survived vs. those that died (survived, B=38.53±3.95 ng/ml, fT4=0.10±0.05 pg/ml; died, B=39.95±3.19 pg/ml, fT4=0.09±0.21 pg/ml; p>0.05, t-tests). After 3 weeks of convalescence, Kemp’s ridleys showed a decrease in B and increase in fT4 (B=0.81±0.19 ng/ml; fT4=1.30±0.34 pg/ml; p<0.01, t-tests). These data provide insight into the endocrine responses of sea turtles to a variety of stressors and may be clinically useful for monitoring the convalescence of hospitalized sea turtles (data shown=mean±SEM).

Acknowledgments

This work was funded by the Marine Conservation Action Fund of the New England Aquarium (NEA). Sea turtle rehabilitation at NEA is authorized by the United States Department of the Interior, National Marine Fisheries Service, United States Fish and Wildlife Service, and Massachusetts Division of Fish and Wildlife. We thank the many staff and volunteers of the Massachusetts Audubon Society and NEA for their contributions to the recovery and rehabilitation of the Kemp’s ridley turtles described herein. Leatherback samples were collected with permission of the National Marine Fisheries Service, Endangered Species Act Section 10 Permit #1557-03, and funded by National Oceanic and Atmospheric Administration Grant #NA04NMF4550391, and National Fish and Wildlife Foundation Grant# 2008-0076-000 to Molly Lutcavage, University of New Hampshire; National Fish and Wildlife Foundation Grant#2003-0206-014, and National Oceanic and Atmospheric Administration contract order #EM113F08SE3672 to Connie Merigo, NEA. Additional leatherback funding was provided by the Cape Cod Commercial Hook Fishermen’s Association. The authors thank Kara and Mike Dodge, Connie Merigo, George Purmont, Mark Leach, Molly Lutcavage, Brian Sharp, and Scott Landry for their important roles in acquisition of leatherback samples, and Katie O’Reilly at the University of Portland for valuable laboratory assistance.