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Size-dependent, sex-dependent and seasonal changes in insulin-lige growth-factor-I in the loggerhead sea turtle

January 1, 1995

This study examines size-dependent, sex-dependent, and seasonal fluctuations in plasma insulin-like growth factor-I (IGF-I) concentrations in loggerhead sea turtles (Caretta caretta). Loggerhead turtles (n = 158) were captured in shrimp trawler nets during a 12-month survey in Cape Canaveral Channel, Florida. Plasma samples were analyzed using a validated heterologous radioimmunoassay. Large turtles (>75 cm straight-line carapace length) had significantly higher plasma IGF-I concentrations than small turtles (⩽75 cm; P < 0.0001). Plasma IGF-I concentrations did not vary seasonally in small turtles, but large turtles had significantly higher plasma IGF-I concentrations during the spring and summer months (P < 0.005). Within the large turtles, adult males had significantly lower IGF-I concentrations than females and subadult males (P < 0.05). These results and a review of loggerhead turtle natural history suggest that the seasonal fluctuations in plasma IGF-I of adult turtles are due to elevated IGF-I levels in reproductively active female turtles. Further research is needed to examine correlations between reproductive activities and plasma IGF-I concentrations in reptiles.

Citation Information

Publication Year 1995
Title Size-dependent, sex-dependent and seasonal changes in insulin-lige growth-factor-I in the loggerhead sea turtle
DOI 10.1006/gcen.1995.1063
Authors D.A. Crain, A.B. Bolten, K.A. Bjorndal, L.J. Guillette, T. S. Gross
Publication Type Article
Publication Subtype Journal Article
Series Title General and Comparative Endocrinology
Series Number
Index ID 1008420
Record Source USGS Publications Warehouse
USGS Organization Florida Integrated Science Center