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

D.A. Crain·A.B. Bolten·K.A. Bjorndal·L. J. Guillette·T. S. Gross
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Abstract

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.

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D.A. Crain, A.B. Bolten, K.A. Bjorndal, L. J. Guillette, T. S. Gross. 1995. Size-dependent, sex-dependent and seasonal changes in insulin-lige growth-factor-I in the loggerhead sea turtle. https://doi.org/10.1006/gcen.1995.1063

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