Seasonal Changes in the Serum Testosterone Titers of Loggerhead Sea Turtles Captured Along the Atlantic Coast of the United States

Wibbels, Thane; Owens, David; Amoss, Max

Serum testosterone titers were recorded for loggerhead sea turtles, Caretta caretta, captured along the Atlantic coast of the United States. Immature females exhibited low testosterone titers throughout the year (<30.0 pg/mL). Immature males bad significantly higher titers than females, ranging from 76.4 pg/mL to 557.5 pg/mL. The mean monthly titers of immature males fluctuated significantly during the year with the highest mean value recorded during August and the lowest during March. Adult males exhibited a wide range of titers (80.0 to 24,275.7 pg/mL). During certain months, adult males showed a distinct dichotomy ill testosterone titers. These data suggest that some turtles were reproductively active and some were not. Our results suggest that reproductively active males appear to have high titers during February through April, followed by a significant decrease in titers during May. Adult female testosterone titers raised from <41.4 pg/mL to 1209.1 pg/mL. Females sampled on the nesting beach had higher titers than adult females captured in the water during the same months. The mean monthly testosterone titers of adult females captured ill the water changed significantly with time, increasing prior to the nesting season and then peaking during the middle of the nesting season. Our results are consistent with those recorded for captive green sea turtles. The possible roles of testosterone in specific reproductive events (I.e., migration, mating, and sperm and egg production) are discussed.