Validation of annual skeletal marks in green sea turtles chelonia mydas using tetracycline labeling

Abstract

The technique of skeletochronology has been widely applied to age and growth studies of most species of sea turtles, although direct validation of annual growth marks has only been demonstrated for loggerheads Caretta caretta and Kemp's ridleys Lepidochelys kempii. In this study we present validation of annual growth mark deposition in green sea turtles Chelonia mydas. Fourteen green sea turtles, previously captured in nearshore waters in the main Hawaiian Islands and injected with oxytetracycline (OTC), were recovered stranded, and the humeri were prepared for skeletochronological analysis. Each sea turtle had received a single dose of 25 mg kg-1 OTC, with half injected into each pectoral muscle. Seven of these sea turtles either were not at large long enough or did not grow enough for either the OTC mark to be discernable in bone cross-sections or for a growth mark to have been deposited after the OTC mark. Based on the hypothesis of one mark per year, the expected number of growth marks was visible exterior to the OTC mark in the humeri of the 7 remaining sea turtles, providing strong validation that growth marks are annual. These results support the use of skeletochronology for age and growth rate estimates in green sea turtles and the need for validation to ensure accurate interpretation of growth marks. & copy Inter-Research 2011.