Skeletochronology Validation from an Adult Loggerhead (Caretta caretta)
Skeletochronology of sea turtle humeral bones has been validated only for juvenile Caretta caretta. Our recovery of a sea turtle marked with oxytetracycline (OTC) and at large for eight years shows that annual growth marks continue to be deposited in adult C. caretta. In addition, the presence of a fluorescent mark eight years after injection shows that OTC can be used in long-term growth studies. Growth and OTC marks are not equally distinguishable around the entire edge of the humerus making the location of bone biopsies critical for determining growth and OTC marks. Although bone biopsy sections may be used with OTC to count growth marks, they cannot be used to measure radial growth or to make back calculations of age. Instead, whole humeral sections must be used.Abstract
(A) Magnified white light (visible) image of a 8-year post-OTC-injected loggerhead sea turtle humerus (Flipper tags: PPX 742, PPX 744; the tetracycline mark is not visible in this image). The number of growth marks both external and internal to the tetracycline mark can easily be counted. Note that the marks become compressed and less distinct on both the dorsal (left) and ventral (right) surfaces. (B) Traces of growth (solid lines) and tetracycline (dotted line) marks of the loggerhead sea turtle humerus at the same magnification as A. (C) Ultraviolet light lateral view of the cross-section of loggerhead sea turtle humerus (Flipper tags: PPX 742, PPX 744). The tetracycline mark is easily identifiable on the lateral edges of the bone but less so on the dorsal and ventral surfaces