FORD, D.K.*; HOLLIDAY, C.M.; Ohio University, Athens, OH; Ohio University, Athens, OH: An investigation into the effects of PCB 126 on bone density in turtles

Bone is a metabolically active tissue functioning as a physiological mineral reservoir while also providing support and defense for the organism. However, the physical properties of skeletal tissues may be affected by environmentally available endocrine disrupting compounds (EDCs). PCB 126 is an EDC known to decrease bone density in laboratory rats. Forty-four, 8-month-old, male, Malaclemys terrapin (diamondback terrapin) individuals were either treated with PCB 126 or left untreated. Euthanized turtles were screened via X-ray film radiography and image analysis (ImageJ, v1.33) for gross contaminant effects. Based on grayscale pixel values, we observed significant differences in skull, carapacial, and appendicular relative bone density. A subset of heads was subsequently hi-res CT-scanned and voxels were analyzed as a proxy for relative bone density in Amira (v3.0) 3D imaging software. CT data confirmed grayscale density interpretations that PCB-exposed turtles had lower bone density, but these data also revealed density differences among specific head skeletal elements. In addition, general osteological features of the skulls, regardless of treatment, demonstrated that the epipterygoid, prootic, and facial skeleton were markedly denser than the other cranial regions. Ashed heads complemented the image data, showing a significant reduction in head organic content. Overall, turtles exposed to PCB 126 exhibited significantly reduced bone density. Though preliminary, these data suggest researchers should be wary of these emergent ecotoxicological effects because contamination-induced metabolic bone disease could affect interpretation of developmental stages, performance, and overall organismal fitness.