Organ Weights and Growth Profiles in Bottlenose Dolphins (<I>Tursiops truncatus</I>) from the Northwestern Gulf of Mexico

Abstract

Systematic necropsies were performed on 63 bottlenose dolphins (Tursiops truncatus), and data on organ mass, standard body length (SBL), body mass (BM), gender, sexual maturity, and age were measured and/or estimated. Animals were extremely fresh and recovered from along the Texas and Louisiana coastline in the northwestern Gulf of Mexico. Organ reference tables were established for this species to facilitate comparisons with other bottlenose dolphins and to provide a baseline for other cetacean species. Organs examined included lungs, adrenal glands, kidneys, testes, ovaries, heart, liver, pancreas, brain, pituitary, thyroid, thymus, and spleen. Individuals were separated into three size classes: 225 cm, based on SBL to further facilitate comparisons. Growth rates of length and mass were described using Gompertz nonlinear models as a function of gender. No sexual dimorphism was identified in BM or organ weights, and SBL was only significantly larger for older mature males. SBL and BM were strongly correlated with age when all animals were included in analyses, although this is not an accurate predictor of age, especially in older individuals. Organ weights were significantly correlated with both SBL (except thymus and spleen) and BM (except left ovary, spleen, and thymus). Age was significantly correlated with all organ weights (except thymus, thyroid, and ovaries). There were no significant differences in the weight of any paired organs (adrenal glands, kidneys, lungs, ovaries, testes), and all were significantly correlated with BM. These data on organ weights of bottlenose dolphins, when interpreted with SBL, BM, and age, are significant tools for pathologists and veterinarians interpreting animal health status.