Serum α- and γ-tocopherols, retinol, retinyl palmitate, and carotenoid concentrations in captive and free-ranging bottlenose dolphins (Tursiops truncatus)

Concentrations of retinol, retinyl palmitate, β-carotene, α-carotene, cryptoxanthin, lutein, lycopene, α-tocopherol, and γ-tocopherol were measured in blood samples collected from 15 captive and 55 free-ranging bottlenose dolphins (Tursiops truncatus). From June 1991 to June 1994, blood samples were collected from captive animals residing at two locations; at Seven Seas (Brookfield Zoo, Brookfield, IL) and Hawk’s Cay (Marathon Key, FL). Blood samples were collected from free-ranging animals from June 1991 to June 1996. Retinol levels were not significantly different between captive dolphin groups. However, Seven Seas animals had higher (P<0.01) serum retinol concentrations compared to free-ranging animals (0.061 vs 0.041 μg/ml). Retinyl palmitate was not detected in the serum of captive or free-ranging dolphins. Alpha-tocopherol levels were significantly (P<0.05) higher for Seven Seas dolphins (16.4 μg/ml) than for Hawk’s Cay (13.0 μg/ml) and free-ranging dolphins (12.5 μg/ml). Gamma-tocopherol concentrations were similar among captive and free-ranging dolphins. Free-ranging dolphins showed levels of circulating carotenoids (lutein and β-carotene) while the captive animals did not. Additional carotenoids (lycopene, α-carotene and cryptoxanthin) were analyzed but not detected in any samples. Serum vitamin differences between captive and free-ranging dolphins may reflect the natural diet or indicate some potential biological or nutritional status significance.