Insects are known to be poor sources of preformed vitamin A, leading to the speculation that insectivorous species, including reptiles, may be able to convert carotenoid precursors to meet dietary requirements for this nutrient. This study was conducted to indirectly evaluate carotenoid and vitamin A metabolism in the panther chameleon (Furcifer pardalis). Eggs were obtained from females in Madagascar that were yolked either early or later in the breeding season, and carotenoid (α-and β-carotene, cryptoxanthin, lutein/zeaxanthin, and lycopene), vitamin A, and vitamin E concentrations were measured in egg contents in early, middle, or late embryonic development. An overall trend of decreased nutrient concentration as eggs matured (from egg period 1 (yolks) to egg period 3 (embryos)) was seen within both clutch groups. The season of clutch deposition was a significant influence on egg weight, α-carotene, and lutein/zeaxanthin concentrations, but on no other nutrients. Chameleon yolks contained considerably higher levels of carotenoids than levels previously reported from two viviparous lizard species, and β-carotene concentrations were of the same magnitude as reported in grazing tortoises. β-Carotene and β-cryptoxanthin were the predominant carotenoids in yolk and embryos, comprising about 95% of total carotenoids detected. Measurable concentrations of retinol at all stages of egg development in the chameleons suggests effective conversion from carotenoid precursors, with concentrations similar to those measured in other lizard eggs. Information from eggs obtained in native habitats may provide baseline data on nutrient interactions to improve and optimize captive dietary management; preliminary data suggest that micronutrient environments may vary over the protracted breeding season, with possible implications for embryo health and survival. Zoo Biol 21: 295-303, 2002.

ABSTRACT. Several disease syndromes in captive rhinoceroses have been linked to low vitamin status. Blood samples from captive and free-ranging black (Diceros bicornis) and white rhinoceros (Ceratotherium simum) and tissue samples of captive individuals from four rhinoceros species were analysed for vitamins A and E. Circulating vitamin A levels measured as retinol for freeranging versus captive black and white rhinoceros were 0.04 (Ϯ0.03 SD) vs. 0.08 (Ϯ0.08) and 0.07 (Ϯ0.04) vs. 0.06 (Ϯ0.02) g/ml, respectively. Circulating vitamin E levels measured as ␣-tocopherol were 0.58 (Ϯ0.30) vs. 0.84 (Ϯ0.96) and 0.62 (Ϯ0.48) vs. 0.77 (Ϯ0.32) g/ml, respectively. In contrast to earlier findings, there was no significant difference in vitamin E concentration between captive and free-ranging black rhinoceros. When the samples of captive black rhinoceros were grouped into those taken before 1990 and after 1990, however, those collected before 1990 had significantly lower (P Ͻ 0.001) vitamin E levels (0.46 Ϯ 0.83 g/ml) and those collected in 1990 or later significantly higher (P Ͻ 0.001) vitamin E levels (1.03 Ϯ 1.04 g/ml) than the captive population as a whole. This is probably due to increased dietary supplementation. There were significant differences in circulating vitamin concentrations in black rhinoceroses from different regions in the wild. Serum 25-hydroxy (OH) vitamin D 3 averaged 55.7 ng/ml in freeranging rhinoceroses; no carotenoids were detected in any blood samples. Captive black and white rhinoceroses appear to be adequately supplemented in vitamin A and E. Captive Indian rhinoceroses (Rhinoceros unicornis) had significantly lower vitamin A concentrations in blood (P Ͻ 0.001) and higher vitamin A concentrations in liver tissue samples (P Ͻ 0.001) than other rhinoceros species. Equine requirements are not recommended as a model for rhinoceros vitamin requirements.

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