Abstract

In captivity some anurans can show poor growth and skeletal development due to inadequate levels of UV-B radiation. From metamorphosis for 84 days the growth and skeletal development of Amazonian milk frogs (Trachycephalus resinifictrix) were assessed between treatments receiving daily UV-B (UV/daily), intense UV-B for 30 min every two weeks (UV/boost), or no UV-B (control). At 14 day intervals snout-urostyle length, weight, and X-ray images were taken. At day 84 five morphometric skeletal variables were measured and compared for absolute values and isometry. At day 42 and 84, X-ray images were compared for maximum opacity. At day 84 the UV/daily treatment showed greater snout-urostyle length, weight, condition index, vertebrae length, head width, and femur length than the other two treatments. The head width:snout-urostyle length ratio was greater in the control than in the UV/daily treatment. Calcification did not vary between treatments at day 84. Skeletal development in the control showed symmorphic growth of increased head width: head length ratio. The UV-B treatment showed preferential allometric skeletal development of components that increased mobility and feeding ability including head width, and vertebrae and femur length. Overall, these results show that in T. resinifictrix; (1) the provision of daily UV-B improved growth and skeletal development, (2) allometric skeletal development occurs during healthy juvenile growth, (3) symmorphic skeletal development occurs under conditions of poor growth, and (4) the provision of UV-B may be necessary in both research of the development of some amphibians and in conservation breeding programs or other husbandry.

Key words: Skeletal development, UV-B, anuran, growth, conservation.