Determination of Select Plasma Vitamin Concentrations and Bone Density in Wild-Caught Bullfrogs (Lithobates catesbeianus)
Six wild-caught bullfrogs (Lithobates catesbeianus) were evaluated for captivity effects, using a repeated measures design, on select serum vitamin concentrations and bone mineral density. Frogs were captured from a local pond in June and blood was collected for determination of serum vitamin A and D3 concentrations. In addition, bone density was evaluated through radiographs, and bone mineral density (BMD) was determined using a bone densitometer. All frogs had passive integrated transponder (PIT) tags placed in the coelomic cavity for identification and then released back into the same pond. The same frogs were captured in September and all the above data were again collected on each frog. At this time all frogs were retained in captivity under current Zoo Atlanta husbandry protocols for the species. Frogs were evaluated as above every 3 months to monitor captive effects on vitamin concentrations and BMD. Wild frogs were captured during the active season, starting at T3, for comparison to captive animals. Bone mineral density (g/cm2) at time zero (T0) was as follows: spine (mean 0.17; range 0.01–0.23; standard deviation 0.05), right and left femurs (0.13; 0.10–0.16; 0.02) and right and left tibias (0.18; 0.14–0.21; 0.03). The mean change in BMD from T0 to T1 (3 months in captivity) was as follows: spine - 1.63%; femurs + 0.39%; tibias + 2.9% and from T0 to T2 (6 months in captivity) was: spine - 12.84% (significant); femurs -2.09% and tibias - 4.63%. Wild frogs had greater BMD compared to captive frogs at T3 (late April): spine (wild 0.19, captive 0.14, % difference +26.3); femurs (0.15, 0.13, +13.3); tibias (0.21, 0.17, +19.0).
Similar data for serum concentrations of vitamin A and vitamin D3 were collected. Serum vitamin D3 (nmol/L) and vitamin A (ng/ml) concentrations (mean and range) respectively, for late spring and early summer, (T0) from wild-caught frogs were 33.2 (13–59) and 483.7 (364–623) and for late summer wild-caught frogs (T1) values were 27 (11–50) and 16.8 (5–33). Wild-caught frogs sampled at (T3) had serum values of 50 and 114, respectively. Captive frog values for 3 months in captivity (T2) were 12.2 (7–18) and 202 (111–272) and for 6 months in captivity (T3) were 21 (17–32) and 78.2 (49–111). Final interpretation of the data will be performed after statistical analysis is complete at the end of the 12-month study.