Meeting Abstract

P3.119  Jan. 6  Fasting increases ¹⁵N/¹⁴N ratios in the uric acid of Anolis carolinensis and Uta Stansburiana CASTILLO, L.P.**; HATCH, K.A.; Brigham Young University, Provo, UT; Brigham Young University, Provo, UT lp_lalis@hotmail.com

It has been suggested that the metabolic state (catabolic or anabolic) can be determined from the ¹⁵N/¹⁴N ratios of an animal�s tissues. In theory, ¹⁵N will be retained by the tissues preferentially and ¹⁴N preferentially excreted. Over time, this should cause an enrichment in the ¹⁵N/¹⁴N ratios of the tissues. However, tests of this assumption have met with mixed results. To date, these studies have focused on endotherms. No studies have considered the effects of fasting on the ¹⁵N/¹⁴N ratios of substrates from fasted ectotherms. We hypothesized that ¹⁵N/¹⁴N ratios of the uric acid of fasted lizards would increase over time, while that of the fed lizards would remain the same. We fasted 5 sideblotched lizards (Uta stansburiana) and 5 green anoles (Anolis carolinensis) for 14 days. At the same time we fed 6 sideblotched and 4 green anoles ad libitum. All lizards were given water ad libitum. During this period, we collected uric acid from each lizard daily and tail tissue one day prior to the study and one day after. We collected dietary samples every other day, beginning on the same day as the fasting. We found the ¹⁵N/¹⁴N ratios of uric acid at the end of the study were ¹⁵N enriched by 2.1 � compared to that of the controlled lizards for both species; however, we found no difference between treatment and controls in the ¹⁵N/¹⁴N of the tails. We also found sideblotched lizards to be slightly, but significantly enriched (0.3 �) compared to anoles.