Sierra Nevada Aquatic Research Laboratory

01 Jul, 05 AM - 12 Jul, 05 AM

Research Project at SNARL: The purpose of this portion of my dissertation work dealing with montane amphibians is to )identify existing populations in the southeastern sierra nevada range, 2) monitor basic environmental parameters (water temperature, pH, animal internal body temperature), 3)obtain amphibian blood samples and 4) collect a small number of frogs from areas of elevation in the Sierra Nevada. I will be collecting small blood samples from up to 50 individuals (<750 microliters per animal) via the facial artery, and collecting up to 30 individuals for shipment back to our laboratory at CU Boulder. No more than 5 adults will be removed from any one location in order to minimize impact on a breeding population. Blood samples will be fixed for later laboratory analysis for blood lactate, glucose, G6P, insulin and glucagon. Additionally, blood samples will be screened for parasite load. Animals shipped back to CU will be sacrificed and muscle glycogen, glycogen phosphorylase/synthase levels will be determined. FULL PROJECT: The purpose of this study is to elucidate mechanisms by which cold tolerant amphibians, such as those native to montane Colorado and California habitats, control metabolism when faced with drastic fluctuation in temperature both daily and seasonally. Most amphibians are thought to conserve metabolic resources over the winter through cessation of activity. However, evidence from field studies indicates that some amphibians are able to remain active at winter temperatures as low as 0.5? C (Cunjack 1986), and must breed and feed in summer in spite of daily temperature fluctuations of up to 25? C (Carey 1979). These findings suggest specialized mechanisms by which cold tolerant frogs may fuel activity under extreme environmental conditions. It is known that many species of amphibian store fuel reserves during fall and early winter in the form of liver and muscle glycogen, as well as in lipid deposits (Farrar & Frye 1979, Donohoe et al 1998). However, it is poorly understood what cues, both endogenous and exogenous, result in mobilization versus sparing of these reserves. Circulating blood glucose, as well as the glycolysis precursors lactate and Glucose-6-Phosphate, are direct indicators of the animals’ ability to be active (Pinder et al 1992), and have been shown to vary with season and temperature in amphibians (Storey 1991, Bicego-Nahas et al 2001, Scapin & Giusseppi 1994). Taken collectively, these data paint an intriguing picture of a highly adaptive and specialized metabolic strategy employed by amphibians. However, key pathways and regulators enabling this strategy have yet to be defined. In order for these processes to be understood, analysis must be conducted on seasonal and temperature dependent utilization of carbohydrate stores (muscle and liver glycogen), metabolites that convert carbohydrate into usable energy or vice versa (Glucose-6-Phosphate, lactate, blood glucose), and on the hormones that modulate how quickly and efficiently these processes work (insulin and Glucagon). Regulation and overall concentrations of metabolites are essential for over-winter survival, as inefficiencies in carbohydrate expenditure will result in starvation during hibernation or insufficient energy stores for breeding upon emergence (Donahoe et al 1998). Therefore this study seeks to examine amphibian strategies for energy storage and expenditure based on temperature and season. This study will provide a unique examination of carbohydrate metabolism in species of frogs native to the Sierra Nevada and Colorado. Initial trials will be conducted utilizing summer frogs from both Colorado and California mountain habitats. By examining the season and temperature dependent metabolic strategies employed by cold (but not freeze) tolerant amphibians, new insight may be gained into the adaptive physiology of North American montane amphibians.

Visit #1370 @Sierra Nevada Aquatic Research Laboratory

Approved

Under Project # 1144 | Research

metabolism in montane amphibians

graduate_student - University of Colorado

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Ann Petersen Jul 1 - 12, 2003 (12 days)

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Dorm 1 Jul 1 - 12, 2003