Exchanges of oxygen, carbon dioxide, nitrogen and water in the caecilian Dermophis mexicanus

Abstract

Oxygen consumption was measured in five Dermophis mexicanus and averaged (+/- SEM) 0.047 +/- 0.004 ml O2 g(-1) x h(-1). Carbon dioxide production averaged 0.053 +/- 0.005 ml CO2 g(-1) x h(-1) in the same five animals 1 week later. This metabolic rate is similar to metabolic rates of other Gymnophionans but lower than metabolic rates reported for Anurans and Urodeles. Total nitrogen excretion averaged 1.37 micromol N g(-1) x h(-1) which is higher than that found for other amphibians. Of this, 82.5% (1.13 micromol N g(-1) x h(-1)) was in the form of urea while 17.5% (0.24 micromol N g(-1) h(-1)) was in the form of NH3 + NH4+. Such ureotelism is typical of terrestrial amphibians like D. mexicanus. Osmotic water flux averaged 0.0193 ml g(-1) x h(-1) in control (sham injected) animals and was not significantly altered by injection of either arginine vasotocin or mesotocin. This osmotic flux is similar to osmotic fluxes found for other terrestrial amphibians. The combined data suggest that metabolism in D. mexicanus is, like most other Gymnophionans, lower than other amphibians. The high rates of nitrogen (especially urea) excretion suggests that this fossorial animal accumulates urea like other burrowing amphibians.