The Uses of Anaerobiosis by Amphibians and Reptiles

Abstract

Amphibians and reptiles rely upon anaerobic glycolysis to support their energetic requirements under a variety of circumstances. Although adult frogs derive most of the energy for muscle contraction during intense, short-term locomotion from glycolysis, anuran tadpoles have a very low rate of lactate formation during 30 sec of burst swimming; instead, they rely largely on the use of phosphocreatine stores. Among squamate reptiles, the rate of lactate formation during vigorous exercise is largely related to the duration of activity and to body temperature. Recent studies have shown that fossorial, limbless reptiles do not differ from surface-dwelling, quadrupedal species in the rate of glycolysis during intense activity. The energetics of locomotion differs significantly between swimming and running turtles; thus the site of activity influences the role of anaerobiosis in movement. Lactate levels increase in some frogs during calling and nest building and in some reptiles during prey capture and ingestion. However, voluntary locomotion and diving by reptiles are rarelyaccompanied by an increase in lactate levels. Freshwater turtles rely heavily on glycolysis during aquatic hibernation. Thus, it can be concluded that amphibians and reptiles derive a significant proportion of their energetic requirements from anaerobic metabolism only under selected circumstances when the benefits outweigh the costs associated with the accumulation of lactate.