Allometric and ecological relationships of ventricle and liver mass in anuran amphibians

Abstract

1. There is an isometric relationship for allometry of ventricle mass (slope = 0.952) and liver mass (slope = 1.027) and phylogenetic correlations of ventricle and liver mass for museum specimens of 42 species of Australian frogs. 2. There was a strong relationship for ventricle mass with body mass, phylogeny and dehydration tolerance, but not habit, body shape or environmental variables. The relatively large ventricle of more dehydration-tolerant species may also be associated with a higher metabolic scope for activity. There was a strong relationship for liver mass with body mass, phylogeny, habit (burrowing, terrestrial, arboreal), body shape and some environmental variables, but not dehydration tolerance. For burrowing frogs, a relatively large liver is presumably important because it is an energy store during long periods of dormancy and is a source of amino acids for cocoon formation or urea synthesis. For arboreal frogs, a small liver might reduce the cost of transport by limiting body mass, and allow a more elongate shape. 3. Relative ventricle mass of museum specimens is representative of values for field-collected frogs. Relative liver mass is higher for museum specimens; this might be an artefact of museum preservation and/or reflect seasonal or geographic variation.