Evaporative Water Loss from Three South-Eastern Australian Species of Water Turtle.

Abstract

In the chelid turtles Chelodina expansa, C. longicollis and Emydura macquarii, over the temperature range 8-34°C and humidity range 25-60% RH, evaporative water loss (EWL; estimated as weight loss) corrected for differences in body weight was greatest in E. macquarii and least in C. longicollis. Interspecific differences were most pronounced at high temperature and low humidity, but may have been exaggerated by variations in experimental airflow. Under progressive dehydration, EWL declined by about 20% in C. expansa and E. macquarii and over 60% in C. longicollis. Cutaneous water loss greatly exceeded pulmonary loss in all three species, but made up the lowest percentage of total EWL in C. longicollis; dehydration further reduced the relative contribution of cutaneous loss in this species. C, longicollis also demonstrated an ability to take up free water via the cloaca. The water-conserving abilities of C. longicollis are ecologically advantageous, since it commonly migrates over land, occupies ephemeral bodies of water, and is capable of aestivation.