Incubation of eggs of the Australian broad-shelled turtle, Chelodina expansa (Testudinata : Chelidae), at different temperatures: effects on pattern of oxygen consumption and hatchling morphology

Abstract

Incubation temperature influences embryonic development and the morphology of resultant hatchlings in many species of turtle but few studies have addressed its effect on oxygen consumption and total embryonic energy expenditure. Eggs of the Australian broad-shelled river turtle, Chelodina expansa, were incubated at constant temperatures of 24˚C and 28˚C to determine the effect of temperature on oxygen consumption, embryonic energy expenditure and hatchling morphology. All embryos at both incubation temperatures experienced a period of developmental diapause immediately after oviposition. Once this initial diapause was broken, embryos underwent a further period of developmental arrest when the embryo was still very small and had minimal oxygen consumption (<20 µL h^–1). However, once rapid embryonic growth started, development appeared to be continuous. Rate of increase and peak rate of oxygen consumption were temperature dependent, both being highest at 28˚C. Net production efficiency (total oxygen consumed during incubation divided by yolk-free hatchling mass) was 120 mL O₂ g^–1 at 24˚C and 111 mL O₂g^–1 at 28˚C. Hatchling mass and yolk-free hatchling mass were independent of incubation temperature, but hatchlings from 28˚C had larger residual yolks and smaller head widths than hatchlings from 24˚C.