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

Incubation temperature influences embryonic development and the morphology of resultant hatchlings in many species of turtle but few studies have addr essed its effect on oxygen consumption and total embryonic energy expenditu re. Eggs of the Australian broad-shelled river turtle, Chelodina expansa, w ere incubated at constant temperatures of 24 degrees C and 28 degrees C to determine the effect of temperature on oxygen consumption, embryonic energy expenditure and hatchling morphology. All embryos at both incubation tempe ratures experienced a period of developmental diapause immediately after ov iposition. Once this initial diapause was broken, embryos underwent a furth er period of developmental arrest when the embryo was still very small and had minimal oxygen consumption (<20 mu L h(-1)). However, once rapid embryo nic growth started, development appeared to be continuous. Rate of increase and peak rate of oxygen consumption were temperature dependent, both being highest at 28 degrees C. Net production efficiency (total oxygen consumed during incubation divided by yolk-free hatchling mass) was 120 mL O-2 g(-1) at 24 degrees C and 111 mL O-2 g(-1) at 28 degrees C. Hatchling mass and y olk-free hatchling mass were independent of incubation temperature, but hat chlings from 28 degrees C had larger residual yolks and smaller head widths than hatchlings from 24 degrees C.