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
Dt. Booth, 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, AUST J ZOOL, 48(4), 2000, pp. 369-378
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.