Journal
PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY
Volume 90, Issue 1, Pages 34-46Publisher
UNIV CHICAGO PRESS
DOI: 10.1086/689744
Keywords
triiodothyronine; T-3; synchronous hatching; environmentally cued hatching; phenotypic plasticity; embryogenesis; egg
Categories
Funding
- University of Western Sydney (UWS) School of Science and Health equipment fund grant
Ask authors/readers for more resources
Metabolic processes are affected by both temperature and thyroid hormones in ectothermic vertebrates. Temperature is the major determinant of incubation length in oviparous vertebrates, but turtles can also alter developmental rate independent of temperature. Temperature gradients within natural nests cause different developmental rates of turtle embryos within nests. Despite temperature-induced reductions in developmental rate, cooler-incubated neonates often hatch synchronously with warmer siblings via metabolic compensation. The physiological mechanisms underlying metabolic compensation are unknown, but thyroid hormones may play a critical role. We applied excess triiodothyronine (T-3) to developing eggs of Murray River short-necked turtle (Emydura macquarii)-a species that exhibits metabolic compensation and synchronous hatching-to determine whether T-3 influences developmental rate and whether changes to incubation period incur metabolic costs. We measured heart rate, oxygen consumption and incubation period of eggs, and morphology and performance of hatchlings. Embryos that were exposed to T-3 pipped up to 3.5 d earlier than untreated controls, despite no change in total metabolic expenditure, and there were no treatment differences in hatchling morphology. Hatchlings treated with T-3 demonstrated similar righting ability to hatchlings from the control groups. Exposure to T-3 shortens incubation length by accelerating embryonic development but without statistically increasing embryonic metabolism. Thus, T-3 is a mechanism that cooler-incubated reptiles could use to accelerate their development to allow synchronous hatching with their warmer clutch mates but at little or no metabolic cost. Thus, metabolic compensation for synchronous hatching may not be metabolically expensive if T-3 is the underlying mechanism.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available