Thyroid Hormones Reduce Incubation Period without Developmental or Metabolic Costs in Murray River Short-Necked Turtles (Emydura macquarii)

被引:18
作者
McGlashan, Jessica K. [1 ]
Thompson, Michael B. [2 ]
Van Dyke, James U. [1 ]
Spencer, Ricky-John [1 ]
机构
[1] Univ Western Sydney, Sch Sci & Hlth, Locked Bag 1797, Penrith, NSW 2751, Australia
[2] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia
来源
PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY | 2017年 / 90卷 / 01期
关键词
triiodothyronine; T-3; synchronous hatching; environmentally cued hatching; phenotypic plasticity; embryogenesis; egg; TUATARA SPHENODON-PUNCTATUS; HATCHLING SNAPPING TURTLES; CHELYDRA-SERPENTINA; OXYGEN-CONSUMPTION; SEX DETERMINATION; BRAIN-DEVELOPMENT; HEART-RATE; COMPREHENSIVE KINETICS; TEMPERATURE INFLUENCES; EMBRYONIC-DEVELOPMENT;
D O I
10.1086/689744
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
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.
引用
收藏
页码:34 / 46
页数:13
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