Eme J, Mueller C A, Manzon R G, Somers C M, Boreham D R, Wilson J Y
Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S 4K1, Canada.
Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada.
Comp Biochem Physiol A Mol Integr Physiol. 2015 Jan;179:71-80. doi: 10.1016/j.cbpa.2014.09.005. Epub 2014 Sep 16.
Critical windows are periods of developmental susceptibility when the phenotype of an embryonic, juvenile or adult animal may be vulnerable to environmental fluctuations. Temperature has pervasive effects on poikilotherm physiology, and embryos are especially vulnerable to temperature shifts. To identify critical windows, we incubated whitefish embryos at control temperatures of 2°C, 5°C, or 8°C, and shifted treatments among temperatures at the end of gastrulation or organogenesis. Heart rate (fH) and oxygen consumption ( [Formula: see text] ) were measured across embryonic development, and [Formula: see text] was measured in 1-day old hatchlings. Thermal shifts, up or down, from initial incubation temperatures caused persistent changes in fH and [Formula: see text] compared to control embryos measured at the same temperature (2°C, 5°C, or 8°C). Most prominently, when embryos were measured at organogenesis, shifting incubation temperature after gastrulation significantly lowered [Formula: see text] or fH. Incubation at 2°C or 5°C through gastrulation significantly lowered [Formula: see text] (42% decrease) and fH (20% decrease) at 8°C, incubation at 2°C significantly lowered [Formula: see text] (40% decrease) and fH (30% decrease) at 5°C, and incubation at 5°C and 8°C significantly lowered [Formula: see text] at 2°C (27% decrease). Through the latter half of development, [Formula: see text] and fH in embryos were not different from control values for thermally shifted treatments. However, in hatchlings measured at 2°C, [Formula: see text] was higher in groups incubated at 5°C or 8°C through organogenesis, compared to 2°C controls (43 or 65% increase, respectively). Collectively, these data suggest that embryonic development through organogenesis represents a critical window of embryonic and hatchling phenotypic plasticity. This study presents an experimental design that identified thermally sensitive periods for fish embryos.
关键期是发育易感性的时期，在此期间，胚胎、幼体或成年动物的表型可能易受环境波动的影响。温度对变温动物的生理有广泛影响，胚胎尤其容易受到温度变化的影响。为了确定关键期，我们将白鱼胚胎在2°C、5°C或8°C的对照温度下孵化，并在原肠胚形成或器官发生结束时改变温度处理。在胚胎发育过程中测量心率（fH）和耗氧量（[公式：见正文]），并在1日龄幼体中测量[公式：见正文]。与在相同温度（2°C、5°C或8°C）下测量的对照胚胎相比，从初始孵化温度向上或向下的温度变化导致fH和[公式：见正文]持续变化。最显著的是，当在器官发生期测量胚胎时，原肠胚形成后改变孵化温度会显著降低[公式：见正文]或fH。在2°C或5°C下孵化至原肠胚形成期，在8°C时会显著降低[公式：见正文]（降低42%）和fH（降低20%）；在2°C下孵化至原肠胚形成期，在5°C时会显著降低[公式：见正文]（降低40%）和fH（降低30%）；在5°C和8°C下孵化至原肠胚形成期，在2°C时会显著降低[公式：见正文]（降低27%）。在发育的后半期，胚胎中的[公式：见正文]和fH与温度变化处理的对照值没有差异。然而，在2°C下测量的幼体中，与2°C对照组相比，在器官发生期在5°C或8°C下孵化的组中[公式：见正文]更高（分别增加43%或65%）。总体而言，这些数据表明，通过器官发生的胚胎发育代表了胚胎和幼体表型可塑性的关键期。本研究提出了一种实验设计，确定了鱼类胚胎的热敏感时期。
