Department of Biology, Boston University, 5 Cummington Mall, Boston, MA, 02215, USA
Department of Biology, Boston University, 5 Cummington Mall, Boston, MA, 02215, USA.
J Exp Biol. 2019 Nov 12;222(Pt 21):jeb206052. doi: 10.1242/jeb.206052.
The widespread ability to alter timing of hatching in response to environmental cues can serve as a defense against threats to eggs. Arboreal embryos of red-eyed treefrogs, , can hatch up to 30% prematurely to escape predation. This escape-hatching response is cued by physical disturbance of eggs during attacks, including vibrations or motion, and thus depends critically on mechanosensory ability. Predator-induced hatching appears later in development than flooding-induced, hypoxia-cued hatching; thus, its onset is not constrained by the development of hatching ability. It may, instead, reflect the development of mechanosensor function. We hypothesize that vestibular mechanoreception mediates escape-hatching in snake attacks, and that the developmental period when hatching-competent embryos fail to flee from snakes reflects a sensory constraint. We assessed the ontogenetic congruence of escape-hatching responses and an indicator of vestibular function, the vestibulo-ocular reflex (VOR), in three ways. First, we measured VOR in two developmental series of embryos 3-7 days old to compare with the published ontogeny of escape success in attacks. Second, during the period of greatest variation in VOR and escape success, we compared hatching responses and VOR across sibships. Finally, in developmental series, we compared the response of individual embryos to a simulated attack cue with their VOR. The onset of VOR and hatching responses were largely concurrent at all three scales. Moreover, latency to hatch in simulated attacks decreased with increasing VOR. These results are consistent with a key role of the vestibular system in the escape-hatching response of embryos to attacks.
广泛的改变孵化时间以响应环境线索的能力可以作为保护卵免受威胁的防御机制。, 树蛙的胚胎在受到攻击时，会提前孵化高达 30%以逃避捕食。这种逃避孵化的反应是由卵在攻击期间受到的物理干扰引发的，包括振动或运动，因此严重依赖于机械感觉能力。与洪水诱导的、缺氧提示的孵化相比，捕食者诱导的孵化出现在发育后期；因此，它的开始不受孵化能力发育的限制。相反，它可能反映了机械感受器功能的发展。我们假设前庭机械感受器介导了蛇类攻击中的逃避孵化，而孵化能力胚胎未能逃避蛇类的发育时期反映了一种感觉限制。我们以三种方式评估了逃避孵化反应和前庭功能指标——前庭眼反射（VOR）的发育同步性。首先，我们测量了两个发育系列的胚胎（3-7 天龄）的 VOR，以与攻击中逃避成功率的已发表发育史进行比较。其次，在 VOR 和逃避成功率变化最大的时期，我们比较了不同同胞系之间的孵化反应和 VOR。最后，在发育系列中，我们将单个胚胎对模拟攻击线索的反应与其 VOR 进行了比较。在所有三个尺度上，VOR 和孵化反应的开始时间基本一致。此外，模拟攻击中孵化的潜伏期随着 VOR 的增加而缩短。这些结果与前庭系统在树蛙胚胎对攻击的逃避孵化反应中的关键作用一致。
