Intrinsic and Extrinsic Factors Modulating the Shift from Paternal Care to Filial Cannibalism

许多动物会照顾幼仔，这对幼仔的早期发育至关重要，但这种关系的破坏可能导致幼仔被忽视、遗弃和死亡。在一些物种中，父母甚至会采取极端措施，吃掉自己的孩子。长期以来，科学家们一直对同类相食的行为很感兴趣，但对于引发这种行为的环境因素，以及决定照顾或吃掉自己的后代的生理变化，人们知之甚少。回答这些问题将有助于深入了解在许多物种中，成年动物是如何以及为什么终止亲代抚育的。这项研究将在一个迷人的研究系统中研究从亲代照顾到同类相食的转变，即东方地狱之子。这些大鲵曾经在美国东部的溪流中很常见，但在过去的30年里，它们的大部分地区都经历了急剧的人口减少。与许多物种不同，雄性御火师会在很长一段时间内（7个月）专门照顾它们的后代。然而，在某些情况下，雄性御火师会停止照顾后代，并吃掉所有的后代。这项研究将在不同的栖息地特征梯度的溪流中使用水下筑巢箱，以确定是什么激素触发了这种行为的转变，以及什么环境因素促进了同类相食。这不仅会提高人们对亲代养育的认识，而且这项研究还将雇用高中科学教师，以综合推广的方式来保护世界上最大、最迷人的两栖动物之一。技术描述亲代抚育是许多动物生活史的一个基本方面。矛盾的是，在一些无脊椎动物和脊椎动物中，照顾子女的父母会自相残杀，吃掉自己的后代。亲子同类相食的适应性基础仍然是一个尚未解决的进化难题，而这种行为的生理基础也未在野生动物中得到探索。此外，很少有研究考虑到在某些情况下，孝子同类相食可能是不适应的，或者在一个物种内可能存在多种驱动因素。这些关键的知识缺口存在，至少在一定程度上，是由于缺乏可处理的野生动物模型来同时识别这种生活史决定的环境和生理方面。地狱火蜥蜴表现出父亲的关爱和子女的同类相食，并拥有一系列特征，使它们成为解决这一迷人的生活史决定的调节相关的先前未经验证的假设的理想系统。利用一个高度整合的框架，包括在栖息地质量和寄生率梯度的溪流中部署的水下巢箱，再加上遗传分析和在整个父亲护理季节从个体收集的血清成分分析，本研究将：1)确定父母决定照顾子女还是吃掉子女的生理调节因子（即激素、血清成分）；2)确定影响这种权衡的关键因素（即人均资源/身体状况、多重父系关系和寄生虫）；3)确定栖息地退化是否增加了子女自相残杀的频率。该奖项由动物行为和综合生态生理学项目共同资助，该项目隶属于综合生物系统部门。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical descriptionMany animals provide care for their young that is critical for early development, but disruption of this relationship can lead to neglect, abandonment, and death of offspring. In some species, parents can even take the extreme step of eating their own young. Cannibalism of offspring has long fascinated scientists, but little is known about the environmental factors that provoke this behavior or the physiological changes that underlie the decision to care for or eat one's young. Answering these questions will provide insights into how and why adults terminate parental care in a broad range of species. This study will examine the switch from parental care to cannibalism in a fascinating study system, the eastern hellbender. These giant salamanders were once common in streams across the eastern U.S., but have experienced drastic population declines across much of their range in the last 30 years. Unlike many species, male hellbenders provide exclusive care for their young for an extended period (7 months). In some circumstances, however, male hellbenders cease providing care and consume all of their young. This study will employ underwater nest boxes in streams across a gradient of habitat characteristics to determine what hormones trigger this switch in behaviors and what environmental factors promote cannibalism. Not only will this advance knowledge of parental care, but the study will also employ high school science teachers in an integrated outreach effort to conserve of one of the largest and most fascinating amphibians in the world. Technical descriptionParental care is a fundamental aspect of the life history of many animals. Paradoxically, in some invertebrates and vertebrates the parent(s) providing care engage in filial cannibalism, the consumption of one's own viable young. The adaptive basis for filial cannibalism remains an unresolved evolutionary conundrum, and the physiological basis for the behavior is unexplored in wild animals. In addition, few studies have considered the possibility that filial cannibalism may be maladaptive in some contexts or that there could be multiple drivers of filial cannibalism within a species. These critical knowledge gaps exist, at least in part, due to a scarcity of tractable wild animal models for simultaneously identifying environmental and physiological aspects of this life history decision. Hellbender salamanders exhibit paternal care as well as filial cannibalism and possess a suite of characteristics that make them an ideal system for addressing previously untested hypotheses related to the modulation of this fascinating life-history decision. Using a highly integrative framework that includes underwater nest boxes deployed in streams across a gradient of habitat quality and parasitism, coupled with genetic analyses and analysis of serum components collected from individuals throughout the paternal care season, this study will: 1) Identify the physiological modulators (i.e., hormones, serum components) that underlie the decision by a parent to either care for or cannibalize one's young, 2) Determine what key factors (i.e., per capita resources/body condition, multiple paternity, and parasites) influence this trade-off, and 3) Determine if habitat degradation increases the frequency of filial cannibalism. This award was co-funded by the Animal Behavior and the Integrative Ecological Physiology Programs within the Division of Integrative Organismal Systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.