BRC-BIO: Pick your poison: The physiological cost of alkaloid sequestration in dendrobatid poison frogs

生物体通常具有适应其生存环境的生理机能。然而，由于人类活动和气候变化，许多栖息地正在迅速变化。这些变化会影响物种在以前适宜的环境中生存的能力。石蛙科的毒蛙因其鲜艳的颜色和独特的隔离生物碱防御能力而具有魅力，它们的天然食物是螨虫和蚂蚁。青蛙使用这些生物碱作为对抗捕食者和微生物的化学防御，但人们对发展这些防御的生理成本知之甚少。更具体地说，生物碱的固存如何影响个体生存所需的能量？反过来，这又如何影响青蛙与环境的互动，比如它们需要花多少时间觅食或寻找配偶？青蛙是冷血动物，这意味着环境温度的变化会直接影响它们的体温。随着温度的升高，代谢率也在上升，这就要求青蛙获取更多的能量（例如，吃更多的食物）或利用不同的热微栖息地。因此，气候变化导致的温度升高有可能增加青蛙吸收生物碱的成本。目前的项目旨在建立一个职业学习系统，以本科生和社区成员为基础。本科生将接受生理学和化学生态学研究的前沿技术培训。青蛙的魅力特性也将允许开展外展活动，让社区了解生态生理学和保护。两栖动物特别容易受到气候变化的影响，因为它们的生理机能，特别是呼吸和新陈代谢的其他方面，都依赖于特定的温度和湿度条件。石蛙科的新热带毒蛙也有特殊的生理机能，使它们能够隔离食物中的生物碱，作为化学防御。BRC-BIO项目的目标是量化石斛蛙的生物碱封存如何影响生态相关的生理过程，如代谢。为了实现这一目标，将在斯克兰顿大学建立一个由10种石斛虫组成的繁殖群落，用于测试三个主要假设：(1)生物碱的隔离具有生理成本，将导致代谢率和能量消耗增加；(2)代谢率的变化会因蛙类谱系的不同而不同，因为生物碱的吸收能力在这个家族中已经进化了多次；(3)代谢率随生物碱固存量成比例增加。这些假设将通过给青蛙提供控制或补充生物碱的饮食，并通过测量和比较二氧化碳产生率和氧气消耗率来量化单个青蛙的代谢率来验证。石斛天然具有20多种不同类型的生物碱，因此生物碱的多样性及其对生理的影响将被测量。BRC-BIO项目产生的数据，结合青蛙繁殖群体的发展，将继续支持更多的问题，重点是学生主导的独立项目，本科课程中的新颖生理学实验，以及与社区和K-12学校的推广。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。

Organisms typically have physiologies adapted to the environments that they inhabit. However, many habitats are rapidly changing due to human activities and climate change. These changes can impact species’ ability to persist in previously adequate environments. Poison frogs in the family Dendrobatidae are charismatic because of their bright colors and unique ability to sequester alkaloid defenses from their natural diet of mites and ants. The frogs use these alkaloids as a chemical defense against predators and microbes, yet little is known about the physiological costs associated with developing these defenses. More specifically, how does alkaloid sequestration influence the energy requirements for individuals to survive? And in turn, how does this impact how frogs interact with their environment such as how much time they need to spend foraging for food or finding a mate? Frogs are poikilothermic, which means changes to environmental temperature will directly impact their body temperature. As temperature increases, so does metabolic rate, which will require frogs to acquire more energy (for example, eat more food) or utilize different thermal microhabitats. Therefore, increases in temperature due to climate change have the potential to increase the cost of alkaloid sequestration for frogs. The current project aims to establish a career study system, rooted in involving undergraduate students and community members. Undergraduate students will be trained in cutting edge techniques for studying physiology and chemical ecology. The charismatic nature of the frogs will also allow for outreach events, engaging the community to learn about ecophysiology and conservation. Amphibians are especially susceptible to climate change as their physiologies, specifically respiration and other aspects of metabolism, are dependent on specific temperature and moisture conditions. Neotropical poison frogs in the family Dendrobatidae also have specialized physiologies that allow them to sequester dietary alkaloids to be used as chemical defenses. The goal of this BRC-BIO project is to quantify how alkaloid sequestration by dendrobatid frogs impacts ecologically relevant physiological processes, such as metabolism. To accomplish this goal, a breeding colony of 10 species of dendrobatids will be established at The University of Scranton, which will be used to test three primary hypotheses: (1) sequestration of alkaloids has a physiological cost that will result in increased metabolic rate and energy expenditure; (2) changes in metabolic rate will vary by frog lineage, as alkaloid sequestration has evolved multiple times within the family; and (3) metabolic rate will increase proportionally with the quantity of alkaloid sequestered. These hypotheses will be tested by providing frogs with a control or alkaloid-supplemented diet and quantifying individual frog’s metabolic rate by measuring and comparing rates of carbon dioxide production and oxygen consumption. Dendrobatids naturally possess more than 20 different types of alkaloids, and therefore a diversity of alkaloids and their effects on physiology will be measured. The data generated by this BRC-BIO project, in conjunction with the development of a frog breeding colony, will continue to support additional questions with an emphasis on student-led independent projects, novel physiology experiments in undergraduate courses, and outreach with the community and K-12 schools.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.