RUI: Growing Up on Ice: Physiological Adaptations and Developmental Plasticity in Weddell Seal Pups Across Two Extreme Physical Environments

幼仔由父母照顾到独立生活的过渡是许多动物生命中的关键阶段。对于极地哺乳动物来说，在这个阶段生存尤其具有挑战性，因为极端寒冷需要额外的能量来保暖，而不是将大部分能量用于生长，发育和身体活动。年轻的威德尔海豹（Leptonychotes weddellii）只有几周的时间来发展在海冰顶部和-1.9 ° C海水中生存的能力，在那里它们可以觅食。该项目旨在更好地了解威德尔海豹幼崽如何快速发展（在几周内）在这两种极端环境之间过渡的能力（它们的导热能力差异很大）以及它们如何在过渡期间预算能量。虽然成年威德尔海豹的生物学和生理学已经得到了很好的研究，但幼海豹在发育过程中的能量和生理策略仍然不清楚。了解可能影响关键生命史事件中生存的因素对于更好地了解可能影响海洋哺乳动物种群的因素至关重要。 威德尔海豹是最南端的繁殖哺乳动物，很容易被认为是典型的南极海豹。确定关键生命阶段对南极环境变化的潜在脆弱性，将有助于研究人员不仅能够获得公众的兴趣，而且还能够传达研究如何揭示极地发生变化的方式以及这些变化如何影响极地生态系统。通过与海洋哺乳动物中心合作，该项目将通过课程教材和公众宣传活动直接接触公众，每年将影响10万多名游客。为了阐明促进威德尔海豹幼崽从出生到独立生存的生理策略，拟议的研究将考察它们的体温调节和潜水能力的发展。为了实现这一目标，该项目将确定威德尔海豹幼崽在空气和水中保持稳定温暖体温的机制，然后检查潜水能力的发展，因为动物准备独立觅食。研究人员将采取一种完全综合的方法-从蛋白质到组织到整个动物水平进行评估-在调查这两个目标时。为了评估体温调节能力的发展，研究人员将量化身体绝缘，空气和水中的静息代谢率，肌肉产热（颤抖）和体表温度。该项目还将通过量化储氧能力和测量早期潜水行为来评估潜水能力的发展。为了确定威德尔海豹在发育过程中如何进行这种权衡的可能细胞机制，该计划将使用qPCR量化几种增加缺氧能力的关键发育调节因子（HIF，VEGF和EPO），并跟踪脂肪和肌肉组织的蛋白质组学变化，其中包括代谢，抗氧化剂，细胞骨架和Ca 2+调节蛋白的丰度变化。对导致鳍足类向独立过渡的生理发育的研究将有助于研究人员更好地预测气候变化对该物种分布和丰度的影响，以及这将如何影响其他营养水平。改变栖息地适宜性的环境变化已被证明会降低种群健康，特别是因为青少年存活率下降。

The transition of young from parental care to independence is a critical stage in the life of many animals. Surviving this stage can be especially challenging for polar mammals where the extreme cold requires extra energy to keep warm, rather than using the majority of energy for growth, development and physical activities. Young Weddell seals (Leptonychotes weddellii) have only weeks to develop the capabilities to survive both on top of the sea ice and within the -1.9°C seawater where they can forage for food. The project seeks to better understand how Weddell seal pups rapidly develop (within weeks) the capacity to transition between these two extreme environments (that differ greatly in their abilities to conduct heat) and how they budget their energy during the transition. Though the biology and physiology of adult Weddell seals is well studied, the energetic and physiological strategies of pups during development is still unclear. Understanding factors that may affect survival at critical life history events is essential for better understanding factors that might affect marine mammal populations. Weddell seals are the southernmost breeding mammal and are easily recognizable as quintessential Antarctic seals. Determining potential vulnerabilities at critical life stages to change in the Antarctic environment will facilitate the researchers' ability to not only gain public interest but also communicate how research is revealing ways in which changes are occurring at the poles and how these changes may affect polar ecosystems. By collaborating with the Marine Mammal Center, the project will directly reach the public, through curricular educational materials and public outreach that will impact over 100,000 visitors annually.To elucidate the physiological strategies that facilitate the survival of Weddell seal pups from birth to independence, the proposed study examines the development of their thermoregulation and diving capability. To achieve this, the project will determine the mechanisms that Weddell seal pups use to maintain a stable, warm body temperature in air and in water and then examine the development of diving capability as the animals prepare for independent foraging. The researchers will take a fully integrative approach- making assessments from proteins to tissues to the whole-animal level- when investigating both these objectives. To assess the development of thermoregulatory capability, researchers will quantify body insulation, resting metabolic rates in air and in water, muscle thermogenesis (shivering), and body surface temperatures in the field. The project will also assess the development of dive capability by quantifying oxygen storage capacities and measuring early dive behavior. To identify possible cellular mechanisms for how Weddell seals navigate this trade-off during development, the program will quantify several key developmental regulators of increased hypoxic capacity (HIF, VEGF and EPO) using qPCR, as well as follow the proteomic changes of adipose and muscle tissue, which will include abundance changes of metabolic, antioxidant, cytoskeletal, and Ca2+-regulating proteins. The study of the physiological development leading up to the transition to independence in pinnipeds will help researchers better predict the effects of climate change on the distribution and abundance of this species and how this will affect other trophic levels. Environmental changes that alter habitat suitability have been shown to decrease population health, specifically because of declines in juvenile survival.