Collaborative Research: The role of maternal iron transfer in the development of heme stores and aerobic diving capacity in grey seal pups

动物生态学的一个基本问题是，生理学何时以及为何限制了动物的行为、繁殖的频率以及生存的可能性。海洋哺乳动物特别适合这些研究，因为它们在水下觅食的能力受到组织血红素和氧气储存大小的限制，而且幼崽出生时血红蛋白（Hb）和肌红蛋白（Mb）水平非常低，这可能会限制呼吸能力。铁是血红蛋白和血红蛋白生物合成所必需的微量营养素，在许多物种中，母体铁状态和乳铁含量强烈影响血红素储存的早期发育。该项目将研究新斯科舍省黑貂岛的灰海豹（Halichoerus grypus），以确定母海豹和幼海豹的饮食铁动态如何影响血红素成熟和随后的觅食活动。研究小组将首先确定母亲的饮食、铁储量、牛奶铁含量和乳汁转运率。然后，研究人员将给一半的研究动物补充铁，以确定铁的摄入是否会限制幼犬的生理发育。最后，评估血红素储存对断奶幼崽潜水行为和运动模式的影响。了解铁摄入量、生理发育和觅食行为之间的相互作用，可能会揭示灰海豹饮食和生态系统结构的持续变化如何影响幼崽的生存和种群轨迹。这项工作将为HSI和阿拉斯加土著服务机构的研究生和本科生提供培训机会，并通过德克萨斯州，阿拉斯加，加拿大和马萨诸塞州的各种活动提供推广。本研究将阐明促进或限制灰海豹幼崽（12只/年/3年）血红素和氧储存个体发生的潜在生态和细胞机制。总体和化合物特定稳定同位素分析将用于确定母亲的饮食和铁摄入量，而乳铁和乳转移率将使用氢同位素动力学来量化幼崽的铁摄入量。幼犬利用乳铁的能力将通过测量铁转运蛋白（二价金属转运蛋白1，铁转运蛋白）的表达和血清hepcidin、转铁蛋白和铁蛋白的浓度来评估。将测量血液和肌肉血红素储存、含铁酶和已知调节血红素蛋白合成的内分泌因子（即促红细胞生成素、缺氧诱导因子-1）的年龄相关变化。在哺乳期开始和结束时给一半的研究幼崽补充铁，将揭示母体铁转运率是否对幼崽的生理发育有显著影响。在断奶后的禁食结束时，幼崽将配备一个与卫星相连的潜水记录器，以监测觅食模式和地点。铁补充组和对照组之间的行为比较将揭示母性效应是否通过微量营养素限制介导影响幼犬觅食能力，或者行为可塑性是否可以补偿表型限制。整合幼年海洋哺乳动物多种生理和行为尺度的研究仍然很少，但随着气候变化和人类活动导致全球海洋生态系统功能发生重大变化，了解这些联系变得越来越重要。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。

A fundamental question in animal ecology is when and why physiology limits how animals behave, how often they reproduce, and how likely they are to survive. Marine mammals are particularly suited for these studies because their ability to forage underwater is constrained by the size of their tissue heme and O2 stores, and pups are born with very low hemoglobin (Hb) and myoglobin (Mb) levels that can limit breathold ability. Iron is an essential micronutrient for the biosynthesis of Hb and Mb, and maternal iron status and milk iron content strongly influences early development of heme stores in many species. This project will study grey seals (Halichoerus grypus) at Sable Island, Nova Scotia to determine how maternal and offspring dietary iron dynamics impact heme maturation and subsequent foraging activities. The team will first determine maternal diet, iron stores, milk iron content and milk transfer rates. Then, researchers will provide supplemental iron to half of the study animals to determine if iron intake limits pup physiological development. Finally, the impact of heme stores on the diving behavior and movement patterns of weaned pups will be evaluated. Understanding the interplay between iron intake, physiological development and foraging behavior, may reveal how ongoing changes in grey seal diet and ecosystem structure could influence pup survival and population trajectories. This work will provide training opportunities to graduate and undergraduate students at HSI and Alaska Native serving institutions and provide outreach through a diverse suite of activities in Texas, Alaska, Canada, and Massachusetts. This study will elucidate the underlying ecological and cellular mechanisms that facilitate or constrain the ontogeny of heme and O2 stores in grey seal pups (12 pups/year/3yrs). Bulk and compound specific stable isotope analysis will be used to identify maternal diet and iron intake, while milk iron and milk transfer rates will be quantified using hydrogen isotope dynamics to determine pup iron intake. The pup’s ability to utilize milk iron will be assessed by measuring the expression of iron transporters (Divalent metal transporter 1, Ferroportin) and serum hepcidin, transferrin, and ferritin concentrations. Age-related changes in blood and muscle heme stores, iron-containing enzymes, and endocrine factors known to regulate heme protein synthesis (i.e., Erythropoietin, Hypoxia-inducible-factor-1) will be measured. Providing half the study pups with supplemental iron at the start and end of the lactation period will reveal if maternal iron transfer rates are a significant influence on pup physiological development. At the end of the post-weaning fast, pups will be outfitted with a satellite-linked dive recorder to monitor foraging patterns and locations. Behavioral comparisons between iron-supplemented and control groups will reveal whether maternal effects as mediated through micronutrient limitations influence pup foraging capacity, or if behavioral plasticity can compensate for phenotypic constraints. Studies integrating across multiple physiological and behavioral scales in juvenile marine mammals remain rare, yet understanding these linkages becomes increasingly important as climate change and human activities are causing significant shifts in the functioning of marine ecosystems across the globe.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.