Thermoregulation in Florida manatees (Trichechus manatus latirostris) -Understanding the cold-stress syndrome in terms of physiology, morphology and early diagnosis

佛罗里达海牛(Trichechus Manatus Laatirostris)属于海牛或Sirenia，一组完全水生的哺乳动物，由四个最近的物种组成。作为唯一的食草性海洋哺乳动物，西里昂生活在热带/亚热带栖息地，并适应高水温。尤其是佛罗里达的海牛对降低水温非常敏感。对该物种的主要威胁之一是所谓的冷应激综合症(Css)，它发生在暴露在水温&20°的海牛身上。尤其是未成年的动物会受到水温下降的影响，当水温下降时，它们无法及时找到温暖的水难民(温暖的淡水泉水，发电厂的温水排放)。在其他症状中，css的症状包括免疫抑制、器官衰竭、心脏、皮肤和其他器官的损伤，最终导致动物死亡。拟议的项目包括三个主要目标：(A)确定指标，以便在出现威胁生命的冷应激症状之前及早识别海牛的冷应激。(B)根据早期诊断的动物(见(A)项)以及有CS症状的动物，确定影响佛罗里达海牛对热应激敏感性的环境、生理和形态参数。(C)根据(A)、(B)及其他对已死亡动物进行的形态研究，就海牛的CS的生理成因提出有充分理据的假设。我的假设是：(1)通过红外热像仪(IRT)可以通过水面以上身体部位表面温度的变化来识别早期的冷应激，特别是在水面呼吸时打开的鼻孔。(2)皮肤上生物污垢的数量和组成是海牛对CSS易感性的指标。在此背景下，还将研究皮肤表面结构对生物污垢的作用。通过IRT和进一步的非侵入性方法，将在患有CS的海牛以及健康动物中进行一系列测量，如皮肤和核心体温、热流和鲸脂厚度。将记录和分析皮肤上的生物污垢的数量和组成以及皮肤表面结构。组织学尸检将提供有关CS易感性的进一步信息。特别是，将检查脂肪厚度和组成、皮肤表面结构以及动静脉吻合口(AVA)的存在或不存在，这些都是调节外周热量损失的重要结构。这项长期的研究将为理解海牛的体温调节，特别是关于热应激的调控奠定基础，并可能对其他哺乳动物物种产生影响。

The Florida manatee (Trichechus manatus latirostris) belongs to the sea cows or Sirenia, a group of fully aquatic mammals consisting of four recent species. As the only herbivorous marine mammals, sireneans live in tropical/subtropical habitats and are adapted to high water temperatures. Particularly the Florida manatees are extremely sensible to lower water temperatures. One of the major threats to this species is the so called cold-stress syndrome (CSS), occurring in manatees that are exposed to water temperatures <20°. In particular subadult animals are affected by CSS, failing to find the way to warm water refugees (warm fresh water springs, warm-water discharges from power plants) in time, when water temperatures decrease. Amongst others, CSS symptoms are immune suppression, organ failure, lesions of heart, skin and other organs, eventually causing the death of the animal. The proposed project comprises three major objectives: (a) The identification of indicators for early recognition of cold stress in a manatee prior to the appearance of life-threatening CSS symptoms. (b) The identification of environmental, physiological and morphological parameters influencing the susceptibility to thermal stress in Florida manatees on the basis of early-diagnosed animals (see (a)) as well as animals with CSS symptoms. (c) Based on (a), (b) and additional morphological studies in deceased animals, to generate well substantiated hypotheses on the physiological causation of CSS in manatees. My hypotheses are: (1) Incipient cold-stress can be recognized by changes in surface temperature of body parts above the water surface via infrared-thermography (IRT), in particular the open nostrils while breathing at the surface. (2) The amount and composition of biofouling on the skin are indicators for the susceptibility of a manatee to CSS. In this context also the role of the skin surface structure for biofouling will be investigated. By means of IRT and further non-invasive methods, an array of measurements, such as skin and core body temperature, heat flux and blubber thickness, will be conducted in manatees suffering from CSS, as well as comparatively in healthy animals. Amount and composition of biofouling on the skin as well as skin surface structure will be documented and analyzed. Histological postmortem examinations will provide further information concerning CSS susceptibility. In particular blubber thickness and composition, skin surface structure, and the presence or absence of arteriovenous anastomoses (AVAs), which are important structures for the regulation of peripheral heat loss, will be examined. This long-term study will lay a foundation to understanding manatee thermoregulation, in particular concerning thermal stress, with possible implications for other mammalian species as well.