ABSTRACT: Few fast-swimming apex fishes are classified as ‘regional endotherms’, having evolved a relatively uncommon suite of traits (e.g. elevated body temperatures, centralised red muscle, and thick-walled hearts) thought to facilitate a fast, predatory lifestyle. Unlike those apex predators, Endangered basking sharks Cetorhinus maximus are massive filter-feeding planktivores assumed to have the anatomy and physiology typical of fully ectothermic fishes. We combined dissections of stranded specimens with biologging of free-swimming individuals and found that basking sharks have red muscle located medially at the trunk, almost 50% compact myocardium of the ventricle, and subcutaneous white muscle temperatures consistently 1.0 to 1.5°C above ambient. Collectively, our findings suggest basking sharks are not full ectotherms, instead sharing several traits used to define a regional endotherm, thus deviating from our current understanding of the species and questioning the link between physiology and ecology of regionally endothermic shark species. With successful forecasting of population dynamics and distribution shifts often improved by accurate physiological data, our results may help explain movement patterns of the species, which could ultimately facilitate conservation efforts.

中文翻译：

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食浮游生物姥鲨的区域吸热特征

摘要：很少有快速游动的顶级鱼类被归类为“区域恒温鱼”，它们进化出了一套相对不常见的特征（例如体温升高、集中的红色肌肉和厚壁的心脏），这些特征被认为有助于快速、掠夺性的生活方式。与那些顶级掠食者不同，濒临灭绝的姥鲨Cetorhinus maximus是大型滤食性浮游动物，被认为具有完全变温鱼类的典型解剖学和生理学特征。我们将搁浅标本的解剖与自由游动个体的生物记录相结合，发现姥鲨的红色肌肉位于躯干内侧，几乎 50% 的心室致密心肌，皮下白色肌肉温度始终高于环境温度 1.0 至 1.5°C。总的来说，我们的研究结果表明姥鲨并不是完全的变温动物，而是具有一些用于定义区域恒温动物的特征，从而偏离了我们目前对该物种的理解，并对区域恒温鲨鱼物种的生理学和生态学之间的联系提出了质疑。通过准确的生理数据通常可以改进对种群动态和分布变化的成功预测，