Department of Biology and Marine Biology and the UNCW Center for Marine Science, University of North Carolina Wilmington, Wilmington, NC, 28403, United States.
Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
Sci Rep. 2019 Jul 11;9(1):10022. doi: 10.1038/s41598-019-46225-5.
In cartilaginous fishes, variability in the size of the brain and its major regions is often associated with primary habitat and/or specific behavior patterns, which may allow for predictions on the relative importance of different sensory modalities. The Greenland (Somniosus microcephalus) and Pacific sleeper (S. pacificus) sharks are the only non-lamnid shark species found in the Arctic and are among the longest living vertebrates ever described. Despite a presumed visual impairment caused by the regular presence of parasitic ocular lesions, coupled with the fact that locomotory muscle power is often depressed at cold temperatures, these sharks remain capable of capturing active prey, including pinnipeds. Using magnetic resonance imaging (MRI), brain organization of S. microcephalus and S. pacificus was assessed in the context of up to 117 other cartilaginous fish species, using phylogenetic comparative techniques. Notably, the region of the brain responsible for motor control (cerebellum) is small and lacking foliation, a characteristic not yet described for any other large-bodied (>3 m) shark. Further, the development of the optic tectum is relatively reduced, while olfactory brain regions are among the largest of any shark species described to date, suggestive of an olfactory-mediated rather than a visually-mediated lifestyle.
在软骨鱼类中，大脑及其主要区域的大小变化通常与主要栖息地和/或特定行为模式相关，这可能允许对不同感觉模态的相对重要性进行预测。格陵兰睡鲨（Somniosus microcephalus）和太平洋睡鲨（S. pacificus）是唯一在北极发现的非 Lamnid 鲨种，也是有史以来描述的最长寿的脊椎动物之一。尽管由于寄生虫性眼部病变的经常存在而导致视觉受损，加上在寒冷温度下运动肌肉力量经常下降的事实，但这些鲨鱼仍然能够捕捉到活跃的猎物，包括鳍足类动物。使用磁共振成像（MRI），通过系统发生比较技术，评估了 S. microcephalus 和 S. pacificus 的大脑组织，涉及多达 117 种其他软骨鱼类物种。值得注意的是，负责运动控制的大脑区域（小脑）很小，并且没有叶状结构，这一特征尚未在任何其他大型 (>3 m) 鲨鱼中描述过。此外，视神经结构的发育相对减少，而嗅觉脑区是迄今为止描述过的任何鲨鱼物种中最大的，表明嗅觉介导的生活方式，而不是视觉介导的生活方式。
