Cetacean brains: How aquatic are they?
Cetacean brains: How aquatic are they?
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DOI：
10.1002/ar.20530
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发表时间：
2007-06-01
影响因子：
2
通讯作者：
Marino, Lori
中科院分区：
文献类型：
--
作者：
Marino, Lori
鲸类动物对完全水生生活方式的适应代表了哺乳动物进化史上最引人注目的转变之一。现代鲸类动物最显著的两个特征是完全的水生生活方式和巨大的大脑。本文将对水生哺乳动物的比较神经解剖学研究进行综述，包括齿形动物、鲸类动物、海龙类动物、鳍形动物和古鲸类动物的大脑分析。特别是，关于完全水生和拥有一个大大脑之间是否存在关系的问题得到了解决。据推测，鲸类动物的大而发达的大脑是完全适应水生生活方式的直接产物。目前的共识是，鲸类动物大脑大小进化的古生物学证据与这一假设不一致。鲸类动物的大脑在完全适应水生生活数百万年后才开始发育。与海蛞蝓和鳍足类动物的神经解剖学比较，没有证据表明齿齿螈的大脑袋、高脑化水平和极端的新皮层旋转是对完全水生生活方式的适应。虽然回声定位被认为是齿形动物高脑化水平的一个原因，但应该注意的是，并非所有的水生哺乳动物都有回声定位，而回声定位的陆生哺乳动物（如蝙蝠）的脑化程度也不是特别高。回声定位不是完全水生生活方式的要求，因此，不能认为是水生生活对大脑发育的唯一影响。这些结果表明，齿螈的高脑化水平可能与它们复杂的社会生活方式有关，这种生活方式超越了水生环境的影响。
The adaptation of cetaceans to a fully aquatic lifestyle represents one of the most dramatic transformations in mammalian evolutionary history. Two of the most salient features of modern cetaceans are their fully aquatic lifestyle and their large brains. This review article will offer an overview of comparative neuroanatomical research on aquatic mammals, including analyses of odontocete cetacean, sirenian, pinniped, and fossil archaeocete brains. In particular, the question of whether a relationship exists between being fully aquatic and having a large brain is addressed. It has been hypothesized that the large, well-developed cetacean brain is a direct product of adaptation to a fully aquatic lifestyle. The current consensus is that the paleontological evidence on brain size evolution in cetaceans is not consistent with this hypothesis. Cetacean brain enlargement took place millions of years after adaptation to a fully aquatic existence. Neuroanatomical comparisons with sirenians and pinnipeds provide no evidence for the idea that the odontocete's large brain, high encephalization level, and extreme neocortical gyrification is an adaptation to a fully aquatic lifestyle. Although echolocation has been suggested as a reason for the high encephalization level in odontocetes, it should be noted that not all aquatic mammals echolocate and echolocating terrestrial mammals (e.g., bats) are not particularly highly encephalized. Echolocation is not a requirement of a fully aquatic lifestyle and, thus, cannot be considered a sole effect of aquaticism on brain enlargement. These results indicate that the high encephalization level of odontocetes is likely related to their socially complex lifestyle patterns that transcend the influence of an aquatic environment.