Published online by Cambridge University Press: 10 March 2010
Introduction
Aquatic habitats were the cradle of sleep many million years before sleep evolved in terrestrial animals. Yet these habitats were the last to be explored in seeking sleep's ultimate function, which I have suggested to be the enabling of highly efficient brain operation at all times. Although the sleep of most fishes is essentially indistinguishable from that of terrestrial vertebrates, by exploiting the rich variety and greater permissiveness of aquatic habitats, some fishes have bypassed a need for sleep. In three continuously active states, they purportedly achieve comparable, and even greater, benefits than is provided by sleep, yet remain perpetually vigilant.
I propose that “schooling” (swimming synchronously in polarized groups) by these fishes plays a major role in the lack of a need for sleep. Thus, by schooling, they are able to achieve sleep's benefits without closing or occluding their eyes, namely, a great reduction in the average school member's reception and processing of external sensory input. Because the evident benefits of schooling by some fishes substitute for the obscure benefits of sleep by closely related fishes, the evident benefits give clues to the obscure ones. These clues support views on the ultimate function of sleep.
After reviewing circumstances relating to the evolution of sleep in terrestrial animals, relevant topics in the lives of fishes are treated, emphasizing their sleep and its awake, almost equivalent functions with eyes open.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.