the platypus
The platypus, apparently, is a surprisingly deep sleeper. What's more, it spends more of its time in so-called 'REM' sleep than any other mammal. These are the conclusions of a study on sleep in the platypus by Jerry M. Siegel of the Sepulveda Veterans' Affairs Medical Center, North Hills, California and colleagues. Their report appears in a special number of Philosophical Transactions of the Royal Society devoted to the biology of the platypus (Ornithorhynchus anatinus), celebrating the bicentenary of the discovery, in Australia, of this remarkable animal. 'REM' stands for 'rapid eye-movement' and is the kind of sleep in which the brain can be more active than in it is while awake, the animal twitches, and the eyelids flicker - hence the name. In humans, REM sleep is associated with But does the platypus have an extraordinarily rich dream life? Possibly not, say the researchers: "cats, opossums, armadillos and other mammals not
Monotremes lay eggs, like birds and reptiles, but unlike all other mammals. Monotremes have taken a cameo role in studies on the evolution of mammalian brain function. First, it turns out that the term 'REM' is a misnomer: animals may show REM sleep even though their eyes don't move, and their bodies don't twitch. 'REM' stands for 'rapid eye-movement' and is the kind of sleep in which the brain can be more active than in it is while awake, the animal twitches, and the eyelids flicker - hence the name. known for their intellectual achievements have far more REM sleep, whether calculated in hours per day or as a percentage of total sleep time, than humans. These are the conclusions of a study on sleep in the platypus by Jerry M. Recordings from discreetly implanted electrodes show that the echidna does, after all, show a kind of REM sleep generated by the brainstem, even though it is rather muted and the animal shows no outward signs. They also have a range of other reptile-like anatomical features, features that have been lost in more 'advanced' mammals. These findings set our understanding of the evolution of sleep on a firmer footing. This is the conundrum that Siegel and colleagues have been investigating. All three species are confined to Australasia. The elaboration of REM sleep into the forebrain is a later innovation: but whether it evolved once and monotremes have since lost it, or if it evolved more than once, is something that only more work on birds and reptiles can establish. Indeed, an account from as long ago as 1860, before REM sleep was discovered, reported that young platypus showed 'swimming' movements of their forepaws while asleep. In humans, REM sleep is associated with dreaming. Their report appears in a special number of Philosophical Transactions of the Royal Society devoted to the biology of the platypus (Ornithorhynchus anatinus), celebrating the bicentenary of the discovery, in Australia, of this remarkable animal.
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,
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Acceptance Essays
