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Whether fish sleep or not is an open question, to the point of having inspired the title of several popular science books. [2] [3] In birds and mammals, sleep is defined by eye closure and the presence of typical patterns of electrical activity in the brain, including the neocortex, but fish lack eyelids and a
Sleep can follow a physiological or behavioral definition. In the physiological sense, sleep is a state characterized by reversible unconsciousness, special brainwave patterns, sporadic eye movement, loss of muscle tone (possibly with some exceptions; see below regarding the sleep of birds and of aquatic mammals), and a compensatory increase following deprivation of the state, this last known ...
Fish portal; Bichirs / ˈ b ɪ ʃ ɪər z / and the reedfish comprise Polypteridae / p ɒ l ɪ p ˈ t ɛ r ɪ d iː /, a family of archaic ray-finned fishes and the only family in the order Polypteriformes / p ə ˈ l ɪ p t ə r ɪ f ɔːr m iː z /. [2] All the species occur in freshwater habitats in tropical Africa and the Nile River system ...
When betta fish sleep, their bright colors will often fade, and when combined with their unusual napping positions, they can appear dead. Predatory fish will often avoid eating a dead fish because of the risk of contracting diseases and parasites, making this an excellent defensive mechanism.
Pacific sleeper shark carcasses. The Pacific sleeper shark (Somniosus pacificus) is a sleeper shark of the family Somniosidae, measuring up to 4.4 m (14 ft) in length, although it could possibly reach lengths in excess of 7 m (23 ft). [2]
Diagrammatic vertical section through the eye of teleost fish. Fish have a refractive index gradient within the lens which compensates for spherical aberration. [4] Unlike humans, most fish adjust focus by moving the lens closer or further from the retina. [5] Teleosts do so by contracting the retractor lentis muscle.
Like other fish, betta fish do "sleep." But fish do not sleep in the same way mammals do. Fish rest by slowing down their activity and metabolism, the National Oceanic and Atmospheric ...
Sleeping Girl, Domenico Fetti, c. 1615 . Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. . During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environm