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The brain might not be able to do this while still assailed by new stimuli and new information to process. Therefore, the role of sleep would be to periodically shut down sensory input to allow the brain to form memories. Pelagic species swim in an open-water environment wherein novel stimuli is uncommon. In such species, the sensory input is ...
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 ...
The Somniosidae are a family of sharks in the order Squaliformes, commonly known as sleeper sharks. [1] The common name " sleeper shark " comes from their slow swimming, low activity level, and perceived non-aggressive nature.
Diurnality, plant or animal behavior characterized by activity during the day and sleeping at night. Cathemeral, a classification of organisms with sporadic and random intervals of activity during the day or night. Matutinal, a classification of organisms that are only or primarily active in the pre-dawn hours or early night.
The Port Jackson shark is a nocturnal species which peaks in activity during the late evening hours before midnight and decreases in activity before sunrise. [2] A study showed that captive and wild individuals displayed similar movement patterns and the sharks' movements were affected by time of day, sex, and sex-specific migrational behaviour.
Sleeper sharks found in Alaskan waters from 2 to 3 m (6.6 to 9.8 ft) seem to feed mostly on flounder, pollock, and cephalopods, while sleeper sharks 3.3 to 4.25 m (10.8 to 13.9 ft) long seem to consume teleosts and cephalopods, as well as marine mammals.
The southern sleeper shark feeds primarily on cephalopods, especially squid — including the giant and colossal squids — and numerous fishes.Documented stomach contents of individual sleeper sharks have also, albeit infrequently, contained the remains of marine mammals or seabirds, possibly as a result of scavenging on sunken carcasses or whale falls. [1]
Many sharks can contract and dilate their pupils, like humans, something no teleost fish can do. Sharks have eyelids, but they do not blink because the surrounding water cleans their eyes. To protect their eyes some species have nictitating membranes. This membrane covers the eyes while hunting and when the shark is being attacked.