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Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints, and in their >400 million year existence have never ventured into fully freshwater habitats. [10] Cephalopods occupy most of the depth of the ocean, from the abyssal plains to the sea surface, and have also been found in the hadal zone. [11]
Cephalopods have large, well-developed brains, [8] [9] [10] and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates. [11] The nervous system of cephalopods is the most complex of all invertebrates.
The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata. [1]The class developed during the middle Cambrian, and underwent pulses of diversification during the Ordovician period [2] to become diverse and dominant in the Paleozoic and Mesozoic seas.
Arms and buccal mass of the squid Taningia danae.As in other Octopoteuthidae, the tentacles are absent in adults. Oral view of the bobtail squid Semirossia tenera Head and limbs of the bobtail squid Rossia glaucopis Oral view of male Bathypolypus arcticus with hectocotylus on arm III (left) Cephalopod suckers and configuration of suckers on tentacular club Serrated suckers of a giant squid ...
This category covers articles about cephalopods as individual species or groups. For more information, see cephalopod . Pages in this category should be moved to subcategories where applicable.
Cephalopods were at one time the largest of all organisms on Earth, [6] and numerous species of comparable size to the largest present day squids are known from the fossil record, including enormous examples of ammonoids, belemnoids, nautiloids, orthoceratoids, teuthids, and vampyromorphids.
Two distinct behaviors have been observed in inking cephalopods. The first is the release of large amounts of ink into the water by the cephalopod in order to create a dark, diffuse cloud (much like a smoke screen) that can obscure the predator's view, allowing the cephalopod to make a rapid retreat by jetting away.
Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions. [1] They have a camera-type eye which consists of an iris, a circular lens, vitreous cavity (eye gel), pigment cells, and photoreceptor cells that translate light from the light-sensitive retina into nerve signals which travel along the optic nerve to the brain. [2]