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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]
All extant cephalopods have a two-part beak, or rostrum, situated in the buccal mass and surrounded by the muscular head appendages. The dorsal (upper) mandible fits into the ventral (lower) mandible and together they function in a scissor-like fashion. [1] [2] The beak may also be referred to as the mandibles or jaws. [3]
The newly oxygenated blood drains from the gill capillaries into the systemic heart, where it is then pumped back throughout the body. [26] Blood volume in the octopus' body is about 3.5% of its body weight [28] but the blood's oxygen-carrying capacity is only about 4 volume percent. [29]
An octopus (pl.: octopuses or octopodes [a]) is a soft-bodied, eight-limbed mollusc of the order Octopoda (/ ɒ k ˈ t ɒ p ə d ə /, ok-TOP-ə-də [3]).The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids.
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails, clams, octopus, squid and relatives). Siphons in molluscs are tube-like structures in which water (or, more rarely, air) flows.
An ammonitic ammonoid with the body chamber missing, showing the septal surface (especially at right) with its undulating lobes and saddles. The ancestors of coleoids (including most modern cephalopods) and the ancestors of the modern nautilus, had diverged by the Floian Age of the Early Ordovician Period, over 470 million years ago.
Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopods. In other cephalopod families it is called a gladius. Cuttlebone is composed primarily of aragonite.
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 ...