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Octopus

The octopus (/ˈɒktəpʊs/ or /ˈɒktəpəs/; plural: octopuses, octopi, or octopodes; see below) is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms and, like other cephalopods, they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms. Octopuses have no internal or external skeleton (although some species have a vestigial remnant of a shell inside their mantles), allowing them to squeeze through tight places. Octopuses are among the most intelligent and behaviorally flexible of all invertebrates.


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Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda (Greek plural κεφαλόποδα (kephalópoda); "head-feet"). These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishermen sometimes call them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites).


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Mollusca

The molluscs or mollusks /ˈmɒləsks/ compose the large phylum of invertebrate animals known as the Mollusca. Around 85,000 extant species of molluscs are recognized. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The phylum is typically divided into 9 or 10 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish and octopus, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The gastropods (snails and slugs) are by far the most numerous molluscs in terms of classified species, and account for 80% of the total. The scientific study of molluscs is called malacology.


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Marine invertebrates

Marine invertebrates are multicellular animals that inhabit a marine environment and are invertebrates, lacking a vertebral column. In order to protect themselves, they may have evolved a shell or a hard exoskeleton, but this is not always the case.

As on land and in the air, invertebrates make up a great majority of all macroscopic life in the sea. Invertebrate sea life includes the following groups, some of which are phyla:

There are a number of marine invertebrates that use minerals that are present in the sea in such minute quantities that they were undetectable until the advent of spectroscopy. Vanadium is concentrated by some tunicates for use in their blood cells to a level ten million times that of the surrounding seawater. Other tunicates similarly concentrate niobium and tantalum. Lobsters use copper in their respiratory pigment hemocyanin, despite the proportion of this metal in seawater being minute. Although these elements are present in vast quantities in the ocean, their extraction by man is not economic.


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Invertebrate

Invertebrates are animal species that do not possess or develop a vertebral column, derived from the notochord (i.e. all animals apart from the subphylum Vertebrata). Familiar examples of invertebrates include insects, worms, clams, crabs, octopuses, snails, and starfish.

The overwhelming majority of animal species are invertebrates. One estimate in the journal Science put the figure at 97%. Many individual invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata and some of the so-called invertebrates, such as the Chaetognatha, Hemichordata, Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrate phyla. This makes the term "invertebrate" almost meaningless for taxonomic purposes.


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Animal

Animals are multicellular, eukaryotic organisms of the kingdom Animalia (also called Metazoa). Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their lives. Most animals are motile, meaning they can move spontaneously and independently. All animals must ingest other organisms or their products for sustenance (see Heterotroph).

Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals are divided into various sub-groups, some of which are: vertebrates (birds, mammals, amphibians, reptiles, fish); molluscs (clams, oysters, octopuses, squid, snails); arthropods (millipedes, centipedes, insects, spiders, scorpions, crabs, lobsters, shrimp); annelids (earthworms, leeches); sponges; and jellyfish.


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Aquatic locomotion

Aquatic locomotion is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish and molluscs.


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Limb (anatomy)

A limb (from the Old English lim), or extremity, is a jointed, or prehensile (as octopus tentacles or new world monkey tails), appendage of the human or other animal body. In the human body, the upper and lower limbs are commonly called the arms and the legs.

Most animals use limbs for locomotion, such as walking, running, or climbing. Some animals can use their front limbs (or upper limbs in humans) to carry and manipulate objects. Some animals can also use hind limbs for manipulation.

Human legs and feet are specialized for two-legged locomotion – most other mammals walk and run on all four limbs. Human arms are weaker, but very mobile allowing us to reach at a wide range of distances and angles, and end in specialized hands capable of grasping and fine manipulation of objects.


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List of meat animals

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Coleoidea

Subclass Coleoidea, or Dibranchiata, is the grouping of cephalopods containing all the primarily soft-bodied creatures. Unlike its sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal bone or shell that is used for buoyancy or support (usually a cuttlebone or gladius). Some species have lost their bone altogether, while in some it has been replaced by a cartilaginous support structure.

The major dividings of Coleoidea are based upon the number of arms or tentacles and their structure. The extinct and most primitive form, the Belemnoidea, presumably had ten equally sized arms, in five pairs numbered dorsal to ventral as I, II, III, IV and V. More modern species either modified or lost a pair of arms. The superorder Decapodiformes has arm pair IV modified into long tentacles with suckers generally only on the club-shaped distal end. Superorder Octopodiformes has modifications to arm pair II; it is significantly reduced and used only as a sensory filament in the Vampyromorphida, while Octopoda species have totally lost that arm pair.


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Common octopus

The common octopus (Octopus vulgaris) is the most studied of all octopus species. Its range in the eastern Atlantic extends from the Mediterranean Sea and the southern coast of England to at least Senegal in Africa. It also occurs off the Azores, Canary Islands, and Cape Verde Islands. The species is also common in the Western Atlantic.