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Tentacle

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Tentacle

An anemonefish seeks refuge amongst the tentacles of an anemone.

Photo © Chris Dascher / iStockphoto.
Definition: When used in a zoological context, the term tentacle refers to a slender, elongated, flexible organ that grows near the mouth of an animal. Tentacles are most common in invertebrates, although they are present in some vertebrates as well. Tentacles serve a variety of functions and can can help the animal to move, feed, grasp objects, and gather sensory information.

Examples of invertebrates that possess tentacles include squid, cuttlefish, bryozoa, snails, sea anemones, and jellyfish. Examples of vertebrates that posses tentacles include caecilians and star-nosed moles.

Tentacles belong to a group of biological structures known as muscular hydrostats. Muscular hydrostats consist mostly of muscle tissue and lack skeletal support. The fluid in a muscular hydrostat is contained within the muscle cells, not in an internal cavity. Examples of muscular hydrostats include the the foot of a snail, the body of a worm, a human tongue, an elephant trunk, and octopus arms.

One important clarification should be noted about the term tentacle—although tentacles are muscular hydrostats, not all muscular hydrostats are tentacles. This means that the eight limbs of an octopus (which are muscular hydrostats) are not tentacles; they are arms.

When used in a botanical context, the term tentacle refers to the sensitive hairs on the leaves of some plants, such as carnivorous plants.

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