tentacle

A tentacle is a long, flexible limb used for sensing, grasping, or capturing prey. The term appears in multiple animal groups, but its exact meaning and anatomy vary by lineage. In general, tentacles are elongated appendages that can be extended, retracted, or moved to interact with the environment, often bearing sensory structures or adhesive surfaces at their tips.

In cephalopods, the distinction between arms and tentacles is important. Octopuses have eight arms with suckers along their length and do not possess a separate pair of tentacles. Squids and cuttlefish, by contrast, have eight arms plus two longer feeding tentacles. These tentacles are typically retractable and end in a club-like structure that bears suckers or hooks, enabling rapid grasping of prey. Both arms and tentacles are controlled by a complex nervous system and rely on muscular hydrostats rather than a rigid skeleton.

Outside cephalopods, tentacles occur in other phyla. In cnidarians such as jellyfish and sea anemones, oral or peripheral tentacles extend from the body and are mainly used for prey capture and defense, often equipped with specialized stinging cells called nematocysts. In such groups, tentacles may be more numerous and evenly arranged around the mouth.

Structurally, tentacles are usually composed of muscle and connective tissue, lacking bone or cartilage. Their versatility supports functions like exploration, capture, locomotion, and sensation, reflecting a broad evolutionary role across diverse animal lineages.