Pedicellarium

Pedicellarium is an anatomical term that refers to a small, jaw-like appendage on the surface of some echinoderms. In contemporary scientific usage, the standard term is pedicellaria (plural pedicellariae), while pedicellarium may appear as a synonym or historical variant in older literature.

Structure and appearance: Each pedicellarium consists of a stalk bearing one or more calcareous ossicles that form a set of valves capable of rapid closure. These valves function like pincers and can grasp tiny particles, organisms, or debris, helping to keep the animal’s surface clean. The morphology and number of pedicellariae vary among species.

Distribution and function: Pedicellariae are common on many starfish (asteroids) and various sea urchins (echinoids), with density and form differing by species and habitat. The primary roles are surface maintenance—removing fouling organisms and debris—and defense, as the closed pincers can deter small attackers. Some pedicellariae may aid in prey capture or sensory perception, depending on the species.

Development and diversity: Pedicellariae develop from dermal tissue during ontogeny and remain integrated into the epidermis as the animal grows. They exhibit a range of shapes from simple to more specialized forms, reflecting ecological and taxonomic differences among echinoderms.

Taxonomic notes: The presence, type, and arrangement of pedicellariae are used in identifying and classifying echinoderm species. The term pedicellarium is less common in modern literature and is typically encountered as a synonym or historical variant of pedicellaria.

See also: pedicellaria.