pedicellariae

Pedicellariae are small, pincer-like appendages on the external surface of many echinoderms, especially sea urchins (Echinoidea) and starfish (Asteroidea). They arise from the epidermis as stalked structures and typically end in one or more calcareous jaws or valves that can open and close like tiny pincers.

Each pedicellarium is moved by muscles that control the valves, allowing the jaws to snap shut to grasp or scrape away objects from the animal’s surface. In some species, the pedicellariae are associated with venom glands and can deliver toxins when engaged, providing a chemical defense in addition to the mechanical one. The principal ecological roles are defense against predators and fouling, including removing parasites, algae, and other small organisms that settle on the animal’s body.

Pedicellariae are especially prominent on many sea urchins and starfish, where they form a dense covering on the skeletal surface. They show variation in size, shape, and arrangement across species and are often used as a morphological feature in taxonomic descriptions. While their primary function is protective and cleansing, their activity can also influence microhabitat interactions on the echinoderm’s surface.