Starfish

Starfish, also called sea stars, are marine invertebrates in the class Asteroidea within the phylum Echinodermata.

Starfish, also called sea stars, are marine invertebrates in the class Asteroidea within the phylum Echinodermata. They live only in saltwater and are closely related to sea urchins, sand dollars, and sea cucumbers. Despite the common name, they are not fish.

Classification

Starfish are marine invertebrates classified in the class Asteroidea within the phylum Echinodermata. They are closely related to sea urchins, sand dollars, and sea cucumbers. There are more than 1,600 known species. Despite the common name, they are not fish.

Anatomy and movement

The starfish body plan typically consists of a central disk with five or more arms arranged in radial symmetry. Their skin is spiny, and they have hundreds of tube feet on the underside. A water vascular system powers these tube feet, allowing for movement, feeding, and sensing the environment. Many species can also regenerate lost arms.

Habitat and distribution

Starfish inhabit marine environments worldwide, from shallow coastal areas to the deep ocean floor. They can be found in habitats such as rocky shores, tide pools, kelp beds, coral reefs, and the seafloor. In Canada, they occur along both the Pacific and Atlantic coasts and are familiar in cold-water marine ecosystems.

Feeding and ecology

Most starfish are carnivorous and often feed on bivalves like clams and mussels, though diets vary among species. They can influence the structure of marine communities and are important predators in many ocean floor ecosystems.

Reproduction and regeneration

Starfish can reproduce sexually, and some species are also capable of asexual reproduction. Many species have the ability to regenerate lost arms, and some can regrow substantial parts of their body.