Oreasteridae Family of Cushion Stars

The Oreasteridae Sea Stars or Cushion Stars, such as Sea Urchins and Sea Cucumbers, are in the Phylum Echinodermata. Echinoderms have spiny skins and are characterized by a larval stage with bilateral symmetry and an adult stage with 5-rayed radial symmetry. They are unsegmented and can be cucumber, disc, sphere or star in shape. They have a water vascular system, tube feet, and a complete digestive system, but they lack a head, eyes, nervous system, or excretory system. They are found only in marine environments.

Cushion Stars are in the Class Asteroidea, which is characterized by having a flattened, star shape. There is a central disc, surrounded by multiple (5 to 40) radiating arms (or rays). The disc contains most of the organs, with the mouth on the ventral side and the anus and madreporite (entry plate for the water vascular system) on the dorsal surface. Asteroidea Sea Stars are one of two major Classes of Astereozoans. The other Class is Ophiuroidea. Asteroideans are easily distinguished from Ophiuroideans by the arms of Asteroideans having a broad attachment point where the arms join the disc. Their arms taper as they extend from the disc. Ophiuroideans have arms that are relatively the same thickness their entire length, giving them a narrow attachment point at the disc. All Asteroideans have the ability to regenerate amputated limbs.

Cushion Stars are in the Order Valvatida. These starfish generally have 5 arms, with 2 rows of tube feet, with suckers, on the underside of each arm. They have conspicuous ossicles (calcareous particles that are part of the endoskeleton) along their margins. Sea Stars in this Family have large central discs relative to the length of their arms. In some species, these stars look more like pentagons than stars. These stars are dome shaped in profile and have stiff bodies. Cushion Stars have well developed marginal plates, but the plates are not always obvious. They have thick skin, with tubercles or granules. These stars have tube feet with terminal discs that have spicules in their walls. The pedicellariae are sunken and may be bivalve or forcipulate, or resemble split granules. Cushion Stars are often brightly colored and can reach up to 50 cm (20 inches) in diameter.

Oreasteridae Sea Stars are found  on coral, mud, rock, or sand substrates. They are often associated with sea grass beds or mangroves. They live intertidally to depths up to 220 m (720 feet). Cushion Stars feed on algae, ascidians, bryozoans, corals, sponges and sea urchins. In turn they are preyed upon by crabs, shrimp and other sea stars.

Oreasteridae Sea Stars are found worldwide in tropical and temperate seas. There are 74 species placed into 20 Genera in the Astropectinid Family of which 2 species are found along Mexico’s Pacific Coast.