Echinasteridae Family of Sea Stars
One Sea Star of the Echinasteridae Family can be found in this website:
Thin-spined Sea Star, Echinaster (Othilia) tenuispinus. A representative of the Echinasteridae Family of Starfishes.
Phylogeny: Sea Stars of the Echinasteridae Family of Starfishes are in the phylum Echinodermata, a large phylum that includes Brittle Stars, Sea Cucumbers, Sea Lilies, Starfish and Urchins. Echinasterid Sea Stars are in the class Asteroidea, the subclass Ambuloasteroidea, the infraclass Neoasteroidea, the superorder Spinulosacea, and the order Spinulosida. The Echinasteridae Family is the only family in this order. The Echinasteridae Family contains eight genera and around one hundred thirty-six species. The name Echinasterid comes from the Greek words meaning “spiny star”. Species in this family are also commonly called Echinasterids.
Morphology: Echinasterids have a central disc that is surrounded by 5 radiating arms with a broad attachment point where the arms join the disk. The arms are long and tapering with a circular cross section. They have a spiny aboral (dorsal) surface with aboral reticulate (net-like) plates with ambulacral grooves that have fine or conical, cylindrical, or thorny spines. They have a water vascular system, tube feet with a singular ampulla, and a complete digestive system. They lack a head, eyes, nervous system, or excretory system. The disk 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. Their mouths are surrounded by triangular plates and these stars lack the pedicellariae found in other sea star families. They have a unique water vascular system that uses hydraulic power to operate a multitude of tiny tube feet that are used in locomotion and food capture. They feed via inserting the stomach out through the mouth surrounding the prey, secreting enzymes to digest the food and then retracting the stomach when finished eating. They are characterized by a larval stage with bilateral symmetry and an adult stage with 5-rayed radial symmetry. All Echinasterids have the ability to regenerate amputated limbs. Starfish in the Echinasteridae Family reach a maximum of 30 cm (12 inches) in diameter.
Distribution: Echinasterids may be found on gravel, mud, rock, or sand substrates. They live in the intertidal zone and at depths up to 1,000 m (3,330 feet). Echinasterids have a cosmopolitan distribution and are found from tropical to polar seas. At least twelve species from this family are found in Mexican waters.
Reproduction: Echinasterids are gonochoric (male or female for life) and reproduce sexually, through broadcast spawning, with external fertilization. The eggs hatch into planktonic larvae. Some species can also reproduce asexually through fission.
Ecosystem Roles: Echinasterids have diverse diets and feeding styles. Some graze on algae, bryozoans, and sponges, while others are predators feeding on hydroids, sea cucumbers, sea pens, other sea stars, sea urchins, and tunicates. In turn they are preyed upon by shore birds, crabs, fish, marine mammals and other sea stars.