Mithrodiidae Family of Starfish
One Starfish from the Mithrodiidae Family can be found in this website:
Bradley’s Sea Star, Mitrodia bradleyi. A representative of the Mitrodiidae Family of Starfish.
Phylogeny: Mithrodiid Sea Stars of the Mithrodiidae Family of Sea Stars are in the phylum Echinodermata, which is a large phylum that includes brittle stars, sea cucumbers, sea lilies, sea stars and sea urchins. They are in the subphylum Asterozoa and the class Asteroidea. Asteroideans are characterized by having a flattened, star shape, with a central disk, surrounded by multiple (5 to 40) radiating arms (or rays). Mithrodiid Sea Stars are in the subclass Ambuloasteroidea, the infraclass Neoasteroidea, the superorder Valvatacea, and the order Valvatida. The Mithrodiidae Family is one of fifteen families in this order. The Mithrodiidae Family is fairly small, containing only two genera and seven species. The name Mithrodiidae comes from the Greek name Mithridates, which means “gift of Mithra”.
Morphology: Mithrodiid Sea Stars are characterized by a larval stage with bilateral symmetry and an adult stage with 5-rayed radial symmetry. They have a small central disk with a round cross section that is surrounded by five elongated arms (or rays), with two rows of feet with suckers, on the underside of each arm. The arms have a broad attachment point where the arms join the disk and they taper as they extend from the disk. Mithrodiid Sea Stars shed their arms more readily that those in other families. They are able to regenerate their amputated arms. 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 aboral (dorsal) surface is covered by a thick skin that has rough granules, tubercles, or tiny spines. They have conspicuous ossicles (calcareous particles that are part of the endoskeleton) along their margins. Their pedicellariae are elongate and multi-valved. They have a unique water-vascular system that uses hydraulic power to operate a multitude of tined tube feet that are used in locomotion and food capture. The tube feet have double ampullae (bulb-like appendages that push water into tube feet, causing them to extend). Some 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 have a water vascular system, tube feet, and a complete digestive system, but they lack a head, eyes, nervous system, or excretory system. These sea stars are often colorful with bands or blotches of brown, orange, red or white. Mithrodiid Sea Stars are medium to large in size, with a maximum diameter of 55 cm (21.5 inches) and a weight of 5.9 kg (13 lbs.).
Distribution: Mithrodiid Sea Stars are found attached to rocks, within coral, and on other hard substrates. They live in the intertidal zone, and to to depths up to 143 m (470 feet). Mithrodiid Sea Stars are found worldwide in tropical to subtropical seas. At least two species from the Mithrodiidae Family are found in Mexican waters.
Reproduction: Mithrodiid Sea Stars are gonochoric (male or female for life). They reproduce sexually, through broadcast spawning, with external fertilization. The fertilized eggs develop into planktonic larvae. They can also reproduce asexually through fragmentation.
Ecosystem Roles: Mithrodiid Sea Stars feed on encrusting organisms, detritus and small invertebrates. In turn they are preyed upon by crabs, fish, and other sea stars.