Asterinidae Family of Sea Starfish

One Sea Starfish of the Asterinidae Family can be found in this website:

Bat Star, Patiria miniata. The sole representative of the Asterinidae Family of Sea Starfish.

Phylogeny: Sea Stars of the Asterinidae Family, like sea urchins and sea cucumbers, are in the Phylum Echinodermata. Echinoderms (meaning spiny skin) 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. Asterinidae Sea Stars are in the class Asteroidea, which is characterized by having a flattened, star shape. There is a central disc, surrounded by multiple (5-40) 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. The Asterinidae Family is one of fifteen families in the order Valvatida. The Asterinidae Family is fairly large and is composed of six subfamilies, thirty-five genera, and one hundred seventy species. Species in the Asterinidae Family are commonly called Asterinids.

Morphology: Sea Stars in the Asterinidae Family have five arms, with two rows of tube feet with suckers. Asterinids are further characterized by being flattened dorsally and by having short arms. The arms may so short as to give the star a pentagonal outline, or they may resemble a webbed star shape. The margins of the star are thin. The aboral surface is textured with crescent-shaped plates, giving the surface a knitted look. Some species in this family have paxillae (umbrella shaped structures made of microcrystals) and some have clamp-like pedicellariae (tiny pincers) recessed in skeletal plates. They are characterized by conspicuous ossicles along their margins. Asterinids can be very colorful. Most Asterinids are tiny or small in size, but a few deep-water species reach a maximum of  45 cm (15.5 inches) in diameter.

Habitat and Distribution: Asterinids are generally found on, or under rocks, or in crevasses. They live intertidally and to depths of at least 500 m (1640 feet). They are found worldwide in tropical to polar waters.  Only one species is found in Mexican waters, and that in  the Pacific Ocean.

Reproduction: Reproduction strategies for Asterinids are very diverse. Some are gonochoric and some are simultaneous hemaphrodites. When they reproduce sexually, some have internal fertilization and some have external. Some fertilized eggs are planktonic, some are laid as a mass attached to the substrate, some are brooded, and some species skip egg laying and give birth to live individuals (viviparity). Asexual reproduction is also a possibility, through fission.

Ecosystem Interactions: Asterinids may feed by grazing on algae or bacterial mats, they may feed on detritus, or they may even be ambush predators feeding on small shrimp. They feed by everting their stomach and digest the prey externally. Asteriids are prey for crabs, shore birds and marine mammals. Since 2013, most Asteroidean species in the Temperate Eastern Pacific have seen dramatic drops in their populations, as high as 80% population loss for some species. This decline is blamed on Sea Star Wasting Disease, a Densovirus (Parvoviridae). It is unknown if this Densovirus is the cause of the high mortality or a symptom of other causes such as environmental stressors. Only recently have some species begun to recover, and only in certain areas.