Bat Star

The Bat Star is most commonly reddish-orange or mottled white, but can be found in a variety of colors and patterns. They usually have five, sometimes four to nine, short, triangular arms. They have a radius of about four inches and have radial symmetry. They have tube-feet that allow them to move. The tube-feet are pressurized by their water-vascular system. (Grzimek 1972, Meinkoth 1981,Dando 1996).

Other Physical Features: ectothermic

Bat Stars live on rocks, sand bottoms, and among surf grass. In order to find the stars it is nessesary to look in crevices and under rocks. They can be found in waters in the low-tide region to the depth of 293m deep. (Meinkoth 1991, Ricketts, et al. 1985)

Aquatic Biomes: coastal

The Bat Star can be found along the Pacific coast from Alaska down to Mexico. They are in the subtidal region to a depth of about 300m. They are numerous in certain kelp forests. (Meinkoth 1981, Ricketts, et al 1985)

Biogeographic Regions: pacific ocean (Native )

The Bat Star is usually an omnivore or a scavenger. It feeds by extending its stomach over a great variety of sessile or dead plants and animals. They start to digest plant growth by molding their flexible lining of the cardiac stomach against the substrate. (Grzimek 1972, Ricketts, et al 1985, Erikson, et al 1997).

Bat Stars have a commensal relationship with a polychaeta, Ophiodromus pugettensis. The worms live on the oral surface of the Bat Star and usually move toward the ambulacral groove. There can be as many as twenty worms on one star. Another scientific name used for the Bat Star is Asterina miniata.(Ricketts, et al. 1985, Erikson, et al 1997)

The specimens of Bat Stars used for the embryological studies are put back into the tide pools to prevent their depletion. Due to other collecting activities it is hard to find Bat Stars intertidally on the Oregon coast. (Ricketts, et al. 1985)

US Federal List: no special status

CITES: no special status

Starfish, including Bat Stars, are in direct competition with humans in the comsumption of mollusks. If they prey on commercial mollusks, such as oysters, they can cause extensive destruction of oyster beds. (Britannica 1999)

Since the Bat Star has a long breeding period, scientists use the star for embryological experimentation. Bat Stars help regulate the numbers of small organisms by preying on them. (Britannica 1999) (Ricketts, et al. 1985)

The Bat Star has an unusually long breeding season. Both males and females will discharge fertile sperm and eggs all year long, but more abundantly during the late winter and spring. A fertilized egg will turn into a motile embryo and then later into a minute larvae. The larvae swims by moving its cilia. Eventually the larvae settles and develops into the seastar. (Ricketts, et al 1985)

A recent study showed that crawling speed is slower in larger, longer-armed bat stars, for both five and six-armed individuals. This may be because of the lower ratio of tube-feet to body mass as the stars grow larger. (Mongomery and Palmer 2012)

Biology/Natural History: An omnivore and scavenger, feeds mainly on surfgrass. Diet also includes echinoids, algae, sponges, bryozoans, and colonial tunicates, plus organic films on rocks. It cannot open clams. Feeds by everting its stomach, which it may even evert to gather particles from the water. Most animals which avoid other seastars have little response to this species, except for the nudibranch Dendronotus iris, which may swim away. Spawn at least from May to July but ripe individuals can be found throughout the year. Individuals may combat one another if they meet, including pushing, placing a ray over the opponent. May have several individuals of the commensal polychaete worm Ophiodromus pugettensis living on the oral surface or in the ambulacral grooves. This species is often used for developmental studies because ripe individuals can be found throughout the year.

This star has 5 short rays , webbed between. The central disk is wider than the rays are long. There are no conspicuous marginal plates along the edges of the rays. The gritty aboral surface is covered with flattened, crescent-shaped ossicles with their concave sides oriented toward the center of the disk and arranged in concentric clusters, giving it a sandpaperlike texture. No pedicellariae. Color of aboral surface highly variable: orange, red, purplish, brown, dark gray, yellow, or green. Diameter to 20 cm.

Depth Range: Low intertidal to 290 m.

Geographical Range: Sitka, Alaska to Baja California and Islas de Revillagigedo, Mexico. Abundant in Central California and Monterey Bay. Uncommon north of California and in Mexico. In our area, only a small population exists at Cape Flattery and another one on the west side of Vancouver Island. In Alaska, only in the extreme low intertidal on the outer coast.

Rocky intertidal, especially near surfgrass, algae, sponges, and bryozoans.

How to Distinguish from Similar Species: Mediaster aequalis has large marginal plates. Pteraster tesselatus has an aboral surface lined with soft tissue and secretes copious slime. Dermasterias imbricata has a smooth aboral surface and is reddish-brown with gray or purple.

Patiria miniata, the bat star, sea bat, webbed star, or broad-disk star, is a species of sea star (also called a starfish) in the family Asterinidae. It typically has five arms, with the center disk of the animal being much wider than the stubby arms are in length. Although the bat star usually has five arms, it sometimes has as many as nine. Bat stars occur in many colors, including green, purple, red, orange, yellow and brown, either mottled or solid. The bat star gets its name from the webbing between its arms, which is said to resemble a bat's wings.

The bat star is usually found in the intertidal zone to a depth of 300 metres (980 ft). Its range extends from Sitka, Alaska to Baja California in the Pacific Ocean. It is most abundant along the coast of Central California and the Monterey Bay.