Animal Diversity Web

Geographic Range

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

Habitat

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

Physical Description

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

Reproduction

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)

Behavior

A large group of bat stars will sometimes engulf the carcass of a decaying fish and consume it in a slow-motion feeding frenzy that can be mistaken for a wrestling match. (Davis 1991).

Like all sea stars, when turned over bat stars will right themselves by using their tube feet and arms to perform a slow, graceful somersault that restores them to their normal position. The main predators of sea stars are other sea stars, mollusks, and crustaceans. They avoid being eaten by secreting chemicals used to stimulate violent escape responses in other animals. (Britannica 1999)

Food Habits

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).

Economic Importance for Humans: Positive

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)

Economic Importance for Humans: Negative

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)

Conservation Status

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)

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Other Comments

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)

Contributors

Jennifer Ervin (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

References

Dando, M., M. Burchett, G. Waller. 1996. SeaLife: A Complete Guide to the Marine Environment. United states of America: Smithsonian Institution Press.

Davis, C. 1991. California Reefs. San Francisco: Chronicle Books.

Encyclopedia Britannica, 1999-2000. "Starfish" (On-line). Accessed April 16, 2000 at http://www.britannica.com/bcom/eb/article/0/0,5716,71256+1+69454,00.html.

Erikson, E., L. Thompson, F. Starkey. 1997. Accessed April 16, 2000 at http://www.catalinaconservancy.org/ccd/EEINDSPP/ASTEMIN.HTM.

Grzimek, D. 1972. Grzimek's Animal Life Encyclopedia; volume three: Mollusks and Echinoderms. New York: Van Nostrand Reinhold Company.

Meinkoth, N. December 1981. The Audubon Society Field Guide to North American Seashore Creatures. New York: Alfred A. Knopf, Inc..

Ricketts, E., J. Calvin, J. Hedgpeth. 1985. Between Pacific Tides. Stanford, California: Stanford University Press.