Pteraster tesselatus

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Geographic Range

Occupies the Bering Sea south along the North American coast to Washington, also in the Uyak Bay and around Kodiak Island and Alaska (Chia, 1966; Zintheo, 1946).

Habitat

The cushion star is found mainly in channels or other places with strong currents. Depths at which the P. tesselatus are found at ranges from 20 to 250 meters but the most abundant populations are at 45 meters. The surrounding elements that are found with the cushion star are mostly scallops, sponges, and shells (Zintheo, 1946).

Physical Description

Pteraster tesselatus is commonly called the cushion star because of its inflated appearance. The disc is high, averaging 35mm in height, and the rays, usually five, are short and thick, causing the cushion star to appear pentagonal in shape. The outer membrane is thick and spongy and has regular reticulation 5 to 8mm across. The surface of the membrane varies greatly in texture from smooth to slimy and rough. On the rays, combs are composed of 5 to 7 spines arranged in a fan-shaped manner. In between the rows of combs lie two rows of large tube feet ending in sucking devices. The last ten pairs of tube feet of each ray have no sucking devices and appear to be tactile. At the end of each ray, there is a red eye spot protected by short spines. A large oral opening at the center of the disc is surrounded by a sphincter-like membrane. The colors of the cushion star include cream, tan, yellow, orange, and a gray purple (Zintheo,1946).

Reproduction

The process of reproduction is a continuous one and begins when the female pumps eggs out through the osculum. The males then spawn. The fertilized eggs float to the surface of the water. They are bright orange or yellow and measure 1.5mm in diameter. Each egg is covered with a coat of jelly, and the fertilization membrane can be seen beneath it. The egg then goes through several transformations in the plankton, and the five primordial arms appear simultaneously. Immediately, the larva sinks to the bottom and ends its planktonic life. The star can then crawl. Metamorphosis takes a total of aproximately thirty days.

Behavior

This species of cushion star is a deep-sea bottom dwelling animal and is therefore very sensitive to strong white light and temperature. The cushion star is mobile, but it is not an agile starfish because of the relative thickness of the disc in proportion to the length of its rays. The cushion starfish does not have a developed social system.

Food Habits

The cushion starfish, as most starfish do, feed by inverting their stomachs to digest their food. P. tesselatus feed on a few types of sponges such as Chaonites latus, as well as hydroids, scallops and the bacteria that covers mussels (Zintheo, 1946).

Economic Importance for Humans: Positive

The cushion stars are dried and then eaten as a source of food . They are also sold as souvenirs for tourists (Hess, 1978).

Economic Importance for Humans: Negative

The use of the cushion stars by humans has a negative influence on the ecosystem because of the disruption during the process of dragging for stars.

Other Comments

There are two species know as the cushion star. The deep-sea one is known as Pteraster tessalatus and the shallow-water one is know as Oreaster reticularus.

Contributors

Courtney E. Ruf (author), University of Michigan-Ann Arbor.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

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coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Chia, Fu-Shiang. "Development of a Deep-Sea Cushion Star, Pteraster Tesslatus." Proceedings of the California Academy of Sciences. Fourth Serier. Vol XXXIV. No. 13. p.505-510. San Francisco, 1966.

Hess, Steven C. "Guide to the Commoner Shallow-Water Asteroids (Starfishes) of Florida, The Gulf of Mexico, and Caribbean Region." Sea Grant Field Guide Studies. No. 7, Sept. 1978.

Zintheo Rodenhouse, Irma & Guberlet, John E. "The Morphology and Behavior of the Cushion Star, Pteraster Tesselatus." The University of Washington Publications in Biology. Seattle, 1946.