|The Robinson Library >> Phylum Echinodermata|
Most individuals of this species have 9 or 10 arms, but some have as few as 7 and others have as many as 14. Although purple is the most common color, individual coloration ranges from dirty cream to orangish-yellow to bright pink-purple dorsally, with a pale orange underside. When at rest, the tips of the arms are commonly turned upwards to reveal the underside and two rows of tube feet with sucking discs. The upper surface is formed of calcareous plates densely covered with peg-like projections covered in tiny spinelets. Purple sunstars can grow to 16 inches in diameter, but the average is about 8 inches.
Distribution and Habitat
The purple sunstar is found in the Atantic Ocean from the coasts off Canada south to the Gulf of Maine, as well as off the coasts of Greenland and the British Isles; it is also found off the western coast of North America between Alaska and Puget Sound. A bottom-dweller, it is typically found on rocky or gravel bottoms at depths between 120 and 1,480 feet.
A voracious carnivore, the purple sunstar preys on sea cucumbers, nudibranches, sea stars, and other invertebrates. Not afraid to go after prey almost as large as itself, the sunstar wraps its arms around its prey, everts its stomach over it, and then releases digestive enzymes; once the victim has been sufficiently softened by the enzymes the sunstar can draw its stomach back in, along with its dinner.
Females lay their eggs in the water, where they are then fertilized by the males. The young resemble tiny adults as soon as they are born. Purple sun stars are also able to reproduce asexually, by regeneration or division, although sexual reproduction is by far the most common method.
Like all other members of class, the purple sunstar can regenerate a part of its body that has been broken off or eaten by a predator. It can also fully regenerate from a small piece of its body, provided that it contains a sufficiently large portion of the central disk.
Purple sunstars use their hundreds of tube feet to adhere to the rocks, as well as for locomotion. The feet are connected to ampullae (tiny disc-like structures). When the ampullae contract, fluid is forced into the tube feet, extending them; small muscles then direct the tube feet in one direction or another.
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>> Phylum Echinodermata
This page was last updated on 08/26/2018.