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Dendraster excentricus
Common name(s): Eccentric Sand Dollar
Description:
Dendraster excentricus is disk-shaped; and when it is alive it's colors range from lavender-grey, brown, reddish-brown or a dark purple-black; the detail of the body is almost circular, flattened and is occupied by 5 petal-shaped loops of tube feet on the upper dorsal surface; both the dorsal and the ventral surface are covered by short, fine spines; the mouth is located at the center on the lower surface and the anus is located at the rear margin.
Size:
Most sand dollars measure from 5 to 10cm in diameter.
Distinctive Characteristic:
Echinoderms have an internal skeleton made from crystalline calcite plates; a water-vascular system of fluid-filled vessels; surface appendages and hollow tentacles.
Relations:
Sand dollars are closely related to sea urchins.
Range:
Dendraster excentricus can be found from the range of Alaska to Baja, California
Habitat:
This sand dollar is usually found on sand bottoms of sheltered bays and on open coasts; from the low-tide line to the water; the deepest habitat that Dendraster excentricus exceeds is 40m.
Ecology:
Dendraster excentricus is strictly a marine animal.
Life Cycle:
As soon as the eggs of Dendraster excentricus are fertilized, they are shed directly into the water. This technique of Echinoderms is known as spawning. Once eggs are fertilized, the larvae eventually find a suitable substratum, then settles and metamorphoses into the adult.
Natural History:
The sand dollar most familiar to beachcombers is the dead, clean test of the species found along sandy shores. The Eccentric Sand Dollar's role in nature is essential in terms of being efficient scavengers of decaying matter on the sea floor, and they tend to prey upon a variety of small organisms which helps to regulate their numbers.
Special Characteristic:
Dendraster excentricus gets it's name from the 5 petal-shaped loops being off-centered.
Interesting Fact:
The name Echinodermata means "spiny-skinned" which refers to the projecting spines of tubercles that give a rough, warty appearance to the surface of most echinoderms
Additional Resources:
Clark, Ailsa M. (1977). Starfish and Related Echinoderms, 3rd ed. Pearse, Vicki. (1987). Living Invertebrates
Biogeography of D. excentricus
Last updated Wednesday, August 23, 2006, by Lisa Ferrier
