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Spiny sea stars reach a maximum size of approximately 7 inches in diameter.  There are 5 thick arms, each approximately 2 times as long as the diameter of the central disk area, tapering to blunt tips.  Both the dorsal and ventral surfaces are covered with a thick, opaque skin. Short, conical spines cover the dorsal body surface and are arranged in longitudinal rows, though some individuals have scattered spines.  Body color ranges from deep red-brown to shades of purple, pale red, and yellow-brown.  Tube feet are orange. 

Spiny sea stars can be found from the intertidal zone to depths of 50 feet in seagrass meadows, rocky coastlines, sand and shell hash habitats.

Similar Species:
A species occurring in the Florida Keys, Echinaster echinophorus, is similar to E. sentus.  The two are distinguished by E. echinophorus having fewer, longer arm spines and more uniform color. E. echinophorus is not known to occur in the Indian River Lagoon. 

Spiny sea stars range from Florida though the Bahamas. 



Echinaster sentus, the spiny sea star, from the Indian River Lagoon.  Photo courtesy of W. Lee, Smithsonian Marine Station.  
Spiny sea stars showing variations in body color.  Photo by J. Miller, Harbor Branch Oceanographic Institution; courtesy of D. Pawson, National Museum of Natural  History.  Used with permission.