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Description:
The six arm brittle star, Ophiactis rubropoda, reaches a disk
diameter of 0.2 inches, with arm length approximately 1 inch. Disk
spines are present only on the ventral surface, and between each arm.
There is one pair of oral papillae, and 4 or 5 arm spines. Body color
is typically brown to green-brown or gray, with alternating dark and light
banding on the arms. The tube feet are bright red, the result of the
hemoglobin being present in the water vascular system.
Habitat:
The six arm brittle star is an epibenthic, shallow water and nearshore
species. It is found in association with hard bottom rock or oyster
reefs, or on fouling communities containing encrusting sponges, barnacles,
and cnidarians. They have also been found among pier pilings.
Similar Species:
This species may be mistaken for the blood brittle star, Hemipholis
elongata, which also possesses hemoglobin and has bright red tube feet.
However, H. elongata has only 5 arms.
Range:
Six arm brittle stars occur along the southeast coast of the United States,
but are most common in Florida.
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The six arm brittle star,
Ophiactis rubropoda. Photo by J.
Miller, Harbor Branch Oceanographic Institution; courtesy of D. Pawson, National Musuem of Natural History. Used with
permission.
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Six arm brittle stars reproduce asexually by dividing their disks and
regenerating new arms to replace lost ones. As in the photo above, it
is fairly common to find animals having 3 short arms and 3 long ones.
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