Using the research submersible Johnson-Sea-link I, a population of the simple-armed gorgonocephalid brittlestar, Asteroporpa annulata, was discovered on a deep-water coral pinnacle off east-central Florida. Information on the habitat, population structure, circadian activity
and feeding was obtained for this previously unstudied species, the only simple-armed member of the suborder Euryalina ever directly examined in situ. The brittle stars were associated with the scleractinian, Oculina varicosa. The clumps of coral bearing Asteroporpa usually carried
only one specimen. Asteroporpa remained perched in an exposed position during the day and night. Some individuals extended single arms during the day, but most brittlestars did not take a suspension-feeding posture until at least several hours after dusk. At that time, they oriented
with their aboral surface facing the current. Generally three or four arms were extended vertically; sometimes, however, the tips of the arms bent into the current, or the arms were thrown into a sinusoidal pattern. The diet mostly consisted of pelagic organisms, predominantly copepods, some
veligers and ostracods, and more rarely larvaceans, bivalve larvae, fecal pellets, eggs, amphipods and larval fish. An unidentified, siphonostome copepod associate was attached to the stomach wall of 26% of the specimens. Twenty percent of the brittlestar arms examined were regenerated, an
indication that the species suffers from predation despite its heavy armor.
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