Common starfish Common starfish The common starfish or common sea star ("Asterias rubens") is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens (up to 52 cm across) are known. The common starfish is usually orange or brown, and sometimes violet; deep-water specimens are pale. The common starfish is to be found on rocky and gravelly substrates where it feeds on molluscs and other benthic invertebrates. The common starfish normally has five arms, broad at their base and gradually tapering to
Crown-of-thorns starfish ward off the starfish as it seeks to spread its stomach over the coral surface. In reef areas of low densities of hard coral, reflecting the nature of the reef community or due to feeding by high density crown-of-thorns, the starfish may be found feeding on soft corals (Alcyonacea). The starfish are cryptic in behavior during their first two years, emerging at night to feed. They usually remain so as adults when solitary. The only evidence of a hidden individual may be white feeding scars on adjacent coral. However, their behavior changes under two circumstances: The elongated sharp spines covering