Crown-of-thorns starfish substrates with their arms and, when offered a choice of substrates, tend to settle on coralline algae, which they will subsequently feed on. In the classic pattern for echinoderms, the bilaterally symmetrical larva is replaced by a pentamerously symmetrical stage at metamorphosis, with the latter's body axis bearing no relationship to that of the larva. Thus the newly metamorphosed starfish are five-armed and are 0.4–1 mm diameter. (Note the size of the tube feet relative to the size of the animal.) They feed on the thin coating layers of hard encrusting algae (coralline algae) on the undersides of dead coral
Common starfish mass strandings have occurred in Britain and elsewhere at such places as Holkham Beach in Norfolk in 2009, near Sandwich in Kent in 2008, and near Brighton ten days later. A similar occurrence occurred on the shore of the White Sea where vast numbers of starfish came ashore on a nine-mile stretch of beach in 2004. It was said that people could not "walk around them because the whole shore was full of starfish". Russian experts expressed mystification as to the cause of the stranding. Common starfish The common starfish or common sea star ("Asterias rubens") is the most common