Why are beadlet anemones so aggressive?

All aggregating anemones are known for their tendency to lash out with stinging tentacles, but beadlets are particularly hostile. They live in colonies, but only tolerate their cloned family members. If an intruder appears, they go on the attack, nudging and stinging until the unwelcome visitor crawls away or falls from the rocks.

Such aggression could be linked to living conditions. Studies have shown that individuals on the lower shore take fewer risks and are less hostile than those on the upper shore. The upper shore is not submerged as frequently as the lower, so prey is harder to come by. Anemones on higher parts of the beach may thus be more aggressive to make the most of limited feeding opportunities.

Beadlet anemones have specific tentacles for snaring prey (here a prawn) and for defence; the latter are known as acrorhagi.