Why are beadlet anemones so ag­gres­sive?

BBC Wildlife Magazine - - Our Wild World - Lewis White

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.

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