The whelks enemies

The greatest threat against adult whelks are cod, wolffish, rays and starfish, while sea-urchins and starfish predate on their eggs. The whelk by smelling the water can detect a predator closing in, and protects itself by violently moving its foot and turning over its shell and thus rolling away from its assailant.

The starfish - enemy and friend

The whelk can appear to have a strange relationship with certain starfish; most studied is its relation with the starfish Leptasterias polaris. This starfish is found the North American coast and resembles the Spiny starfish (Marthasterias glacialis), a common species in Swedish waters. Although the starfish is a predator, whelks can sometimes surround it. There are three possible explanation for this strange behaviour; (1) the whelk steals food from the starfish with its long siphon, (2) they are waiting for remains, (3) they eat food such as worms and mussels that have became more accessable after the starfish has stirred up the bottom sediment. The reasons why whelks congregate around Leptasterias polaris which eats large mussels are several; (1) large prey emits several chemical signals that make it easier for whelks to find food, (2) starfish have difficulty covering large prey, which makes it easier for the whelk to reach the prey, and (3) the starfish can be satisfied earlier when devouring larger prey and therefore leave more remains for the whelk.


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Bo Johannesson | Martin Larsvik | Lars-Ove Loo | Helena Samuelsson