Wild Harris

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Common starfish

There are many different kinds of starfish in the seas around Harris, but the species you are most likely to see on the shore is the common starfish. Like all echinoderms, it has a spiny skin, a five- sided body plan, and tube feet to help it move around. There is no front or back; a primitive nervous system coordinates the actions of the arms to move for instance towards the scent of a food source. If you look closely you will see a single spot near the middle of the starfish's back - this is a pore where the water gets in to supply the hydraulic system that operates the starfish's tube feet. (See Starfish and their Spiny Cousins)  Although the starfish will eat carrion (dead animals), its main method of feeding is predating other animals, particularly those that are too slow or unable to escape. Mussels are a favourite prey item: a starfish will attach its arms to both shells by means of its sticky tube feet, and begin to pull. At first the mussel is able to resist the pull, but the starfish has greater stamina than the mussel and eventually the shellfish grows tired. As soon as the shells are pulled apart enough, the starfish turns its stomach inside out and pushes it inside the mussel shell, where it secretes deadly digestive juices. The poor mussel is digested to death; once it becomes a soupy mass the starfish sucks it up and sends it on to the five extra stomachs it has, one in each arm.

(Photo: Paul Tyler)

A common starfish. The large white spot is the pore that feeds water to its hydraulic system which operates the tube feet. 

(Photo: Paul Tyler)

A deadly embrace. This starfish is trying to pull apart the shells of this clam in order to eat it. The clam is probably doomed. Starfish have great powers of regeneration i.e. they can grow back lost body parts

by Paul Tyler

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