Sea background

There are not many echinoderm species in Icelandic waters compared to the other groups, but they are large and conspicuous animals. These are starfishes, sea urchins, brittle stars, sea cucumbers and feather stars. Echinoderms have a skeleton composed of calceous plates. Sometimes this forms a rigid skeleton, like most sea urchins while for others the plates are small and not attached to each other, for example the soft sea cucumbers. The five groups of echinoderms have quite different habits.

Sea stars are probably the best known group. Although innocent looking, they are in fact voracious predators on other slow moving or sessile animals. Fishermen consider them a pest when they invade scallop beds and mussel growing lines.

Brittle stars are closely related to starfishes. They have a circular central plate with 5 narrow arms extending from the plate. They can walk on these arms and are quite mobile compared to other echinoderms. Brittle stars are harmless detritus feeders.

Sea urchins are also harmless to other animals and eat algae and detritus. The best known is the green sea urchin (Strongylocentrotus droebachiensis). Under certain conditions their numbers can grow enormously and they start eating up the kelp forests like a plague of locusts. This has been recorded in a few locations around the world, including in Eyjafjörður.

Sea cucumbers vary in shape and size but the largest and most common is the orange-footed sea cucumber (Cucumaria frondosa). It is the size and shape of a fat sausage. Sea cucumber are leathery and soft unlike other echinoderms. Sea cucumbers are detritus or filter feeders.

Feather stars are the most primitive of the echinoderms, they are almost sessile on the bottom and filter microscopic food from the ocean. They are mostly found in the deep sea.

Two species of echinoderms have been harvested in Icelandic waters, green sea urchin and orange-footed sea cucumber.


erlendur bogason-30 Sólstjarna (Mynd: Erlendur Bogason) Sólstjarna (Mynd: Erlendur Bogason)

skrapdyr Litlir roðakrossar (Mynd: Erlendur Bogason) Litlir roðakrossar (Mynd: Erlendur Bogason)

erlendur bogason-33 Stóri krossi að éta kúfskel (Mynd: Erlendur Bogason) Stóri krossi að éta kúfskel (Mynd: Erlendur Bogason)


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