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Sea anemones

A sea anemone clinging to the rocks in a tide pool. The calliactis sea anemone forms partnerships with hermit crabs. The anemone...Read More >>A sea anemone clinging to the rocks in a tide pool. The calliactis sea anemone forms partnerships with hermit crabs. The anemone lives on the crab's shell and protects its host both by providing camouflage and using its stinging tentacles to repel predators. In return, the crab carries the anemone to new places to catch victims. Also each partner may share in the leftovers of the other’s meal. Sea anemones belong to the cnidarian group of invertebrates, which also includes jellyfish and coral polyps. Looking like flowers, their bodies consist of a sticky foot ("pedal disc"), a column-like body and a set of stinging tentacles grouped around a central mouth. The tentacles are used both to paralyse and capture prey, and to fend off enemies. Although they generally stay in one place, sea anemones can move if conditions become unfavourable to them. They can creep slowly about on their foot, or by swimming, either by flexing their bodies or using their tentacles.



A colony of sea anemones

Tentacles

Sea anemones anchor themselves to rocks with their stinging tentacles pointing upwards. The tentacles are used to catch zooplankton and shrimps (larger species can prey on fish), paralyse them and draw them into the anemone's mouth. The tentacles are lined with hairs. When a hair is touched, it shoots out a tiny venomous "harpoon", called a nematocyst, which attaches itself to the animal that triggered it.
 
 

Avoiding danger

There are more than 1000 species of sea anemone.

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