GEORGETTE DOUWMA / SCIENCE PHOTO LIBRARY GEORGETTE DOUWMA / SCIENCE PHOTO LIBRARY
Fire coral (Millepora dichotoma). Fire corals are not true corals, but hydrozoans or hydroids. Visible here are small stinging hairs covered in cells called nematocysts. The fire coral uses these as a defence mechanism against fish that may feed upon it as well as against prey for food. Photographed in the Red Sea off the coast of Egypt.
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