ALEXIS ROSENFELD / SCIENCE PHOTO LIBRARY ALEXIS ROSENFELD / SCIENCE PHOTO LIBRARY
Sea cucumber (Holothuria tubulosa) standing erect on the seabed ready to eject reproductive cells. A fertilised egg is formed when a male sperm and a female egg meet in the water. A sea cucumber is an elongated, worm-shaped echinoderm (the group of animals that includes starfish) whose body wall is elastic and leathery. There is no rigid skeleton only a highly developed body musculature. These muscles are also used for movement, though few sea cucumbers can swim and most tend to crawl about on the sea floor. They fed on plankton and decaying matter and algae on the seabed. The largest of the sea cucumbers are 2 metres in length. Photographed off Levant Island, France, Mediterranean Sea.
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