Sea urchins (sea apples, sea urchins; class Echinoidea) are spiny, invertebrate animals that belong to the phylum echinoderms (Echinodermata).There are app. 900 different kinds.

Sea urchins are usually more or less spherical, heart-shaped or disc-shaped and have an inferior mouth. They have a hard shell that is usually covered with spines. The shell consists of small plates on which there are knobs on which the spines are movably attached by means of a ball and socket joint. The spines serve for locomotion in many species. Some species dig themselves in with the help of the spines. The spines also have a protective function. Some species can even emit poison. Between the spines are short-stalked, divergent pedicellaria. These also serve for defense and for keeping the skin clean.

Large numbers of sea urchins lead to the destruction of kelp forests that sea urchins graze on. Kelp forests are essential ecosystems for many other marine species.

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Vertaalresultaten

VertaalresultaatLarge numbers of sea urchins lead to the destruction of kelp forests that sea urchins graze on. Kelp forests are essential ecosystems for many other marine species.