Morphology
Symmetry- Radial symmetry
Structure- is a radially symmetrical animal that can hunt, move and see in all directions equally well. Appearance- P. lividus has a circular, flattened greenish test with a diameter of up to seven centimetres. The test is densely clothed in long and sharply pointed spines that are usually purple but are occasionally other colours including dark brown, light brown and olive green. Distribution Map
Facts
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BiologyAdaptations for survival- The shells within the test of these creatures are made up of packed, fitted plates which protect them from being damaged. As for the spines outlining their shell, these are movable and help the sea urchin to camouflage or protect itself from predators.
ImportanceEcological- Sea urchins are major components of marine communities. Their grazing limits algal biomass, and they are preyed upon by many predators.
Economic- Sea urchins have some economic significance. The roe is considered a delicacy, especially in Mediterranean regions and Japan, and burrowing species may damage sea walls. Sea urchins also are used in embryological studies. Vocabulary
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