6. Do starfish have a skeleton?

Starfish have an internal skeleton just underneath the skin. It is composed of blocks of magnesium calcite (termed ossicles) which are arranged as a lattice network joined by connective tissue. In some starfish the space between these blocks is quite small forming plates which make the starfish extremely tough. Some blocks bear spines or swollen projections (tubercles) which give the animal a spiny or warty appearance -- hence the general name, echinoderm (meaning spiny skin).

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