Sea urchins are members of the phylum Echinodermata, which also includes sea stars, sea cucumbers,
Specifically, … See more

Urchins typically range in size from 3 to 10 cm (1 to 4 in), but the largest species can reach up to 36 cm (14 in). They have a rigid, usually spherical body bearing moveable spines, which give the class the name Echi… See more

The internal organs are enclosed in a hard shell or test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is referred to as an endoskeleton rather than exoskeleton even though it e… See more

Sea urchins are dioecious, having separate male and female sexes, although no distinguishing features are visible externally. In addition to their role in reproduction, the gonads are also nutrient storing org… See more