"spiny skin"
Radial symmetry (5 points/arms)
Internal skeleton
Water Vascular system - radial canals with ampulla (bulbs) on inside and tube feet extending out bottom surface. Madreporite on aboral surface (back), water intake.
External fertilization - sperm and eggs released into water
Complete digestive system - mouth on bottom, oral surface in middle. Cardiac stomach everts out mouth to digest prey externally and suck into pyloric stomach, anus on aboral side. Many digestive glands fill radial arms (pyloric caeca)
Asexual reproduction - can regenerate lost limbs
No brain - tiny eyespots on ends of arms to detect light, ring of nerves
Poorly developed respiration - diffusion through tube feet.
Excretion - diffusion through tube feet.
Examples: sea stars, sea urchins, sea cucumbers, sand dollars
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