GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms have no heart, brain or eyes; they move their bodies with a unique hydraulic system called the water vascular system.

Detailed explanation-2: -One characteristic of an echinoderm is that they all have pentamerous radial symmetry. This simply means they all have 5 equal body parts. You can divide these animals into five equal parts, and every part is the same. For example, most sea stars have five arms or a multiple of five arms.

Detailed explanation-3: -Echinodermata: Systematics. In traditional taxonomy, there are five classes of living echinoderms: Crinoidea (sea lilies), Asteroidea (starfish), Ophiuroidea (brittle stars or snake stars), Echinoidea (sea urchins and sand dollars), and Holothuroidea (sea cucumbers).

Detailed explanation-4: -The echinoderms have an open circulatory system, meaning that fluid moves freely in the body cavity. But echinoderms have no heart. This may be due to their simple radial symmetry-a heart is not needed to pump the freely moving fluid.