• Echinoderms exhibit an endoskeleton of calcareous ossicles.
  • Digestive system is complete with mouth on the lower side i.e. ventral side and anus on the upper side i.e. dorsal side.



Body Organisation:

    • Echinoderms are triploblastic organisms with a unique pentaradial symmetry as adults, although they exhibit bilateral symmetry during their larval stage.
    • Echinoderms have an organ-system level of organisation.
    • They possess spiny skin, which gives them their name (echino = spiny, derm = skin).
    • Echinoderms have a coelom (body cavity) and a unique water vascular system that aids in locomotion, feeding, and respiration.
    • They lack a centralised brain but have a decentralised nervous system with nerve rings and radial nerves.


    • Echinoderms exhibit diverse modes of locomotion.
    • Most echinoderms have tube feet, which are part of the water vascular system, and use them for slow crawling or attachment to surfaces.
    • Some echinoderms, like sea stars, move by alternating the action of their tube feet and muscle contractions.
    • Some echinoderms, such as sea cucumbers, can contract their bodies to move or use muscular contractions for limited crawling.


    • Echinoderms reproduce sexually, with separate sexes (male and female).
    • Fertilisation is typically external, with the release of eggs and sperm into the water column.
    • Echinoderms exhibit indirect development, where a larval stage called a bipinnaria or a brachiolaria develops into the adult form through metamorphosis.

Feeding Strategies:

    • Echinoderms exhibit diverse feeding strategies depending on their ecological niche.
    • Many echinoderms are scavengers or detritivores, feeding on decaying organic matter or small particles.
    • Some echinoderms are herbivores, consuming algae or other plant material.
    • Predatory echinoderms, like sea stars, use their tube feet to capture and feed on other invertebrates.


Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).