Animal Kingdom

Phylum Echinodermata

Echinoderms are animals that you must be knowing. If you know a starfish, then you are well aware of what an echinoderm is. Echinoderms are animals that are invertebrates. The name actually means spiny skin! All the animals in this phylum exhibit spiny skin and hence are grouped together. Let us find out more about them.


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Phylum Echinodermata

Sea Lily

(Source: Wikipedia)

Echinodermata may look morphologically (structure and form) dissimilar at a glance, but they all share the same characteristic features. These animals have some really unique shapes and have beautiful colours. They are important ecologically and geologically, as they provide valuable clues about the geological environment.

Did you know that they can regenerate limbs? When a starfish, with five arms, losses one arm, it has the capacity to regenerate the lost arm. This regeneration can take any time between several months to years, as the wound has to heal and then only are the new cells regenerated.

Echinoderms are marine animals and can be found in the depths of the ocean as well as in the intertidal zone. An interesting feature of this phylum is that all animals belonging to Echinodermata are marine. There are no freshwater or terrestrial organisms in this phylum. Water vascular system present in the echinoderms is a unique circulatory system. This accounts for the gaseous exchange, circulation of nutrients, waste elimination as well as locomotion. This system has a central ring canal and radial canals that extend along each arm. Through these structures, water circulates. The madreporite is a structure present on top of the body. This is responsible for regulation of the water in the water vascular system.

Characteristic Features of Phylum Echinodermata

  • These are exclusively marine animals.
  • The larval forms show bilateral symmetry and adult forms show radial symmetry.
  • They are triploblastic.
  • It exhibits organ system grade of organisation.
  • They have a true coelom.
  • The body is uniquely shaped. It can star like, elongated or spherical.
  • The body is unsegmented without a head.
  • The body surface is covered with calcareous spicules.
  • Body cavity has the distinguishing water vascular system.
  • Tube feet help in locomotion.
  • The brain is absent but a nervous system is present with a nerve ring and radial nerve cords.
  • Respiration occurs through tube feet and gills.
  • Sense organs are poorly developed and include tactile organs, chemoreceptors, terminal tentacles etc.
  • Sexes are separate.
  • Fertilisation is external.
  • Lost parts can be regenerated.

Classification of Phylum Echinodermata

Phylum Echinodermata is classified into the following classes:

  • Asteroidea
  • Ophiuroidea
  • Echinoidea
  • Holothuroidea
  • Crinoidea



(Source: Wikipedia)

  • Asterias (Starfish)
  • Echinus (Sea urchin)
  • Antedon (Sea lily)
  • Cucumaria (Sea cucumber)
  • Ophiura (Brittle star)

Learn more about Phylum Aschelminthes here in detail.

Solved Questions For You

  1. Water vascular system is a peculiar feature of which phylum?

Ans. Phylum Echinodermata.

  1. Give an example of an Echinoderm that is found in freshwater habitat.

Ans. Echinoderms are exclusively marine animals. There is no freshwater echinoderm.

  1. The organs of locomotion in Echinodermata are called?

Ans.  Tube feet.

  1. Aristotle’s Lantern is a characteristic feature of which echinoderm?

Ans. Sea Urchin



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