Notes on Echinodermata | Grade 11 > Biology > Introduction to kingdom Animalia | KULLABS.COM

Echinodermata

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source:tolweb.org example of phylum echinodermata
source:tolweb.org
example of phylum Echinodermata

Echinos→ spine

derma → skin

Jacob Klein introduced the term Echinodermatain 1734.

General characteristic feature of phylum Echinodermata:

  • They are exclusively marine, not found in Nepal.
  • The body possesses numerous spines, five radiating ambulatory groups used for protection to the body.
  • They are triploblastic and radial symmetrical ( larval forms are bilaterally symmetrical.)
  • They are coelomate animals. Coelom is the enterocoelous type.
  • The body is of various shapes like globular, star-shaped, spherical, elongated and flattened. The distinct head is absent. The body has distinct oral and aboral surfaces. The body surface is marked by five radiating areas called ambulacral areas.
  • A characteristic feature of echinoderms is the water vascular system. This system helps the animal in feeding, locomotion. It takes place by tube feet. It is present on each arm.
  • The alimentary canal is complete which is coiled or straight. Mouth is present on the oral surface and anus on aboral surface.
  • Respiration takes place through gills or cloacal respiratory trees.
  • Blood vascular system is enclosed in coelomic peri haem channels. Respiratory pigments are absent.
  • The excretory organ is absent.
  • The nervous system is without the brain but a circumoral ring and radial nerves are present. Hence, it is of the primitive type.
  • Sexes are separated. Fertilisation is external. They have the remarkable power of regeneration.
  • It is indirect through free-swimming larval forms such as bipinnaria and auricularia.

Classification:

Phylum Echinodermata is classified on the basis of number and type of arm and form of the body.

Subphylum-1 Eleutherozoa:

There are the free swimming stemless echinoderms. It has five classes:

Asterias
Asterias

Class-1: Asteroidea

  • The body is star-shaped with five radiating arms, which are not sharply marked off from the central disc.
  • Ambulacral grooves with tube feet.
  • Oral and aboral surfaces are distinct.
  • Example: Asterias
Ophioderma
Ophioderma

Class-2: Ophiuroidea

  • The body is star-shaped having five arms, which are sharply marked off from the central disc.
  • Ambulacral grooves absent or covered with ossicles.
  • The anus is absent.
  • Example: Ophioderma
Echinus
Echinus

Class-3: Echinoidea

  • The body is spherical or disc-like oval.
  • Arms are absent.
  • Ambulacral grooves covered with ossicles.
  • Aristotle's lantern is a masticatory apparatus present.
  • Example: Echinus
Holothuria
Holothuria

Class-4: Holothuroidea:

  • The body is elongated without arm and spine.
  • Mouth surrounded by tentacles.
  • Longitudinalambulacral grooves and scattered ossicles.
  • Example: Holothuria
Subphylum:2 Pelmatozoa ( attached to substratum by stalk)
Antedon
Antedon

Class-5: Crinoidea

  • Usually stalked animal with more or less globular body.
  • Many arms with pinnules forming feathers.
  • Ambulacral grooves and scattered ossicles.
  • Mouth and anus are present on the oral side.
  • Example: Antedon



  • The word Echinodermata means the spiny skin as the members of this phylum bears spines on their body surface.
  • The membersof this phylum are exclusively marine and possess large number  of spines on their body.
  • They posses tube feet for locomotion.
  • Respiratory organs in Echinodermata are dermal branchiae, genital bursae, peristomial gills, cloacal trees and tube feet.
  • There are four sub - phylum of Echinodermata which are Eleutherozoa and Pelmatozoa.
  • The examples of class Asteroidea is star fish, Ophiuroidea is brittle - star, Echinoidea is sea - urchin and Holothurion is sea- cucumber.
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