Department of Zoology at ANDC/Zoology Museum/Museum specimens/Echinodermata

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Phylum Echinodermata

Date & Time : 23, October 2017 11:46


General Characteristics of Echinodermata

  • exclusively marine and cosmopolitan in distribution.
  • Body triploblastic,radially symmetrical,divided into oral and aboral surface.
  • Body surface covered with radiating grooves called Ambulacra with five inter ambulacra.
  • Mouth usually present on oral surface and anus on aboral surace.
  • Blood lacunar system present.
  • Sense organs are poorly developed.
  • Sexes are usually separate with only a few exceptions

Classification of Echinodermata

A Few Examples

1. Antedon

Antedon.jpg

Common name- feather star or sea-lily.

Distribution- found in all seas.

Habit and Habitat- marine, remain attached to the rocks by cirri.

Food- feed on microscopic living organism.

IDENTIFYING CHARACTERS:-

  • Body- consist of calyx (central part), and arms radiated from calyx.
  • calyx- differentiated into oral surface and aboral surface.
  • Oral surface- contains mouth and anus
  • aboral surface- contains arms and cirri.
  • Cirri- composed of skeletal ossicles.
  • mouth- present in central, surruonded by sensory podia, but no suckers are present.
  • Ambulacral grooves- 10 in number, leading into the arms.
  • Arms- actually arms are 5 in muber, each arm is divided into two.
  • Each arm contain pinnules having gonads.
  • sexes are separate.
Labelled diagram of ANTEDON.jpg

2.Asterias

Common Name- star fish or sea star.

Distribution- abundant in North Atlantic Coast, found in India and U.S.A.

Habit- marine.

Food- microscopic organisms
Asterias rubens

IDENTIFYING CHARACTERS-

  • Appearance- star shaped, pentagonal.
  • Body- differentiated into oral and aboral surfaces.
  • Body color- yellow or brown(preserved).
  • Arms- 5 in number, and are prolongation of coelom, gonds and alimentation.
  • Oral surface- consist of mouth (actinostome).
  • Ambulacral grooves- extend from mouth, accomodate a large number of tube feet.
  • Aboral surface-consist of conical spines, madreporite plate and pedicellariae.
  • Skeleton system- it is only about meshwork of ossicles and closely packed discrete plates.
  • Sexes are separate.
Labelled diagram of ASTERIAS.jpg

3. Echinus

Echinus.jpg

Common name:- sea urchin.

Distribution:-found in Atlantic, the Mediterrnean and Pacific waters.
Habit and Habitat:-marine in habit, benthic animal.

IDENTIFYING CHARACTERS:-

  • Body:- spherical.
  • Body color:- brownish.
  • Body covering:- enclosed in corona(rigid) or test is made up of calcareuos plates.
  • Body division:- oral and aboral surface.
  • Oral  surface:- contain mouth
  • Mouth:- contain peristome, buccal tube, calcareous ossicles.
  • Pedicullariae and spheridia:- located between articulated spines.
  • Test:- divided into ambulacral and inter ambulacral zones

              - contain spines and tube feet.

  • Ambulacral grooves:- closed.
Labelled diagram of ECHINUS.jpg

4. Cucumaria

Common name:- sea cucumber.

Distribution:- cosmopolitan, found in Europe, U.S.A. and India.

Habit and Habitat:- marine in habit, like to live partially burried in mud.

Food:- detritus and plankton.

Cucumaria.jpg

IDENTIFYING CHARACTERS:-

  • Body:- elongated horizontally along the oral and aboral axis.
  • Body color:- may be whitish, reddish or brown.
  • Body wall:- dermo-muscular, having separate ossicles.
  • Mouth:-anterior in position.
  • Tentacles:- modified tube feet, surrounds the terminal mouth.
  • tube feet possesses suckers, either arranged in rows or scattered.
  • Body division:- rest of the body is divided into various zones

                                                                1.five ambulacral and

                                                                2.inter ambulacral zones.

  • Ambulacral grooves:- run longitudinally and are covered.
  • Genital aperture:- placed between two adjacent inter-ambulacral tentacles near mouth

                               - single in number.

  • Anus:- aboral with respiratory trees.
Labelled diagram of CUCUMARIA.jpg


5. Clypeaster

Common name:- cake urchin.

Habit and Habitat:- marine in habit, like to live partially burried in mud in tropical and sub tropical waters.

Food:- detritus and plankton.

Sea biscuits.jpg

IDENTIFYING CHARACTERS:-

  • Body:- flattened and oval,covered with dense brown spines.
  • Body color:- reddish or brown.
  • Body wall:- dermo-muscular.
  • Mouth:- central in position, on the concave oral surface. Teeth or masticatory apparatus present.
  • madreporic plate:- petaloid ambulacra enclose the madreporic plate.
  • Pedicellariae and spaeridia are present.
  • podia:- respiratory in function.
  • Ambulacral grooves:- run longitudinally and are covered.
  • Genital plates:- fused with central pentagonal plate.
  • Aristotle's lantern:- present.
Labelled diagram of CUCUMARIA.jpg

6. Astropecten

Common name:- large star fish

Habit and Habitat:-found in seas below tide line.lives partly buried in sand.

IDENTIFYING CHARACTERS:-

Astropecten.jpg
  • Body:- star shaped,flattened,has five arms.
  • Arms:- flexible,triangular, have tappering tips.
  • Body division:- oral and aboral surface.
  • Oral  surface:- contains mouth.
  • Ambulacral grooves:- extend from the mouth and pass along entire arm.
  • Tube feet:- Conical structures, project in two rows along each ambulacral groove.
  • Aboral surface:- contains madreporite, having numerous minute pores.


  • Paxillae numerous short blunt spines on aboral surface.
  • Dermal branchiaesmall,soft,hollow,finger like outgrowths arise between paxillae
  • Anus absent.
  • Sexes are separate.

7. Ophiothrix

Ophiothrix.jpg

Common Name- spiny brittle star

Distribution- found in Atlantic coast.

Habit and habitat- marine in habit.

IDENTIFYING CHARACTERS:-

  • Body- consist of central disc and arms.
  • Arms-symmetrical and are fused with central disc, five in number.,covered by spines.
  • Body division-body is divided into oral and aboral surface.
  • Oral surface- consists of mouth with jaws,madreporite,oral shields,podial pores.
  • Bursal slits- deep grooves present on base of each arm. Mature sex cells pass through it.
  • Shows great power of regeneration of its lost arm.


8. Pentaceros

Common Name- sea pentagon.

Distribution- found in India, Panama, U.K., U.S.A.

Habit and habitat- marine in habit.

IDENTIFYING CHARACTERS:-

  • Body- consist of central disc and arms.
  • integument- tough, hard and and leathery. It contain spines of different size, and vessicles.
  • Arms-symmetrical and are fused with central disc, five in number.
  • Body division-body is divided into oral and aboral surface.
  • Oral surface- concave and brown in color. containing mouth.