A brief account of the phylum Echinodermata. By:- Sabahat Batul Khusnuma Christ University, Banglore

1. • GENERAL CHARACTERS OF
PHYLUM
•CLASSIFICATION UPTO CLASSES
WITH SUITABLE EAXMPLES.

2. Echinoderms are one of the most beautiful and
most familiar sea creatures.
Sea star Star fish has become a symbol of sea life.
There are 7000 species known in echinodermata

3. History :-
Echinoderms are known since very ancient times.
Name of this phylum was introduced by Klein in
1734 .
For many years echinoderms and coelenterates
were included as a class among Radiata, because
of the radial symmetry of the adults.
Echinodermata first recognized as a group distinct
from the Radiata by Leukart in 1847.

4. What's in the name ?
Echinodermata literally means “spiny or prickly
skinned” ( Gr ., echinos, hedgehog; derma, skin)
and refers to the conspicuous spines they
possessed by their skin.
This Purple sea urchin from California has hundreds of
pointy spines for protection.
A starfish showing spines.

5. General characteristics
The phylum constitutes only major groups of
deuterostome invertebrates . Bather stated the
phylum as “ one of the best characterized and
most distinct phyla of the animal kingdom”.
 They are exclusively marine i.e., they are free-
living forms (on the sea shore) and sedentary
(bottom of the sea).

6.  Organ-system grade of body organization.
 Triploblastic, coelomate and radially symmetrical;
often pentamerous.
 Body is unsegmented with globular,
star-like, spherical,
discoidal or elongated shape.
Picture showing pentamerous symmetry

7. Cepalisation is absent, i.e., head is not present.
Endoskeleton of dermal calcareous ossicles with
spines , covered by the epidermis.
→Spines are outward projection of calcareous ossicles
diverted from the mesoderm during cleavage of egg.
They are also called as pedicelleria or tuber cells ,
which helps in the removal of body waste from the
body surface.
Body is differentiated into Oral and Aboral surfaces.
They are Euceolomate , coelome if filled with
coelomic fluid called coelomocytes. It helps in the
digestion of food particles.

8. Internally they have Water Vascular System /
Ambulacral system.
The water vascular system(WVS) of coelomic origin,
including podia or tube feet for locomotion an
usually with a madreporite.
→Madreporite are sieve like sub-circular plates with
minute pores present of Aboral surface, helps in
entry on water into the coelome of the body
Tube feet of echinoderms madreporite

9.  Alimentary canal is straight or coiled .
Respiratory organs include dermal branchiae, tube
feet, respiratory tree and bursae.
Nervous system is without a brain and with a
circumoral ring around the mouth and radial nerves.
Sense organs are poorly developed include tactile
organs, chemoreceptors , terminal tentacles,
photoreceptors and statocysts.
Excretory system is absent without any excretory
organs.

10. Sexes are separate.
They are usually dioecious
Gonads are large and single or multiple.
Fertilization is external.
Development is indirect, through free-swimming
larval forms.
They exhibit great power of regeneration.

11. Classification
STAR FISH
Basket Star
Heart Urchin
Cucumaria
Antedon

12. References
Modern textbook of Zoology ‘INVERTEBRATES’ by
R.L.Kotpal.
www.onlinebiologynotes.com
www.kullabs.com
Picture reference –
www.shutterstock.com

13. Presented by :
SABAHAT BATUL KHUSHNUMA
1 ST BSC CBZ
GWC , Kolar