Echinodermata General Feature Examples with diagram

 

ECHINODERMATA 

Definition : Echinodermata represents the group of marine invertebrate true coelomate deuterostomus animals with pentamarous radially symmetrical adult body having calcareous ossicles and spines, characteristic water vascular system showing bottom dwelling habit.

Salient Characters of Echinodermata

1. Adult body is radially symmetrical with pentamerous organization.

2. Triploblastic in nature with true coelom.

3. Body with distinct oral and aboral surface.

4. Presence of calcareous plates or ossicles as endoskeleton in the body.

5. Presence of spacious coelom with peritoneal lining.

6. Presence of characteristic water vascular system.

7. Presence of ambulacral groove in most of the cases.

8. Tube feet as locomotory organs.

9. Alimentary canal is usually a coiled tube.

10. Presence of haemal or blood lacunar system.

11. Nervous system diffuse and primitive type consisting of networks

concentrated into ganglionated radial nerve cords.

12. Excretory system wanting.

13. No definite respiratory system, in some cases respiration occurs through

papullae in the skin and in some cases there are peristomeal gills

(sea urchins)/ genital bursae/cloacal respiratory tree (Holothuroids)

for this purpose.

14. Sexes are separate. Fertilization external.

15. Presence of bilaterally symmetrical larva in the life cycle.

16. Mostly marine and bottom dwelling by habit.