Phylum Echinodermata: Definition, General Characters, Identifying Characters, Examples

Phylum Echinodermata represents the most advanced invertebrate phylum closer to the chordates. They vary substantially in size which may range from 1 cm to about 2 m in length. In 1734 Jacob Klein has coined the name Echinodermata.

The name Echinodermata is derived from the Latin words Echinos and Derma.
” Echinos = spine and Derma = skin “

The group of animals in this phylum having spiny skin. The phylum Echinodermata containing more than 7000 described living species. Most of the animals are marine.

Definition:

Phylum Echinodermata is the group of marine invertebrates having radially symmetrical, true coelomate deuterostomus body with characteristic water vascular system containing calcareous ossicles and spines.

Fig: Echinus sp.

General characters:

1. In adult animals, the body is radially symmetrical with pentamerous Organization but the larva has a bilaterally symmetrical body.
2. All animals are triploblastic in this phylum.
3. Presence of calcareous plates or ossicles as an endoskeleton in the body.
4. Ossicles are made of calcium carbonate.
5. The body with distinct oral and aboral surfaces.
6. True coelom is present in the body.
7. Ambulacral groove is present in most animals.
8. Presence of characteristic water vascular system in the body.

Fig: Asterias sp.

9. Locomotory organs are tube feet or podia.
10. Celia is present on the exterior part of the body.
11. Alimentary canal is usually a coiled tube.
12. Respiration occurs through papulae or peristomal gills.
13. No definite excretory system in the body.
14. Nervous system is a diffuse and primitive type.
15. Open circulatory system is present. My heart is absent.
16. Reproduction is completed in the process of sexual reproduction. Fertilization occurs externally.
17. Bipinnaria, Brachiolaria, Ophiopkiteus, Pluteus, and Pentacrinoid larva are present in the life cycle.
18. Most of the animals are marine.

Identifying characters of phylum Echinodermata:

1. Body structure: Triploblastic bilaterally symmetrical body.
2. Locomotory organs: Tube feet or podia are the laboratory organs.
3. Water vascular system: The presence of a characteristic water vascular system in the body.
4. Spines and Tentacles: Numerous spines and tentacles are present in the outermost part of the body.
5. Body surface: Distinct oral and aboral surfaces are present in the body.

Fig: Cucumaria sp.

Examples:

Some common animals of the phylum Echinodermata are Asterias, Cucumaria, Ophiura, Echinus, Antedon, Clypeaster, Thyone, etc.

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