PHYLUM ECHINODERMATA | classification

 

PHYLUM ECHINODERMATA | classification

Echinodermata

The word Echinodermata means “spiny skin”.

They usually live in shallow coastal water and ocean trenches.

Organisms in this class involve:

• ·        Sea stars
• ·        Brittle stars
• ·        Sand dollars
• ·        Sea cucumbers

General characteristics of Echinodermata

1. ·        Exclusively marine
2. ·        Have unsegmented body
3. ·        Adults have pentamerous secondary radial symmetry
4. ·        Larvae bilaterally symmetrical
5. ·        Have unique water vascular system
6. ·        This is the first phylum having internal skeleton
7. ·        Have complete digestive system
8. ·        They have no kidney
9. ·        Monoecious
10. ·        Movement by tube feet and/or arms
11. ·        They respire by dermal branches, respiration tree or tube feet.
12. ·        They have nervous system with no head or brain

Echinodermata classification

They are classified into five classes

1. Class Asteroidea – sea stars
2. Class Ophiuroidea – brittle stars
3. Class Echinoidea – sea urchin
4. Class Holothuroidea – sea cucumbers
5. Class Crinoidea – sea feathers

Class Crinoidea

1. They are lily like.
2. This class include sea lilies, feather stars etc.
3. They are sessile.
4. They have long stalk that attach to rocks or to the ocean floor. But the feather stars eventually detach themselves.
5. Sticky tubes are present at the end of each arm. They catch food and function as a respiratory surface.

Class Asteroidea

1. They are star like.
2. This class include sea stars or starfish.
3. They are present all over the coastal shores around the world.
4. They prey on oysters, and other sea food used by people.

Class Ophiuroidea

• This is the largest echinoderms class includes basket stars and brittle stars.
• They primarily inhabit under stones and in crevices and holes of coral reefs.
• They have thin brittle arms. They break and regenerate themselves quickly.

Class Echinoidea

They are hedgehog like. Their locomotion is by the tube feet. For the protection, they have barbs on their spines which are sometimes venomous. They have complex jaw like mechanism which is used for grinding of food called Aristotle’s lantern.

Class Holothuroidea

Their bodies are soft. Their lost parts are later regenerated. They eject internal organ through anus for protection.