characteristics of orders of classes Holothuroidea.

order1:- Aspidochirota

        1) They have numerous tube feet or podia.

        2) They have mouth surrounded by 10-30 mostly 20 peltate or  branched tentacles.

        3) They have pharynx without retractor muscles.

        4) They have a pair of well developed respiratory trees.

order2:- Elasipoda

        1) They have many tube feet or podia.

        2) They have mouth present on ventral surface and is surrounded by 10-20 peltate or branched

              tentacles.

        3) They do not have oral retractor.

        4) They do not have respiratory tract.

 order3:-Dendrochirota
        1) They have numerous tube feet or podia.

        2) They have dendritic oral tentacles or branched or branched like tree branches.

        3) They do not have oral retractors.

        4) They have respiratory trees.

order4:- Molpadonia

        1) They do not have tube feet except as anal papillae

        2) They have digitate or finger shaped oral tentacles.

        3) They do not have oral retractors.

        4) They have respiratory trees.

        5) They have posterior region generally tapering into a caudal portion.

Order5:- Apoda

1) They have vermiform shaped body with smooth and warty surface.

2) They do not have tube feet or podia.

3) They have simple, digitate or pinnate 10-20 oral tentacles.

4) Some of them have pharyngeal retractor.

5) They do not have respiratory trees.

      6)  They have greatly reduced water vascular 

          system.