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CLASSIFICATION OF MOLLUSCA

Phylum Mollusca is classified into 6 different classes, which are as follows:

  1. Monoplacophora

  2. Amphineura

  3. Scaphopoda

  4. Gastropoda

  5. Pelecypoda

  6. Cephalopoda

   1.  MONOPLACOPHORA

  • Marine animals.

  • Body segmentation is found.

  • Dioecious forms.

  • Heart bears  2 pairs of auricle and 1 ventricle.

  • 6 pairs of nephridia are present, out of which 2 serve as gonads.

  • 5 pairs of gills are found in pallial groove.​

  • Ex- Neopilana.

   2.  AMPHINEURA

  • Marine animals.

  • They may be monoecious or dioecious.

  • 8 dorsal plates are present, which serves as shell.

  • Heart bears 2 auricles and 1 ventricle.

  • Development through Trochophore larval stages.

  • Ex- Chiton.

   3.  SCAPHOPODA

  • Marine animals.

  • Dioecious animals.

  • Shell is tusk shaped, cylindrical in structure, with both ends open.

  • Heart is absent.

  • Head and eyes are absent.

  • Mouth with tentacles.​

  • Ex- Dentalium.

   4.  GASTROPODA

  • They may be marine, fresh water or terrestrial in habitat.

  • Monoecious forms.

  • Torsion occurs at some stage of their life.

  • Heart with one or two auricles and one ventricle.

  • Respiration by gills or lungs or both.​

  • Ex- Pila

   5.  PELECYPODA

  • They are also termed as bivalves and hence, the class is called Bivalvia.

  • They may be marine or fresh water in habitat.

  • Most of them are dioecious, but some monoecious forms also exists.

  • Shell is bivalved.

  • Heart is with one median ventricle and two auricles.

  • Radulla is absent.

  • Development is indirect.​

  • Ex- Clam.

   6.  CEPHALOPODA

  • All marine forms.

  • Dioecious animals.

  • Large distinct head which bears eyes.

  • A series of three hearts are found i.e., 2 branchial and 1 systemic heart. 

  • Ex- Octopus.

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