How do gastropods differ from bivalves?

1 Answer

Molluscs possess a soft body, which is divided in visceral mass and foot. Visceral mass remains covered by special skin called mantle, which is capable of secreting a shell.

Gastropods and Bivalve belong to the same phylum, Mollusc, but different classes due to very striking differences.


Class: Gastropod

  • Symmetry: The gastropods are asymmetrical because of an embryonic event, which is called torsion: this could be followed by coiling; visceral mass is covered by a single piece, usually coiled, shell.
  • Habitat: They are either aquatic or terrestrial (in damp environment).
  • Respiration: The aquatic gastropods have gills while in terrestrial gastropods the mantle cavity is converted into lungs.
  • Example: garden snail and slug (shell lost).

Class: Bivalve

  • Symmetry: These animals are bilaterally symmetrical. Their body is laterally compressed and is enclosed in two pieces of shells.
  • Habitat: Bivalves are aquatic animals.
  • Respiration: The process of respiration is carried out by plate-like gills.
  • Example: marine mussel and oyster