Question

Classification of mollusca with examples

Answer 1

Classification of Phylum Mollusca

There are six classes of which three are more prominent.

Class 1 Pelecypoda or Bivalvia

• Habitat: mostly marine
• They burrow in mud and sand.
• Symmetry: bilateral and the body is laterally compressed.
• No distinct head
• Examples: Mussels, Unio, Mytilus,

Class 2 Gastropoda

• Habitat: These are either aquatic or terrestrial
• They possess a spiral shell.
• The foot is large and flat.
• Head is well developed with tentacles and eyes.
• Examples: Hilex (Snail), Limax (Slug), Pila (Apple snail)

Class 3 Cephalopoda

• Habitat: mostly marine.
• They are adapted for swimming.
• The foot is modified into eight to ten long tentacles in the head region.
• The shell is either external, internal or absent.
• Examples: Octopus, Loligo, Sepia, spirula, Nautilus

Class 4 Monoplacophora

• Habitat: exclusively marine
• Head is present without eyes and tentacles
• Gills are external
• Excretion: by serially arranged nephridia
• Examples:

Class 5 Amphineura

• Habitat: mostly marine
• Body is elongated
• Eye and tentacles are absent
• Radula is present
• Examples; Chiton, Neomenia

Class 6 Scaphopoda

• Habitat: marine
• Body is bilateral symmetry elongated and enclosed in tusk shell
• Foot is reduced
• Excretion: a pair of Kidney
• Examples: Cadulus, Dentalium