Molluscs (Phylum Mollusca) are a highly diverse group of animals that include cephalopods (squid, octopuses, cuttlefish), gastropods (nudibranchs, snails, slugs, limpets, sea hares), bivalves (mussels, clams, oysters, scallops) and many other groups of organisms. There are an estimated total of more than 250,000 species of molluscs.
Some of the main characteristics that define molluscs are quite technical in nature. For instance, molluscs are triploblastic. This means that during the early stages of their embryonic development molluscs have three primary germ layers (ectoderm, mesoderm, and endoderm). Molluscs are also protosomes. This means that during their development the blastopore (an opening in the primitive gut of the embryonic organism) becomes the mouth of the animal.
Classification:
- Kingdom: Animalia
- Phylum: Mollusca
The Phylum Mollusca contains the following subgroups:- Class: Aplacophora (solenogasters, deep-sea wormlike creatures)
- Class: Bivalvia (clams, oysters, scallops, mussels)
- Class: Cephalopoda (squid, octopodes, nautilus, cuttlefish)
- Class: Gastropoda (nudibranchs, snails, slugs, limpets, sea hares, and relatives)
- Class: Monoplacophora (deep-sea limpet-like creatures)
- Class: Polyplacophora (chitons)
- Class: Scaphopoda (tusk shells)
References:
- Burnie D, Wilson DE. 2001. Animal. London: Dorling Kindersley. 624 p.
- Ruert EE, Fox RS, Barnes, RD. 2004. Invertebrate Zoology. Belmont: Thomson Learning. 963 p.
