Invertebrate Zoology/Molluscs

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Chapter 11 ~ The Molluscs

Contents ~ CHAPTERS: Chapter 1 - Introduction to Zoology ~ Chapter 2 - Protozoans Chapter 3 ~ Metazoans (Introduction) ~ Chapter 4 - Sponges ~ Chapter 5 - Cnidaria Chapter 6 - Comb jellies ~ Chapter 7 - Flatworms ~ Chapter 8 - Nemerteans Chapter 9 - Pseudocoelomates ~ Chapter 10 - Annelids ~ Chapter 11 - Molluscs Chapter 12 - Arthropods ~ Chapter 13 - Chelicerates ~ Chapter 14 - Crustaceans Chapter 15 - Insects ~ Chapter 16 - Echinoderms ~

Some representative molluscs: Apple snail egg clusters, Melampid snails, Flume clam, and juvenile squid.

[edit] Introduction to the Molluscs

Molluscs are metazoan animals that take a variety of forms. However, almost all molluscs are characterized by a body with several main regions: a muscular foot, a visceral mass covered by a mantle that secretes a shell, paired gills (called ctenidia) and a unique feeding organ called a radula. The radula is a tongue-like organ that is covered with a chitinous ribbon with numerous rows of teeth, which are used to tear food off substrate and bring it into the mouth. In terms of species, they are the second-most diverse phylum next to the Arthropods, but few phyla can rival their diversity in form, from giant clams to minute sea slugs to fast moving squid.

Commonly accepted molluscan classes include:
Aplacophora
Monoplacophora
Polyplacophora (chitons)
Gastropoda (snails and slugs)
Cephalopoda (squid, octopus, nautilus)
Bivalvia (clams, oysters, mussels)
Scaphopoda (Tusk shells)