Molluscs
•Download as PPT, PDF•
9 likes•4,395 views
Molluscs are a diverse phylum that includes over 100,000 species like snails, slugs, clams, oysters, octopuses and squids. They have a mesoderm lined body cavity called a coelom and a larval stage called a trochophore, similar to annelid larvae. The major classes of molluscs are chitons, gastropods, bivalves and cephalopods.
![Phylum Mollusca ,[object Object]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Recommended
More Related Content
What's hot
What's hot (20)
Viewers also liked
Similar to Molluscs
Similar to Molluscs (20)
More from Jackie Carl
Molluscs
- 1. Molluscs
- 10. Shells
- 11. Mantle Cavity
- 12. Internal Structure & Function
- 16. Bivalvia Class
- 17. Cephalopod Class Show squid video
- 18. Videos Giant Squid Slug Sex
Editor's Notes
- Molluscs evolved in the sea and most molluscs are still marine. Some gastropods and bivalves inhabit freshwater. A few gastropods (slugs & snails) are terrestrial.
- The study of similarities and differences in early development of animals is comparative embryology. Triloblastic: three layers develop into species (the rest of the animals we study will be).
- As food – mussels, clams, oysters, abalone, calamari (squid), octopus, escargot (snails), etc. Pearls – formed in oysters and clams. Shiny inner layer of some shells used to make buttons.
- Shipworms – burrow through wood, including docks & ships. Terrestrial snails and slugs damage garden plants. Molluscs serve as an intermediate host for many parasites. Zebra mussels – accidentally introduced into the Great Lakes and reeking havoc with the ecosystem.
- All molluscs have a similar body plan with two main parts: A head - muscular foot used for locomotion and sensory perception. A visceral mass – containing digestive, circulatory, respiratory and reproductive organs. Above that is the mantle – houses the gills and in some secretes a protective shell over the visceral mass. Most molluscs have separate sexes with gonads located in the visceral mass.
- Most molluscs have well developed head ends with sensory structures including photosensory receptors that may be simple light detectors or complex eyes (cephalopods).
- The radula is a rasping, protrusible feeding structure found in most molluscs (not bivalves). Ribbon-like membrane with rows of tiny teeth.
- In some gastropods, an operculum is found on the dorsal, posterior margin of the foot and when the foot is drawn into the shell, seals the opening.
- When present, the calcareous shell is secreted by the mantle and is lined by it. It has 3 layers:
- The space between the mantle and the visceral mass is called the mantle cavity . The respiratory organs (gills or lungs) are generally housed here.
- Many molluscs have an open circulatory system with a pumping heart, blood vessels and blood sinuses. Most cephalopods have a closed circulatory system with a heart, blood vessels and capillaries.
- Greatest number in Gastropoda
- Umbo is the oldest part. Will be dissecting in lab. No head needed
- Pigment that allows them to change colors is chromatophores. Tiny muscles attached to these pigment cells contract to change the color of the animal. Color is very important in courtship displays. Some are bioluminescent. Male takes a spermatophores (encased sperm packet) in his modified tenetacle (hectocotylus) and deposits the spermatophore near the females oviduct so that the eggs are fertilized as they leave it.