The Phylum Mollusca
image courtesy of Univ. of Calif. Museum of Paleontology
General Information:
- molluscs are a phylum of organisms
- many go through larval stages in which they are free-swimming (trochophore and veliger larvae)
- Mollusca are bilaterally symmetrical
- They are eucoeloms
- All molluscs have a head-foot region
- They have a well developed head, that has a mouth and nervous/sensory functions
- Attached to the head is a foot which is used for movement
- Most molluscs have a mantle, which secrets their shell (if they have one)
- In snails the shell has a horny layer called periostractum
- Shells decay slowly and fossilize well, so the phylum has excellent records
- Molluscs have a complicated digestive system, with the anus opening into the mantle cavity
- The radula is used in feeding, except in bivalves and aplacophora
- The radula is usually toothed and very complex
- They have adapted to a wide variety of feeding styles in different species, with scraping, tearing,etc.
- Mollusca have open circulatory system that has a heart, blood vessels and respiratory pigments
- Breathing is done by gills, lungs, or the surface of the body
- Excretion is done by the kidneys that pump waste into the mantle cavity
- Some molluscs have extremely complicated nervous systems
Image courtesy of Dennis Anderson
Go to our other mollusca webpage or to the honors biology home page.
This web page designed by Brittney Romriell, Christine Magagna, Holly Young