In class on Thursday we went over mollusks in a little more detail covering what you read. I had a powerpoint that highlighted the main differences between the three classes of Mollusks and a few pictures of some of these creatures. I cannot figure out how to post the powerpoint slides here but I will put the information I think important for you to know below.
Mollusks have a soft body and most either have an internal or external shell. Three classes of mollusks are gastropods, bivalves, and cephalopods. All mollusks have a FOOT, MANTLE, VISCERAL MASS, DIGESTIVE SYSTEM, and GILLS.
- Foot - helps with movement and catching prey
- Mantle - a tissue that protects the body
- Visceral mass - this refers to the internal organs of a mollusk
- Digestive system - like the segmented worms and roundworms, this is a one-way digestive tract with two openings
- Gills - help mollusks take in oxygen that is present in the water to breath and in bivalves it the way they eat as they are filter feeders
Gastropods - Literally means stomach foot in Greek. Some are poisonous and brightly colored to warm predators. They move by their muscular foot on a thin layer of mucus that protects their internal organs. Some gastropods are herbivores while others are carnivores but all have a radula that they use to obtain their food They either have a single shell or are shell-less
Ex. Snails, limpets, and slugs (shell less)
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| Snail |
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| Limpet |
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Orange slug
Photos courtesy of Google Images
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Bivalves - The prefix bi means two so naturally all bivalves have two shells that are attached with a muscle. These creature move slowly with their foot and they have the ability to make pearls. The generic name given to all bivalves is clams. Bivalves do not have a radula but rather use their gills to eat by filtering the water and eating whatever happens to be in it, this makes them omnivores.
When a piece of sand gets stuck inside a clam it irritates them and since they do not have the ability to spit it out they cover it with a mineral. Here is a website explaining the pearl making process if you are interested -
http://www.lifeslittlemysteries.com/197-how-do-oysters-make-pearls.html
Ex. Oysters, Mussels, Scallops
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| Oysters |
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| Blue Mussels |
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Scallops
Photos courtesy of Google Images
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Cephalopods - Literally means head foot in Greek. Their foot is divided into tentacles that have sucking disks on them. The only present day cephalopods with a shell is a Nautilus. These animals are the most complex of the mollusks and are extremely intelligent. Some of these animals are poisonous and have the ability to shoot ink to escape from potential predators.
Ex. Nautilus, Cuttlefish, Squid, and Octopus
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| Nautilus |
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| Cuttlefish |
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| Squid |
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Octopus
Photos courtesy of Google Images
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