This is an octopus resting on a reef.
Click on image for full size
Windows Original, adapted from Corel Photography


The phylum Mollusca contains a variety of animals, including snails, octopi and squid, along with lesser known creatures like Cowry and Limpets. Over 90,000 species of molluscs fall into the Gastropoda class. The beautiful shells you see when walking along the beach were probably part of this class at one time. They are rather simple creatures, feasting on sponges or other small animals. Some live near reefs, while others prefer the mud or even sandy shores.

Oysters, scallops and clams are part of the Bivalvia class because they have two shell halves compared to the Gastropods, which only have one. Bivalves enjoy tiny organisms like plankton and sometimes algae. They aren't as beautiful as the Gastropods, but they make a much better dinner!

Finally, there are the Cephalopods, probably the most famous molluscs but also the most mistaken. Cephalopods are more biologically advanced than the other molluscs, so many people don't realize they are all in the same phylum. Squids and octopi are the most common cephalopods, and they are also the largest. Some giant squids can reach lengths of 50 feet! These larger animals, like the octopus in the image, eat fish, crustaceans and other molluscs.

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