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Molluscs - Windows to the Universe

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


A variety of animals, including snails, octopi and squid, are called molluscs. Over 90,000 species of molluscs are called gastropods. The beautiful shells you see when walking along the beach are probably from one of these animals. 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 called bivalves because they have two shell halves. Bivalves enjoy tiny organisms like plankton and sometimes algae. They aren't as pretty as the gastropods, but they make a much better dinner!

Finally, there are the cephalopods, probably the most famous molluscs and the most intelligent. Squids and octopi are the most common the largest ones. 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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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF