Limpet Shell Exercise
Author: Crissy Huffard, adapted from Matt Wedelís bone exercise
Grade span: 6-8
In California, and most paces on earth, the water along the coasts rises and falls twice a day. This happens because of the pull of the moon (and a little bit the sun) on the oceans, and the movement/ sloshing of a bulge of water as the earth rotates.
For a good explanation of tides visit this online tutorial:
The Intertidal zone includes the shoreline that spans from what gets wet at high tide (short periods, twice/24hr here) to what dries out during low tide (also short periods twice/24 hr here). The sub-tidal zone is always underwater, with fish swimming around, some surge, maybe waves during a storm. When the tide comes up, the fish come in to feed in areas that were just recently high and dry. When the tide recedes, the most (but not all) fish swim back to the sub-tidal zone and intertidal animals hang out, either in tide pools (pools left in/between rocks), of they hang out on the rocks. Some animals (like anemones, mussels, barnacles) canít move and must deal where they are. Others, like limpets and snails can move, but tend not to.
Common intertidal organisms: sea stars, mussels, barnacles, crabs, fish (even eels!-they hang out in the pools), chitons, snails, limpets, sea urchins, sea slugs, clams.
Limpets are gastropod mollusks (so are snails and slugs) that have a single, uncoiled, cap-like shell. They are important grazers of algae along rocky intertidal shorelines (such as along the California coast). They graze along the rocks when the water comes up, and go back to a ďhome spotĒ when the tide goes out (water falls). This home spot on the rock fits their shell well, so when they clamp down on a rock it makes a good fit, and a predator or wave canít get under the lip to flip it over or peel it off. Limpets donít move very far from their home spot, so they tend to stay in one zone of the intertidal. They offer an interesting system for investigating vertical zonation of body types in the intertidal. Weíre going to look at the shell types.
Also- Dave was on his way out the door when I got these limpets/shells and I donít know which zone theyíre actually from, (or even if some technically arenít limpets- our little secret) so we couldnít test our hypotheses. There was no time for it anyway.