MadSci Network: Zoology |
They're actually called limpets. The small, almost star shaped animals stuck VERY tightly to rocks at low tide. Limpets are molluscs (ie. sea snails) that have a small shell "hat", rather than the traditional coiled shell like the common garden snail has. Limpets move around at high tide and slowly graze on the algae on their rocks. At low tide, they have proven homing instincts and always return to their "home scar", where their shell fits into the rock EXACTLY. Barnacles are similar in description, but they have a cemented carapace (ie. house) that a small filter feeding arm pokes out of in the middle. Barnacles are modified crustaceans (same family as crabs, lobsters etc.) and the little arm that sticks out is called a "cirri". Barnalces are immobile - they feed on planktonic life drifting past. They settle from the plankton onto rocks using specialised homing cues and actively seek out adult barncles while they are in the free swimming planktonic stage. Once they're happy, they settle on a chosen piece of rock and begin to change into an adult barnacle. Sometimes even whales are considered a good home for a colony of barnacles! You can easily see barnacles on the pier pilings on a wharf - lean over and have a good look at low tide. Hope this helps! -Alastair
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