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Snorkel Mosman - Barnacles, oysters, anemones and limpets

Barnacles, oysters, anemones and limpets


Globally there are more than 100 different species of barnacles. You would be forgiven for thinking that they are always attached to rocks and other surfaces as adults. As juveniles though they are usually mobile and free swimming. Most barnacles are hermaphrodites, which means they can produce offspring by themselves if there are no other barnacles around.


Oysters play a vital role in the marine ecosystem. They are filter feeders, filtering microscopic plankton, bacteria and particles from the water through their gills. Oysters also provide habitat and shelter for other small animals like snails, marine worms and crabs.

Did you know? The two shells (or valves) of an oyster are different sizes? It has one deep valve that attaches to the rock, jetty pylon or other hard surface, whilst the other valve is flat and sits on top.


Anemones are solitary animals which are found on hard surfaces like rocks and jetty pylons. They have coloured tentacles (at Chowder Bay they are green, white or red) which are seen when the animals is submerged underwater. At low tide the tentacles are withdrawn and the anemones look like slimey blobs!


Limpets have an oval shaped shell which protects the animal inside. Their strong, muscular foot enables them to attach to surfaces, and withstand powerful wave action and currents.


Information sources:

  • Davey, K. 2009. A photographic guide to Seashore Life of Australia. New Holland Publishers, Sydney.
  • Norman, M and Reid, A. 2000. Guide to squid, cuttlefish and octopus of Australasia. The Gould League of Australia, Sydney.