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Saccostrea glomerata
Only a brief encounter, but this tiny little Sydney rock oyster made me smile from ear to ear. Not content with be rock-bound and boring like everyone else, it is spending its life riding jockey on a black nerite snail (Nerita atramentosa). I watched it for a minute or so as it raced around the rock pool. This species is endemic to Australia and New Zealand, and is a commercially important species of the oyster family (Ostreidae) from Australian waters, and much-prized by restaurants worldwide, not that this little fellow cares that much. It can grow to a length of over 100 mm, sometimes much larger under cultivation conditions. Oysters are filter feeders, straining planktonic algae from the water. Rock oysters may change sex half way through their lives - they start off as males and then change to females. Birds, fish, stingrays, mud crabs, and starfish all eat Sydney rock oysters, with the Australian pied oystercatcher being particularly fond of them. They also fall prey to the mulberry whelk (Morula marginalba), and that is probably its greatest threat in these rock pools.
Spotted in a rock pool at North Avoca Beach, on the NSW Central Coast. They are usually found in the intertidal zone to 3 metres (9.8 ft) below the low-water mark. This rock platform encounters massive surf at times, and usually the rock pools are very clean.
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