A gallery of images of Pacific Oyster shells (Crassostrea gigas Thunberg) – sometimes also known as the Portuguese Oyster although recent work suggests this is a separate species despite the fact that the two species can interbreed.
Click on any image to enlarge the picture and view in a gallery.
This post was previously published on Oysters Etc.
Jessica's Nature Blog 
They look very different from the flat oyster shell I picked up at Whiteford Point on Gower the other day.
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Beautiful pictures!😊 So many different shapes.
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The top picture makes them look pretty but I can’t stop finding them somewhat repellent in real life.
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Now we have entered a whole new world for me. Shells are totally out of my experience. I love the ruffly look here, I think of ball gowns and itch to think of a pattern for a skirt and get to work on sewing it, looking at these photos.
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Yes, fresh shells do look so different from beach worn ones, and of course the species is different. I am surprised that we don’t find more Crassostrea shells on British beaches given that it is the oyster species that has most frequently been cultivated over the last forty years. It is only recently that there has been a surge in restocking Native (Ostrea) oyster beds.
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Thank you, John. I like to study the variations and think of the reasons why they differ.
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I guess, Lucy, that it is possible to be interesting without being pretty, as you know from the thought-provoking images that you post on your own blogs – Loose and Leafy in Halifax and Message in a Milk Bottle. I am not just aiming to post pretty pictures here although it is what most people respond to. I find these shells with their intricate structures interesting and attractive even though they have a dark and somewhat aggressive appearance. As for the oyster meat itself within the shells, I could never bring myself to eat it.
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The frills and pleats only occur on the left or lower shell of the pair. Like you, they remind me of the dresses worn by flamenco dancers in Spain. As a child, I always wanted one of those costumed dolls that people brought back as souvenirs from holidays on the Costa Blanca. Structurally, I am uncertain why the oyster has these frills on the shell but suspect that it might be to increase buoyancy and prevent the mollusc from sinking in the seabed sediments.
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Yes, that is interesting, increased surface area being the idea, maybe? You comment on the doll makes me think of my father had a friend who traveled to Spain when I was young (an almost unimaginable trip to us back in those days, very exotic) and my father let me keep some postcards from that trip that I still have, no flamenco, bullfighting!
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I think saw a frilly one like this on Oxwich beach this morning!
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Thank you, Claudia.
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That’s very interesting. I will have to look out for similar the next time I am able to visit. You are so fortunate to have Gower on your doorstep.
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I wonder what is the biological function of these shell structures? What advantage to the give to the animal? Why are they so different from most other bivalves?
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You are right, Nannus, oysters are very different from other bivalves in the form that the shell takes. Why do they have such shells? Apart from the role of protection, the capacity of the oyster to form a shell that responds and adapts to the shape and substance of the substrate on which it settles and grows, gives the oyster a wider range of substrates, habitats, and locations on which it can thrive in the wild. The shape of oyster shells, at least in the European flat oyster Ostrea edulis, is just one of the features in archaeological deposits of oyster shell that may provide clues about the type of location in which the oyster was living, and therefore the place which was being exploited for this food resource by people in earlier times. Different species of oyster have different shell shape and growth characteristics. Oysters species growing naturally on the east coast of America, for example, grow a longer and narrower shell in softer sediments; and this is considered to be the result of the animal’s need to maintain a clear waterway for feeding and breathing while the heavier hinge end of the shell sinks in the soft mud. Shells of the same species assume a rounder shape when the oysters grow on firmer, more clay-like sea beds. It may also be speculated that the frilly outgrowths found on the left or lower valve of an oyster shell increase surface area to prevent sinking in softer muds. It is an interesting subject area.
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