Dear Manuja,

Ostrea edulis has a round ventral, anterior and posterior margin. Geriontic specimens are also dorsally round. External right / upper shell is usually flat, white juvenile, brown and grey adult phase, circular scaly. The left / lower valve is rounded, (light) grey. Its fixo-sessile attachment is mostly near the umbo only and not the whole valve. The interior is white, including the main kidney-shaped muscle scar. It does rarely have nodular teeth on the margin.

It is possible you deal with the genus Ostrea but its extremely flat attachment to the substrate is less common. Can you open one of your specimens; I would expect a brown or purple muscle scar. Your specimens appear too irregular for Ostrea edulis.

Suggest to ask Henk Dekker as well but try to show the inside and possibly the left valve from the outside.

Best regards, Leon

Thank you Professor for the valuable information on O. edulis identification. I will get to Professor Henk Dekker as well and come to a conclusion. One more question Professor, can we identify O.edulis only by examining morphological features. Or is it mandatory to perform a genetic analysis to comment on the species level identification?

Thank you again for your response Professor.

Best regards,

Manuja Promodya

Dear Manuja:

I'm agree with Mr. Hoffman. We need to see the muscle scar.

About your photos, the first one I think that could be Saccostrea cucullata. About the others,

they aren't O. edulis, but I don't know what species could be. Sorry.

Thank you very much professor Juan for your comments. Really appreciated them.