The smooth shell giant clam, Tridacna derasa, is readily identified by the smooth shells with a complete lack of scutes (outward projecting scales). Itty bitty Derasa clams are so smooth they look like litte finger nails. Right? Well apparently at least one batch of farm raised T. derasa didnt get the memo because we spotted almost a dozen at Tat Tropical Illusion in Thousand Oaks, CA which were all sporting a significant amount of scute development. Besides the out-of-place scales on the shell, the shape of it and the mantle pattern were 100% consistent with how we expect a Derasa clam to look. In trip to French aquarium stores back in 2003 we spotted a similar group of Derasa clams in a dealer’s tank which were twice as large, about 3-4″, which also showed the same well developed scutes.
Perhaps the scalyness of this batch of Derasa clam has to do with their farm raised origin; we don’t believe there was any gene transfer from the scaly clam, T. squamosa, but perhaps there exists a mechanism for RNA from one clam species to affect another. This scenario sounds more plausible for farm-raised clams which have been raised in close proximity from a very early age but it is beyond our knowledge of RNA and gene expression to hammer out whether this could really happen. Many more pictures of the scaly derasa clams after the break and if there are any RNA experts who care to support or shoot down our theory, please feel free to expound in the comments.