Clam colors and patterns, where do they come from?

For many years it has been thought that the bright colors and patterns exhibited by giant clams comes from the symbiotic algae (zooxanthellae) housed in the clams mantle. In recent years there have been studies done to find out exactly what causes these brilliant colors. Although more work needs to be done in this area, the structures responsible for giant clam coloration and patterns have be identified.

The mantle of a giant clam is complex and multifunctional. Most notably it contains a network known as the Zooxanthellal Tubular System which houses the symbiotic algae that provide the main source of food for the clam. The mantle also houses hundreds to thousands if primitive eyes and tiny structures called pinocytosing microvillous epidermal cells which are capable of adsorbing dissolved nutrients and tiny particulate matter which can be used by the symbiotic algae to produce food for the clam.

As if that wasn't enough going on in a clams mantle there is another network of cells in the mantle called iridophores. Iridophores are arranged in groups and clusters called iridocytes and held together with proteins to forum iridosomal platelets. The arrangement and shape of these platelets along with the proteins that hold them together cause interference with certain wavelengths of light producing the different colors and patterns we see. The clam has some ability to move or contort these structures depending on light spectrum and intensity to reflect or redirect light. If the clam is receiving very intense light or a spectrum of light that may harm the clam or its symbiotic algae it can arrange these platelets to reflect the light away from its self. Conversely if the intensity is low the platelets can be moved again to direct more light to its symbiotic algae to help aid in photosynthesis. In the case when the platelets are arranged to direct more light to the symbiotic algae the bright colors you would normally see, which are really just reflected light, is being directed to the algae, exposing the algae to your eyes. This is why some clams that are kept under less intense light appear brown.

Which platelet shapes and protein combinations produce what colors hasn't been completely figured out yet. Hopefully with more research the combinations will be figured out but the mechanism is known. The symbiotic algae plays a minor role in the over all coloration of the clam and for the most part the contribution to color from the algae is in the brown's.

Excellent information! ...hard to believe there's that much going on eh?!

I know, it is pretty crazy in there, very cool to learn the complexities of these animals

BUT still WHY are the patterns like they are?? what advantage is a teardrop or zebra pattern to a clam?

I have no idea why they have the patterns they do. Im sure it all comes down to natural selection in some way. Some patterns might camouflage them better then others so over thousands and millions of years the weaker patterns are weeded out.

Chris,

I have a special clam that is half ultra (superd stunning color) and the other half as just normal. I have been keeping it for almost two years and it remain the same color. ( some area on the side was ultra orange) I have been hoping that the color will spread but it didn't. I wonder if the mantle of the whole clam is link together (means if it's mantle is really a network that will adjust the reflection evenly)

Originally Posted by Jeff

Chris,

I have a special clam that is half ultra (superd stunning color) and the other half as just normal. I have been keeping it for almost two years and it remain the same color. ( some area on the side was ultra orange) I have been hoping that the color will spread but it didn't. I wonder if the mantle of the whole clam is link together (means if it's mantle is really a network that will adjust the reflection evenly)

Do you have a pic of the clam?

Originally Posted by Jeff

Chris,

I have a special clam that is half ultra (superd stunning color) and the other half as just normal. I have been keeping it for almost two years and it remain the same color. ( some area on the side was ultra orange) I have been hoping that the color will spread but it didn't. I wonder if the mantle of the whole clam is link together (means if it's mantle is really a network that will adjust the reflection evenly)

I thought i replied to this?

This is just guess work on my part but if the clams difference in color is caused by being shaded or something like that than i would guess that it could color back up to about what the other half is.

If its not caused by an environmental factor but a genetic factor then i think it will stay the way it is. For example a blue clam can become brighter blue or duller darker blue But IMO wont turn red.