How do clams "see"?

DiverGirl82 · Jan 6, 2016

Just got my first clam yesterday. I knew that if you wave a shadow over them they close up. Well mine seems like it knows I'm there even if I'm just standing in front of the tank, not leaning over making a shadow. It seems like if I stand just to the right side of the clam (the mouth side I think) it notices me every time. Whereas if I stand just slightly to the left side it doesn't seem to notice me. I just fed the tank and I was standing to the left and I could see the clam really fully opening up and opening up it's mouth and I was so excited I shifted a little to the right to see better and and it closed right up. Lol I was like dang it! I guess I'm going to have to start sneaking up on it like a ninja.

But anyway, all that aside, it's got me curious how they know. They don't actually physically see do they? Just curious

saltyfilmfolks · Jan 7, 2016

Probably mostly vibration but there are primitive eyes. Only sensing bright and dark and they move up the range from there.
Google the scientific name of the clam and look for scientific papers. Usually there are drawings and descriptions.

evolved · Jan 7, 2016

Photoreceptor cells (proteins)

Not exactly eyes, but that's how the "sense" light.

bsagea · Jan 7, 2016

Here's some info on the clams "eyes" from a article I had written for another forum. The info comes from books by Daniel Knopf and James Fatherree

"If looking close at the surface of the mantle, you can see a row of thin elevations on the rim. These are called iridophores. These are small eye organs which comprise a simple lens for the clam. Though primitive, they give the animal a picture of its environment. A clam does not recognize objects, but can measure the amount of incoming light. These help the clam distinguish between day and night. The iridophores tell the nervous system, if a shadow falls on the body indicating a predator is approaching. When looking to purchase a clam at your LFS, be sure to run your hand over the water above the clam. A healthy clam will snap partially or totally shut in fear of a predator. It will also open immediately once the “threat” is gone. "

saltyfilmfolks · Jan 7, 2016

bsagea said:
Here's some info on the clams "eyes" from a article I had written for another forum. The info comes from books by Daniel Knopf and James Fatherree

"If looking close at the surface of the mantle, you can see a row of thin elevations on the rim. These are called iridophores. These are small eye organs which comprise a simple lens for the clam. Though primitive, they give the animal a picture of its environment. A clam does not recognize objects, but can measure the amount of incoming light. These help the clam distinguish between day and night. The iridophores tell the nervous system, if a shadow falls on the body indicating a predator is approaching. When looking to purchase a clam at your LFS, be sure to run your hand over the water above the clam. A healthy clam will snap partially or totally shut in fear of a predator. It will also open immediately once the “threat” is gone. "

Thank you!