Did you know that you can estimate how old a clam is by counting the number of the dark rings on its shell?
A clam shell is made of calcium carbonate and grows its shell by secreting a protein called conchiolin that forms the matrix within which the calcium carbonate is deposited. The conchiolin is secreted from the mantle of the clam, which is a muscular tissue that lies between the clam’s shell and its internal body.
The darker rings of a clam are grown during the winter and fall. Clams usually do most of their growing between the months of April through October, when the water is warmer and phytoplankton, the clam’s food source, is more abundant. The width of the bands between the darker rings are an indicator of the kind of year the clam had. Wider bands can indicate that the clam received more nutrients that year.
Counting the darker rings can provide an estimate of how old the clam is. But to find out exactly how old it is, you would have to open the clam and count its rings internally from a cross section of the shell.
A clam found in Florida made the news recently and was given the name “Abra-clam Lincoln” because it was believed to be 214 years old and was found on President’s Day weekend. It was originally determined to be that age because that was the number of rings that could be counted on its external shell. It’s not out of the realm of possibility for a clam to be that old since quahog (hard-shelled) clams can live up to 200 years or more.
Recent follow-up articles have stated that after consulting with scientists who are experts in aging clams, Abra-clam Lincoln’s true age would remain unknown unless they could examine it internally. That will not happen because the clam was returned to the water alive.
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