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  • José H. Leal

Shrinking Conch Shells?

Shells preserved in ancient middens throughout the planet are good evidence that humans have been eating seafood for thousands of years. And our fondness for hooking the largest fish, shucking the largest oysters, and netting that jumbo shrimp has probably been around since time immemorial.


To test the hypothesis of whether intense foraging for larger versus smaller individuals of the same species may in the long run drive the species size to decrease, Alexis Sullivan (Penn State University) and her collaborators set out to study the dimensions and genetics of modern and ancient shells of the West Indian Fighting Conch, Strombus pugilis. The premise is that smaller individuals are the survivors, whereas larger ones get eliminated by constant harvesting.


West Indian Fighting Conch with lime. Credit: Felix Rodriguez, STRI.

The West Indian Fighting Conch has been historically gathered for food in several areas of the Caribbean and northern South America, and its shells preserved in middens throughout the region. Working at the Smithsonian Bocas del Toro Research Station in Panama, Sullivan developed, with local staff scientists, special techniques to consistently extract DNA from conchs from 1,000-year-old archaeological sites, and from more than 7,000-year-old conch shells! The goal is to assess whether the reduction in size through time can be associated with particular genetic changes. And, in the process of doing so, Sullivan and her collaborators developed novel and valuable techniques to extract DNA from shells. Read the Smithsonian release and papers here.