Using the impressed odostome is a cost-effective way to supplement other methods of dating shell specimens from archaeological sites. Cannarozzi said it’s important to study how oysters have lived in their environments over time to understand the health of the region’s coastal ecosystems. FLORIDA MUSEUM PHOTO BY KRISTEN GRACE

Only eat oysters in months with an 'r'? Rule of thumb is at least 4000 years old

oodie tradition dictates only eating wild oysters in months with the letter “r” – from September to April – to avoid watery shellfish, or worse, a nasty bout of food poisoning. Now, a new study suggests people have been following this practice for at least 4,000 years.

An analysis of a large shell ring off Georgia’s coast revealed that the ancient inhabitants of St. Catherines Island limited their oyster harvest to the non-summer months.

How can scientists know when islanders were collecting oysters? By measuring parasitic snails.

Snails known as impressed odostomes, Boonea impressa, are common parasites of oysters, latching onto a shell and inserting a stylus to slurp the soft insides. Because the snail has a predictable 12-month life cycle, its length at death offers a reliable estimate of when the oyster host died, allowing Florida Museum of Natural History researchers Nicole Cannarozzi and Michal Kowalewski to use it as a tiny seasonal clock for when people collected and ate oysters in the past.


Read study, Seasonal oyster harvesting recorded in a Late Archaic period shell ring

Citation: Cannarozzi NR, Kowalewski M (2019) Seasonal oyster harvesting recorded in a Late Archaic period shell ring. PLoS ONE 14(11): e0224666.