Tag Archives: snails

Sustainable harvesting practices 4,000 years ago still shape shellfish eating today

The custom of only eating wild oysters in months with the letter “r” seems to have been followed for at least 4,000 years, one study finds.

Image credits University of Washington Fishery Sciences Friedman Lab.

The study focused on a large shell ring — essentially, a shellfish waste dump — off Georgia’s coast, analyzing how ancient inhabitants at the site limited their oyster harvest to the non-summer months. Today, such practices are meant to protect people from unappealing oysters and food poisoning. The team measured parasitic snails on the oysters to determine when they were harvested by locals.

Seasonal food

“People have been debating the purpose of these shell rings for a very long time,” said Cannarozzi, the study’s lead author and Florida Museum environmental archaeology collection manager.

“Were they everyday food waste heaps? Temporary communal feasting sites? Or perhaps a combination? Understanding the seasonality of the rings sheds new light on their function.”

Snails known as impressed odostomes (Boonea impressa), are common parasites of oysters. These tiny snails anchor themselves onto a shell and insert a needle-like stylus to feed on the mollusks’ 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, the team explains.

The team analyzed oysters and snails from a 230-foot-wide, 4,300-year-old shell ring from the island, comparing them with live oysters and snails. They found that ancient oysters were mostly harvested during late fall, winter, and spring. The authors say this points to human populations thinning or migrating out completely in the summer.

It’s possible that this is one of the earliest examples of sustainable harvesting, Cannarozzi said. In the area of the study, oysters spawn from May to October. It’s possible that not harvesting them in the summer allowed oysters to replenish their numbers and prevent overexploitation.

The team says their approach is very cost-effective and can be used alongside other methods in dating shell specimens in archeological sites. Mapping the history of oysters in a particular area can help us understand the health of the broader coastal ecosystems they were part of.

“It’s important to look at how oysters have lived in their environment over time, especially because they are on the decline worldwide,” Cannarozzi adds. “This type of data can give us good information about their ecology, how other organisms interact with them, the health of oyster populations and, on a grander scale, the health of coastal ecosystems.”

“People have affected the distributions, life cycles and numbers of organisms over time,” Cannarozzi said. “Understanding how people in the past interacted with and influenced their environment can inform our conservation efforts today.”

In preparation for the spawning season, oysters start converting glycogen (i.e. fat stores) into sperm and eggs, making them “soft and rank”, according to Rowan Jacobsen, author of A Geography of Oysters. Warmer waters also tend to carry more bacteria and algae, which can lead to food or shellfish poisoning. Today it’s pretty safe to eat oysters any time of the year due to oyster farming, refrigeration, and food safety practices. However, for fresh-caught oysters, I’d stick with the folk wisdom.

The paper “Seasonal oyster harvesting recorded in a Late Archaic period shell ring” has been published in the journal PLOS ONE.


Antibiotics of the future might come from the bottom of the oceans

The advent of antibiotics has spared humanity of a great deal of suffering and has saved countless lives through the years. Infectious diseases do not bore too easily and have always put out a fight, though. The bad news is that they’re winning and as the battle rages on, more and more strains become resistant to drugs. The consequences are broad and dire, and this is why scientists today want to be one step ahead and prepare for tomorrow.

Two separate studies recently published by a research partnership called the Philippine Mollusk Symbiont International Cooperative Biodiversity Group discuss how the future’s new class of antibiotics might reside at the bottom of the oceans. Like the name implies, both studies were concentrated on mollusks, a phylum of invertebrates which includes such animals as snails, clams and squid. Many of these ocean animals have been living in harmony with their bacterial companions for millions of years, and it’s in these bacteria that the key to the future’s antibiotics might lie. Having passed the test of time, rending no side effects to their animal companions, these bacteria have already shown promising results.

Ocean bacteria might be key to tomorrow’s antibiotics

ship-wormThe first study, published in the journal Proceedings of the National Academy of Sciences, the researchers tackled shipworms, but don’t let the name fool you too much. These mollusks have more to do with ships themselves than worms. Typically these are considered pests due to their ill-viewed habit of affixing themselves to the sides of wooden ships. Over time they feed on the wood, causing damage to the boat, which can be most unpleasant.

Then comes the question, however. How do these animals feed on wood? Wood is an extremely poor nutrient, far from being an ideal meal for a multicell organism, since it lacks proteins or nitrogen. Here’s the kicker though. The shipworm has a bacteria that converts the wood into a suitable food source where the animal can both live and feed. One such bacteria apparently also secretes a powerful antibiotic, which might hold great promise for combating human diseases.

“The reason why this line of research is so critical is because antibiotic resistance is a serious threat to human health,” said Margo Haygood, Ph.D., a member of the OHSU Institute of Environmental Health and a professor of science and engineering in the OHSU School of Medicine.

“Antibiotics have helped humans battle infectious diseases for over 70 years. However, the dangerous organisms these medications were designed to protect us against have adapted due to widespread use. Without a new class of improved antibiotics, older medications are becoming less and less effective and we need to locate new antibiotics to keep these diseases at bay. Bacteria that live in harmony with animals are a promising source. “

cone snailThe second paper, published in journal Chemistry and Biology, looked at cone snails collected in the Philippine. Previously, only a few studies actually were made to determine whether or not bacteria associated with these mollusks might prove useful in drug development. Mostly, this is due to the fact that cone snails aren’t that welcoming to outside visitors, featuring thick shells and quite a nasty toxic venom why they aren’t too shy about using. Since they pose a sort of miniaturized defense arsenal, it was previously assumed that these animals do not require additional chemical defense, meaning there could be no interest in human medication in turn. This was a false assumption.

Scientists proved that bacteria associated with cone snails actually produce a chemical which is neuroactive, impacting nerve cells (neurons) in the brain. Based on initial findings alone, the bacteria is already considered promising as a viable candidate for a highly powerful painkiller.

“Mollusks with external shells, like the cone snail, were previously overlooked in the search for new antibiotics and other medications,” said, Eric Schmidt, Ph.D., a biochemist at the university of Utah and lead author of the article.

“This discovery tells us that these animals also produce compounds worth studying. It’s hoped that these studies may also provide us with valuable knowledge that will help us combat disease.”