You know those oysters that you’re admiring on the half shell, the ones served on ice that you’re getting ready to squirt with fresh lemon to slurp back? We think you should know that those slimy guys are still alive.

This should be common knowledge, but it’s surprisingly not. And it may sound gross, but it’s actually a good thing because when those raw oysters die, they are no longer safe to eat. A dead oyster can harbor large numbers of bacteria, which can make you ill if eaten raw.

So when exactly do oysters die after after you put them in your mouth? This is an issue that has been heavily debated, and the verdict is still out.

Julie Qiu, an oyster expert who pens the blog In A Half Shell, says oysters probably die when the meat is separated from the shell, because the oyster’s heart is right next to the bottom adductor muscle. That would mean that they aren’t technically still alive when you throw them down the hatch.

But whether the oyster’s death happens so swiftly is unclear ― one could speculate that the final moment doesn’t actually happen until the oyster comes in contact with the chomp of some hefty molars, or the acids in our stomachs.

But don’t fret, oysters aren’t the only thing people eat when alive ― sea urchins, shrimp and even octopus also make the list (though we often eat those foods cooked, too).

Either way, make sure you know how to shuck an oyster for the freshest experience possible. You should never, ever eat pre-shucked oysters that you bought at a store raw ― those should be cooked.

If you do buy fresh oysters to bring home, it’s best to keep the raw oysters on ice and eat them as soon as they’re shucked, within a day of purchase. If you spot one with a damaged shell, toss it. Chances are the oyster is already dead.

If you absolutely must refrigerate your live oysters, make sure it’s no longer than 1-2 days. Optimum storage temperature is below 40 degrees Fahrenheit, but anything below 35 degrees F can kill shellfish, so be sure your refrigerator thermometer is accurate.