Believe it or not, there is such a thing known as “amnesic shellfish poisoning”. Eating the wrong piece of shellfish — or occasionally just the wrong anchovy — can make you lose your memory.
When you’re an oyster, you can’t be picky about what you eat. So oysters and other shellfish crunch down diatoms regularly. These tiny sea creatures have shells made of silica, and they’re extremely tough. But when the oysters eat the diatom Nitzschia navis-varingica they take in domoic acid with no ill effects.
That’s good for them, but not so good for us. Domoic acid can accumulate in their system, building up until the moment they’re plucked out of the water by humans and eaten. Humans and other mammals aren’t able to shrug off the acid. In our brains, domoic acid binds to glutamate receptors, stimulating them.Glutamate runs a number of processes in the brain, so over-stimulating the receptors for it wrecks the body both physically and mentally.
Slight domoic acid toxicity involves low level nausea and diarrhea. If you get these after eating domoic-acid-contaminated shellfish, count yourself lucky. The next step up is confusion and hallucinations. Increase the dose any more and you get the symptom that gives domoic acid exposure the nickname “amnesic shellfish poisoning.” Glutamate receptors control learning and memory, so too much bad shellfish can give you temporary amnesia. Yep, your memory can get temporarily wiped out just by eating the wrong batch of seafood.
And that’s still not as severe as the syndrome gets. Enough domoic acid can give people permanent brain damage, put them in a coma, or kill them. There isn’t a known treatment for the poisoning, but getting to a hospital as soon as possible after it kicks in can let doctors manage the symptoms.