Seals, dolphins, and seabirds are becoming ill and dying in disturbing numbers on West Coast beaches. The culprit is an algae-based toxin named domoic acid. The way this works is fascinating.
It's becoming increasingly common to find seals washed up on Southern California beaches—the victims of a potent neurotoxin called domoic acid. And it's not just seals; dolphins, whales, and seabirds are falling prey, too. But not fish. In fact, fish are at least indirectly part of the problem. More on that in a moment. Why? It all comes down to glutamic acid receptors—something that's far from intuitively obvious. I'll try to make this discussion as non-neurotoxic as possible. Glutamic acid receptors—including a subtype called kainate receptors belong to a class called ionotropic receptors. This is one of several ways the nervous system regulates ion movement—and, in turn, neurological function—in mammals and birds. These receptors fall into two broad categories, acting like molecular on-off switches for nerve signaling. Voltage-gated ion channels open or close in response to changes in the electrical charge across a cell's membrane. This allows specific ions (like Na⁺, K⁺, or Ca²⁺) to flow in or out, creating the electrical signals that drive everything from thought to muscle movement. One well-known example is the voltage-gated sodium channel—the molecular spark behind every nerve impulse in your body. open or close in response to changes in the electrical charge across a cell's membrane. This allows specific ions (like Na⁺, K⁺, or Ca²⁺) to flow in or out, creating the electrical signals that drive everything from thought to muscle movement. One well-known example is the voltage-gated sodium channel—the molecular spark behind every nerve impulse in your body. Ionotropic receptors, on the other hand, are ligand-gated ion channels. They open when a specific chemical—usually a neurotransmitter—binds to them. Glutamic acid receptors fall into this broad category. Specifically, the domoic acid screws up the machinery at the kainate receptor [1], one member of the glutamic acid receptor family. And that's what makes domoic acid so dangerous. It mimics glutamic…