Which sea snail's venom is used in pain medication?

The cone snail, a beautiful and extremely dangerous marine gastropod that harpoons fish with a modified tooth fired like a dart, injecting a venom that paralyses within seconds. Larger species have killed people, and there is no antivenom.

The venom is a chemical library rather than a single toxin. Each species produces perhaps a hundred or more distinct peptides, each precisely targeting a particular ion channel or receptor, and different snails use entirely different cocktails - so the group represents something like a hundred thousand distinct pharmacologically active compounds, most never examined.

One of them became a drug. Ziconotide, from the magician cone snail, blocks a specific calcium channel involved in transmitting pain signals and is roughly a thousand times more potent than morphine without being addictive - though it must be delivered directly into the spinal fluid and has serious side effects, so it is a last resort for severe chronic pain. It is one of the better arguments for why an obscure reef animal is worth not losing.