Conotoxin: A toxin made by cone snails (Conidae), also called cone shells, which are fish-eating snails that inhabit tropical coral reefs, mangroves and associated habitats. Each of the 500 species of cone snail produces roughly 50 to 100 distinct conotoxins which they use to immobilize prey. These toxins are selective in their receptor binding sites. Conotoxins have been used to characterize receptors in heart muscle, skeletal muscle and brain. Calcium, potassium, and sodium ion channels have also been characterized using conotoxins.