Batrachotoxin is a potent neurotoxin primarily found in the skin of certain species of poison dart frogs, particularly those in the genus Phyllobates. It is one of the most toxic substances known, capable of causing paralysis and even death in small doses. The toxin affects the nervous system by blocking sodium channels, disrupting normal nerve signal transmission. This toxin is not produced by the frogs themselves but is derived from their diet, which includes beetles and other insects that contain toxic compounds. Indigenous people have historically used the toxin to poison the tips of their blow darts for hunting, hence the name "poison dart frog."