Common minnows can detect the predators’ presence and communicate with their shoalmates by a chemical signal that is detected by olfactory nerves. The chemical, named Schreckstoff after a German word meaning "fear substance" by Karl von Frisch who first described it, is contained in specialized skin cells called alarm substance cells and is released from an injured or killed minnow.[8] The shoalmates can detect the chemical and respond to the increased risk of predation.