The answer to this question was again provided by Karl von Frisch. He demonstrated that fish with experimentally impaired sense of smell do not respond to the alarm substance and show no fear reaction. Thus, alarm pheromones are perceived via the sense of smell. For us as air-breathing organisms, it is difficult to imagine that fish can also possess a sense of smell. The sense of smell is essentially a form of remote perception. Its organs respond to chemical signals, regardless of whether they are dissolved in water or air. Like us, fish have noses, but their mucous membrane is surrounded not by air, but by water.