ABSTRACT
The present review concerns the alarm reactions in fishes and includes the history of discovery and the attempts to isolate the alarm pheromone. A short account is given of the experiments that led to present knowledge of the origin of the alarm substance and variation in expression of the alarm reaction. The review stresses the distribution among various species, the thresholds, and the chemical nature of the alarm substances. Particular emphasis is given to new information concerning the elements of the olfactory system that mediate the alarm reaction with discussions of the peripheral sensory organ, projection of
134 Fish Chemosenses
the sensory neurons to the olfactory bulb, and the olfactory tract. The pathways of these neurons in the central nervous system in crucian carp are described. Some of the electrophysiological responses of the olfactory system to srimuli containing the alarm pheromone are demonstrated. Key Words: Cypriniformes; Fright reaction; History; Alarm pheromone; Chemical nature; Olfactory system, Olfactory bulb; CNS; Pathways; Electrophysiology.
