The reaction of pearl dace (Pisces, Cyprinidae) to alarm substance: time-course of behavior, brain amines, and stress physiology

Abstract

Pearl dace, Semotilus margarita (Pisces, Cyprinidae), respond behaviorally and physiologically to conspecific alarm substance. The behavioral alarm reaction was biphasic. A brief initial phase of rapid and unpredictable swimming was followed by a period of inactivity that was observable even after 5 h. In nature, biphasic behavioral reactions may function to remove alarmed fish from the area of greatest danger and then render them inconspicuous. The physiological alarm reaction included elements of a stress response. Concentrations of plasma cortisol and glucose were elevated at 15 min after the detection of alarm substance, but had returned to control levels by 5 h. There were no odor-induced changes observed in brain concentrations of dopamine, norepinephrine, 5-hydroxytryptamine, or tryptophan. The biphasic behavioral response and the physiological stress response were interpreted as adaptations that permit pearl dace to successfully react to threats of predation.