Alarm reactions in crucian carp

The alarm reaction in cyprinids discovered by Karl von Frisch has been a challenge to neurophysiologists. In particular, the alarm substance has evaded proper identification, and the pathways mediating the reaction have been unknown. Due to previous resea rch programs supported by the Research Council, we are now at the brink of identifying this elusive pheromone. We also have evidence indicating which sensory neurones participate in detecting the alarm signals, and the neural pathways to the brain. The pr incipal aim of this research project is to study the biological impact of the alarm substances. The first part of the study is related to the physiological mechanisms of the sensory neurones detecting the alarm substances. The second part concerns t he od our threshold for the alarm reaction, to establish if the chemical compounds that induce nervous activity in the olfactory bulb are also the ones mediating the alarm response in fish. The third part is devoted to the behaviour and physiology underlyi ng m orphology changes during alarm signal exposure. This part includes the coupling between behavioural activity of animals exposed to alarm signals and body depth increase, as well as the properties of alarm substance cells during continuous exposure to dang er (i.e. chemical alertness).