Fish Lateral Line Neurophysiological and Neurobehavioral Responses as a Sensitive Water Quality Monitoring System

Cadmium is a heavy metal ion that can cause deleterious effects on aquatic animals. This study uses both electrophysiological recordings from lateral line nerves and videotaping of schooling behavior to investigate the effects of cadmium exposure on fish. The fathead minnows were exposed to cadmium at a concentration of 450 μg/1 over a 24-hr period. Extracellular recording with a silver hook electrode was used to record compound action potentials from the lateral lines of control and experimental fish. After a short time exposure (24 hr) to cadmium ions, all of the electrophysiological activities of the lateral line nerves were suppressed. However, after a 10-day recovery in clean water, the function of the lateral line nerves was regained. Schooling behavior observed under lighted conditions showed no significant difference (in terms of percentage of time forming a school) between control and experimental fish. Schooling behavior, however, was completely lost for experimental fish when observed under complete darkness but it was regained after a 10-day recovery in clean water. The current study shows that both electrophysiological recording from the lateral line nerve and observation of schooling behavior can be used as effective assay methods for cadmium toxicity studies