Monitoring the course of bacterial infections by hemolymph pressure pulses in insects

Abstract

Changes in rhythmic pulsations of hemolymph pressure have been continuously monitored from several hours before injection of the pathogenic bacteria until death of the infected Tenebrio pupae. Lethality induced by five different species of entomopathogenic bacteria was associated with specific changes in the hemolymph pressure pattern. During the initial stages of infection (incubation period) the pupae continued to produce regular and synchronized series of normal pulsations. The pathophysiological symptoms of the acute disease became manifested by successive desynchronisation of the frequency and simultaneous depression of the amplitude of the pulsations. This irreversibly proceeded, with species specific modifications, until death of the pupae when all peaks in hemolymph pressure disappeared. Duration of the incubation period was inversely proportional to the injected dose, while the later period characterized by development of the pathophysiological symptoms had more or less constant course in infection with each bacterial species. Certain toxic enzymes, protease and phospholipase C, had similar action on hemolymph pressure pulses. Application of the tensometric method to pathophysiological studies in insects has been discussed.