Neural activity in the abdominal nervous system of aeschnid nymphs

Abstract

1. 1. The afferent input to the central nervous system of the abdomen of Aeschna nymphs contains a regular discharge of varying frequency from each of the stretch receptors, and two types of bursts corresponding to the two types of epidermal sensilla. In addition the last ganglion receives information from mechanoreceptors at the bases of the anal appendages. 2. 2. With the aid of microelectrodes responses were obtained from the central nervous system to different forms of peripheral stimulation. 3. 3. Spontaneous activity was recorded in the form of both regular discharges and bursts of impulses. Many of the latter were correlated with, but not caused by, respiratory movements. 4. 4. Stimulation of the first roots elicited efferent responses in the ipsilateral first, second and third roots, in the contralateral first roots, and also in the ipsilateral first roots of both anterior and posterior ganglia. 5. 5. Stimulation of the fifth roots was used to investigate the synapses and efferent responses concerned in the “evasion response”. The results are comparable with those obtained in other insects, except that the interneurons transmitting the post-synaptic response synapse with motor fibres in each abdominal ganglion, and not only in the thoracic ganglia, as seems the case in the cockroach.