Neural control in the immunocytotoxic destruction of muscles in Diptera

Following successful escape from the puparium (eclosion), sets of muscles in all three segments of dipteran flies degenerate. Whereas the head and abdominal muscles degenerate in response to hormonal triggers released before, and immediately after eclosion, the thoracic muscles require a specific neural trigger encountered following eclosion. Evidence is presented for the role of neural activity in the activation of immunocytes that destroy the thoracic muscles. Removal of the neural input by severing the nerve to any particular muscle results in survival of the muscle and inactivation of the immunocyte. The destruction process can be stopped at any time by severing the nerve and the muscle fibres that remain continue to show normal physiology and response to stimulation. Elcctrophysiological recordings of the response to lethal attack are presented together with ultrastructural evidence demonstrating the invasion of muscle fibres by processes of the immunocyte.