Observation on the gross innervation of the firefly light organ

Abstract

A correlated anatomical and physiological study of the gross innervation of the firefly light organ revealed that in this respect the luminous segments did not differ from non-luminous segments except for having larger segmental nerves due to the added function of light organ innervation in addition to spiracles and musculature. Ganglia of both luminous segments are located in the sixth abdominal segment, allowing nerves to the seventh segment to be easily severed while the sixth remains undamaged as a control. Nerve degeneration experiments utilizing this fact showed a large elevation of response threshold at 21–24 hr after sectioning; this was interpreted as a loss of functional effector-neural junctions requiring intense stimulation for direct activation of photocytes. Physiological studies confirming neural control of light organ activation showed that excitation of small areas of the lantern is possible by stimulating specific segmental nerves via small electrodes. Peripheral intersegmental neural linkages were observed and confirmed physiologically. The right and left sides of the peripheral system in the lantern may function independently although central excitation is bilateral.