Neural control of the corpus allatum in the Colorado potato beetle, Leptinotarsa decemlineata: An electron microscope study utilizing the in vitro tannic acid Ringer incubation method

The release of material from neurosecretory synapses in the corpora allata of the Colorado potato beetle, Leptinotarsa decemlineata was visualised by an electron microscope procedure which involved tissue incubation in tannic acid. Using morphometry, the frequency of exocytosis phenomena was quantified in beetles kept under two different photoregimes. The number of exocytosis phenomena in the neurosecretory synapses in the corpora allata of beetles kept under short days was significantly higher than that of beetles reared under long-day conditions. In addition, the corpus allatum gland cells appeared to be more richly innervated by neurosecretory synapses under short-day than under long-day conditions. Previous studies using the in vitro radiochemical assay showed that the corpus allatum activity of short-day beetles is at least partly restrained by neurally mediated factors. The present morphological data strongly imply that this corpus allatum inhibitory substance is released from the neurosecretory synapses.