Storage of the photoperiodic information within the implanted neuroendocrine complexes in females of the linden bug Pyrrhocoris apterus (L.) (Heteroptera)

Abstract

The problem as to whether the inhibition of the corpus allatum by the brain in short-day females is a primary effect of short days or a consequence of unsufficient humoral stimulation due to reduced feeding was studied by transplantations of the neuroendocrine complex (comprising the brain-corpora cardiaca-corpus allatum) between long-day (non-diapause) and short-day (pre-diapause or diapause) females. The experiments revealed that in the neuroendocrine complex from both pre-diapause and diapause females, the inhibition of the corpus allatum induced by short days is stronger than the inhibition induced by starvation in long days because it cannot be overcome by the stimulatory internal milieu of feeding long-day females. The strong inhibition of the corpus allatum is the primary effect of short days because a humoral stimulation in pre-diapause short-day females is still sufficiently high to overcome the weak inhibition within the starving brain-corpora cardiaca-corpus allatum from long-day females. In contrast, the decrease in stimulation from the internal milieu is a secondary effect of short days because it occurs as late as in diapause females in which nutritional reserves have been accumulated and feeding activity has been considerably reduced. The photoperiodic information governing the diapause or non-diapause developmental programme which is manifested by different levels of the inhibition of corpus allatum, is maintained within the transplanted neuroendocrine system irrespective of the photoperiodic conditions of the recipients.