Stimulation of corpora allata by extract from neuroendocrine complex; Comparison of reproducing and diapausing Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

The effect of extracts from neuroendocrine complexes of brain-suboesophageal ganglion-corpora cardiaca-corpus allatum (NEC) on synthetic activity of corpora allata (CA) in vitro was investigated by a radiochemical assay in Pyrrhocoris apterus. NEC extracts from short-day (diapausing) females and long-day (active) females and males were compared. NEC extracts from both short-day and long-day insects stimulated synthetic activity of the CA from long-day females. The CA from shea-day females were refractory to stimulation. The stimulating activity of the NEC extract was retained after removal of proteins using 10,000-molecular weight limit centrifugal ultrafiltration, but was destroyed by treatment with proteinase K. Therefore, the stimulating factor appears to be a peptide. The culture medium containing a mixture of synthetic products of the CA was extracted by hexane and subjected to TLC analysis. It was revealed that the NEC extract stimulated synthesis of a product from radiolabelled methionine which elutes on TLC in the same position as the major product of the CA of four other heteropteran species.