Abstract
The biosynthetic activity of the corpus cardiacum-corpus allatum (CC-CA) complexes taken from adults of a stink bug, Plautia stali, was stimulated by adding precursors of JH III, farnesoic acid or farnesol, to the incubation medium. This stimulation was mainly attributed to an increase of a product with an Rf value of 0.5 on thin layer chromatography (TLC) sheets. A comparison of the TLC profile of the CA products of P. stali with that of M. domestica indicated that the major fraction of CA products in the bug was neither JH III nor JHB 3. A bioassay system was established using last instar nymphs of P. stali to test the JH activity of the CA products: last instar nymphs implanted with CC-CA complexes taken from reproductively active adults or topically applied with synthetic JHs or JH analogues were reared until the following moult and their forewing and scutellum lengths relative to pronotum width were recorded as well as the number of antennal segments. After CA implantations, the tested bugs had reduced forewing and scutellum lengths and had the 4-segmented antennae characteristic of nymphs, instead of the 5-segmented, adult type antennae. JH applications caused similar juvenilizing effects in a dose dependent manner. This assay system revealed that the JH activity of the CA products was limited to the TLC fraction at an Rf value of 0.5 where the major CA product released in the presence of farnesoic acid or farnesol was found. From these results, it was suggested that the JH produced by P. stali is different from any known JHs.
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