Modulation of juvenile hormone synthesis by an analogue in the cockroach

Abstract

The juvenile hormones (JH) are novel insect sesquiterpenoid products synthesised by paired endocrine glands known as the corpora allata (CA). These glands are innervated by neural and neurosecretory elements originating in the central nervous system (CNS)^1–3 and are known to undergo predictable changes in synthesis and release of JH during the reproductive cycle^4–8. This implies that the CA are regulated by intrinsic physiological signals. For example, in the viviparous cockroach, Diploptera punctata, if the haemolymph titres of JH are experimentally altered by removal of one member of the pair or by implantation of additional CA, the original CA undergo appropriate corrective responses in JH synthesis^9,10. This is partly due to signals from the CNS because denervation of the CA attenuates the compensatory change¹⁰. The depression in JH synthesis after addition of exogenous JH to the system has also been observed^11,12. However, there have been no direct measurements of JH synthesis following treatment with exogenous JH analogues in vivo. We show here that in Diploptera punctata, topical application of a JH analogue (JHA) depresses the synthesis of JH at high doses but stimulates synthesis at low doses and that the analogue can support oocyte growth and maturation in the absence of the CA and that application to intact animals stimulates oocyte growth rates. These results indicate that the analogue can replace authentic JH.