The effect of constant darkness on the content of adipokinetic hormone, adipokinetic response and walking activity in macropterous females of Pyrrhocoris apterus (L.)

Abstract.  Changes in the content of adipokinetic hormone (AKH), the adipokinetic response and the walking activity of 10-day-old adult macropterous females of the firebug, Pyrrhocoris apterus (L.), reared under long-day (LD) photoperiod (LD 18 : 6 h) are compared with those exposed for 3 days to constant darkness (DD). Diel changes of all the parameters studied in LD females persist in females kept in constant dark. A positive correlation exists between diel changes of AKH content in the central nervous system (CNS) in the LD and DD females, and a negative correlation in the AKH level in haemolymph and walking activity. In addition, there is a positive correlation between diel changes of AKH level in haemolymph and walking activity in macropterous females reared under LD conditions, as well as in those transferred to constant darkness. The data suggest that there is some feedback between the release of AKH from CNS into the haemolymph and walking activity in macropterous females. Preliminary studies on the simultaneous expression of mRNA for the period gene and a positive reaction to an antibody against AKH in the same corpus cardiacum cells suggest that the period gene may be involved in regulating the AKH content in this gland.