Effects of a daily temperature cycle on ecdysteroid and cyclic nucleotide titres in adult female crickets, Gryllus bimaculatus

ABSTRACT. Ecdysteroid and cyclic nucleotide titres were determined in ovaries, fat body, muscles, haemolymph and the remaining carcass tissue (cyclic nucleotides only in ovaries and fat body) of females of the Mediterranean field cricket, Gryllus bimaculatus de Geer, during its adult life span. Under a daily temperature cycle 24°: 12°C (16:8h), ecdysteroid levels of the ovaries and fat body reached maximal values 5 times as great and about 10 days earlier than they did under constant 20°C. Under both temperature regimes the highest ecdysone concentrations coincided with the maximum in ovarian fresh weight as well as with the maximum oviposition rate. In the ovaries, titres of c-AMP and c-GMP changed roughly in parallel, the levels of c-GMP, however, were much lower than those of c-AMP. A comparison of the cyclic nucleotide profiles in the ovaries with the ecdysteroid profile shows that the cyclic nucleotide concentrations increase when ecdysteroid titres are still low, and that the highest cyclic nucleotide levels were reached 6–12 days earlier than the highest ecdysteroid titres.