Clock-controlled rhythm of ecdysteroid levels in the haemolymph and testes, and its relation to sperm release in the Egyptian cotton leafworm, Spodoptera littoralis

Regulation of Drosophila circadian rhythms by miRNA let-7 is mediated by a regulatory cycle

“…The prothoracic gland in Drosophila larvae and pupae, where ecdysone is secreted, is reported to strongly express clock genes 48,49 . The rhythmic changes in 20E levels were also regulated by an endogenous circadian oscillator in the haemolymph and testes of adult males in cotton leafworm and in Rhodnius prolixus 50,51 , and 20E is also present in Drosophila adults 52 . In this study, we found that the PTTH is a direct target of CLK/CYC, most likely because the 2-kb promoter region of ptth contains 10 noncanonical E-box sequences (CANNTG other than CACGTG).…”

Peripheral regulation by ecdysteroids of olfactory responsiveness in male Egyptian cotton leaf worms, Spodoptera littoralis

“…To increase the ecdysteroid concentration in the haemolymph during the scotophase to levels observed during the photophase (Polanska et al, 2009), we injected 20E into the abdomen of males at the beginning of the scotophase. The ecdysteroid titer in the haemolymph was quantified by EIA at 10 min, 3 h, and 6 h postinjection (Table 1).…”

“…Circadian variation of haemolymph ecdysteroids is due to a clock-controlled rhythm of 20E titers in testes, the major source of ecdysteroid (Polanska et al, 2009). During scotophase, ecdysteroids titers are low, inducing sperm release, high mating activity, female pheromone production and release, and male pheromone responsiveness (Silvegren et al, 2005;Polanska et al, 2009).…”

“…In adult male Spodoptera littoralis, ecdysteroid levels in the haemolymph and testes are controlled by the circadian clock (Polanska et al, 2009). The decline of ecdysteroid levels from the photophase to the scotophase corresponds to sperm release, when S. littoralis has high mating activity, female pheromone production/ release, and male pheromone responsiveness (Dreisig, 1986;Silvegren et al, 2005).…”

Circadian Window of Opportunity: What Have We Learned From Insects?

“…Rhythmic PTTH release generates rhythmic synthesis and release of ecdysone from cells, which also possess clock properties (Steel and Vafopoulou, 2006). Rhythmic changes in ecdysone levels were recently demonstrated in the testis of adult moth (Polanska et al, 2009) leaving one to wonder about the significance of the parallel occurrence of steroidogenesis in testicular tissues in both insects and vertebrates.…”