![]() Two plausible systems that have been targeted for genetic adaptations driven by diurnal preference are the visual system and the circadian clock, the endogenous pacemaker that drives daily rhythms. Nocturnality and diurnality most likely evolved through different physiological and molecular adaptations. The nocturnality of mammals, for example, was explained by the nocturnal bottleneck hypothesis, which suggests that all mammals descended from a nocturnal ancestor. The fact that diurnality preference is usually similar within phylogenetic groups alludes to an underlying genetic mechanism. The genetic basis for such phase preference is largely unknown and is the focus of this study. Selection for activity during a specific time of the day is driven by various factors, including preferred temperature or light intensity, food availability and predation. Most animal species exhibit locomotor activity that is restricted to a defined part of the day, and this preference constitutes the species-specific temporal niche. The diurnal and nocturnal selection strains provide us with a unique opportunity to understand the genetic architecture of diurnal preference.Īlthough time is one of the most important dimensions that define the species ecological niche, it is often a neglected research area. We identified candidate genes associated with diurnality/nocturnality, while data emerging from our expression analysis and behavioural experiments suggest that both clock and clock-independent pathways are involved in shaping diurnal preference. Our study demonstrates that genetic variation segregating in wild populations contributes to substantial variation in diurnal preference. This finding was congruent with behavioural experiments indicating that both light masking and the circadian pacemaker are involved in driving nocturnality. Other than one circadian clock gene ( pdp1), most differentially expressed genes were associated with either clock output ( pdf, to) or input ( Rh3, Rh2, msn). We used whole-genome expression analysis to identify differentially expressed genes in diurnal, nocturnal and crepuscular (control) flies. After 10 generations, we obtained highly diurnal and nocturnal strains. Using a highly diverse population, we performed an artificial selection experiment, selecting flies with extreme diurnal or nocturnal preference. However, a survey of strains derived from wild populations indicated that high variability among individuals exists, including flies that are nocturnal. Under laboratory conditions, Drosophila melanogaster is crepuscular, showing a bi-modal activity profile. The genetic basis underlying diurnal preference is largely unknown. The influence of sleep disturbances post-menopausal is associated with irregular synthesis and secretion of female sex steroid hormones.Most animals restrict their activity to a specific part of the day, being diurnal, nocturnal or crepuscular. Poor quality of sleep is observed in middle-aged and older men and this also contributes to reduced testosterone concentrations. Sleep deprivation in women has also be found to be associated with altered gonadotropin and sex steroid secretion which all together lead to female infertility. ![]() Sleeplessness among female shift workers suppresses melatonin production as well as excessive HPA activation which results in early pregnancy loss, failed embryo implantation, anovulation and amenorrhea. Sleep deprivation produces a commensurate effect on women by reducing the chances of fertility. The elevated level of corticosteroids results in a reduction in testosterone production. Sleep deprivation generates stressful stimuli intrinsically, due to circadian desynchrony and thereby increases the activation of the Hypothalamus-Pituitary Adrenal (HPA) axis, which, consequently, increases the production of corticosterone. In animal models, sleep disturbances impair the secretion of sexual hormones thereby leading to a decrease in testosterone level, reduced sperm motility and apoptosis of the Leydig cells in male rats. Sleep deprivation among men and women is increasingly reported as one of the causes of infertility. Sleep patterns produce generic signatures that physiologically drive the synthesis, secretion, and metabolism of hormones necessary for reproduction. The reproductive function of humans is regulated by several sex hormones which are secreted in synergy with the circadian timing of the body.
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