Daytime light intensity affects seasonal timing via changes in the nocturnal melatonin levels

Abstract

Daytime light intensity can affect the photoperiodic regulation of the reproductive cycle in birds. The actual way by which light intensity information is transduced is, however, unknown. We postulate that transduction of the light intensity information is mediated by changes in the pattern of melatonin secretion. This study, therefore, investigated the effects of high and low daytime light intensities on the daily melatonin rhythm of Afro-tropical stonechats (Saxicola torquata axillaris) in which seasonal changes in daytime light intensity act as a zeitgeber of the circannual rhythms controlling annual reproduction and molt. Stonechats were subjected to light conditions simulated as closely as possible to native conditions near the equator. Photoperiod was held constant at 12.25 h of light and 11.75 h of darkness per day. At intervals of 2.5 to 3.5 weeks, daytime light intensity was changed from bright (12,000 lux at one and 2,000 lux at the other perch) to dim (1,600 lux at one and 250 lux at the other perch) and back to the original bright light. Daily plasma melatonin profiles showed that they were linked with changes in daytime light intensity: Nighttime peak and total nocturnal levels were altered when transitions between light conditions were made, and these changes were significant when light intensity was changed from dim to bright. We suggest that daytime light intensity could affect seasonal timing via changes in melatonin profiles.

Effects of photophase illuminance on locomotor activity, urine production and urinary 6-sulfatoxymelatonin in nocturnal and diurnal South African rodents

“…Nevertheless, the significant interactive effect between the photophase illuminance and the time of the day under the 330 lx ILC suggests that the photoreception system of the mice was not yet saturated at this intensity. Also, in contrast to what was observed in M. namaquensis, Afrotropical stonechats (Saxicola torquota axillaris) show higher melatonin levels (with activity peaking in the early and late night) when exposed to bright light (Kumar et al, 2007), but the light presented to the birds was orders of magnitude higher than that for the mice.…”

Does light pollution alter daylength? A test using light loggers on free-ranging European blackbirds (Turdus merula)

“…Daytime light intensity has been found to affect daylength perception, with lower intensities usually perceived as a shorter photoperiod than brighter levels of daytime irradiance [17,34]. The rural forest inhabited by our rural blackbird population is quite dense compared with the tree cover in the city of Munich; thus light might penetrate later in the forest and daylength appear shorter than in the city.…”

Quantitative Systems Pharmacology: A Framework for Context

“…On the other end, shift-work, often associated with disrupted feeding patterns, is a known disease pre-disposition factor (Yoon et al 2012; Barclay et al 2012). Similarly well-established are the links between sleep disruption and immunity (Besedovsky et al 2012) whereas the daily (Smolensky et al 2015) and seasonal patterns of inflammation and chronic inflammatory diseases (Dopico et al 2015; Iikuni et al 2007; Kumar et al 2007) are well established. Well characterized as well are the links between circadian disruption, inflammation and mood disorders (Alesci et al 2005; Geoffroy et al 2015; Quera Salva et al 2011).…”