Abstract
Light is an important environmental cue, and exposure to artificial light at night (ALAN) may disrupt organismal physiology and behavior. We investigated whether ALAN led to changes in clock-gene expression, diel activity patterns, and fecundity in laboratory populations of the mosquito Culex pipiens f. molestus (Diptera, Culicidae), a species that occurs in urban areas and is thus regularly exposed to ALAN. Populations were kept under 16 h:8h light:dark cycles or were subjected to an additional 3.5 h of light (100–300 lx) in the evenings. ALAN induced significant changes in expression in all genes studied, either alone (period) or as an interaction with time (timeless, cryptochrome2, Clock, cycle). Changes were sex-specific: period was down-regulated in both sexes, cycle was up-regulated in females, and Clock was down-regulated in males. ALAN-exposed mosquitoes were less active during the extra-light phase, but exposed females were more active later in the night. ALAN-exposed females also produced smaller and fewer eggs. Our findings indicate a sex-specific impact of ALAN on the physiology and behavior of Culex pipiens f. molestus and that changes in clock-gene expression, activity, and fecundity may be linked.
Highlights
Artificial light at night (ALAN) is a prominent feature of most urban and semi-urban areas
We examined changes in expression of five genes of the circadian clock relative to the housekeeping gene ribosomal protein 49 to test for the effect of treatment, sex, length of exposure, and sampling time. cDNA synthesis was carried out using AffinityScript Multiple Temperature Reverse Transcriptase (Agilent Technologies, Waldbronn, Germany) following the manufacturer’s protocol with 14 ng cDNA/μL in a final volume of 12.7 μL
In extra-light, period was down-regulated in males and females, cycle was up-regulated in females, and Clock was down-regulated in males (Figure 3)
Summary
Artificial light at night (ALAN) is a prominent feature of most urban and semi-urban areas. The urbanization of the human population, i.e., the number of people living in urban areas, is projected to increase from the current 4 billion to 6.3 billion people by 2050 [1]. This is accompanied by a yearly increase of artificially lit surface of Earth at night of 2–6%, both in radiance and extent [2,3]. Less studied are the effects ALAN may have on diel rhythms of exposed organisms
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