Exposure to artificial light at night increases innate immune activity during development in a precocial bird

Humans have greatly altered Earth's night-time photic environment via the production of artificial light at night (ALAN; e.g. street lights, car traffic, billboards, lit buildings). ALAN is a problem of growing importance because it may significantly disrupt the seasonal and daily physiological rhythms and behaviors of animals. There has been considerable interest in the impacts of ALAN on health of humans and other animals, but most of this work has centered on adults and we know comparatively little about effects on young animals. We exposed 3-week-old king quail (Excalfactoria chinensis) to a constant overnight blue-light regime for 6 weeks and assessed weekly bactericidal activity of plasma against Escherichia coli - a commonly employed metric of innate immunity in animals. We found that chronic ALAN exposure significantly increased bactericidal activity and that this elevation in immune performance manifested at different developmental time points in males and females. Whether this short-term increase in immune activity can be extended to wild animals, and whether ALAN-mediated increases in immune activity have positive or negative fitness effects, are unknown and will provide interesting avenues for future studies.