Artificial light at night and captivity induces differential effects on leukocyte profile, body condition, and erythrocyte size of a diurnal toad

Abstract

Light pollution or artificial lighting at night (ALAN) is an emerging threat to biodiversity that can disrupt physiological processes and behaviors. Because ALAN stressful effects are little studied in diurnal amphibian species, we investigated if chronic ALAN exposure affects the leukocyte profile, body condition, and blood cell sizes of a diurnal toad. We hand‐captured male toads of Melanophryniscus rubriventris in Angosto de Jaire (Jujuy, Argentina). We prepared blood smears from three groups of toads: “field” (toads processed in the field immediately after capture), “natural light” (toads kept in the laboratory under captivity with natural photoperiod), and “constant light” (toads kept in the laboratory under captivity with constant photoperiod/ALAN). We significantly observed higher neutrophil proportions and neutrophils to lymphocytes ratio in toads under constant light treatment. In addition, we observed significantly better body condition and higher erythrocyte size in field toads compared with captive toads. In summary, ALAN can trigger a leukocyte response to stress in males of the diurnal toad M. rubriventris. In addition, captivity can affect the body condition and erythrocyte size of these toads.

Differential Effects of Constant Light and Dim Light at Night on the Circadian Control of Metabolism and Behavior

“…The negative consequences of exposure to light at inappropriate times of the day can especially be observed in long-term shift-workers, who may suffer from metabolic diseases [24,25], cardiovascular diseases [26,27] and cancer [28,29]. The detrimental effects of artificial light at night are not observed only in humans but also in other ecosystems [30][31][32]. Moreover, recently, the rate of light pollution has been increasing rapidly due to urbanization and the introduction of efficient and cost-effective light-emitting diodes that accelerate the process of light pollution.…”

A Systematic Review for Establishing Relevant Environmental Parameters for Urban Lighting: Translating Research into Practice

“…A total of 216 studies were identified. These studies included behavioral and physiological responses in plants [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77]; arthropods, including insects and spiders [71,; fish ; amphibians [148][149][150][151][152][153][154][155][156][157][158][159]; reptiles [160][161][162][163][164][165][166][167]; birds ; and non-human mammals, including bats, primates, rodents, and marsupials [24,160,161,174,, when their habitats, aquatic or terrestrial, were artificially illuminated with direct or indirect emissions of ALAN (i.e., all light sources of artificial light). The results of our systematic review show that the most studied organism groups exposed to night-time illumination were birds (76 studies); arthropods, insects and spiders (43 studies); non-human mammals, including bats, primates, rodents, and marsupials (30...…”

“…Physiological responses in amphibians when they were exposed to ALAN included reduced growth [157] and high production levels of neutrophil proportions and altered ratios of neutrophils to lymphocytes [158].…”

Working with Inadequate Tools: Legislative Shortcomings in Protection against Ecological Effects of Artificial Light at Night

“…Only if light is applied at very high intensities, evidence for stress symptoms such as anxiety can be observed, e.g., salmon exposed to 160 lux [73]. In a diurnal toad (Melanophryniscus rubriventris), stress symptoms were observed when exposed to ALAN throughout the whole night analyzing the leukocyte composition in blood samples [74] and the stress hormone corticosterone of nesting great tits (Parus major) was increased [75]. The proof of the stress level in the wild bird required blood samples, which makes it difficult to provide evidence to determine stress levels and, subsequently, to apply the prohibition to disturb protected specimen.…”