Abstract
A functioning immune system is crucial for protection against disease and illness, yet increasing evidence suggests that species living in urban areas could be suffering from immune suppression, due to the presence of artificial light at night (ALAN). This study examined the effects of ecologically relevant levels of ALAN on three key measures of immune function (haemocyte concentration, lytic activity, and phenoloxidase activity) using a model invertebrate species, the Australian black field cricket, Teleogryllus commodus. We reared crickets under an ecologically relevant daily light‐cycle consisting of 12 hr bright daylight (2600 lx) followed by either 12 h darkness (0 lx) or dim environmentally relevant ALAN (1, 10, 100 lx), and then assessed immune function at multiple time points throughout adult life using haemolymph samples. We found that the presence of ALAN had a clear negative effect on haemocytes, while the effects on lytic activity and phenoloxidase activity were more complex or largely unaffected by ALAN. Furthermore, the effects of lifelong exposure to ALAN of 1 lx were comparable to those of 10 and 100 lx. Our data suggest that the effects of ALAN could be large and widespread, and such reductions in the core immune response of individuals will likely have greater consequences for fitness and survival under more malign conditions, such as those of the natural environment.
Highlights
The global presence of artificial light at night (ALAN) is increasing rapidly in terms of its intensity and distribution making it one of the most pervasive recent forms of anthropogenic pollution (Bennie et al, 2015; Gaston et al, 2015; Falchi et al, 2016)
Following a wounding challenge, adults reared under the presence of artificial light at night were less able to upregulate their haemocytes and
We found a correlation between haemocyte count and lytic activity but neither lytic activity nor PO activity varied in response to the presence of ALAN, they did increase across the three sampling periods
Summary
The global presence of artificial light at night (ALAN) is increasing rapidly in terms of its intensity and distribution making it one of the most pervasive recent forms of anthropogenic pollution (Bennie et al, 2015; Gaston et al, 2015; Falchi et al, 2016). Correlated with (and potentially underpinning) these physiological impacts are the largely negative effects of ALAN on immune function demonstrated in birds and mammals, including Japanese quail (Moore & Siopes, 2000), rats (Oishi et al, 2006; Cisse et al, 2017), Siberian hamsters (Aubrecht et al, 2014), blackbirds (Russ et al, 2015a), and great tits (Raap et al, 2016b; Ouyang et al, 2017).
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