Dietary melatonin supplementation mitigates the negative effects of artificial light at night in the Pacific field cricket, Teleogryllus oceanicus

Abstract

Artificial light at night (ALAN) is linked to negative behavioural and physiological consequences in animals. A potential mechanism for these adverse effects is artificial light at night's inhibition of melatonin synthesis, a zeitgeber for cellular processes and a powerful antioxidant. Accordingly, melatonin supplementation can ameliorate artificial light at night-linked pathologies. Most studies expose animals to artificial light at night across their whole lifespan or a single life stage, but many nocturnal species experience variable exposure across heterogeneously lit landscapes. We investigated the effects of artificial light at night during both early- and late-juvenile development on adult reproduction in the Pacific field cricket Teleogryllus oceanicus, and whether dietary melatonin supplementation could mitigate these effects. We found life-stage-specific developmental effects of artificial light at night. Lifelong artificial light at night exposure accelerated juvenile development, yet did not affect late-juvenile development, total development time or adult body mass. Moreover, we confirm the potential for melatonin supplementation to rescue male sperm viability and daily egg production by females. The degree of 'rescue' was sex, and potentially age specific, which may be explained by the differential effect of artificial light at night on early-juvenile development. Critically, this effect would have been masked had we not partitioned this early life stage, underscoring the importance of considering life-stage-specific artificial light at night exposure when evaluating ecological and physiological consequences.