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

Artificial light at night (ALAN) is linked to negative behavioural and
physiological consequences in animals. A potential mechanism for these
adverse effects is ALAN’s inhibition of melatonin synthesis, a zeitgeber
for cellular processes, and a powerful antioxidant. Accordingly, melatonin
supplementation can ameliorate ALAN-linked pathologies. Most studies
expose animals to ALAN 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 ALAN 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 ALAN. Life-long ALAN exposure
accelerated juvenile development, yet did not affect late-juvenile, 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 ALAN 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 ALAN exposure when evaluating
ecological and physiological consequences.