Artificial light at night (ALAN) is a pervasive environmental stressor, yet its effects are often assessed without considering ontogeny, cross-group variation, or interactions between spectral composition and illuminance. The transition to LED lighting makes this issue increasingly relevant. Amphibians may be vulnerable because many species rely on natural light cycles and undergo habitat transitions during development. We tested direct and carryover effects of ecologically realistic LED light in crested newts (Triturus macedonicus, T. ivanbureschi) and reciprocal hybrids. Larvae were exposed to warm (2700 K) or cool (6500 K) light at 5 or 30 lx. We quantified oxidative status, development, and growth; carryover was assessed only in T. ivanbureschi after 5 lx larval exposure. ALAN altered oxidative physiology and life-history traits, with responses depending on spectrum, illuminance, and cross group. Warm light at 30 lx reduced catalase activity and glutathione and increased protein carbonyls, whereas cool light at 30 lx most strongly delayed development and reduced growth. In juvenile T. ivanbureschi, carryover responses were clearest after cool 5 lx exposure. Observed cross-group patterns were exploratory because cross type was confounded with family composition and breeding mesocosm. These findings identify LED-based ALAN as a multidimensional stressor and challenge spectrum-only mitigation strategies.
