Influence of Artificial Light at Night on Thyroid Gland Histology in Triturus Newts (Urodela, Salamandridae)

Artificial light provides many benefits to humankind, allowing fundamental activities to continue during night; however, it also poses multiple risks to humans and wildlife and is recognized as a significant driver of global environmental change. Changes in natural light/darkness cycles caused by artificial light at night (ALAN) can affect amphibians, the most threatened vertebrate group globally. The aim of this study was to determine the effects of long-term exposure to constant nighttime light on the morphology of the thyroid glands of Triturus ivanbureschi metamorphosed juveniles using histological analysis. A cool LED light with a color temperature of 6000 K was selected, as this spectrum is commonly used in outdoor lighting. Larvae were raised at a natural day–night light regime. After metamorphosis, juveniles were randomly divided into a control group maintained under natural dark nighttime conditions (