Data from: Crustacean photoreceptor damage and recovery: Applying a novel scanning electronic microscopy protocol in artificial light at night studies

As sources of artificial light at night (ALAN) expand worldwide, research on their impacts has also increased. Most of these studies, including those in coastal habitats, have focused on behavioral and ecological responses to ALAN, overlooking impacts on the photoreceptor, the basic functional structure of animals to absorb light. Examining structural changes in the photoreceptor is essential to understand the mechanisms by which ALAN may be impacting species, particularly those adapted to different light backgrounds. This study examined the photoreceptor (rhabdom) of two sandy beach crustaceans exhibiting different light tolerances at night: the amphipod Orchestoidea tuberculata and the isopod Tylos spinulosus. We developed a novel protocol to measure these species' photoreceptor areas and quantify the damage caused by ALAN using histological sections and scanning electron microscopy (SEM). Our results showed that in the isopod, a species naturally adapted to lower light intensities at night than the amphipod, the rhabdom surface was 20-times larger, and presented a tapetum, an adaptive feature found in species living in low light conditions. This confirmed that this species is potentially more sensitive to ALAN than the amphipod. Consistently, a brief period of exposure to ALAN (1 h, 20 lux) caused 3-6 times more damage in the isopod' rhabdom. In fact, ALAN caused structural damage in the isopod' but not in the amphipod' rhabdom, a damage that did not show signs of recovery from ALAN after 1 and 24 h. Thus, the damage caused by ALAN on an organism's photoreceptors is likely to be more severe and persistent in species naturally adapted to lower light levels at night. Installation of permanent ALAN sources nearby the burrowing area of these light sensitive species may have differential effects on their activity and interactions at night. ALAN may also become a new selection pressure on these species, a concern with wide implications given the ubiquity among animals of the photoreceptor structure and its response to light.