Physiological responses of invasive round goby (Neogobius melanostomus) to environmental stressors across a latitudinal span

Ecosystems worldwide are struggling with increasingly high levels of human-induced stressors, impacting their ecological health at local, regional, and global scales. Among the factors affecting freshwater organisms, temperature stands out, especially given the recent escalation of global warming, with possible adverse effects. In this study, we examined the basal levels of oxidative stress parameters in the round goby Neogobius melanostomus, spanning its native and non-native ranges of occurrence. We aimed to assess five populations across transcontinental scale (Turkey, Croatia, Slovakia, Poland, Finland) to determine whether individuals already experiencing conditions other than their thermal optimum (such as those in Turkey and Finland) would display elevated non-enzymatic indicators (level of lipid peroxidation and reduced glutathione levels) and enzymatic indicators (activity of glutathione peroxidase and catalase activity) of oxidative stress compared to those inhabiting milder ecosystems. The results obtained did not align with our initial predictions. The native Turkish population exhibited the lowest values for both antioxidants and oxidative damage, indicating an efficient redox system in this species. All tested parameters showed variation among populations, as well as between tissues and sexes. Temperature did not emerge as significant factor in any of the parameters tested, while for glutathione peroxidase, our analysis indicated a positive relationship with enzyme activity and salinity. The lack of a continuous latitudinal pattern in the non-native populations suggests the species’ potential for adaptive shifts, indicating superior adaptive abilities, especially in human affected ecosystems, rather than strictly adhering to environmental gradients.