Melatonin and thyroxine response to pollution in white stork nestlings (Ciconia ciconia): aspects of rhythmicity and age

From wetlands to landfills: white stork (Ciconia ciconia L., 1758) as a reliable bioindicator of ecosystem health

White storks (Ciconia ciconia L., 1758) and their nestlings have emerged as valuable bioindicators of environmental pollution, particularly in ecosystems affected by human activities. This review explores the role of white storks in biomonitoring, focusing on the use of biomarkers and pollutant analysis to understand the physiological consequences of environmental stressors. Key biomarkers, such as oxidative stress markers, immune responses, and hormonal alterations provide insight into the effects of pollutants like heavy metals, pesticides, and other toxic compounds. The biomarkers are typically measured in matrices such as blood, feathers, eggs, and tissues, each offering unique advantages in assessing pollutant exposure. However, ethical concerns regarding wildlife monitoring and the potential harm caused by invasive sampling techniques call for non-invasive methods. Future research should explore novel non-invasive techniques and employ long-term monitoring programmes to understand the cumulative effects of pollution. Despite challenges such as biological variability and environmental factors, white storks remain reliable indicators of ecological change and pollutant burden, providing critical data that can guide pollution management policies, inform conservation strategies, and protect both wildlife and human health from current environmental threats.

Effect of short-term intermittent exposure to waterborne estradiol on the reproductive physiology of the round goby (Neogobius melanostomus)

The objective of this study was to determine how the short-term exposure to a supraphysiological concentration of waterborne 17β-estradiol (E₂) influences on melatonin (Mel) and thyroxine (T₄) concentrations in plasma and E₂ and 11-ketotestosterone (11-KT) concentrations in plasma and gonads in both sexes of round goby (Neogobius melanostomus) during the pre-spawning, spawning, late spawning and non-spawning phases. The experimental protocol was based on short-term, repeated exposures of fish to a supraphysiological dose of waterborne E₂. Mel level was unchanged on exposure to E₂ during the investigated phases, and its role in determining a time frame for spawning in both sexes of round goby seems to be stable in those conditions. T₄ and sex steroids (E₂ and 11-KT) were sensitive to the exposure of E₂, and those changes influence gonads by accelerating oocyte development, ovulation and regression and inhibiting spermatogenesis in this species. The results demonstrate that the physiological responses of fish in all investigated phases were altered over a short window of exposure, indicating that short-term exposure to a supraphysiological dose of E₂ may impact fish in the wild. Furthermore, round goby can be recommended as a very suitable model for studying endocrine disruptors, which is sensitive to even short exposure to E₂.

Stress Response System in the Fish Skin-Welfare Measures Revisited

The skin of vertebrates acts as a biological barrier defending the organism against many harmful environmental factors. It is well established that the main stress hormone cortisol, together with antioxidants such as melatonin (Mel) and its biologically active metabolites set up a local stress response system in the mammalian skin. Recently, our research group has shown that in fish there are basic conditions for the functioning of a cutaneous stress response system (CSRS) similar to that in mammals, where Mel with its biologically active metabolite AFMK (N1-acetyl-N2-formyl-5-methoxykynuramine) and cortisol act together to protect organism against unfavorable environment. Since aquaculture is making an increasing contribution to the global economy and new laws are demanding people to respect the welfare requirements of animals there has been increasing interest in indicators of fish well-being in aquaculture. This article addresses the problem of on-farm assessment of fish welfare and proposes the CSRS as a new source of information on the welfare status of farmed fish.

Hormones in the city: endocrine ecology of urban birds

Urbanization dramatically changes the landscape, presenting organisms with novel challenges and often leading to reduced species diversity. Urban ecologists have documented numerous biotic and abiotic consequences of urbanization, such as altered climate, species interactions, and community composition, but we lack an understanding of the mechanisms underlying organisms' responses to urbanization. Here, I review findings from the nascent field of study of the endocrine ecology of urban birds. Thus far, no clear or consistent patterns have been revealed, but we do have evidence that urban habitat can shape endocrine traits, and that those traits might contribute to adaptation to the urban environment. I suggest strong approaches for future work addressing exciting questions about the role of endocrine traits in mediating responses to urbanization within species across the globe.