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In the context of increasing environmental contamination, our study employed fish as bioindicators, focusing on non-invasive cortisol measurements in scales and fins in response to severe PFAS pollution in the Veneto area of Italy. Our preliminary findings showed species-specific stress responses, as observed in Squalius cephalus and Padogobius bonelli , suggesting the need for broader biomonitoring to capture the complex impact of environmental stressors on aquatic organisms. Moreover, due to the unusual characteristics of the rivers selected for the biomonitoring activity, a possible link between PFAS exposure and cortisol levels in S. cephalus demonstrates the method's potential. [Display omitted] • Fish accumulate PFAS following environmental levels. • PFAS induce chronic stress with elevated cortisol levels in S. cephalus. • PFAS exhibit species-specific impacts on stress responses. [ABSTRACT FROM AUTHOR]

Soy isoflavones (the phytoestrogens genistein, daidzein and glycitein) may act as estrogen receptor agonists or antagonists. The aim of this study was to examine the effect of dietary isoflavones on growth, reproduction and health in rainbow trout (Oncorhynchus mykiss). Rainbow trout fed three experimental diets containing different concentrations of isoflavones (0, 500 and 1,500 ppm). Growth, estrogenic activity, plasma estradiol levels, gonadal development, state of stress and histological changes in selected tissues were evaluated at the end of 70 days. Neither growth performance nor the relative mRNA levels of Insulin Growth Factor I (igf-I) in the liver were influenced by different levels of dietary isoflavones. Plasma and liver vitellogenin (VTG) protein levels and plasma 17-β-estradiol (E2) were unaffected by treatments, although the correlation between plasma levels of E2 and VTG densitometry values was significant (p < .05). The fish gonadosomatic index (GSI) did not significantly differ among the three experimental groups but correlated with plasma VTG densitometry values (p < .05). Plasma, muscle and fin cortisol concentrations fell within the normal welfare range and were not correlated with isoflavone levels. Histologically, the distal intestine showed a normal morphology with well-differentiated enterocytes and in the liver hepatocytes were also normal. A supranuclear accumulation of lipid droplets in enterocytes and some lipid droplets in hepatocytes were observed in all tested groups, suggesting an impact of basal dietary lipid on transport/metabolism of fat in the fish. Overall, the present results suggest that the doses of isoflavones tested do not compromise rainbow trout reproduction, growth and health. [ABSTRACT FROM AUTHOR]

Plasma cortisol is the most commonly used indicator of stress in fish but, as the blood sampling procedure itself can be a source of stress, it would be helpful to measure cortisol using less invasive matrices. It is also necessary to find alternative matrices as stress indicators in dead fish in which blood sampling is impossible. In the present study, we investigated transport stress in three aquaculture species, European sea bass ( Dicentrarchus labrax L.), common carp ( Cyprinus carpio L.) and rainbow trout ( Oncorhynchus mykiss Walbaum), by cortisol determination (radioimmunoassay) in plasma and other matrices (skin mucus, gut content, lateral muscle and caudal fin). Cortisol significantly increased after transport in all species and matrices, except in the sea bass gut content, where it remained unchanged. The three species responded to transport stress by producing different cortisol levels. In conclusion, the significant correlation found between plasma cortisol and most of the other matrices opens up the possibility of using them to evaluate stress in fish: mucus sampling is a less invasive method than blood sampling, and in addition to muscle and fin sampling, it can be used in postmortem fish. [ABSTRACT FROM AUTHOR]

Simple Summary: Gilthead seabream (Sparus aurata) is a teleost fish of great relevance in marine aquaculture, especially in the Mediterranean area and one of the most important farmed food marine species in Europe. Nevertheless, in captivity fish are usually exposed to stressful conditions, with a consequent negative impact on animal welfare and growth. The principal goal of this study was to shed light on the acute stress response of gilthead seabream juveniles exposed to different stressors using a multidisciplinary approach. For this purpose, gilthead seabream have been exposed to three different stress tests (temperature, salinity, and ammonia changes) and several laboratory techniques have been used to evaluate their growth and stress response. Results revealed that all the tested stressors had an impact on fish growth and health, particularly thermic and chemical exposure, whereas salinity seems to have a minor effect since this species can efficiently face with extreme variations in environmental salinity. The present work aimed to obtain relevant information on acute stress response of gilthead seabream to be used for improving farming condition and ensuring fish welfare. The present study aimed to investigate the acute response of gilthead seabream (Sparus aurata) juveniles exposed to temperature, salinity and ammonia stress. Radioimmunoassay was used to evaluate cortisol levels, whereas insulin-like growth factors (igf1 and igf2), myostatin (mstn), heat-shock protein 70 (hsp70) and glucocorticoid receptor (gr) gene expression was assessed trough Real-Time PCR. The presence and localization of IGF-I and HSP70 were investigated by immunohistochemistry. In all the stress conditions, a significant increase in cortisol levels was observed reaching higher values in the thermic and chemical stress groups. Regarding fish growth markers, igf1 gene expression was significantly higher only in fish subjected to heat shock stress while, at 60 min, igf2 gene expression was significantly lower in all the stressed groups. Temperature and ammonia changes resulted in a higher mstn gene expression. Molecular analyses on stress response evidenced a time dependent increase in hsp70 gene expression, that was significantly higher at 60 min in fish exposed to heat shock and chemical stress. Furthermore, the same experimental groups were characterized by a significantly higher gr gene expression respect to the control one. Immunostaining for IGF-I and HSP70 antibodies was observed in skin, gills, liver, and digestive system of gilthead seabream juveniles. [ABSTRACT FROM AUTHOR]

Abstract: Whole body cortisol levels were determined during early larval developmental stages of sea bass (Dicentrarchus labrax) subjected to a heat shock with the aim to investigate the correlation between the stress event and the activation of the hypothalamic–pituitary–interrenal axis. Moreover, the mRNA expression of inducible heat shock protein 70 (HSP70), insulin-like growth factor I (IGF-I) and myostatin (MSTN) was also detected. Whole body cortisol was determined by a radio-immunoassay (RIA) technique whereas the expression of HSP70, IGF-I and MSTN mRNAs was quantified by Real-Time PCR. Cortisol was detectable in all the larvae from hatching but its level increased significantly in larvae submitted to heat shock from 2-day post hatching onwards. An effect of the sole transfer on cortisol levels was detectable at day 10, indicating an increase of the hypothalamic–pituitary–interrenal axis sensitivity from this stage of sea bass development. In animals exposed to heat shock, the expression of inducible HSP70 resulted in a marked increase of mRNA levels already at hatching. This increase was significantly higher from 6days onwards if compared to controls. Moreover, heat shock resulted in a decrease (although not significant) in IGF-I mRNA expression of stressed larvae if compared to controls. On the contrary, heat shock did not influence the expression of MSTN mRNA in all groups. The results indicate a very early activation of the hypothalamic–pituitary–interrenal axis and in general of the stress response during the development of European sea bass. Moreover, these results suggest the importance of cortisol and inducible HSP70 as bioindicators of stress in aquaculture and confirm the role of IGF-I and MSTN as regulatory factors during development and growth of fish. [Copyright &y& Elsevier]