Browsing by Subject "HPI axis"

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    Cortisol and finfish welfare
    (Springer, 2012) Ellis, Tim; Yavuzcan, Hijran; López Olmeda, José Fernando; Spedicato, Maria Teresa; Tort, Lluis; Overli, Oyvind; Martins, Catarina; Fisiología
    Previous reviews of stress, and the stress hormone cortisol, in fish have focussed on physiology, due to interest in impacts on aquaculture production. Here, we discuss cortisol in relation to fish welfare. Cortisol is a readily measured component of the primary (neuroendocrine) stress response and is relevant to fish welfare as it affects physiological and brain functions and modifies behaviour. However, we argue that cortisol has little value if welfare is viewed purely from a functional (or behavioural) perspective—the cortisol response itself is a natural, adaptive response and is not predictive of coping as downstream impacts on function and behaviour are dose-, time- and context-dependent and not predictable. Nevertheless, we argue that welfare should be considered in terms of mental health and feelings, and that stress in relation to welfare should be viewed as psychological, rather than physiological. We contend that cortisol can be used (with caution) as a tractable indicator of how fish perceive (and feel about) their environment, psychological stress and feelings in fish. Cortisol responses are directly triggered by the brain and fish studies do indicate cortisol responses to psychological stressors, i.e., those with no direct physicochemical action. We discuss the practicalities of using cortisol to ask the fish themselves how they feel about husbandry practices and the culture environment. Single time point measurements of cortisol are of little value in assessing the stress level of fish as studies need to account for diurnal and seasonal variations, and environmental and genetic factors. Areas in need of greater clarity for the use of cortisol as an indicator of fish feelings are the separation of (physiological) stress from (psychological) distress, the separation of chronic stress from acclimation, and the interactions between feelings, cortisol, mood and behaviour.
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    Daily rhythms of acute stress responses and antioxidant systems in the European sea bass (Dicentrarchus labrax): effects of the time of the year
    (Elsevier, 2024-04-15) Samorì, Elisa; Rodríguez, Inmaculada; Paullada Salmerón, José Antonio; Sánchez Alacid, Laura; Muñoz Cueto, José Antonio; Sánchez Vázquez, Francisco Javier; López Olmeda, José Fernando; Fisiología
    Fish reared in aquaculture face various acute stressors, including air exposure during handling. Research on the stress response in fish can provide essential insights into their physiology and help define better aquaculture practices. In this study, we investigated the daily rhythms in the stress-axis response of the European sea bass (Dicentrarchus labrax) subjected to an acute stressor consisting of air exposure (1 min), and how this response is influenced by the time of the day and the season of the year. In addition, rhythms in antioxidant systems were also assessed. The experiments were performed in late Autumn (December) and late Spring (June), with natural photoperiod (10 L:14D and 15 L:9D, respectively) and water temperature (ranging from 19.47 ± 0.17 °C in December to 22.13 ± 0.13 °C in June). Samples were collected throughout a 24-h cycle at Zeitgeber time (ZT) 0.5, 4, 7.5, 12, 16, 20, and 24.5 h at both seasons. At each sampling point, an untreated control (CTRL) group was sampled, while a STRESS group was exposed to air for one minute, returned to the tank, and sampled one hour later. Fish were sacrificed to collect plasma samples, hypothalamus and liver. Plasma samples were analyzed for cortisol, glucose, and lactate. In the hypothalamus, the mRNA expression levels of corticotropin-releasing hormone (crh) and crh-binding protein (crh-bp) were quantified using quantitative RT-PCR (qPCR). In the liver, genes related to antioxidant systems (catalase, superoxide dismutase 1, glutathione peroxidase,and glutathione reductase) and mitochondrial markers of stress (uncoupling protein 1, cytochrome c oxidase IV and peroxiredoxin3) were also analyzed by qPCR. The results revealed that most stress indicators (cortisol, cat, sod1, gsh-px, gsr, ucp1, coxIV) displayed daily rhythms. Furthermore, the stress response was significantly influenced by the time of day and the season in which the stressor was applied. In June, cortisol and glucose responses to stress were higher during the day than at night. The increase observed after stress in genes related to the antioxidant system was more significant in June than in December. Conversely, the response of mitochondrial markers was greater in December. Taken together, these findings highlight that the stress response of the European sea bass is time-dependent, both on a daily and a seasonal basis. This emphasizes the importance of considering cyclic environmental factors and circadian rhythms in aquaculture procedures to enhance fish welfare.