The stress response in teleost fish shows many similarities to that of the terrestrial vertebrates These concern the principal messengers of the brain-sympathetic-chromaffin cell axis (equivalent of the brain-sympathetic-adrenal medulla axis) and the brain-pituitary-interrenal axis (equivalent of the brain-pituitary-adrenal axis), as well as their functions, involving stimulation of oxygen uptake and transfer, mobilization of energy substrates, reallocation of energy away from growth and reproduction, and mainly suppressive effects on immune functions There is also growing evidence for intensive interaction between the neuroendocrine system and the immune system in fish Conspicuous differences, however, are present, and these are primarily related to the aquatic environment of fishes For example, stressors increase the permeability of the surface epithelia, including the gills, to water and ions, and thus induce systemic hydromineral disturbances High circulating catecholamine levels as well as structural damage to the gills and perhaps the skin are prime causal factors This is associated with increased cellular turnover in these organs In fish, cortisol combines glucocorticoid and mineralocorticoid actions, with the latter being essential for the restoration of hydromineral homeostasis, in concert with hormones such as prolactin (in freshwater) and growth hormone (in seawater) Toxic stressors are part of the stress literature in fish more so than in mammals This is mainly related to the fact that fish are exposed to aquatic pollutants via the extensive and delicate respiratory surface of the gills and, in seawater, also via drinking The high bioavailability of many chemicals in water is an additional factor Together with the variety of highly sensitive perceptive mechanisms in the integument, this may explain why so many pollutants evoke an integrated stress response in fish in addition to their toxic effects at the cell and tissue levels Exposure to chemicals may also directly compromise the stress response by interfering with specific neuroendocrine control mechanisms Because hydromineral disturbance is inherent to stress in fish, external factors such as water pH, mineral composition, and ionic calcium levels have a significant impact on stressor intensity Although the species studied comprise a small and nonrepresentative sample of the almost 20,000 known teleost species, there are many indications that the stress response is variable and flexible in fish, in line with the great diversity of adaptations that enable these animals to live in a large variety of aquatic habitats

The stress response in fish

The brain is the key organ of the response to stress because it determines what is threatening and, therefore, potentially stressful, as well as the physiological and behavioral responses which can be either adaptive or damaging. Stress involves two-way communication between the brain and the cardiovascular, immune, and other systems via neural and endocrine mechanisms. Beyond the "flight-or-fight" response to acute stress, there are events in daily life that produce a type of chronic stress and lead over time to wear and tear on the body ("allostatic load"). Yet, hormones associated with stress protect the body in the short-run and promote adaptation ("allostasis"). The brain is a target of stress, and the hippocampus was the first brain region, besides the hypothalamus, to be recognized as a target of glucocorticoids. Stress and stress hormones produce both adaptive and maladaptive effects on this brain region throughout the life course. Early life events influence life-long patterns of emotionality and stress responsiveness and alter the rate of brain and body aging. The hippocampus, amygdala, and prefrontal cortex undergo stress-induced structural remodeling, which alters behavioral and physiological responses. As an adjunct to pharmaceutical therapy, social and behavioral interventions such as regular physical activity and social support reduce the chronic stress burden and benefit brain and body health and resilience.

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Physiology and Neurobiology of Stress and Adaptation: Central Role of the Brain

The fish gill is a multipurpose organ that, in addition to providing for aquatic gas exchange, plays dominant roles in osmotic and ionic regulation, acid-base regulation, and excretion of nitrogenous wastes Thus, despite the fact that all fish groups have functional kidneys, the gill epithelium is the site of many processes that are mediated by renal epithelia in terrestrial vertebrates Indeed, many of the pathways that mediate these processes in mammalian renal epithelial are expressed in the gill, and many of the extrinsic and intrinsic modulators of these processes are also found in fish endocrine tissues and the gill itself The basic patterns of gill physiology were outlined over a half century ago, but modern immunological and molecular techniques are bringing new insights into this complicated system Nevertheless, substantial questions about the evolution of these mechanisms and control remain

https://people.clas.ufl.edu/devans/files/PRVGill.pdf

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste

http://aerg.canberra.edu.au/library/sex_general/2002_Devlin_Nagahama_sex_determination_in_fish_review.pdf

Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental influences

Cortisol is the principal corticosteriod in teleost fishes and its plasma concentrations rise dramatically during stress. The relationship between this cortisol increase and its metabolic consequences are subject to extensive debate. Much of this debate arises from the different responses of the many species used, the diversity of approaches to manipulate cortisol levels, and the sampling techniques and duration. Given the extreme differences in experimental approach, it is not surprising that inconsistencies exist within the literature. This review attempts to delineate common themes on the physiological and metabolic roles of cortisol in teleost fishes and to suggest new approaches that might overcome some of the inconsistencies on the role of this multifaceted hormone. We detail the dynamics of cortisol, especially the exogenous and endogenous factors modulating production, clearance and tissue availability of the hormone. We focus on the mechanisms of action, the biochemical and physiological impact, and the interaction with other hormones so as to provide a conceptual framework for cortisol under resting and/or stressed states. Interpretation of interactions between cortisol and other glucoregulatory hormones is hampered by the absence of adequate hormone quantification, resulting in correlative rather than causal relationships.

Cortisol in teleosts: dynamics, mechanisms of action, and metabolic regulation

Methods for fish biology , Methods for fish biology , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

/pdf/methods-for-fish-biology-iil6tx3ryn.pdf

Methods for Fish Biology

Effects of stress on fish reproduction, gamete quality, and progeny

https://www.webpages.uidaho.edu/fish511/Readings/Readings%202010/Schreck%20Stress%20and%20Reproduction.pdf

Stress and fish reproduction: The roles of allostasis and hormesis

We examined the effects of acute stress on the immune system and disease resistance of juvenile chinook salmon (Oncorhynchus tshawytscha) in laboratory and clinical trials Immune function, as measured by the ability of lymphocytes from the anterior kidney to generate specific antibody-producing cells (APC) in vitro, was depressed 4 h after stress, when plasma cortisol levels were highest At the same time, resistance to the fish pathogen, Vibrio anguillarum, was also depressed Compared with controls, plasma cortisol and APC of stressed fish were unchanged after 24 h, and disease resistance was enhanced as evidenced by higher survival rate and longer mean time to death of mortalities After 7 days, even though numbers of APC were depressed, plasma cortisol concentration and disease resistance did not differ from controls This pattern was generally the same, independent of the type of stress applied: ie being held out of water in a dipnet for 30 s, manipulation during hatchery operations for 4 h, or transportation for 9 h These and earlier findings suggest that similar endocrine-immune interactions operate in the mammalian and salmonid systems during acute stress

Stress alters immune function and disease resistance in chinook salmon (Oncorhynchus tshawytscha).

The corticosteroid and hyperglycemic stress responses to multiple acute disturbances were cumulative in juvenile chinook salmon Oncorhynchus tshawytscha. This was demonstrated by the stepwise pattern of increased plasma cortisol and glucose concentrations in fish subjected to a 30-s handling stress applied repeatedly at 3-h intervals over 6 h. The accumulation of physiological stress responses was substantiated by the resultant combined effects of these repeated disturbances on changes in concentrations of plasma lactate and of ionic sodium and potassium, and on the rate of decline of hepatic glycogen concentrations, all of which were greater than those that followed a single handling. Healthy fish appeared more able than diseased fish to elevate plasma cortisol after each of the three successive disturbances, but plasma glucose concentrations following the repeated handlings were higher in the unhealthy fish. As judged from plasma cortisol and glucose responses in fish subjected to a single 30-s...

Carl B. Schreck

Papers

Methods for Fish Biology

Effects of stress on fish reproduction, gamete quality, and progeny

Stress and fish reproduction: The roles of allostasis and hormesis

Stress alters immune function and disease resistance in chinook salmon (Oncorhynchus tshawytscha).

Multiple Acute Disturbances Evoke Cumulative Physiological Stress Responses in Juvenile Chinook Salmon