The stress response in fish

Abstract

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.

Environmental Parasitology. Interactions between parasites and pollutants in the aquatic environment

“…With respect to the endocrine system it is surprising that only a limited number of studies concentrates on combined effects of concurrently occurring parasites and pollutants (see e.g. Klar & Sures, 2004;Sures et al, 2006) although it is clear that both modify hormonal responses (Wendelaar Bonga, 1997). In a laboratory study, Sures et al (2006) suggest an antagonistic relation between parasites and pollution.…”

Analisis Proksimat Kadar Kolesterol Ikan Nila Yang Diberi Suplemen Daun Jaloh Dan Dikombinasi Dengan Kromium Dalam Pakan Setelah Pemaparan Stres Panas

“…Selain itu, tindakan untuk mengembalikan keseimbangan ini dapat memberikan mineral dan glukokortikoid (Maule et al, 1993;Wendelaar, 1997;Colombe et al, 2000). Salah satu mikromineral adalah kromium trivalen merupakan kofaktor dari faktor toleransi glukosa (glucose tolerance factor) dan yang telah diketahui berperan penting terhadap metabolisme karbohidrat melalui peningkatan bioaktivitas insulin.…”

Respostas fisiológicas de tambaqui a banhos terapêuticos com mebendazol

“…Nesse sistema, os peixes são expostos continuamente a vários estressores (Barton & Iwama, 1991;Wendelaar Bonga, 1997), como alterações na química da água, altas densidades de estocagem, manuseio excessivo e uso indiscriminado de drogas no tratamento de doenças (Wedemeyer, 1996).…”

“…Em geral, diante de um estressor, a resposta primária consiste na liberação de hormônios como o cortisol (Barton & Iwama, 1991;Acerete et al, 2004); a secundária está relacionada ao metabolismo energético, como hiperglicemia e alteração da homeostase eletrolítica no sangue e tecidos (Barton & Iwama, 1991;McDonald & Milligan, 1997;Wendelaar Bonga, 1997); a terciária inclui o comprometimento no desempenho, mudanças no comportamento e aumento da suscetibilidade a doenças (Wedemeyer, 1996;Wendelaar Bonga, 1997).…”

“…A dosagem da glicose sangüínea é considerada um método valioso no diagnóstico da ocorrência de estresse fisiológico em peixes (Wendelaar Bonga, 1997;Acerete et al, 2004), por sua precisão e praticidade. A elevada concentração de glicose dos peixes expostos a 300 mg L -1 de mebendazol, em 120 minutos, pode estar relacionada à resposta individual, visto que diversos fatores ambientais e não ambientais influem nos níveis de glicose em peixes (Barton & Iwama, 1991;TavaresDias & Mataqueiro, 2004).…”