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| Physiological Changes during Starvation In Fish pp. 347-356 |
$100.00 |
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Authors: (Miriam Furné, Ana Sanz, Departamento de Biología Animal, Universidad de Granada, Granada, Spain)
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Abstract:
Starvation is a situation undergone and tolerated by many species of fish in their natural environment in response to several factors (e.g. temperature, spawning migration, reproduction, etc.). To survive these periods of unfavorable feeding conditions, fish reduce their energy expenditures, which in a high percentage are derived from protein synthesis, and mobilize their endogenous reserves to obtain the energy required to maintain the vital processes. This response entails physiological and metabolic changes that are species dependent. Moreover, intra-specific adjustments to these conditions will depend on different factors such as fish age, nutritional state, etc. Starvation has been reported to have pro-oxidant effects, and both the inadequate neutralization of the reactive oxygen species (ROS) generated by oxidative metabolism and the reduced level of antioxidant defenses, both enzymatic and non-enzymatic, may be responsible for some of the detrimental effects of starvation. (When the rate of ROS generation exceeds that of their removal, oxidative stress occurs. Its deleterious effects include oxidation of proteins, DNA, and steroid components, as well as peroxidation of unsaturated lipids in cell membranes. Together these effects lead to reversible or irreversible cell damage, and eventually to cell death.) Studies regarding digestive enzymes during starvation show a decrease in their activities and synthesis. Decreases in digestive enzymes synthesis during starvation suppose energy conservation due to in this situation is not necessary for the animal. This fact depends on species and specifies enzyme activities (protease, lipase or carbohydrase) and could be adaptative purposes. Fluctuations in food availability are natural in most aquatic systems, and fish show an impressive capacity to withstand prolonged periods of food limitation, particularly in comparison with mammals.
The aim of this chapter is to give an overview of the influence of food deprivation on digestive physiology, metabolic status and antioxidant defences of fish. |
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