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| Author(s): |
Carlos Eduardo Tolussi
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-12-09 |
| Examining board members: |
Renata Guimarães Moreira;
Neuza Sumiko Takahashi;
Elisabeth Criscuolo Urbinati
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| Advisor: | Renata Guimarães Moreira |
| Abstract | |
The climatic changes due to anthropogenic actions tend to alter several environment factors, among them, temperature. A recent prognostic about the temperature increase mentions that in an optimistic level the earth temperature will raise 1.8 degress C until 2100. This change may cause many modifications on the physiological processes, justifying the studies to assess the effects of the temperature in animals physiology. The Paraíba do Sul Basin, for a long time, has been suffering with the anthropogenic actions, culminating in the extinction risk of the endemic species. This is the case of surubim do Paraíba, Steindachneridion parahybae. With the possible rise in the environmental temperature, the risk of species extinction can be even more eminent, therefore, the aim of this study is to evaluate if the water temperature variation, within the values predicted in the optimistic level, i.e., 1.8 degrees C influences in the growth and in the physiological processes of surubim do Paraíba juveniles. It was established an experimental design in which two ponds were covered with a plastic greenhouse (Greenhouse group) and another two ponds were kept without the plastic coverage (No Greenhouse group), with an initial population of 100 animals in each tank. In September/2009 (beginning), November/2009, January/2010 and March/2010 the biometrical parameters were registered in all animals in order to obtain the morphometric and weight data, and in addition, to calculate the following parameters: hepatossomatic index (HSI), condition factor (K), specific growth rate (SGR), daily specific growth rate (DSGR), coefficient of variation (CV), feed efficiency (FE) and survival (S). The muscle and liver samples, and also the plasma were collected from 5 fish from each experimental tank in each sampling, and the tissue concentration of carbohydrates, proteins and lipids, fatty acids percentage profile in the neutral (triglycerides) and polar (phospholipids) lipids fractions were measured. The cortisol and glucose concentration were also quantified in the plasma. The Greenhouse group animals, where the water temperature was kept around 2 degrees C higher than the No Greenhouse group, showed an increased weight gain in relation to the animals of the No Greenhouse group, with the same result also found for SGR, DSGR and FE. Even with an increased growth, the proteins and lipids concentration both, in muscle and in the liver were unchanged between both groups, and the same occurred with the liver glycogen. However, the muscle glycogen was higher in the last sampling in the animals vi that were kept in the lower water temperature. In the polar fraction, both groups presented an increase in the percentage of saturate fatty acids and a decrease in the polyunsaturated percentage, probably related with a homeoviscous adaptation, due to the gradual increase in temperature. In the neutral fraction, the animals kept in higher water temperature utilized a higher percentage of polyunsaturated fatty acids as energy source, that, in long-term may be prejudicial for reproduction. These results suggest that the increasing temperature could result in a higher enzymatic activity and/or a higher efficiency of these enzymes and consequently, increased growth and feed efficiency in Greenhouse group animals. However, the results do not allow establishing whether the increasing temperature would be beneficial at all stages of development in the surubim do Paraíba. (AU) | |