Effects of low temperatures and fasting on hematology and plasma composition of gilthead sea bream (Sparus aurata) |
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Authors: | M Sala-Rabanal J Sánchez A Ibarz J Fernández-Borràs J Blasco MA Gallardo |
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Institution: | (1) Departament de Fisiologia (Centre de Referència i Desenvolupament en Aqüicultura de la Generalitat de Catalunya, CRAC), Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, Barcelona, E-08028, Spain |
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Abstract: | Low temperatures, and the voluntary fasting that they induce, have been implicated in outbreaks of winter syndrome in farmed
gilthead sea bream (Sparus aurata). Two experiments were performed with the objective of studying if a decrease in water temperature is sufficient to induce
this disease or some of its associated signs. In the first experiment, water temperature was either acutely or gradually reduced
to 8 °C. In the second experiment, fish were exposed to either 8 °C or 12 °C, or fasted at 14 °C.
Although no mortalities due to winter syndrome were registered during any of the experiments, some of the signs described
in affected sea bream were observed in 8 °C-exposed fish. Among the most relevant were the paleness and friability of the
liver and the occurrence of fatty degeneration in the hepatocytes.
During the experiments, the general state of health of fish was monitored by measuring hematic parameters and the plasma concentration
of proteins, glucose and ions. Low temperatures (8 and 12 °C) and fasting at 14 °C resulted in significant decreases in the
levels of the different plasma protein fractions. This drop was more important in all the 8 °C-exposed fish, due mainly to
a higher descent of albumin, α1-globulins and fibrinogen. Moreover, 8 °C-exposed fish showed a fall in total white blood cells and a rise of plasma glycemia,
as well as a significant drop of plasma potassium and calcium levels and a transient increase of plasma magnesium concentration.
In 8 °C-exposed fish, the rate of water temperature descent did not modify the profiles of change of any of the studied parameters.
These results indicate that at 8 °C gilthead sea bream are unable to maintain the levels of plasma protein fractions and ions
present in control animals.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | fish hematology plasma protein plasma ions winter disease winter syndrome |
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