Respostas fisiológicas ao estresse em Prochilodus scrofa durante a exposição ao cobre e subseqüente recuperação em água sem cobre.
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Date
2004-04-30Author
Pinheiro, Guilherme Henrique Dyonísio
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Copper is an essential trace-element for all live organisms however, when its
concentration is high in the aquatic environment, copper is potentially toxic. Most
physiological changes caused by copper in fish has been analyzed after acute exposure
(96h). The aim of this study was investigate the physiological responses of Prochilodus
scrofa to stress, during acute copper exposition (24, 48, 72 and 96 hours) and recovery
period after animal transference to clean water, and the time necessary to recovery after
animals transference to clean water. The changes associated to fish transference to
experimental systems were also evaluated. Juveniles Prochilodus scrofa were
acclimated during 30 days and then fish were sampled to take blood for pH, hematocrit,
plasma cortisol glucose and ions (Na+, Cl- e K+) analyses and specific Na+/K+-ATPase
activity of gills. The remaining fish were divided in two groups: control (C) and
exposed to copper (CU) and transferred to glass aquariums where was kept for 4 days.
CU groups were exposed to copper (96h-CL50 = 29 µgCu L-1). Sampling was done 1, 2,
3 and 4 days of copper exposure. Surviving fish were then transferred to aquariums with
flowing water without copper and sampling was done 1, 2, 7, 15 and 30 days of
recovery. Blood sampling was taken for the same analyses above cited. Plasma cortisol
concentration increased 300 a 400% in control and copper exposed groups related to
acclimated fish, plasma glucose increased 800% only in the copper exposed groups
during the exposure period and returned to normal levels in the 2nd day of recovery. In
general, the changes in plasma ion (Na+, Cl- e K+) concentrations and pH were not
significant in relation to those of acclimated fish however, significant changes were
found between the values of control and copper exposed groups during copper exposure
and recovery period. The activity of Na+/K+-ATPase of gills was lower in the CU group
during the copper exposure period and on the 1st day of recovery. The hematocrit
increased during metal exposure but on the 1st day of recovery reached the normal
values. Although changes were found on the analyzed parameters, on the 7th days after
the transference to clean water all parameters evidenced a tendency to recovery the
physiological changes reaching the values of acclimated fish. The present study showed
that the stress responses to copper exposure is complex and P. scrofa presents high
susceptibility to handling evidencing the importance of comparative analyses involving
acclimated and/or unstressed fish together with the controls and exposed fish to a given
stressor.