Acute morphological and physiological effects of lead in the neotropical fish Prochilodus lineatus

O presente estudo investigou os efeitos do chumbo na morfologia branquial, nos hematócritos e nas concentrações plasmáticas de sódio, glicose, lipídeos, proteínas e colesterol de Prochilodus lineatus exposto a duas concentrações subletais de chumbo durante 96 h. Inicialmente, testes agudos (96 h) e estáticos determinaram a CL50 (96 h) de chumbo para P. lineatus em 95 mg Pb.L-1. As concentrações de chumbo utilizadas nos testes subletais foram 24 e 71 mg Pb.L-1, que correspondem a 25% e 75%, respectivamente, da CL50 (96 h). As brânquias de P. lineatus expostos a ambas as concentrações de chumbo apresentaram maior incidência de lesões histopatológicas, como elevação epitelial, hiperplasia e aneurisma lamelar. P. lineatus não apresentou alterações significativas no hematócrito durante a exposição a ambas as concentrações de chumbo. Peixes expostos a 71 mg Pb.L-1 apresentaram decréscimo significativo do Na+ plasmático após 48 h, o que pode estar se refletindo na redução das taxas de influxo desse íon. P. lineatus expostos a ambas as concentrações de chumbo apresentaram resposta clássica ao estresse, como verificado pela hiperglicemia associada ao decréscimo dos lipídeos e proteínas plasmáticas. A magnitude da resposta ao estresse foi dose-dependente. A resposta apresentada na concentração mais baixa representa um processo adaptativo, enquanto na maior concentração caracteriza a exaustão.

Effect of benzene on the swimming activity of Mysidopsis juniae (Crustacea, Mysidacea)

The effects of benzene on the swimming activity of the crustacean Mysidopsis juniae were investigated. The swimming activity of M. juniae was observed after 1.3 and 6 h of exposure to 5, 10 15 and 20 ppm benzene in sea water (35 ñ 1 grade/00 S, 25 ñ 1 grade C). The mysids were observed with a pair of coupled to a camara lucida, and the swimming activity was measured in a Petri dish, corresponding to the distance (cm) covered by the animals in 1 min (N=150 animals). The swimming activity of mysids exposed to 20 ppm benzene decreased significantly after all three periods of exposure to values which were 80-90% smaller than the control value. On the other hand, after 6 h exposure to 5 ppm benzene, the swimming activity of the mysids was significantly higher, increasing by 87% in relation to the control (29.8 ñ 8.9 cm?min). Furthermore, a slight nonsignificant increase in swimming activity was also observed in mysids submitted to 5, 10, 15 and even 20 ppm benzene, as the period of exposure to the pollutant increased from 1 to 6 h. These results indicate that short-term exposure to sublethal benzene concentrations can affect the swimming activity of mysids. in these situations, mysid populations can be seriously damaged since alterations in swimming activity could lead to a reduction in food intake and to a marked increase in their susceptibility to predation by other organisms