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

RESUMO

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