Acute and sublethal effects of a non-ionic surfactant, Genapol OXD-080, on mosquitofish Gambusia holbrooki (Girard).
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1999
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Resumo
Application of the biodegradable non-ionic surfactant Genapol OXD-080, a fatty alcohol
polyglycol ester, in rice paddies has been considered as a method to mitigate damage caused by the
Louisiana red swamp crayfish, Procambarus clarkii, to rice crops. The damages are a consequence of
crayfish digging activities. The acute and sublethal effects of Genapol on a non-target key species were
examined to assess the potential risk of contaminating the irrigation channels following its application in
the rice paddies. Mosquitofish, Gambusia holbrooki, due to its abundance in irrigation channels, and
because it is a predator with an intermediate position in the food chain, was selected as the key
non-target species. The LC50 value for Genapol to mosquitofish was 2.9 mg ly1 , a value 17.2 times lower
than the Genapol concentration needed to decrease crayfish digging activity 50 mg ly1 .. For sublethal
tests, three biological parameters were considered in laboratory experiments with mosquitofish: respira-
tory metabolism, food energetic. consumption, and clutch survival. A significant decrease in the resting
metabolism of mosquitofish was observed, even when Genapol exposure concentrations were very low
e.g., 0.75 mg ly1 .. Thus, oxygen consumption rates of mosquitofish are strongly affected by to the
presence of this surfactant in water. In contrast, mosquitofish food consumption and clutch survival
seemed not to be affected by sub-lethal concentrations of Genapol. Yet, sub-lethal effect concentrations
for mosquitofish are so much lower than the concentration necessary to decrease significantly crayfish
activity, we conclude that there is a reasonable potential risk of damaging local mosquitofish populations
if contamination of the irrigation channels with Genapol occurs.
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Mosquitofish , Gambusia holbrooki , Surfactant , LC50 , Respiratory metabolism , Food consumption , Clutch survival
Citação
Cabral J. A. et al., 1999