Behavioural toxicity of endosulfan and a novel approach to the study of its ecotoxicity in aquatic microcrustaceans.

GUTIERREZ, FLORENCIA; GAGNETÉN, ANA MARÍA; PAGGI, JUAN CESAR

Berlín

Congreso; 6º SETAC World Congress - SETAC Europe 22nd Annual Meeting; 2012

SETAC

Despite the organochlorine insecticide endosulfan is currently banned in over 30 countries, it is still widely used in most Latin American countries.  Recently, values from 0.2 to 13.5 ìg L−1 have been found in neotropical wetlands, exceeding the maximum permitted concentration. Its continued use might respond to the hegemonic agroeconomic model, despite several works have demonstrated its negative consequences to humans and environment. In addition to it direct effects on non-target organisms it has also been reported indirect effects, such as alterations in predator prey interactions, in aquatic and terrestrial organisms. The importance of these lasts studies lies in providing relevant information on the actual ecological processes that take place after anthropogenic interventions.The purpose of this work was to demonstrate an indirect effect of the early impact of an endosulfan based-insecticide on the escape behaviour of four subtropical microcrustaceans: two copepods (Notodiaptomus conifer, Argyrodiaptomus falcifer) and two cladocerans (Pseudosida variabilis and Ceriodaphnia dubia). The experimental assays were carried out using a novel hydraulic devise designed to mimic three-speed predator capture behaviour. This allows to quantify the organisms? ability to perceive and react to the approach of possible predators. Two environmental relevant concentrations of endosulfan were used. They were prepared from a commercial formulation containing 35% of the active ingredient (Zebra Ciagro®).  Endosulfan concentrations in water was quantified by GC-ECD showing recoveries >95% of the nominal value. The exposure time was 15 (±5) minutes. Analyses of data were carried out using the Deviance as variability means (ANODEV). The magnitude and the kind of responses were different depending on species, capture speed and toxic concentration, however the following pattern was recognized: endosulfan made cladocerans more capturables (p<0.05) but copepods enhanced their escape ability at lower concentrations (p<0.05), which might be the result of an early toxicant stimulation. The immediate apparent advantage of this last effect will be discussed in the context of ecophysiological theory, since an increase in one physiological or behavioural process may be at the expense of other biological attributes. Considering the comparatively high sensitivity of the escape, the proposed method is suggested as an effective complement (and ecologically relevant) in ecotoxicology.