Endemic shrimp Macrobrachium pantanalense as a test species to assess potential contamination by pesticides in Pantanal (Brazil).

Pantanal is a biome characterized by an extraordinary diversity and abundance of wildlife and houses several endemic species such as the freshwater shrimp Macrobrachium pantanalense. However, the increase in agriculture and husbandry activities in the region has contributed with residues of pesticides reaching aquatic systems. The main objective of this study is to assess the sensitivity of the endemic shrimp M. pantanalense compared with other freshwater species: the shrimp M. amazonicum, the crustacean Daphnia similis and the fish Danio rerio. The sensitivity of these organisms was assessed through acute exposure to copper and cypermethrin (through the formulation Barrage®, widely used in Pantanal). For copper the species sensitivity decreased in the following order: D. similis (48 h-EC50 0.051 mg/L) > M. pantanalense > D. rerio > M. amazonicum (48 h-LC50 26.34 mg/L). Copper caused reduced length of shrimps and zebrafish and reduced heartbeat of zebrafish embryos. For cypermethrin the species sensitivity decreased in the following order: M. pantanalense (96 h-LC50 0.05 μg/L) > M. amazonicum > D. similis > D. rerio (144 h-LC50 1680 μg/L). Major effects of cypermethrin included reduced length of shrimps and zebrafish, as well as early hatching and increased incidence of developmental deformities in zebrafish embryos. This study highlights the importance of using endemic species for risk evaluations in sensitive biomes such as Pantanal. Moreover, it emphasizes the importance of testing pesticides toxicity as commercial formulations. Furthermore, we suggest that the endemic shrimp species M. pantanalense can be successfully used as a test species in ecotoxicology.