Chronic Toxicity of Pesticides and Metals to the Tropical Species Allonais inaequalis (Oligochaeta: Naididae).

Lower-tier toxicity assessments of chemicals, such as metals and pesticides, are typically focused on a few standard test species representing different taxonomic levels. Invertebrate taxa most frequently used are the crustacean and insect larvae. In recent years, some species of Oligochaeta have received increasing attention as test organisms, although the number of taxa evaluated so far is still limited. In previous studies, we successfully used the indigenous tropical oligochaete Allonais inaequalis to assess the acute toxicity of metals (cadmium, copper, mercury, and manganese) and pesticides (diuron and carbofuran). The aim of the present study was therefore to assess the sensitivity of this species to chronic (12d) exposure to these compounds. The order of chronic toxicity was the same as that denoted in the acute tests: copper (mortality 12d-EC10 2.22 µg Cu2+/L) > mercury (22.29 µg Hg2+/L) > cadmium (138.59 µg Cd2+/L) > manganese (5650 µg Mn2+/L) and carbofuran (46.32 µg/L) > diuron (6751.42 µg/L). Chronic toxicity did not increase significantly compared to the acute toxicity tests. Growth, measured as body length, was hindered after exposure to the metal and pesticides due to an energy reallocation needed to cope with the chemical stress.