Effects of organic pesticides on enchytraeids (Oligochaeta) in agroecosystems: laboratory and higher-tier tests

Enchytraeidae (Oligochaeta, Annelida) are often considered to be typical forestliving organisms, but they are regularly found in agroecosystems of the temperate regions of the world. Although less known than their larger relatives, the earthworms, these saprophagous organisms play similar roles in agricultural soils (but at a smaller scale), e.g., influencing soil structure and organic matter dynamics via microbial communities, and having a central place in soil food webs. Their diversity is rarely studied or often underestimated due to difficulties in distinguishing the species. New genetic techniques reveal that even in anthropogenically highly influenced soils, more than 10 species per site can be found. Because of their close contact with the soil pore water, a high ingestion rate and a thin cuticle, they often react very sensitively to a broad range of pesticides. Firstly we provide a short overview of the diversity and abundance of enchytraeid communities in agroecosystems. Afterwards, we explore the available data on enchytraeid sensitivity toward pesticides at different levels of biological organization, focusing on pesticides used in (mainly) European agroecosystems. Starting with non-standardized studies on the effects of pesticides on the sub-individual level, we compile the results of standard laboratory tests performed following OECD and ISO guidelines as well as those of higher-tier studies (i.e., semi-field and field tests). The number of comparable test data is still limited, because tests with enchytraeids are not a regulatory requirement in the European Union. While focusing on the effects of pesticides, attention is also given to their interactions with environmental stressors (e.g., climate change). In conclusion, we recommend to increase the use of enchytraeids in pesticide risk assessment because of their diversity and functional importance as well as their increasingly simplified use in (mostly standardized) tests at all levels of biological organization

Lethal and sublethal toxic effects of a test chemical (ivermectin) on the Yellow Dung Fly Scathophaga stercoraria based on a standardized international ring test

A standardized bioassay using the yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), was developed to test the lethal and sublethal toxicity of parasiticide residues in livestock dung. The repeatability of the bioassay was assessed for the parasiticide, ivermectin, in thirteen tests performed in seven laboratories in Germany, the UK, Switzerland and Canada. Test results had an acceptable range of heterogeneity. The calculated concentration at which 50% egg-adult mortality was observed (Effect Concentration (EC50) averaged 20.8 +/- 19.1 (Standard Deviation (SD)) microg ivermectin / kg fresh dung (range: 6.33 - 67.5). Mortality was not observed below an average calculated No Observable Effect Concentration (NOEC) of 8.1 +/- 7.7 microg / kg. However, prolonged developmental time, and in a subset of tests reduced body size, was observed above an average calculated NOEC of 0.8 +/- 0.8 microg / kg. An oviposition choice test revealed further that yellow dung fly females do not discriminate among dung of different ivermectin concentrations. We conclude that the yellow dung fly is suitably sensitive, and the methods sufficiently repeatable, to support use of this standardized bioassay by the international community in the registration of new veterinary pharmaceuticals