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 13 tests performed by seven laboratories in Germany, the United Kingdom, Switzerland, and Canada. Test results had an acceptable range of heterogeneity. The calculated median effective concentration for 50% (EC50) egg-to-adult mortality was 20.9 +/- 19.1 microg ivermectin/kg dung fresh weight (FW) (mean +/- standard deviation; range, 6.33-67.5 microg/kg). Mortality was not observed below a calculated no-observable-effect concentration (NOEC) of 8.1 +/- 7.7 microg/kg FW. However, prolonged development time (and, in a subset of tests, reduced body size) was observed above a calculated NOEC of 0.8 +/- 0.8 microg/kg FW. An oviposition site choice test revealed that yellow dung fly females do not discriminate among dung of different ivermectin concentrations. Thus, the yellow dung fly is suitably sensitive, and the methods are sufficiently repeatable, to support use of this standardized bioassay by the international community in the registration of new veterinary pharmaceuticals.
1. Elevational gradients influence the distribution and abundance of species drastically and can lead to variation in community composition. Although coprophagous flies are of ecological and economic importance, their biodiversity and distribution are largely neglected. We studied the impact of steep elevational gradients and geography on the distribution of sepsid flies in the Swiss Alps.2. Sepsidae are a family of acalyptrate flies strongly associated with decaying organic matter and vertebrate dung, and characterised by a high extent of sympatry in their breeding substrates. Historical, haphazardly sampled specimens from 116 locations covering an elevational range from 200 to 2000 m were available in ethanol collections of various Swiss museums.3. Nineteen species encompassing all native genera (Meroplius, Nemopoda, Saltella, Sepsis and Themira) were recorded. Local species richness increased linearly with elevation, while area-corrected regional species richness of elevational belts increased asymptotically. Species occurring at higher altitudes had lower wing loadings and greater elevational ranges than lowland species, supporting Rapoport's elevational rule.4. Despite compositional similarities, the sepsid communities of the northern lowlands differed significantly from the alpine sepsid fauna. The southern lowlands were particularly differentiated in community composition due to a number of presumably thermophilic species that predominantly occur south of the Alps.5. Relative abundances of several species were thus strongly affected by elevation and climatic variables. We illustrate the impact of elevational gradients and geography on a community of closely related, often sympatric species, and discuss potential mechanisms of niche partitioning via temporal succession, thermal adaptation and differential resource use.
To register veterinary medicinal products (VMPs) as parasiticides on pastured animals, legislation in the European Union requires an environmental risk assessment to test the potential nontarget effects of fecal residues on dung-dwelling organisms. Products with adverse effects in single-species laboratory tests require further, higher-tier testing to assess the extent of these effects on entire communities of dung-dwelling organisms under more realistic field or semifield conditions. Currently, there are no documents specifically written to assist researchers in conducting higher-tier tests or to assist regulators in interpreting the results of such tests in an appropriate context. Here we provide such a document, written by members of the SETAC Advisory Group DOTTS (Dung Organism Toxicity Testing Standardization) with research experience on dung fauna in central and southern Europe, Canada, Australia, and South Africa. This document briefly reviews the organisms that make up the dung community and their role in dung degradation, identifies key considerations in the design and interpretation of experimental studies, and makes recommendations on how to proceed.
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