A staged approach using ants as test organism in ecotoxicology

Abstract

Although ants (Hymenoptera: Formicidae) are ecological key components, they are currently not included in ecotoxicity testing. Based on their social organization, ecology and exposure routes to pesticides, we propose a multilevel testing scheme for ants starting from isolated workers (level-1), workers and brood (level-2) and founding queens or entire colonies (level-3). To evaluate feasibility, we tested three ant species (Camponotus maculatus, Crematogaster sp., Lasius niger) using the neonicotinoid imidacloprid as a test substance. Ants were orally exposed through liquid food. At level-1, worker survival showed a clear concentration response and allowed to estimate LC50 with sufficiently narrow confidence intervals. In level-2, worker mortality and sublethal effects negatively affected larval survival and development, e.g. occurrence of naked pupae, with a lower NOEC for larvae (<0.05 mg/L feeding solution) than workers (1.7 mg/L). At level-3, the test substance significantly reduced the reproductive output of newly mated L. niger queens over 21 days after a single exposure to 0.5 mg/L. Our results confirm that ants can be easily handled and tested in the laboratory, making them a valuable extension for ecotoxicity testing. Given their ecological relevance, easy culture in laboratory settings and promising first results, we recommend further research using our new testing scheme, e.g. testing other stressors, species and endpoints. Establishing a robust test protocol for ants would provide coverage of a new and ecologically important group of non-target insects, which contributes to a broader protection of biodiversity and ecosystems. HighlightsO_LIAnts play key roles in many ecosystems but are not covered in ecotoxicity testing. C_LIO_LIWe propose a testing scheme for ants with 3 different levels of complexity. C_LIO_LIAnts can be cultured and tested cost- and space-efficient in the laboratory. C_LIO_LIThree ant species were tested using imidacloprid in parts of our testing scheme. C_LIO_LILethal and sublethal endpoints can be linked to individual and colony fitness. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/641392v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@11387feorg.highwire.dtl.DTLVardef@1456368org.highwire.dtl.DTLVardef@8171b5org.highwire.dtl.DTLVardef@504536_HPS_FORMAT_FIGEXP M_FIG C_FIG