Affordable chironomid housing: proposed modifications of standard OECD substrate for testing of chemicals on aquatic midges

This study was conducted in order to formulate a modification of standard substrate for laboratory bioassays (OECD protocol number 218: ”Sediment water chironomid toxicity test using spiked sediment“), with as few constituents as possible, yet enabling the highest larval survival of model organism: Chironomus tentans (Chironomidae, Diptera). Laboratory experiment consisted of two bioassays: first with substrate mixture of two and more ingredients tested: standard OECD substrate, standard substrate with medical clay, peat + clay, peat + sand, clay + sand; second with every ingredient individually tested: coarse sand, fine sand, peat, clay and no substrate. Highest larval survival was observed in sand + peat (~85%) and coarse sand substrate (~82%), whilst clay + peat (~65%) and peat substrate (~46%) caused the highest larval mortality. No larvae survived in treatment without any substrata, indicating the absolute necessity and importance of substrate presence for larval survival.