The potential effects of ionic liquids (ILs) on the aquatic ecosystem are assessed using zebrafish embryos as a model. Zebrafish is a small, freshwater fish that offers many advantages as a model organism in toxicological and pharmaceutical investigations. This hardy, prolific fish is relatively small (adults approximately 30 mm in length), easy to maintain, and has a 4-month generation time. Furthermore, the eggs and embryos are transparent, facilitating greatly the detection of developmental abnormalities in both morphology and behavior. The present study examines the dose-dependent effects of ILs on the growth and survival of zebrafish eggs and embryos. Viability and discernible abnormalities are documented.

Preliminary studies on several ILs show that various compounds have a wide range of toxicity. Lethal concentrations (LC50) range between 1 to 100 mM, depending on the compound. At concentrations below the LC50, retarded embryonic growth, reduced motility and hatching rate, and inability to inflate swimbladder are commonly observed abnormalities. Many of the embryos that survive fail to hatch, suggesting a motor defect. Many of those that manage to hatch fail to inflate their swimbladder, and are therefore unable to swim and feed. At concentrations above the LC50, the high mortality rate appears to be attributable to a disruption of tissue integrity. The relationship between IL structure and toxicity, and the mechanisms underlying the graded toxic effects are unknown. (This study was supported by PSC-CUNY award # 69605-00-38.)