Abstract: 8711 A. Introduction

Daphnia sp. are small freshwater crustaceans (Figure 8711:1). They have been used for many years to assess the acute and chronic effects of single chemicals and complex environmental mixtures, such as wastewater effluents. Several methods have been published.^1–5

Daphnia are used extensively in toxicity testing as test organisms because of their sensitivity to toxic substances, ease of identification and handling, and ubiquitous distribution. Daphnia are fecund and reproduce parthenogenically, which allows for the establishment of clones with little genetic variability and with reproducible testing results.