title: Growth evaluation method by live imaging of  Daphnia magna and its application to the  estimation of an insect growth regulator.
abstract: The zooplankton Daphnia magna has been widely used as a test organism to assess the toxicity of chemical substances because of its important position in aquatic ecology and its ease of handling. Among the various endpoints for toxicity evaluation, growth rate is one of the most critical and many studies have been conducted. However, measurement f growth rate was time-consuming and not an ideal endpoint in terms of screening. In this study, we demonstrated a live imaging method to monitor the growth of daphnids by area measurement. In this method, daphnid images were directly obtained from a swimming chamber and these images were processed for the evaluation of growth. The reliability of this method was confirmed by comparison with the conventional dry weight method of the same animals. The body area of daphnids using this method showed a strong correlation with the dry weight method, with R(2) = 0.930. In addition, we quantified the effect of a toxicant, fenoxycarb, on the growth of the animal. Fenoxycarb concentrations of 0, 0.027,0.27 and 2.7 μg l(–1) were tested and their effects on growth were estimated by the live imaging method. In the toxicity test,the area of daphnids decreased significantly with increasing fenoxycarb concentration. These results indicate that the present live imaging method is a reliable approach for daphnid toxicity testing. This method is promising for high through put Daphnia toxicity tests and real-time individual observations.
authors.forename: Akiko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kato
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Matsuura
authors.forename: Hajime
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects* / Q000254:growth & development*; D004305:Dose-Response Relationship, Drug; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted; D061848:Optical Imaging / Q000379:methods*; D048448:Phenylcarbamates / Q000633:toxicity*; D018675:Toxicity Tests / Q000295:instrumentation / Q000379:methods*
chemical_list: D048448:Phenylcarbamates; C052034:fenoxycarb