Quantitative characterization of response behaviors and individual variation in Chironomus riparius after treatments of diazinon

摘要

Response behaviors of indicator species in aquatic conditions were characterized by multivariate statistical methods after an insecticide, diazinon, was treated at low concentration (1 ppb). Seventeen larvae of Chironomus riparius were individually monitored using a CCD camera before (8 hours) and after (8 hours) the treatments. The variables presenting inactivity such as proportion of stops (p.stop) and mean weighting time for movement (m.wt) were increased, while mean speed (m.speed) and mean acceleration (m.acc) decreased after the treatments. A principal component analysis (PCA) based on the normed differences was conducted to elucidate toxic effects on the variables in an integrative manner after the treatments of the insecticide. The variables related to activity were accordingly grouped on the principal axes: the group of variables presenting inactivity (e.g., p.stop, m.wt) on the positive side and the group of variables associated with activity (e.g., m.speed, m.acc) on the negative side. The normed PCA could also illustrate degree of individual variation in behavioral changes in response to the treatments.