RAPID TOXICITY ASSESSMENT USING ESTERASE BIOMARKERS IN BRACHIONUS-CALYCIFLORUS (ROTIFERA)

We have developed biomarkers of sublethal toxicity in the freshwater rotifer Brachionus calyciflorus based on the reduction of enzyme activity. Esterase and phospholipase A2 activity was quantified in single rotifers using image analysis and a fluorescence detection system. Esterase activity was localized in the gut and phospholipase A2 activity in the corona of females. Quantitation of enzyme activity demonstrated that toxicant stress reduced activity in a dose-dependent manner. Concentration-response relationships are described for 10 compounds representing a variety of toxicant classes and NOECs are reported. Esterase and phospholipase A2 activities were generally less sensitive end points than reproduction NOECs, but usually were more sensitive than LC50s. Since in vivo enzyme activity can be assessed in 1 h, these biomarkers will be useful where rapid results are important. The cost of performing in vivo enzyme inhibition tests is substantially less than traditional whole animal tests because these require three times more person-hours to execute. Obtaining test animals by hatching cysts, their sensitivity to toxicants, and the rapid results make the rotifer esterase and phospholipase A2 tests good candidates for inclusion in a test battery for rapid toxicity assessment. (C) 1994 by John Wiley & Sons, Inc.