A 2-D LIFE-CYCLE TEST WITH THE ROTIFER BRACHIONUS-CALYCIFLORUS

A 2-d life cycle test using the freshwater rotifer Brachionus calyciflorus is described for assessing chronic toxicity. The end point for this test is r, the intrinsic rate of increase, which has high ecological relevancy because it measures the growth potential of a population. The test is multi-generational because two-thirds of the reproduction is attributable to parental females and one-third to F1 females. Despite its brevity, the rotifer test includes 30% more of test animal life span than a 7-d Ceriodaphnia test. Test protocol is simple to execute, with test animals obtained by hatching cysts and the algal food obtained from petri dish cultures. A small volume of test solution (120 ml) is required for a test, making the rotifer test potentially useful for conducting chronic toxicity identification evaluations (TIEs), in which test solution availability and exposure duration can be important. Analysis of the person hours required to execute a test shows that the rotifer test requires 70% less effort than 7-d Ceriodaphnia or fathead minnow tests. The simplicity of the rotifer test contributes to its excellent reproducibility; C.Vs are commonly < 10%. The comparative sensitivity of the rotifer life cycle test is not yet fully characterized, but for the five compounds compared in both Ceriodaphnia and Brachionus, the chronic values of four were within a factor of six of one another. At the chronic value concentrations of 11 toxicants tested in rotifers, there was on average a 33% reduction in r as compared to controls.