Students commonly test the effects of chemical agents on the heart rate of Daphnia magna, a small crustacean. We investigated whether club soda and isopropanol are suitable test agents. Treatment groups contained 6-12 animals. Club soda caused a dose-dependent decrease in heart rate, presumably because of the anesthetic effects of CO2. Ten percent, 30%, and 50% club soda reduced mean heart rates to 78%, 57%, and 47% of initial values. The effect was transient; heart rates recovered quickly to control values even though the club soda remained present. Isopropanol’s effect was dose-dependent and sustained. Three percent, 5%, and 10% isopropanol reduced mean heart rate to 45%, 35%, and 12% of initial values. Removal of the isopropanol failed to fully reverse its effects. Ten percent isopropanol proved fatal to one animal out of the eight tested at that concentration. Both club soda and isopropanol are suitable agents for students to test. If reversibility is to be investigated, club soda should not be used. Its effects wear off even when the club soda is still present. Isopropanol is best used at 3-10% as it causes marked heart rate suppression and partial reversibility.

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