High performance liquid chromatography purification of mate recognition pheromone from ethylenediaminetetraacetic acid extract. x-axis refers to minutes that the high performance liquid chromatography (HPLC) fractions were retained on the column. Live category is live female rotifers that served as a positive control. Ethylenediaminetetraacetic acid (EDTA) category is rotifer females that had their surface glycoproteins removed by EDTA extraction (negative control). Percent circling on the y-axis is from the mating bioassay. The inset is the HPLC chromatogram with retention time in minutes on the x-axis and absorbance units at 280 nm on the y-axis. Asterisk indicates fraction with significant mating activity.