Endocrine-disrupting chemicals are exactly what they sound like — synthetic compounds that mess with hormone signaling. And they’re everywhere in modern waterways. Runoff from agriculture, industrial discharge, pharmaceutical waste — all of it carries compounds that weren’t part of these ecosystems fifty years ago. Two of the more interesting ones are testosterone and flutamide. Testosterone is an androgen. Flutamide is an anti-androgen, used clinically to block androgen receptors. Both are on the U.S. EPA’s list of environmental hormone substances, and both find their way into aquatic systems. The question is: what happens when tiny freshwater animals get exposed to them, alone or together? A recent study on the rotifer Brachionus calyciflorus took…