Estrogen effects linger in male fish.

Estrogen-mimicking pollutants can trigger gender-bending effects in wildlife. For instance, male fish exposed to such hormonally active pollutants will make vitellogenin, an eggyolk protein that's normally fashioned only by females (SN: 1/8/94, p. 24). A new study finds that once initially spurred to make vitellogenin, males don't need a steady bath of estrogen to maintain high levels of the motherly protein.

Grace H. Panter of AstraZeneca in Brixham, England, and her colleagues exposed male fathead minnows (Pimephales promelas) to up to 120 parts per trillion (ppt) estrogen in water for 3 or 6 weeks. Some fish lived in tanks continuously laced with the hormone. Other fish spent half their time in clean water, either every other day or 3 days straight of every 6.

Minnows intermittently exposed to 120 ppt estrogen produced almost as much vitellogenin as those continuously bathed in that amount, Panter's team found. These fish also had roughly seven times as much vitellogenin as did males that had been continuously exposed to 60 ppt--the average amount the intermittent group experienced.

More unexpectedly, even long interludes in clean water didn't substantially erase the hormone's impact. Male minnows spending 3 weeks in 120 ppt estrogen, followed by an equal time in clean water, ended up with vitellogenin concentrations "not significantly different" from those of fish that had spent the entire 6 weeks in the estrogen-tainted water, note Panter and her coworkers.

They report their findings in the July 1 ENVIRONMENTAL SCIENCE & TECHNOLOGY.

No one yet knows what the long-term consequences are for male fish that have made vitellogenin. However, members of Panter's team previously showed that exposure to estrogenic pollution during a male fish's development can stunt the growth of its testes (SN: 2/26/94, p. 142).