Common chemical makes species interbreed

Posted by Emma Woollacott

A chemical found in many common plastics could have you copulating with other species and producing strange hybrid offspring... if you're a fish, at any rate.

A study has found that the hormone-mimicking chemical known as Bisphenol A (BPA) used to harden many plastics, disrupts mating choices and leads to inter-species breeding.

BPA's used in the manufacture of polycarbonate plastic - used widely in plastic bottles and the like. It's been known for some while to have hormone-like properties, and has been banned for use in baby bottles in Canada and the EU, along with some - but only some - US states.

"Chemicals from household products and pharmaceuticals frequently end up in rivers, and BPA is known to be present in aquatic ecosystems across the United States," says Jessica Ward of the University of Minnesota.

"Until now, studies have primarily focused on the impact to individual fish, but our study demonstrates the impact of BPA on a population level."

The team collected individuals of Blacktail Shiner (Cyprinella venusta) and Red Shiner (Cyprinella lutrensis), which are found in rivers across the United States.

The species were kept separated for 14 days in tanks, some of which contained BPA, and introduced to one another on the 15th. And, they found, the BPA-affected fish were more likely to court and mate with members of the other species.

"Our research shows how the presence of these manmade chemicals leads to a greater likelihood of hybridization between species," says Ward.

"This can have severe ecological and evolutionary consequences, including the potential for the decline of our native species."

Earlier this year, the US Food and Drug Administration rejected calls to ban BPA from plastic food containers, saying there wasn't enough evidence that it was harmful.

It's now considering banning it in baby bottles, at least; perhaps the prospect of little human chimeras lurching about the place will help it make up its mind.