Penis of the Phallomedusa Solida (a Mangrove Snail From The Sydney Harbour)
Penis of the Phallomedusa solida (a mangrove snail from the Sydney Harbor).
John Brash/Maria Fernanda Cardoso

There’s nothing wrong with switching genders, but you want that process to be voluntary. And for female marine snails who found themselves with penises and vas deferens so big they blocked eggs from coming out, it definitely was not.

The sneak-attack peens were caused by the chemical tributyltin (TBT), which leached out of the paint on ship hulls and into the ocean. The chemical has been messing with marine life since the 1970s, and we’ve understood the extent and gravity of the problem since the ’80s, says the Australian Broadcasting Corporation – but it took until 2008 for a global ban on TBT to finally take effect.

But it’s only taken a few years, ABC says, for the snail populations to settle back in their correct secondary sex characteristics:

Wilson has noticed not only a reduction in the severity of the condition but also some of his study sites are for the first time showing no signs of imposex at all. He has even noticed snail populations occurring in regions where they weren’t found before.

We imagine most of the snails are pretty relieved. No disrespect to wangs, but there’s nothing worse than having one show up where it’s not wanted.