SCIENTISTS at a Hampshire university have discovered some see creatures are fighting back against a forced sex change.

Researchers have found male crustaceans are able to ‘lock down’ their masculinity and avoid being completely feminised by contaminated seawater.

The scientists from the University of Portsmouth have shown the crustaceans retain male characteristics in water containing feminising pollutants like oestrogen.

And they believe the creatures have learned how to do this through evolutionary battles with parasites.

Dr Alex Ford, marine biologist at the university, said: “We’ve known for some time that fish change sex if they’re subjected to even small amounts of oestrogen in the water, but until now we didn’t know what was happening to crustaceans.

“What we found is that once a crustacean has decided to be male, it can lock down its maleness. It will still become feminised in many respects, but at its core, it will remain male. This has important implications for how we study the effects of potential feminising pollutants on these creatures.”

Study co-author Dr Stephen Short, also a marine biologist, added: “We don't know why crustaceans, but not vertebrates, have this ability to hold on to their maleness, but we know crustaceans have been engaged in long evolutionary battles with feminising parasites which turn males into females in order to transmit to the next generation via the eggs of their hosts.

“It could be that this history has given crustaceans strategies to cope with feminisation and this is now proving useful in the face of human pollution.”

The research was part of a four-year project that looked at the effects of parasites and pollution on crustaceans and was funded by the Natural Environment Research Council (NERC).