Male crustaceans can ‘lock down’ their maleness to avoid being completely feminised by seawater contaminated by feminising pollutants, according to scientists.

Research by scientists at the University of Portsmouth has shown that crustaceans turned partially into females retain a core of masculinity, and they may have learned how to do it after evolutionary battles with parasites.

Alex Ford 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.

This is now proving useful in the face of human pollution

“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.”

Fish and some other aquatic creatures are increasingly changing sex because the rivers and oceans are receiving a steady stream of feminising pollutants in sewage and industrial effluent.

Ford and his co-author Stephen Short are marine biologists at the Institute of Marine Sciences at Portsmouth and have been studying the effect of different chemicals on a range of organisms for several years.

Short said: “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.”