The murex, one of Sicily's best-loved shell-fish, is facing extinction because of widespread sex changes caused by compounds in paints protecting the hulls of boats, environmentalists warn.
The alarm was launched by Italy's premier marine research institute, the Institute for Environmental Protection and Research (ISPRA, formerly known as ICRAM), after it carried out tests in Sicilian coastal waters and compared them with uncontaminated waters farther out.
The results show that the females of three species of murex have almost completely changed sex around the coasts while the gender pattern remains intact on the unsullied seabeds.
ISPRA experts have identified the culprit as TBT, a so-called organotin which causes female murexes to become males.
TBT is one of the prime ingredients of anti-fouling paints, used to coat the bottom of ships to prevent sea life such as algae and molluscs from attaching themselves to hulls - thereby slowing ships and increasing fuel consumption.
In 2001 the International Maritime Organisation banned TBT and other harmful organotins but they have still not been phased out and the sex lives of the molluscs are still at risk.
''The situation will only be improved by getting rid of the paints and dredging and cleaning the bottom of harbours,'' said ISPRA's Franco Andaloro.
Andaloro said studies had shown the murexes were also being turned into males by the seabed sludge they graze on.
The gender-bending TBT seeps into the water and builds up on harbour beds, Andoloro said.
The exact mechanism behind the transexual molluscs is still being studied.
A handful of Italian researchers are at the cutting edge.
One of them, Antonio Terlizzi of Lecce University, explained that TBT boosts the production of testosterone in the female murexes, making them sterile and eventually turning them into males.
''It's a little bit like all those women shot-putters with moustaches you used to see a few years ago,'' he said.
According to the Worldwide Fund for Nature, the problem could become wider, with populations of murexes under threat of sex changes all around the Italian coast.
The murex, a type of sea snail, is a spiny shelled marine gastropod of the genus 'Murex', formerly used as a source of the dye Tyrian purple.
It is one of the most characteristic sights on shell-fish stalls in Palermo, the Sicilian capital.
So far the possible health effects on people who eat the transgender snails have not been investigated.
In the biodiversity study, conducted with the help of the University of Malta, ISPRA also found that the breakdown of temperature 'barriers' due to global warming has led to an increasing influx of non-native fish from both the Atlantic and the Red Sea.
There are now ten Atlantic species and 12 Red Sea ones in the Sicilian Channel.
In the whole of the Mediterranean, ISPRA said, 110 exotic fish can now be found, equal to 15% of the fish population.
Native species are also threatened by sewage containing pesticides and DDT which was banned several years ago but is still found coming out of sewage pipes in some areas, especially Malta.
