SURVIVAL OF NUCELLA-LAPILLUS IN A TRIBUTYLTIN POLLUTED AREA IN WEST BRITTANY - A FURTHER EXAMPLE OF A MALE GENITAL DEFECT (DUMPTON SYNDROME) FAVORING SURVIVAL

A male genital defect was reported in a Nucella lapillus (L.) populati on at Dumpton Gap (England). This defect was termed ''Dumpton syndrome '' (DS) and appears to be a genetic feature. Its main characteristic i s the absence of penis (aphally) in males and in females. In 1992, suc h a phenomenon was discovered in populations in the vicinity of Brest (Brittany, France). DS-affected females exhibit fewer tributyltin-indu ced imposer characteristics than expected in normal individuals. The p ercentage of female sterilization is thus lower, favouring population survival. In consequence, the DS is considered to be a ''pollution-res istance'' feature. Comparison with the Dumpton population revealed sim ilarities and differences in the DS characteristics. It is thus hypoth esized that the DS observed at the two locations is due to two differe nt biological mechanisms. Indeed, aphallic males with a split prostate were observed but no underdevelopment of their vas deferens and testi s was noted in the present study. In this gonochoristic gastropod spec ies, the most DS-affected males in Brest possess an ovotestis and it i s thus hypothesized that feminity is remnant in N. lapillus. Incidence of abnormality is ten times higher in females than in males. This sug gested that a sex-difference operates in the Brest phenomenon.