ENVIRONMENTALLY MEDIATED SEX CHANGE IN THE ENDANGERED LIMPET PATELLA FERRUGINEA (GASTROPODA: PATELLIDAE)

The endangered patellid limpet Patella ferruginea is a protandrous species endemic to the Mediterranean. Previous studies have shown that sex change occurs in the species when individuals reach a range of 4-6 cm shell length. In our study individuals were sexed and population structure, mean density, mean shell length and sex ratio determined for seven populations in Ceuta (North Africa, Strait of Gibraltar). Our results indicate that sex change appears to occur at smaller sizes when large individuals (presumably females) are rare. All of the populations had a male-biased sex ratio. The greatest differences between the number of males and females were recorded in those populations that had the largest females and the greatest densities of large individuals, suggesting that a shortage of this fraction of the population would affect the proportion of sex-changing individuals. The fact that P. ferruginea may exhibit environmentally mediated sex change could influence population management decisions.