Two-way sex change in the endangered limpet Patella ferruginea (Mollusca, Gastropoda)

Direct observations of sex change were made on the endangered limpet Patella ferruginea in Chafarinas Islands (Alboran Sea) between 2006 and 2011. Individuals of the species were sexed and tagged during spawning season for subsequent monitoring to determine possible sex changes. Mortality was minimized by following a carefully designed sexing protocol. Out of 49 tagged specimens (41-88mm in size) that could be sexed in successive years (28 males and 21 females), 16 males changed into females between consecutive years (50.0% of males smaller than 70mm and 100% of males larger than this size), while two females changed sex to males between consecutive spawning seasons (both were smaller than 70mm). Overall, 36.7% of the limpets monitored changed sex between consecutive years: 57.1% of males became females and 9.5% of females changed to males These observations confirms the occurrence of two-way sex change, or reverse sequential hermaphroditism, in P. ferruginea. Our findings unveil this sexual strategy in this endangered limpet and provide new direction for studies designed to address the mechanisms and factors that determine sex change and its effects on population dynamics.