Abstract

The age and growth of the warm-water species P. depressa were determined from central and poleward populations in Britain. The two poleward edges of P. depressa have different abundance patterns, which suggest differences at individual performance levels between both marginal populations. By reading and measuring annual lines from acetate-peels preparations, individuals at both poleward borders of P. depressa exhibited different age and growth patterns. Individuals collected from the range-edge at North-Wales had a significantly higher number of annual lines, when compared with individuals from the range-edge at South-east England and central populations at South-west England. Rapid growth was identified in shells collected from the range-edge at South-east England, where most individuals reached over 30-mm in length by the fourth or fifth annual increment. In contrast, shells collected from the poleward-edge at North-Wales showed slower growth and most shells only reached over 30-mm between the seventh and tenth annual line. Growth coefficient (K-values) was affected by density of limpet at each region; individuals with higher K-values were found in lower densities of limpet species across central and marginal regions of P. depressa distribution. These results confirm differences between the two leading edges of P. depressa at poleward populations of its distribution.