Fecundity Of The Invasive Marine Gastropod Crepidula Fornicata Near The Current Northern Extreme Of Its Range

The calyptraeid gastropod Crepidula fornicata is native to the eastern coast of the United States but has now become an extremely successful invader along much of the European coastline. As the northern limit of its spread is thought to be determined by an inability of adults to tolerate prolonged exposure to low winter temperatures, this study sought to compare the fecundity of females collected from two sites along the Norwegian coastline with that of females collected from Rhode Island, USA. Few other studies have compared the fecundities of marine invertebrates from invasive populations with those found in native populations. For both populations studied, fecundities increased with increasing shell length. However, contrary to expectations, size-related fecundities were significantly higher for Norwegian females than for Rhode Island females, with Norwegian females producing larger egg capsules and a greater number of embryos per capsule, but not a greater number of egg capsules per brood. Current evidence suggests that at the northern extreme of its invaded range, the fecundity of C. fornicata is increased rather than compromised.