Littorina saxatilis

This species is native to the shores of the North Atlantic Ocean, including Hudson Bay, Baffin Island, Greenland, and the Barents Sea, south along the American East Coast to Chesapeake Bay, and along the European coast to the Straits of Gibraltar. Only one population of this intertidal species occurred in the Mediterranean basin i.e., Venice lagoon. The Venice population represents the earliest confirmed introduction of an exotic species in the Mediterranean Sea. Abiotic environmental features such as salinity and water temperature have influenced the past and current distributions of this snail and limited its invasion of the Mediterranean Sea. This species has also been introduced to San Francisco Bay, on the West Coast of the United States, where it was first observed in 1992.

The marine snail Littorina saxatilis has separate sexes, internal fertilization, and a brood pouch with non-planktonic shelled embryos.