Rough periwinkle

Appearance

The shell in life often appears green with algae, but the shell itself can be white, red, or brown, sometimes with checkered lines. The shell has 4–5 whorls. Maximum recorded shell length is 19 mm.

Distribution

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.

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.

Behavior

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

Habitat

This species frequently lives in salt marshes. it can also be found in crevices of intertidal bedrock, in empty barnacle shells, and under rocks. Like many other periwinkles, this species can survive long exposures out of the water.

The species has been recorded alive from depth range 0 – 46 m or up to 183 m .

In the exposed Galician coast in the Northern Spain, two well differentiated ecotypes are adapted to different shore levels and habitats. The RB ecotype lives on barnacles in the upper shore. This ecotype displays a larger and more robust shell to resist the attack from predators such as crabs, and a smaller shell aperture in order to reduce the desiccation due to high sunshine exposure. The SU ecotype is found at the lower shore living on mussels. This ecotype shows a smaller and thinner shell with a wider shell aperture to allocate a relatively larger muscular foot providing a higher ability to avoid the dislodgment caused by the heavy wave action. Both ecotypes coexist in an intermediate habitat at the middle shore.

Food

This snail is a herbivore which grazes on the surface of rocks and mud flats.