The snail Littorina saxatilis or rough periwinkle, can be found in rock crevices in the Upper Intertidal zone. It feeds on algae by scraping the rock surface with its radula or tongue. The rough periwinkle can survive for extended periods of time with little to no oxygen, using anaerobic metabolism to obtain energy. It also has a lung-like organ, similar to land snails, that allows it to breathe air directly. It is the smallest of the three Littorina spp. in the intertidal zone.