Mollusca – Gastropoda


Various species of periwinkles – dark blue, black, brown or grey – live on rocks in the splash zone above the high tide mark. They can survive for long periods out of the water due to the horny, tight-fitting trap door, or operculum, which retains the moisture within the shell. Periwinkles graze mainly on microscopic algae and diatom films on rock surfaces.

Periwinkle cluster Periwinkles in a group

Did you know?

Most periwinkles reproduce by releasing egg capsules into the water, which form planktonic larvae before settling on the reef.