Periwinkles

Description:

Periwinkles are rarely are over three-quarters of an inch. They come in an assortment of shell colors and patterns, from uniform dull gray to shiny shells checkered or striped with white. These snails often cluster together in a crack or crevice. They secrete a special mucus around the opening to their shell. This hardens, cementing them to the rocky shore where they spend days on the rocky surface. When they are hungry they emerge, first eating the hardened mucus and then they crawl about leaving slime trails, like land snails. They glide along; scraping the plant scum off the rocky surface with a special structure in their mouth called a radula. This radula is common to many molluscs and is similar to a mini chainsaw - having rows and rows of sharp, hooked teeth for scraping. In fact, they are so efficient that they wear away the rock in some areas, deepening the high intertidal pools. The teeth get dull quickly, but they continue to produce new rows of radular teeth their entire life - dropping off the old dull ones at the end of the radula. Periwinkles can replace up to seven rows of teeth a day.

Habitat:

Cabrillo National Monument The park offers a superb view of San Diegos harbor and skyline. At the highest point of the park stands the Old Point Loma Lighthouse, which has been a San Diego icon since 1854. A statue and museum in the Visitor Center commemorate Juan Rodrguez Cabrillo's exploration of the coast of California. In a former army building an exhibit tells the story of the coast artillery on Point Loma. In the winter, migrating gray whales can be seen off the coast. The two-mile Bayside Trail affords spectacular views of San Diego Bay and the city beyond, and takes you through one of the last remaining remnants of coastal sage scrub habitat in the world. The rocky intertidal area is one of the best protected examples of these unique ecosystems in Southern California.

Notes:

Periwinkles prefer to crawl up above the highest water level to the area that gets just the smallest splash from the highest high tide waves. It has the record for the marine animal that can stay out of the ocean the longest. Some remain above the splash of the ocean for two to three months.