Classes of Mollusks in Intertidal Zones

The diversity of gastropods in exposed habitats was compared to that in protected habitats in the three major intertidal zones at San Simeon in over two days in March, 2000. Collections were made in a 25 cm x 25 cm area at 10 different locations in each of the three intertidal zones of a protected habitat on one day, and at 10 different locations in each of the three intertidal zones in an exposed habitat on the second day. The data were analyzed statistically using the Shannon-Weaver Diversity Index and the Student t test, and the results showed that there was no difference in diversity of gastropods between the exposed site and the protected site.

There are two main classes of mollusks in the intertidal zone - gastropods and bivalves. Gastropods are characterized by their large foot, rasping radula (tongue), and mantle or shell (The Intertidal Zone, 2000). There are five main types of gastropods in the intertidal zone and they are each found in different areas of the zone. The rough periwinkle is common in the splash zone and beneath rocks in other parts of the shore. Among the gastropods of the intertidal zone, these are the ones most able to withstand the highest variation in environmental conditions. They are the sma