STUDIES ON ROCKY SHORE MOLLUSCS AS BIOLOGICAL INDICATORS FOR POLLUTION IN THE COASTAL AREAS OF ALEXANDRIA

Abstract

Molluscs represent one of the greatest phyla of invertebrate animals. They are among the most abundant of all animals. In the number of species, Mollusca is the second phylum to the Arthropoda (Kotpal, 1979). The plane of the molluscan body has proved to be sufficiently flexible to permit the development of a great variety of types (Gardiner, 1972). Molluscs have been a dominant group of animals ever since their origin in the Cambrian period over 500 million years ago. Beside the 110,000 existing species, there are over 55,000 fossil molluscs. Molluscs have successfully adapted to fresh and marine water as well as the terrestrial environment (Webber and Thurman, 1991). There is scarcely any portion of the coastline of the world without molluscan life, except in regions of extreme cold (Kotpal, 1979). Molluscs, as a whole, constitute an attractive field for biologists.