Snails, Slugs, Shellfish and Octopus

Overview

Snails, slugs, shellfish and octopus have soft mucus coated body, with no limbs or segments, protected by a hardened shell. Have well developed digestive, circulatory and nervous system all permanently enclosed by the shell. The basic body plan, with bilateral or no symmetry, is modified to give rise to six main classes of molluscs. Most common are, gastropods (whelks and limpets with common spiralling shell), cephalopods (Active squids, cuttlefish and octopuses, with the foot modified into tentacles surrounding the mouth).

Common gastropods, such as oysters and mussels are very good indicators of an areas pollution level, as their body tissue accumulates equal amounts of contaminants from their surrounding environment relatively quickly. Bivalves, (oysters and mussels) rely on filter feeding to maintain health, as they ingest large amounts of water they remove nutrients and also any trace elements that may be in the area. Scientists measure characteristics such as animal condition, tissue growth, percent of fat and survival rates to evaluate to what extent an area may be affected, and to prioritize problem sites or pollution pathways. Scientists can further evaluate which contaminants may be transferred to higher trophic levels of the food web, and to what extent certain contaminants may pose health risks to wildlife and humans.