Zoology 10th Edition by Stephen Miller,John Harley

Exercise 11

The class Gastropoda is the largest of the molluscan classes. Members of the class live in a wide variety of habitats and serve as intermediate hosts for important human parasites. Torsion is a gastropod developmental process that changes the orientation of the visceral mass and head-foot. Shells, when present, are usually coiled. Gastropods have diverse structural and functional attributes that are often characteristic of their subclass, and they are often specialized for particular environments.
Most gastropods have shells for protection from desiccation and predators. Slugs, however, do not have shells. What is a slug's protective mechanism?