Mollusk Characteristics

Habitat

• Occupying habitats from terrestrial mountaintops to deep sea, most mollusks inhabit marine environments. Mollusks often cling to the hard substrate of coral reefs, beaches and mud flats, in addition to the hydrothermal vents at the bottom of the deep sea. Some terrestrial mollusks like snails and slugs live in leaf litter and moist areas, with sometimes up to 70 species cohabiting a particular area, according to the University of California Museum of Paleontology.

Visceral Mass

• While the size and shape of mollusks may vary from species to species, they retain common characteristics in their body parts. The visceral mass, which contains the digestive and reproductive system and circulatory organs, lies sandwiched between the head-foot and the mantle and shell of the mollusk.

Mantle

• Stretched over the visceral mass, the mantle forms the skin of the dorsal body wall. In some species, it excretes a shell, which arcs over and covers the visceral mass and foot. In others, like slugs and octopuses, the mantle no longer exists. In other species, the mantle helps with activities like respiration. In the empty space between the foot and the mantle lies the mantle or pallial cavity where the gills and sensory organs for smell lie. While marine species have gills, terrestrial mollusks have developed lungs, according to the Department of Biological Sciences at Florida State University.

Head-Foot

• Situated at the base of the mollusk, the head-foot encompasses the sensory organs as well as muscles. Used for locomotion, the foot moves by muscular waves, microscopic hair-like structures called cilia and mucus. The foot also helps the mollusk capture food.

Radula

• Located at the anterior of a mollusk in the mouth cavity, the radula works like a tongue. A ribbon of tiny teeth attached to the radula enables the mollusk to scrape food off a surface and in turn, draw the food into the mouth. Common to most species, the radula helps the mollusk to feed.