What is Malacology?
Malacology is the study of mollusks.
What are mollusks?
The phylum Mollusca includes soft-bodied invertebrates such as snails, clams, oysters, and squid. Most seashells were once living mollusks.
Why study Malacology?
Studying mollusks helps scientists understand some of the most complicated problems of this century, such as ecosystem management, pollution control, cancer treatments, and neural development.
What good are mollusks?
Mollusks can be used for a wide range of applications. They are an enormous source of food for both humans and animals. Their shells were once used to make tools, and are still used to make roads and medical supplements. Bivalves filter toxic chemicals out of the water, and Cone Shell venom is used in cancer research. Some current and historical uses for mollusks include:
- Food- escargot, calamari, shellfish, etc.
- Tools/weapons- tough shells make rudimentary implements
- Decoration- abalone shell (mother of pearl), seashells, pearls
- Clothing- mussel shell buttons, purple dye (Murex sp.)
- Infrastructure- crushed shell used to pave streets
- Medical- Calcium supplements, disease and cancer research
- Pest control- carnivorous snails prey on harmful pest species
- Pollution control- Bivalves filter toxins from water
- Horticulture- many snails and slugs recycle dead plants to create a natural fertilizer
- Aquarium trade- aquatic snails look pretty and eat algae off the glass
- Religion- Jewish culture uses Murex trunculus to create a blue dye for tassels
- Currency- some shells used as money in certain countries
All mollusks are classified under the phylum Mollusca. There are six classes of mollusks:
1. Class Cephalopoda
This class includes the highly intelligent, many-armed orders of mollusks. Cephalopods are only found in marine environments. Each animal has at least eight arms, and some have two additional tentacles. All cephalopods have a parrot-like beak with which they dismantle their prey and ward off predators. Squid and octopi can bite, and some species are dangerously venomous. Scientists use these intelligent animals to study how the brain develops and functions.
2. Class Gastropoda
This is the largest class of mollusks. It includes all slugs and snails, including terrestrial, freshwater, and saltwater species. This website focuses primarily on gastropods found on the land and in shallow, freshwater ponds around Houston, Texas.
- Land Snails
- Freshwater Snails
- Marine snails
- Nudibranchs & Sea Slugs
3. Class Monoplacophora
This class contains gastroverms, mollusks with a single, solid dorsal shell and an exposed ventral side. These live on rocks in the deep sea. If one senses danger, it will seal itself to a rock to protect itself. It can require several hundred pounds of pressure to break a gastroverm free of a rock.
4. Class Pelecypoda
Mollusks in this class are bivalves, which means they have hinged shells with two distinct halves. Bivalves are strictly aquatic, and account for the vast majority of mollusks used for food. Most bivalves live in saltwater, but many freshwater species can also be found around the world. Many of North America's freshwater mussel species are critically endangered.
5. Class Polyplacophora
This class features chitons, tidal zone mollusks with jointed dorsal armor. Each chiton has eight armored plates on its back that protect it from predators. When disturbed, a chiton seals itself tightly to rocks or other hard surfaces in its environment.
6. Class Scaphapoda
This class includes the small, tooth-shaped mollusks which live buried under mud in the ocean. Some species live at depths of over 15,800 feet.
- Tusk Shells
- Deep-sea Cadulus
Land snails are categorized as Pulmonates under the class Gastropoda. There are three orders of gastropods:
1. Order Opisthobranchia
These mollusks are marine sea slugs, most of which lack external shells. Some of these animals have bright colors and stinging cells.
- Sea Hares
- Bubble Shells
- Pteropods (sea butterflies)
2. Order Prosobranchia
Marine snails belong to this order. These mollusks are prized by collectors for their beautiful shells. Most marine snails have an operculum.
3. Order Pulmonata
These mollusks can use their mantle cavity as a lung. Pulmonate mollusks include all aquatic and terrestrial snails and slugs.
- Land Snails
- Pond Snails
- Aperture: The opening of a shell.
- Apex: The top or peak of the dorsal side of a shell.
- Comnunella: The spiraled column that runs up the center of shells, kind of like the center column of a spiral staircase.
- Mantle: This part of the body differs in function for each type of mollusk: in gastropods, it is a sheet-like organ that covers the visceral mass, contains organs, and secretes calcium onto the shell; in bivalves, it is most recognizable as the part that is eaten; in cephalopods, it is the sac or tube that contains internal organs and serves as a cranium.
- Operculum: A tough, trapdoor-like shield that covers a shell's aperture and protects the animal when it retracts into its shell. Found only in some gastropods.
- Periostracum: A thin, film-like layer that covers the surface of many shells, and gives some their color. It is comparable to the periosteum that covers bones.
- Radula: A tongue-like organ with thousands of tiny teeth which certain mollusks use to rasp away at their food. It's like a belt with teeth, or a cheese grater.
- Umbilicus: The hole that is formed by the inside of the comnunella that runs up the center of a univalve shell, open at the anterior end and ending at the posterior, or apex.
- Whorl: The twisting form of a gastropod shell; the number of whorls depends on how many times the shell twists around in a complete circle.
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