The molluscs include clams, snails, slugs, and squid. Molluscs are found in most freshwater and marine environments, and some on land. Most mollusks live in shallow to deep marine habitats. Some mollusks have shells. The mollusc has a single, limpet-like shell on top, secreted by a mantle. The underside is a single muscular foot. Mollusca is one of the most diverse animal groups. It includes snails, octopuses, squid, clams, scallops, oysters, and chitons. Gastropods include 80 percent of mollusks – snails, slugs, abalones, conchs. “Gastropod” means “stomach foot” – their stomach is near the head and they move slowly on one muscular foot. Mollusks belong to three classes: cephalopods, gastropods, bivalves. Bivalves have two movable shells – clams, oysters, mussels. Gills filter oxygen and food from water. Mollusks lack heads. Some birds eat mollusks – snail kites, limpkins, ducks. Mollusk predators include molluscs, arthropods like crabs, vertebrates like fish. Squid, octopuses are ocean hunters with intelligence beyond fish.
What are the 4 major molluscs?
The three major groups of mollusks are gastropods, bivalves, and cephalopods. Gastropods include snails and slugs. They have one shell or no shell and creep along on a broad foot. Around 85,000 species of molluscs exist. Molluscs comprise about 23% of named marine organisms. Numerous molluscs live in freshwater and land habitats too. Prawns are crustaceans, not molluscs. Edible molluscs prepare dishes like Oysters Rockefeller. Molluscs have a mantle, radula and nervous system. Their body includes a head, foot and visceral mass covered by a mantle. Despite diversity they share these traits. There are nearly 100,000 described mollusc species. The gastropods are the largest and most diverse mollusc group.
What is classified as a mollusk?
Mollusks are soft-bodied invertebrates that usually have a hard shell made of calcium carbonate secreted from a mantle that covers their bodies. The three main groups of mollusks are gastropods, bivalves, and cephalopods.
Gastropods like snails and slugs make up over 80% of mollusk species. They typically have a single shell or no shell, and a muscular “foot” that helps them move. Bivalves like clams and oysters have two shells hinged together. Cephalopods like squids and octopuses have tentacles and other adaptations for active predation. There are around 50,000 to 200,000 living mollusk species.
Most mollusks share three main features: a mantle cavity used for breathing and excretion, a radula “tongue” covered in teeth for feeding, and a similar nervous system structure. The seven classes differ mostly by the shape and features of their shell or lack of an external shell. The subclasses have more specialized features for locomotion, feeding, etc.
The two largest classes by number of species are gastropods and bivalves. Scaphopods have a conical shell for burrowing. Monoplacophorans are a small class with limited diversity. Polyplacophorans or “chitons” have eight overlapping shell plates and look somewhat like woodlice. Cephalopods like octopuses have tentacles and other adaptations for being active predators rather than filter feeders. Aplacophorans lack shells and look similar to worms.
What is a mollusk in seafood?
A mollusk is a soft-bodied invertebrate in the phylum Mollusca, which includes snails, clams, and squid. Oysters are a type of mollusk. All mollusks have soft bodies and many have protective shells. Oysters specifically belong to the bivalve family, meaning they have two hinged shells.
Other types of mollusks are very popular kinds of seafood, like clams, mussels, and squid. Mollusks live in oceans, lakes, and rivers. They filter food from the water. Many dishes use mollusks, like paella in Spain or pasta in Italy.
Eating mollusks provides protein, vitamins, minerals and omega-3s. Consuming too many can cause food poisoning. Shellfish allergies are also common. Symptoms include swollen throat, shock, and dizziness.
Mollusks play vital ecological roles. They filter water and provide food for other creatures. Humans rely on harvesting mollusks. Coastal towns earn income from selling mollusks.