Phylum Molluscs Overview

Molluscs are a diverse phylum of invertebrates characterized by a soft, unsegmented body, a muscular foot, and a mantle that usually secretes a shell.

Molluscs exhibit a true body cavity, called a coelom, which allows for specialized organ systems to develop.

The radula is a unique feeding structure found in most molluscs. It consists of a ribbon of teeth used for scraping food from surfaces.

Most molluscs have an open circulatory system, where blood circulates through vessels and then bathes the organs in a fluid called hemolymph.

The mantle is a fold of tissue in molluscs that encloses a space called the mantle cavity, which houses the gills (for breathing) and anus.

Molluscs can reproduce both sexually (gonochoristic) and by being hermaphrodites, often with internal fertilization and development into larvae.

The gastropods, a class of molluscs, are asymmetrical, with a spiral shell, a muscular foot modified for movement, and often possess tentacles with eyes.

Bivalves, another class of molluscs, are aquatic animals with two shells hinged together. They lack a head and radula and feed by filtering water for food.

They are triploblastic organisms, which means they have three germ layers (ectoderm, mesoderm, endoderm).

Their body cavity, called a coelom, is filled with hemolymph, a fluid that acts like blood.

Molluscs have a soft, non-segmented body.

A muscular foot, used for movement, can be modified into different structures.

A visceral mass houses their internal organs.

The mantle is a fold of skin that secretes a calcium carbonate shell.

It lies between the mantle and the body, and often contains gills or lungs.

They breathe through gills in aquatic species, or pulmonary sacs in terrestrial species.

They typically have an open circulatory system, with blood flowing through vessels and then bathing the organs.

They have a nervous system with paired ganglia, which are specialized groups of nerve cells.

A mollusc subphylum that includes marine and primitive creatures, often lacking a shell or having one made of organic materials, with underdeveloped heads lacking eyes and tentacles.

A mollusc subphylum that includes organisms with shells made of calcium carbonate, encompassing three important classes: Gastropoda, Bivalvia, and Cephalopoda.

A class of molluscs with an asymmetrical body, a spiral-coiled shell, a clearly defined head with eyes and tentacles, a muscular foot for movement, gills or pulmonary sacs for breathing, and complex reproductive organs with proterandrous hermaphroditism.

The twisting process of a gastropod's visceral mass (organs) and mantle by 180 degrees relative to the head and foot, resulting in a looped internal organization.

A class of molluscs characterized by their bilaterally symmetrical body, two hinged shells, lack of a head and radula, aquatic lifestyle, filter feeding, and specialized gills for breathing.

A class of molluscs that are exclusively marine, bilaterally symmetrical, often lack shells or have reduced ones, are carnivorous, possess tentacles with suckers, have a jet-propulsion system for rapid movement, and exhibit complex nervous systems.

A structure in cephalopods that allows for the expulsion of ink-like fluid as a defense mechanism.

A type of eye found in cephalopods, similar to vertebrate eyes, characterized by a camera-like structure with a lens that focuses light onto a retina.

A specialized duct in male cephalopods used to transfer spermatophores (sperm packages) to the female's body during mating.

A muscular foot modified into tentacles in cephalopods, equipped with suckers for grasping and locomotion.