lamellibranch

Lamellibranch is a historical term used to describe a large group of bivalve mollusks characterized by lamellate gills and a two-part shell. The name derives from the lamellae, or thin plate-like gill filaments, which are highly developed in these animals and function in both feeding and respiration. In older classifications, lamellibranchia was treated as a distinct subclass or group within Mollusca; in modern taxonomy, the concept is largely superseded and the organisms are encompassed within the class Bivalvia.

Morphology of lamellibranchs typically includes a pair of identical, hinged shells that enclose a laterally compressed body. The mantle cavity houses feathery gills with many lamellae, which increase the surface area for filtering water. The head is reduced or absent in many species, and a muscular foot is usually present for locomotion or burrowing. Most species possess adductor muscles to close the shell, and many have siphons that channel water to and from the gills.

Feeding and respiration are accomplished by filter feeding. Water is drawn into the mantle cavity through incurrent siphons, passes over the lamellated gills where food particles are trapped by mucus and transported to the mouth, and undergoes gas exchange across the gill surfaces.

Lamellibranchs inhabit a wide range of aquatic environments, including marine and freshwater habitats. They exhibit diverse life cycles, with many releasing sperm and eggs into the water for external fertilization, while others have larval stages such as free-swimming veligers or parasitic glochidia in freshwater species. The term is largely of historical use, and current classifications refer to the broader group as Bivalvia.