The Mollusca phylum encompasses a vast diversity of invertebrates, including snails, clams, and cephalopods like squids and octopuses. These creatures are characterized by a muscular foot, mantle, and often a radula. Originating over 500 million years ago, molluscs have a rich fossil record and play significant roles in human economies and ecosystems. Conservation efforts are crucial for nearly 2,000 endangered non-marine species.
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Molluscs display remarkable diversity in size, form, behavior, and habitat
Gastropoda
Gastropoda is the largest class, accounting for 80% of living molluscs
Bivalvia
Bivalvia is a class of molluscs with two shells and includes clams, oysters, and mussels
Cephalopoda
Cephalopoda is a class of molluscs known for their complex nervous systems and includes squids, octopuses, and cuttlefish
Molluscs have diverse reproductive strategies, with many species laying eggs that develop into larvae or miniature adults
Molluscs are thought to have emerged during the Cambrian period, over 500 million years ago
The transition from their Lophotrochozoan ancestors to the present-day diversity is a topic of ongoing research
The fossil record, including well-preserved specimens like ammonites, provides valuable insights into the phylum's ancient diversity and the environmental conditions of past eras
Molluscs have been integral to human diets and economies, providing food, pearls, mother of pearl, and other luxury items
Venomous species
Some molluscs, such as the blue-ringed octopus and certain cone snails, pose risks to humans due to their venom
Agricultural pests and invasive species
Molluscs can also be agricultural pests or invasive species, disrupting local ecosystems
Disease carriers
Some freshwater snails are intermediate hosts for the parasite causing schistosomiasis, a disease affecting millions globally
The term "mollusc" originates from the Latin "mollusca," meaning "soft," which was first applied to these animals in the 17th century
Malacology is the branch of zoology that focuses on the study of molluscs
The outdated term "Molluscoida" has been discarded due to advances in phylogenetic understanding, which previously grouped unrelated animals such as brachiopods and tunicates with molluscs
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Mollusca phylum rank in invertebrate diversity
Second to Arthropoda in species variety among invertebrates.
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Number of extant and fossil mollusc species
Approximately 85,000 living species, 60,000 to 100,000 fossil species.
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Molluscs' habitat diversity
Inhabit marine, freshwater, and terrestrial environments.
