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Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks [a] (/ ˈ m ɒ l ə s k s /). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda . [ 5 ]
The mollusc (or mollusk [spelling 1]) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
This space contains the mollusk's gills, anus, osphradium, nephridiopores, and gonopores. The mantle cavity functions as a respiratory chamber in most mollusks. In bivalves it is usually part of the feeding structure. In some mollusks the mantle cavity is a brood chamber, and in cephalopods and some bivalves such as scallops, it is a locomotory ...
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails, clams, octopus, squid and relatives). Siphons in molluscs are tube-like structures in which water (or, more rarely, air) flows.
Scaphopoda / s k æ ˈ f ɒ p ə d ə / (plural scaphopods / ˈ s k æ f ə p ɒ d z /, from Ancient Greek σκᾰ́φης skáphē "boat" and πούς poús "foot"), whose members are also known as tusk shells or tooth shells, are a class of shelled marine invertebrates belonging to the phylum Mollusca with worldwide distribution and are the only class of exclusively infaunal marine molluscs.
The odontophore is part of the feeding mechanism in molluscs. It is the cartilage which underlies and supports the radula, a ribbon of teeth. [1] The radula is found in every class of molluscs except for the bivalves. [2] The feeding apparatus can be extended from the mouth of the animal, and the radular ribbon can slide over the odontophore.
The number of gastropod species can be ascertained from estimates of the number of described species of Mollusca with accepted names: about 85,000 (minimum 50,000, maximum 120,000). [9] But an estimate of the total number of Mollusca, including undescribed species, is about 240,000 species. [10]
Other studies of nudibranch molluscs have concluded they are aposematically coloured, for example, the slugs of the family Phylidiidae from Indo-Pacific coral reefs. [23] Nudibranchs that feed on hydrozoids can store the hydrozoids' nematocysts (stinging cells) in the dorsal body wall, the cerata. [24]