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The mantle cavity is a central feature of molluscan biology. This cavity is formed by the mantle skirt, a double fold of mantle which encloses a water space. 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 ...
The mantle cavity, a fold in the mantle, encloses a significant amount of space. It is lined with epidermis, and is exposed, according to habitat , to sea, fresh water or air. The cavity was at the rear in the earliest molluscs, but its position now varies from group to group.
Siphons in molluscs are tube-like structures in which water (or, more rarely, air) flows. The water flow is used for one or more purposes such as locomotion, feeding, respiration, and reproduction. The siphon is part of the mantle of the mollusc, and the water flow is directed to (or from) the mantle cavity. A single siphon occurs in some ...
The osphradium is a pigmented chemosensory epithelium patch in the mantle cavity present in six of the eight extant classes of molluscs (it is absent in the scaphopoda and monoplacophora; among cephalopoda, only the nautilus has what appears to be a set of osphradia), on or adjacent to the ctenidia (gills).
In some nudibranchs, the mantle cavity and the original gill have disappeared altogether. Instead, the upper surface of the body has numerous club-shaped or branched projections called cerata that function as secondary gills. Secondary gills are also present in the unrelated genus Patella, in which they are found as folds within the mantle cavity.
It usually presents itself as a thickening of the tissue located in the roof of the animal's mantle cavity. [3] This is in association with parts of the aquatic mollusk anatomy that perform sediment consolidation in these organisms. [4] However, this gland is absent in all terrestrial gastropods except the Neritacea. [4]
Although chitons lack osphradia, statocysts, and other sensory organs common to other molluscs, they do have numerous tactile nerve endings, especially on the girdle and within the mantle cavity. The order Lepidopleurida also have a pigmented sensory organ called the Schwabe organ. [ 26 ]
Gastropods (snails and slugs) as the largest taxonomic class of the mollusca are very diverse: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites. In particular, the radula is often highly adapted to the specific diet of the various group of gastropods.