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Shell of marine snail Lunella torquata with the calcareous operculum in place Gastropod shell of the freshwater snail Viviparus contectus with corneous operculum in place. The operculum (Latin for 'cover, covering'; pl. opercula or operculums) is a corneous or calcareous anatomical structure like a trapdoor that exists in many (but not all) groups of sea snails and freshwater snails, and also ...
The main function of the epiphragm is to reduce water loss through the aperture during inactivity. [1] An operculum is a somewhat similar but permanent anatomical feature that is found in other clades of gastropods. The operculum serves some of the same functions as an epiphragm. Sometimes it protects the snail against predation.
In the most primitive gastropods, however, the stomach is a more complex structure. In these species, the hind part of the stomach, where the oesophagus enters, is chitinous, and includes a sorting region lined with cilia. [1] In all gastropods, the portion of the stomach furthest from the oesophagus, called the "style sac", is lined with cilia.
Turbo marmoratus, known as the green turban, the marbled turban or great green turban, is a large species of marine gastropod with a thick calcareous operculum in the family Turbinidae, the turban snails. [1] The shells of these large sea snails have a very thick layer of nacre; this species has been commercially fished as a source of mother of ...
Gastropods typically have a well-defined head with two or four sensory tentacles with eyes, and a ventral foot. The foremost division of the foot is called the propodium. Its function is to push away sediment as the snail crawls. The larval shell of a gastropod is called a protoconch.
Turbinidae have a strong, thick calcareous operculum readily distinguishing them from the somewhat similar Trochidae or top snails, which have a corneous operculum. This strong operculum serves as a passive defensive structure against predators that try to enter by way of the aperture or that would break the shell at the outer lip.
An old empty shell of Megastraea undosa, wedged under a rock and covered in the pink coralline alga Lithothamnion, which has cemented it to the substrate.. Megastraea undosa, common name the wavy turban snail, is a species of sea snail, a marine gastropod mollusk in the family Turbinidae, the turban snails. [2]
[2] [3] [4] The shell of Telescopium telescopium differs from most other gastropods because it contains 0.12% magnesium carbonate. [7] The operculum is rigiclaudent, meaning that the last growth increment always lies tangentially against the labial lip of the previous whorl.