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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 ...
Examples include: An operculum (gastropod), a single lid that (in its most complete form) closes the aperture of the shell when the animal is retracted, and thus protects the internal soft parts of the animal that are not completely covered by the shell. The operculum lies on the top rear part of the foot.
Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group. [1]
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.
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.
In gastropods in many ancient lineages, the gills are bipectinate, having an overall shape that is similar to a bird's feather, with narrow filaments projecting either side of a central stalk. Gastropods such as abalone and keyhole limpets have two gills, which is believed to be the arrangement in the earliest fossil gastropods. The water ...
The common periwinkle or winkle (Littorina littorea) is a species of small edible whelk or sea snail, a marine gastropod mollusc that has gills and an operculum, and is classified within the family Littorinidae, the periwinkles. [2] This is a robust intertidal species with a dark and sometimes banded shell.
Drawing of the animal and shell of Viviparus viviparus; a) head b) tentacles c) eyes d) foot e) operculum. The height of the shell is 25–35 mm. The width of the shell is 20–26 mm. Males are 2 mm smaller than females of the same age. The shell colour is dark greenish brown or greyish yellow, with three reddish brown spiral bands.