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The mouth contains a long, cylindrical, annulated proboscis and a small tongue. The mantle forms a thin-edged flap over the branchial cavity. On the left side, it has an elongated, open canal, that emerges by a notch or groove in the shell. The two gills are elongated, unequal and pectinate (i.e. in a comb-like arrangement).
Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
Pomacea bridgesii, common name the spike-topped apple snail or mystery snail, is a South American species of freshwater snail with gills and an operculum, an aquatic gastropod mollusk in the family Ampullariidae. These snails were most likely introduced to the United States through the aquarium trade.
In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function. Vestigiality is the retention, during the process of evolution , of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [ 1 ]
The anatomy of a common air-breathing land snail: much of this anatomy does not apply to gastropods in other clades or groups. Snails are distinguished by an anatomical process known as torsion, where the visceral mass of the animal rotates 180° to one side during development, such that the anus is situated more or less above the head. This ...
The gills are symmetrical and both well developed. [7] These snails cling solidly with their broad muscular foot to rocky surfaces at sublittoral depths, although some species such as Haliotis cracherodii used to be common in the intertidal zone. Abalone reach maturity at a relatively small size.
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.
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 ...