Haliotis Discus Hannai 01

''Haliotis'', common name abalone, is the only genus in the family Haliotidae.

This genus once contained six subgenera. These subgenera have become alternate representations of ''Haliotis''. The genus consists of small to very large, edible, herbivorous sea snails, marine gastropod molluscs. The number of species recognized worldwide ranges between 30 and 130, with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.

Other common names are ear shells, sea ears, and, rarely, muttonfish or muttonshells in parts of Australia, ormer in the UK, perlemoen in South Africa, and the Maori name for three species in New Zealand is pāua.

Description

The shells of abalones have a low, open, spiral structure, and are characterized by having several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre, which in many species of abalone is highly iridescent, giving rise to a range of strong, changeable colors, which make the shells attractive to humans as decorative objects, in jewelry, and as a source of colorful mother-of-pearl.

The shell of abalones is convex, rounded to oval shape, and may be highly arched or very flattened. The shell of the majority of species is ear-shaped, presenting a small, flat spire and two to three whorls. The last whorl, known as the body whorl, is auriform, meaning that the shell resembles an ear, giving rise to the common name "ear shell". ''Haliotis asinina'' has a somewhat different shape, as it is more elongated and distended. The shell of ''Haliotis cracherodii cracherodii'' is also unusual as it has an ovate form, is imperforate, shows an exserted spire, and has prickly ribs.

A mantle cleft in the shell impresses a groove in the shell, in which are the row of holes (known as tremata), characteristic of the genus. These holes are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the water column. They make up what is known as the selenizone which forms as the shell grows. This series of eight to 38 holes is near the anterior margin. Only a small number are generally open. The older holes are gradually sealed up as the shell grows and new holes form. Therefore, the number of tremata is not characteristic for the species. Each species has a number of open holes, between four and 10, in the selenizone. This number is not fixed and can vary within a species and between populations. Abalones have no operculum. The aperture of the shell is very wide and nacreous.

The exterior of the shell is striated and dull. The color of the shell is very variable from species to species, which may reflect the animal's diet. The iridescent nacre that lines the inside of the shell varies in color from silvery white, to pink, red and green-red, to deep blue, green to purple.

The animal shows fimbriated head-lobes. The side-lobes are also fimbriated and cirrated. The rounded foot is very large. The radula has small median teeth, and the lateral teeth are single and beam-like. About 70 uncini are present, with denticulated hooks, the first four very large. The soft body is coiled around the columellar muscle, and its insertion, instead of being on the columella, is on the middle of the inner wall of the shell. The gills are symmetrical and both well developed.

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. Abalones reach maturity at a relatively small size. Their fecundity is high and increases with their size (from 10,000 to 11 million eggs at a time). The spermatozoa are filiform and pointed at one end, and the anterior end is a rounded head.

The larvae are lecithotrophic. The adults are herbivorous and feed with their rhipidoglossan radula on macroalgae, preferring red or brown algae. Sizes vary from ('' Haliotis pulcherrima'') to , while '' Haliotis rufescens'' is the largest of the genus at .

By weight, about one-third of the animal is edible meat, one-third is offal, and one-third is shell.

Structure and properties of the shell

The shell of the abalone is exceptionally strong and is made of microscopic calcium carbonate tiles stacked like bricks. Between the layers of tiles is a clingy protein substance. When the abalone shell is struck, the tiles slide instead of shattering and the protein stretches to absorb the energy of the blow. Material scientists around the world are studying this tiled structure for insight into stronger ceramic products such as body armor. The dust created by grinding and cutting abalone shell is dangerous; appropriate safeguards must be taken to protect people from inhaling these particles. There is much discussion of this topic online.

Species

The number of species that are recognized within the genus ''Haliotis'' has fluctuated over time, and depends on the source that is consulted. The number of recognized species ranges from 30 to 130. This list finds a compromise using the "WoRMS" database, plus some species that have been added, for a total of 57. The majority of abalone have not been evaluated for conservation status. Those that have been reviewed tend to show that the abalone in general is declining in numbers, and will need protection throughout the globe.

Extant species

File:Ass’s ear abalone (Haliotis asinina) S01.jpg, A dorsal view of a live ass's ear abalone, ''Haliotis asinina''
File:Pinkabalone 300.jpg, the pink abalone, ''Haliotis corrugata''
File:Haliotis cracherodii.JPG, The black abalone, ''Haliotis cracherodii''
File:Blacklip abalone.jpg, Dorsal (left) and ventral (right) views of the blacklip abalone, ''Haliotis rubra''
File:Whiteabalone 300.jpg, The white abalone, ''Haliotis sorenseni''
File:Haliotis varia f. dohrniana 001.jpg, A shell of ''Haliotis varia'' form ''dohrniana''

Image:Haliotis asinina 01.JPG, ''Haliotis asinina''
Image:Haliotis australis 001.jpg, '' Haliotis australis''
Image:Haliotis clathrata 01.JPG, ''Haliotis clathrata''
Image:Haliotis coccoradiata.jpg, ''Haliotis coccoradiata''
Image:Haliotis corrugata.jpg, ''Haliotis corrugata''
Image:Haliotis cracherodii.jpg, ''Haliotis cracherodii''
Image:Haliotis cyclobates.jpg, ''Haliotis cyclobates''
Image:Haliotis discus discus 01.JPG, ''Haliotis discus discus''
Image:Haliotis diversicolor 01.jpg, '' Haliotis diversicolor''
Image:Haliotis elegans 001.jpg, ''Haliotis elegans''
Image:Haliotis fatui 001.jpg, ''Haliotis fatui''
Image:Haliotis fulgens fulgens 01.JPG, ''Haliotis fulgens fulgens''
Image:Haliotis gigantea f. sieboldii 01.JPG, ''Haliotis gigantea f. sieboldii''
Image:Haliotis glabra 01.JPG, ''Haliotis glabra''
Image:Haliotis iris 01.JPG, '' Haliotis iris''
Image:Haliotis jacnensis 002.jpg, ''Haliotis jacnensis''
Image:Haliotis kamtschatkana assimilis 01.JPG, ''Haliotis kamtschatkana assimilis'' (South California).
Image:Haliotis laevigata 01.JPG, ''Haliotis laevigata'' (South Australia).
Image:Haliotis madaka 001.jpg, ''Haliotis madaka''
Image:Haliotis mariae 002.jpg, '' Haliotis mariae''
Image:Haliotis marmorata 002.jpg, ''Haliotis marmorata''
Image:Haliotis midae 01.jpg, ''Haliotis midae''
Image:Haliotis ovina ovina 01.JPG, ''Haliotis ovina''
Image:Haliotis parva 001.jpg, ''Haliotis parva''
Image:Haliotis planata 01.JPG, ''Haliotis planata''
Image:Haliotis pulcherrima 001.jpg, '' Haliotis pulcherrima''
Image:Haliotis queketti 001.jpg, ''Haliotis queketti''
Image:Haliotis roei 002.jpg, ''Haliotis roei''
Image:Haliotis rubra P2164176.JPG, ''Haliotis rubra''
Image:Haliotis rufescens 22a.jpg, '' Haliotis rufescens''
Image:Haliotis rugosa 2.jpg, ''Haliotis rugosa''
Image:Haliotis scalaris (staircase abalone) (Quinn's Rocks, Western Australia) 1 (23565526643).jpg, ''Haliotis scalaris''
Image:Haliotis semùiplicata 001.jpg, ''Haliotis semiplicata''
Image:Haliotis sorenseni 001.jpg, ''Haliotis sorenseni''
Image:Haliotis spadicea (blood-spotted abalone) (South Africa) 3 (24139744761).jpg, ''Haliotis spadicea''
Image:Haliotis squamosa 001.jpg, ''Haliotis squamosa''
Image:Haliotis stomatiaeformis 002.jpg, ''Haliotis stomatiaeformis''
Image:Haliotis supertexta 001.jpg, ''Haliotis supertexta''
Image:Haliotis thailandis 002.jpg, ''Haliotis thailandis''
Image:Haliotis tuberculata tuberculata 01.JPG, '' Haliotis tuberculata'' (Europe)
Image:Haliotis unilateralis 002.jpg, ''Haliotis unilateralis''
Image:Haliotis varia 01.JPG, ''Haliotis varia''
Image:Haliotis virginea shell 2.jpg, ''Haliotis virginea''
Image:Haliotis walallensis.jpg, ''Haliotis walallensis''

Fossil species

*†''Haliotis benoisti'' Cossmann, 1896 (Aquitaine, France)
*†''Haliotis flemingi'' Powell, 1938 (New Zealand)
*†''Haliotis lomaensis'' Anderson, 1902
*†''Haliotis mathesonensis'' (Eagle, 1996)
*†''Haliotis (Marinauris) matihetihensis'' (Eagle, 1999)
*†''Haliotis powelli'' C. A. Fleming, 1952
*†''Haliotis stalennuyi'' Owen & Berschauer, 2017
*†''Haliotis volhynica'' Eichwald, 1829
*†'' Haliotis waitemataensis'' Powell, 1938

Conservation

Over half of the modern ''Haliotis'' species with sufficient data are considered threatened to some extent on the IUCN Red List, with all but one species from the Pacific coast of North America being critically endangered as a consequence of massive historical overharvesting, withering abalone syndrome, and recent marine heatwaves which have caused collapses of both abalones and their habitat. ''Haliotis'' species from elsewhere are also threatened by overexploitation and climate change. In addition, abalones as a whole are considered highly vulnerable to ocean acidification due to their accretion of aragonite and dependence on susceptible coralline algae for development, and thus may eventually go extinct unless the rate of ocean acidification is arrested.

Synonyms

See also

* Abalone
* ''Concholepas concholepas''

References

Notes

Sources

* Linnaeus, C. 1758. Systema Naturae per Regna tria Naturae, secundem Classes, Ordines, Genera, Species, cum Characteribus, Differentis, Synonymis, Locis. Tom.1 Editio decima, reformata. Holmiae : Laurentii Salvii 824 pp.
* Iredale, T. 1927. ''Caloundra Shells.'' The Australian Zoologist 4: 331-336, pl. 46
* Iredale, T. 1929. ''Queensland molluscan notes, No. 1''. Memoirs of the Queensland Museum 9(3): 261-297, pls 30-31
* Cotton, B.C. & Godfrey, F.K. 1933. ''South Australian Shells. Part 9''. South Australian Naturalist 15(1): 14-24
* Cotton, B.C. 1943. ''Australian Shells of the Family Haliotidae''. Transactions of the Royal Society of South Australia 67(1): 175-180
* Moore, R.C. (ed.) 1960. ''Treatise on Invertebrate Paleontology. Part I. Mollusca 1''. Boulder, Colorado & Lawrence, Kansas : Geological Society of America & University of Kansas Press xxiii + 351 pp.
* Wilson, B. 1993. ''Australian Marine Shells. Prosobranch Gastropods.'' Kallaroo, Western Australia : Odyssey Publishing Vol. 1 408 pp.
* Geiger, D.L. & Poppe, G.T. 2000. ''A Conchological Iconography. The family Haliotidae''. Germany : ConchBooks 135 pp.
* Bouchet, P.; Gofas, S. (2014). Haliotis Linnaeus, 1758. Accessed through
World Register of Marine Species
*

External links

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Haliotidae
Extant Late Cretaceous first appearances
Gastropod genera
Taxa named by Carl Linnaeus