Haliotis

Haliotis Temporal range: Late Cretaceous – Recent[1] PreЄ Є O S D C P T J K Pg N
Living abalone in tank showing epipodium and tentacles, anterior end to the right.
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Clade:	Vetigastropoda
Superfamily:	Haliotoidea
Family:	Haliotidae
Genus:	Haliotis Linnaeus, 1758
Type species
Haliotis asinina Linnaeus, 1758
Synonyms[2]
Euhaliotis Wenz, 1938 Eurotis Habe & Kosuge, 1964 Exohaliotis Cotton & Godfrey, 1933 Haliotis (Haliotis) Linnaeus, 1758 Haliotis (Marinauris) Iredale, 1937 Haliotis (Nordotis) Habe & Kosuge, 1964 Haliotis (Notohaliotis) Cotton & Godfrey, 1933 Haliotis (Padollus) Montfort, 1810 Haliotis (Paua) C. Fleming, 1953 Haliotis (Sulculus) H. Adams & A. Adams, 1854 Marinauris Iredale, 1927 Neohaliotis Cotton & Godfrey, 1933 Nordotis Habe & Kosuge, 1964 Notohaliotis Cotton & Godfrey, 1933 Ovinotis Cotton, 1943 Padollus Montfort, 1810 Paua C. Fleming, 1953 Sanhaliotis Iredale, 1929 Schismotis Gray, 1856 Teinotis H. Adams & A. Adams, 1854 Tinotis P. Fischer, 1885 (invalid: unjustified emendation of Teinotis) Usahaliotis Habe & Kosuge, 1964

Haliotis, common name abalone (US), pāua (NZ), or ormer (UK), is the only genus in the family Haliotidae.^[2]

This genus used to contain 6 subgenera. These subgenera have become alternate representations of Haliotis.[4] The genus consists of small to very large edible herbivorous sea snails, marine gastropod molluscs. The number of species recognized worldwide ranges between 30^[3] and 130 ^[4] with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.[8]

Description

The iridescent inside surface of a red abalone shell from Northern California. The coin is about one inch in diameter.

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 (mother-of-pearl), 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 form as the shell grows. This series of 8 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 ten, 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.^[5] 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. There are about 70 uncini, 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.^[6]

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.^[7]

The larvae are lecithotrophic. The adults are herbivorous and feed with their rhipidoglossan radula on macroalgae, preferring red or brown algae. Sizes vary from 20 millimetres (0.79 in) (Haliotis pulcherrima) to 200 millimetres (7.9 in) while Haliotis rufescens is the largest of the genus at 12 inches (30 cm).^[8]

Abalones are herbivorous on hard substrata.

By weight, approximately 1/3 of the animal is edible meat, 1/3 is offal, and 1/3 is shell.

Distribution

Abalone with a live sponge on its shell in Póvoa de Varzim, Portugal.

The haliotid family has a worldwide distribution, along the coastal waters of every continent, except the Pacific coast of South America, the East Coast of the United States, the Arctic, and Antarctica^[9] The majority of abalone species are found in cold waters, such as off the coasts of New Zealand, South Africa, Australia, Western North America, and Japan.

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.^[10] The dust created by grinding and cutting abalone shell is dangerous; appropriate safeguards must be taken to protect people from inhaling these particles.

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 range from 30^[3] to 130.^[4] This list finds a compromise using the "WoRMS" database, plus some species that have been added, for a total of 57.^[2][11] The majority of abalone have not been rated for conservation status. Those that have been reviewed tend to show that the abalone in general is an animal that is declining in numbers, and will need protection throughout the globe.

• 
  A dorsal view of a live ass's ear abalone, Haliotis asinina
• 
  the pink abalone, Haliotis corrugata
• 
  The black abalone, Haliotis cracherodii
• 
  Dorsal (left) and ventral (right) views of the blacklip abalone, Haliotis rubra
• 
  The white abalone, Haliotis sorenseni
• 
  A shell of Haliotis varia form dohrniana

Synonyms

See also

• Abalone
• Concholepas concholepas

References

• 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.

External links