Haliotis Explained

Haliotis should not be confused with Halitosis.

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.[1]

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 Māori 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.[2] [3]

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

Species of abalone! Species !! Range !! Conservation status
Haliotis alfredensis Bartsch, 1915
Haliotis arabiensis Owen, Regter & Van Laethem, 2016 Off Yemen and Oman
Haliotis asinina Linnaeus, 1758 Philippines
Haliotis australis Gmelin, 1791
Haliotis brazieri Angas, 1869 Eastern Australia
Haliotis clathrata Reeve, 1846 Seychelles
Haliotis coccoradiata Reeve, 1846 Eastern Australia
Haliotis corrugata Wood, 1828 , Species of Concern National Marine Fisheries Service; Vulnerable (global) and imperiled (California) California Department of Fish and Wildlife
Haliotis cracherodii Leach, 1814 California, USA; Baja California, Mexico , Vulnerable (Global, Nation: US, State: California) California Department of Fish and Wildlife; Listed endangered National Marine Fisheries Service
Haliotis cyclobates Péron & Lesueur, 1816 Southern Australia
Haliotis dalli Henderson, 1915 Galapagos Islands, western Colombia
Haliotis discus Reeve, 1846 Japan
Haliotis dissona (Iredale, 1929)
Haliotis diversicolor Reeve, 1846
Haliotis drogini Owen & Reitz, 2012 Cocos Island
Haliotis elegans Koch & Philippi, 1844 Western Australia
Haliotis exigua Dunker, R.W., 1877 (synonym of H. diversicolor) Japan Not evaluated
Haliotis fatui Geiger, 1999
Haliotis fulgens Philippi, 1845 California, USA; Baja California, Mexico , Vulnerable (Global, State: California California Department of Fish and Wildlife); Species of Concern NMFS
Haliotis geigeri Owen, 2014 São Tomé and Príncipe Islands
Haliotis gigantea Gmelin, 1791 Japan
Haliotis glabra Gmelin, 1791 Philippines
Haliotis iris Gmelin, 1791 New Zealand
Haliotis jacnensis Reeve, 1846 Japan; Nicobar Islands; Ryukyu Islands; Pacific Islands;
Haliotis kamtschatkana Jonas, 1845 Western North America , Imperiled (Alaska, British Columbia), Vulnerable (global, US), critically imperiled (California); Species of Concern NMFS
Haliotis laevigata Donovan, 1808
Haliotis madaka (Habe, 1977) Japan; South Korea
Haliotis mariae Wood, 1828 Oman
Haliotis marmorata Linnaeus, 1758 Liberia
Haliotis melculus (Iredale, 1927) Australia (New South Wales, Queensland)
Haliotis midae Linnaeus, 1758 South Africa
Haliotis mykonosensis Owen, Hanavan & Hall, 2001 Greece
Haliotis ovina Gmelin, 1791 Thailand
Vietnam; southern part of the Pacific Ocean; Andaman Islands; Maldives; Ryukyu Islands
Haliotis papulata Reeve, 1846Australia; Papua New Guinea; Philippines; Sri Lanka; Thailand
Haliotis parva Linnaeus, 1758
Haliotis planata G. B. Sowerby II, 1882
Haliotis pourtalesii Dall, 1881
Haliotis pulcherrima Gmelin, 1791
Haliotis queketti E.A. Smith, 1910 Eastern Africa
Haliotis roei Gray, 1826 Australia
Haliotis rubiginosa Reeve, 1846
Haliotis rubra Leach, 1814 Southern and Eastern Australia
Haliotis rufescens Swainson, 1822 Western North America , apparently secure (global, US); critically imperiled (Canada)
Haliotis rugosa Lamarck, 1822
Haliotis scalaris (Leach, 1814) Southern and Western Australia
Haliotis semiplicata Menke, 1843 Western Australia
Haliotis sorenseni Bartsch, 1940 California, USA; Baja California, Mexico , critically imperiled (global, US, California); Endangered NMFS
Haliotis spadicea Donovan, 1808 South Africa
Haliotis speciosa Reeve, 1846 (synonym of H. tuberculata)Eastern South Africa Not evaluated
Haliotis squamosa Gray, 1826 Southern Madagascar
Haliotis stomatiaeformis Reeve, 1846 Malta
Sicily
Haliotis supertexta Lischke, 1870 (synonym of H. diversicolor) Not evaluated
Haliotis thailandis Dekker & Patamakanthin, 2001 (synonym of H. papulata) Andaman Sea Not evaluated
Haliotis tuberculata Linnaeus, 1758
Haliotis unilateralis Lamarck, 1822 Gulf of Aqaba
East Africa; Seychelles;
Haliotis varia Linnaeus, 1758 Mascarene Basin
Red Sea; Sri Lanka; Western Pacific;
Haliotis virginea Gmelin, 1791
Haliotis walallensis Stearns, 1899 Western North America

Fossil species

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.[4] [5] [6] [7]

Synonyms

See main article: List of abalone synonyms.

See also

Sources

Notes and References

  1. D.L.. Geiger. 1999. Distribution and biogeography of the recent Haliotidae (Gastropoda: Vetigastropoda) world-wide. Bollettino Malacologico. en.
  2. Abalone Toxicity https://orchid.ganoksin.com/t/abalone-toxicity/9357/2
  3. Shell Dust Dangers https://www.banjohangout.org/archive/187285
  4. Web site: Peters. H.. Rogers-Bennett. L.. De Shields. R. M.. 2021-05-21. Haliotis rufescens. The IUCN Red List of Threatened Species . 2021: e.T78771583A78772573. IUCN. 10.2305/IUCN.UK.2021-3.RLTS.T78771583A78772573.en. 2022-12-24. 245151062. free.
  5. Web site: Kerlin . Katherine E. . 2022-12-12 . All West Coast Abalones at Risk of Extinction on the IUCN Red List . 2022-12-24 . UC Davis . en.
  6. Web site: First-ever global Red List assessment of abalone underlines urgency of combatting illegal trade - Wildlife Trade News from TRAFFIC . 2022-12-24 . www.traffic.org . en.
  7. Byrne . Maria . Ho . Melanie . Wong . Eunice . Soars . Natalie A. . Selvakumaraswamy . Paulina . Shepard-Brennand . Hannah . Dworjanyn . Symon A. . Davis . Andrew R. . 2010-12-22 . Unshelled abalone and corrupted urchins: development of marine calcifiers in a changing ocean . Proceedings of the Royal Society B: Biological Sciences . 278 . 1716 . 2376–2383 . 10.1098/rspb.2010.2404 . 21177689 . 3119014 . 0962-8452.

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