''Aylacostoma'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

freshwater snails with an operculum, aquatic gastropod molluscs in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Hemisinidae Hemisinidae is a family of snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of t ...

. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely extinct and another is extinct in the wild.Vogler (2013). The Radula of the Extinct Freshwater Snail Aylacostoma stigmaticum (Caenofastropoda: Thiaridae) from Argentina and Paraguay. Malacologia 56 (1-2): 329-332.Vogler, Beltramino, Strong & Rumi (2015). A phylogeographical perspective on the ex situ conservation of Aylacostoma (Thiaridae, Gastropoda) from the High Paraná River (Argentina–Paraguay). Zoological Journal of the Linnean Society 174(3): 487-499.

Species

Species within genus ''Aylacostoma'' include: * '' Aylacostoma brunneum'' Vogler & Peso, 2014 * ''

Aylacostoma chloroticum ''Aylacostoma chloroticum'' is a species of freshwater snail, aquatic gastropod mollusc in the family Thiaridae. This species is found in Argentina and Paraguay. It was feared that the species had become extinct in the wild as a consequence ...

'' Hylton-Scot, 1953 * ''

Aylacostoma ci ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' Simone, 2001 * ''

Aylacostoma exoplicatum ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' Simone, 2001 * ''

Aylacostoma francanum ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' (Ihering, 1909) * ''

Aylacostoma glabrum ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' Spix, 1827 * ''

Aylacostoma guaraniticum ''Aylacostoma guaraniticum'' is a species of freshwater snail, an aquatic gastropod mollusc in the family Thiaridae. This species disappeared after the building of the Yacyretá Dam on the Paraná River, in between Argentina and Paraguay. Altho ...

'' Hylton-Scot, 1953 * ''

Aylacostoma osculati ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' (Villa, 1857) - synonym: ''

Hemisinus osculati ''Hemisinus'' is a genus of freshwater snails with an operculum, aquatic gastropod mollusks in the family Hemisinidae. Species Species within the genus ''Hemisinus'' include: * '' Hemisinus brevis'' Vázquez A. A. & Perera S. (2010). "Ende ...

'' * ''

Aylacostoma stigmaticum ''Aylacostoma stigmaticum'' is a species of freshwater snail, aquatic gastropod mollusc in the family Thiaridae. This species disappeared after the building of the Yacyretá Dam on the Paraná River, in between Argentina and Paraguay. Although ...

'' Hylton-Scot, 1953 * ''

Aylacostoma tenuilabris ''Aylacostoma'' is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Hemisinidae. They are found in South and Central America. As a consequence of the Yacyretá Dam, two species are entirely ext ...

'' (Reeve, 1860)

Distribution

The native distribution of this genus includes Central and South America.Paschoal L. R. P., Andrade D. d. P. & Cavallari D. C. (2013). "First record of ''Aylacostoma francana'' (Ihering, 1909) (Gastropoda, Thiaridae) in Minas Gerais state, Brazil". '' Biotemas'' 26(2): 277-281. .

Life habits

Some species in this genus used to live in areas of white water in the Yacyretá Rapids, Paraná River, feeding on the

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e that grow attached to the rocks on the bottom. The water in the area is saturated with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, from the fast-moving waters. ''Aylacostoma'' is a

parthenogenic Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

species: the population consists of only females, which increase in number by asexual reproduction. The females give birth to a small number of

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

e, no more than three, that are born very well developed, so they have the physical strength needed to attach to a rock and resist the strong current.

Conservation status

With the building in 1993 of the Yacyretá Dam, almost all the suitable habitat for ''Aylacostoma'' living in this region was flooded. Consequently, ''A. guaraniticum'' and ''A. stigmaticum'' became entirely extinct, ''A. brunneum'' extinct in the wild (survives in captivity), and ''A. chloroticum'' restricted to single small wild population and a captive "safety" population. The captive populations of the last two species are jointly managed by the National University of Misiones and

Bernardino Rivadavia Natural Sciences Museum The Bernardino Rivadavia Natural Sciences Argentine Museum ( es, Museo Argentino de Ciencias Naturales Bernardino Rivadavia) is a public museum located in the Caballito section of Buenos Aires, Argentina. History and overview The museum owes it ...

References

External links

* Simone L. R. L. (2006). ''Land and freshwater molluscs of Brazil: an illustrated inventory on the Brazilian malacofauna, including neighbour regions of the South America, respect to the terrestrial and freshwater ecosystems''. São Paulo: FAPESP, 390 pp. {{Taxonbar, from=Q2874897 Hemisinidae Taxonomy articles created by Polbot