Aylacostoma

Aylacostoma is a genus of tropical freshwater snails with an operculum, aquatic gastropod molluscs in the family Thiaridae. 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.[3][4]

Aylacostoma
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Caenogastropoda
clade Sorbeoconcha
Superfamily:
Cerithioidea
Family:
Thiaridae
Genus:
Aylacostoma

Spix, 1827[1]
Type species
Aylacostoma glabrum Spix, 1827
Diversity[2]
32 species

Species

Species within genus Aylacostoma include:

  • Aylacostoma brunneum Vogler & Peso, 2014
  • Aylacostoma chloroticum Hylton-Scot, 1953
  • Aylacostoma ci Simone, 2001
  • Aylacostoma exoplicata Simone, 2001
  • Aylacostoma francana (Ihering, 1909)[2]
  • Aylacostoma glabrum Spix, 1827
  • Aylacostoma guaraniticum Hylton-Scot, 1953
  • Aylacostoma osculati (Villa, 1857) - synonym: Hemisinus osculati[5]
  • Aylacostoma stigmaticum Hylton-Scot, 1953
  • Aylacostoma tenuilabris (Reeve, 1860)

Distribution

The native distribution of this genus includes Central and South America.[2]

Life habits

Some species in this genus used to live in areas of white water in the Yacyretá Rapids, Paraná River, feeding on the algae that grow attached to the rocks on the bottom. The water in the area is saturated with oxygen, from the fast-moving waters.

Aylacostoma is a parthenogenic species: the population consists of only females, which increase in number by asexual reproduction. The females give birth to a small number of larvae, 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.[3][4] The captive populations of the last two species are jointly managed by the National University of Misiones and Bernardino Rivadavia Natural Sciences Museum.[3]

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References
  1. Spix J. B. von (1827). Testacea fluviatilia quae in itinere per Brasiliam annis MDCCCXVII-MDCCCXX. page 15.
  2. 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. doi:10.5007/2175-7925.2013v26n2p277.
  3. Vogler (2013). The Radula of the Extinct Freshwater Snail Aylacostoma stigmaticum (Caenofastropoda: Thiaridae) from Argentina and Paraguay. Malacologia 56 (1-2): 329-332.
  4. 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.
  5. Pastorino G. & Darrigan G. (2011). "Aylacostoma osculati". In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 07 December 2013.
  • 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.
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