Biomphalaria


Biomphalaria is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails and their allies.
Biomphalaria is the type genus of the tribe Biomphalariini.
Taphius is a synonym for Biomphalaria.
The shell of this species, like all planorbids is sinistral in coiling, but is carried upside down and thus appears to be dextral.
''. Scale bar is 3 mm.

Species

As of 2008 there were recognized 34 extant species in the genus Biomphalaria in total. There were also described number of fossil Biomphalaria species.
American species include:
  1. Biomphalaria amazonica Paraense, 1966
  2. Biomphalaria andecola
  3. Biomphalaria cousini
  4. Biomphalaria edisoni Estrada, Velásquez, Caldeira, Bejarano, Rojas & Carvalho, 2006
  5. Biomphalaria glabrata
  6. Biomphalaria havanensis
  7. Biomphalaria helophila
  8. Biomphalaria intermedia
  9. Biomphalaria kuhniana
  10. † Biomphalaria manya Cabrera & Martinez, 2018
  11. Biomphalaria obstructa
  12. Biomphalaria occidentalis Paraense, 1981
  13. Biomphalaria oligoza Paraense, 1974
  14. Biomphalaria orbignyi Paraense, 1975
  15. Biomphalaria peregrina
  16. Biomphalaria prona
  17. Biomphalaria schrammi
  18. Biomphalaria straminea
  19. Biomphalaria subprona
  20. Biomphalaria temascalensis Rangel-Ruiz, 1987
  21. Biomphalaria tenagophila
Old World species include:
  1. Biomphalaria alexandrina
  2. Biomphalaria angulosa Mandahl-Barth, 1957
  3. Biomphalaria barthi Brown, 1973
  4. Biomphalaria camerunensis
  5. Biomphalaria choanomphala
  6. Biomphalaria pfeifferi
  7. Biomphalaria salinarum Morelet
  8. Biomphalaria smithi Preston, 1910 - type species
  9. Biomphalaria stanleyi
  10. Biomphalaria sudanica
  11. Biomphalaria tchadiensis Germain, 1904
  12. Biomphalaria ruppellii Auet. - subspecies: Biomphalaria ruppellii ruppellii Auet.; Biomphalaria ruppellii katangae Haas
There is one known hybrid Biomphalaria glabrata × Biomphalaria alexandrina from Egypt.
A cladogram showing phylogenic relations of species in the genus Biomphalaria:

Distribution

The origin of the genus Biomphalaria is American. The ancestor of Biomphalaria glabrata colonized Africa 2.3–4.5 or 2-5 millions years ago and speciated into all the African Biomphalaria species.
Natural populations of these snails are usually found in tropical standing water or freshwater in South America and Africa, but they also reach 30° latitude in subtropical areas. Many species of these red-blooded planorbid snails are able to survive a long time when removed from their freshwater habitat. Of the 34 Biomphalaria species, 4 have recently expanded their native ranges. They have been introduced to areas where other Biomphalaria species are endemic or to subtropical zones that have no frost period.
All species in the genus Biomphalaria except of native Biomphalaria obstructa has not yet become established in the US, but they are considered to represent a potentially serious threat as a pest, an invasive species which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore, it has been suggested that this species be given top national quarantine significance in the USA.

Parasites

This genus of snails is medically important, because the snails can carry a parasite of humans which represents a serious disease risk: the snails serve as an intermediate host for the human parasitic blood fluke, Schistosoma mansoni, that infects about 83 million people.
The human disease schistosomiasis caused by all Schistosoma species infects 200 million people. The fluke, which is found primarily in tropical areas, infects mammals via contact with water that contains schistosome larvae which have previously been released from the snail. Infection occurs via penetration of cercariae through the skin.
Eighteen species of Biomphalaria are intermediate hosts for Schistosoma mansoni; seven species of the genus have not been tested for this susceptibility and nine species are resistant.
Altogether about 30 species of parasites from Africa and at least 20 species from the Neotropics are known to parasitize Biomphalaria.