Biomphalaria

There are a suspected 35 extant species in the genus Biomphalaria in total (21 American species and 14 Old World species). However, there are a large number of invalid taxa within the Biomphalaria literature, which is likely the result of several (if not all) species of Biomphalaria being subject to various sources of intraspecific variation such as ecophenotypic variation and indeterminate shell growth. New World (South American) species include: • Biomphalaria amazonica (Paraense, 1966) • Biomphalaria andecola (d'Orbigny, 1835) • Biomphalaria cousini (Paraense, 1966) • Biomphalaria edisoni (Estrada, Velásquez, Caldeira, Bejarano, Rojas & Carvalho, 2006) • Biomphalaria glabrata (Say, 1818) • Biomphalaria havanensis (L. Pfeiffer, 1839) • Biomphalaria helophila (d'Orbigny, 1835) • Biomphalaria intermedia (Paraense & Deslandes, 1962) • Biomphalaria kuhniana (Clessin, 1883) • † Biomphalaria manya (Cabrera & Martinez, 2018) • Biomphalaria obstructa (Morelet, 1849) • Biomphalaria occidentalis (Paraense, 1981) • Biomphalaria temascalensis (Rangel-Ruiz, 1987) • Biomphalaria tenagophila (d'Orbigny, 1835) Suspected species identified using morphological methods: • Biomphalaria arabica (Melvill & Ponsonby, 1896) • Biomphalaria barthi (Brown, 1973) • Biomphalaria rhodesiensis (Mandahl-Barth, 1957) • Biomphalaria ruppellii (Dunker, 1848) - subspecies: B. ruppellii ruppellii; B. ruppellii katangae Haas • Biomphalaria salinarum (Morelet, 1868) • Biomphalaria tchadiensis (Germain, 1904) == Phylogeny ==

A cladogram created from mitochondrial and nuclear DNA showing the phylogenic relationships of both New World (16) and Old World (7) species: The topology was consistent with the proposed Neotropical origins of the genus, with the oldest Biomphalaria fossils being dated from approximately 60 million years ago. However, further analysis of the African Biomphalaria species found only B. camerunensis and B. pfeifferi were the only definitive African species, with the remain species being a part of (or a sister taxa to) the "Nilotic species complex": All of the African Biomphalaria species have low levels of genetic diversity, which is likely the result of their relatively recent evolutionary history. == Distribution ==

The origin of the genus Biomphalaria is American. million years ago and speciated into all the African Biomphalaria species. == 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 (vector) for the human parasitic blood fluke, Schistosoma mansoni, that infects about 83 million people. The human disease schistosomiasis (aka snail fever) caused by all Schistosoma species (transmitted also by other snails) infects 200 million people. The fluke, which is found primarily in tropical areas, infects mammals (including humans) via contact with water that contains schistosome larvae (cercariae) 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. ==References==