''Oncomelania'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of very small

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 snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

s, aquatic

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

s in the

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

Pomatiopsidae Pomatiopsidae is a family of small, mainly freshwater snails, (some also occur in other habitats) that have gills and an operculum, aquatic gastropod mollusks in the superfamily Truncatelloidea (according to the taxonomy of the Gastropoda by ...

. These ''Oncomelania'' snails are distantly related to the marine periwinkle, and more closely related to the small

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

snails of the family

Rissoidae Rissoidae is a large family of very small and minute sea snails with an operculum, marine gastropod mollusks in the superfamily Rissooidea and the order Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting pr ...

Species

There are twoKameda Y. & Kato M. (2011). "Terrestrial invasion of pomatiopsid gastropods in the heavy-snow region of the Japanese Archipelago". ''

BMC Evolutionary Biology ''BMC Ecology and Evolution'' (since January 2021), previously ''BMC Evolutionary Biology'' (2001–2020), is a peer-reviewed open access scientific journal covering all fields of evolutionary biology, including phylogenetics and palaeontology. It ...

'' 11: 118. . species in the genus ''Oncomelania'': * ''

Oncomelania hupensis ''Oncomelania hupensis'' is a species of very small tropical freshwater snail, an aquatic gastropod mollusk in the family Pomatiopsidae. Distribution ''Oncomelania hupensis'' has been found in China, Taiwan, and also in Japan, the Philipp ...

'' Gredler, 1881 - type species, this polytypic species has a number of subspecies * ''

Oncomelania minima ''Oncomelania minima'' is a species of freshwater snail, an aquatic gastropod mollusk in the family Pomatiopsidae.Kameda Y. & Kato M. (2011). "Terrestrial invasion of pomatiopsid gastropods in the heavy-snow region of the Japanese Archipelago". ...

'' P. Bartsch, 1936 Woodruff et al. (1999) recognized also the following species: * ''

Oncomelania lindoensis ''Oncomelania'' is a genus of very small tropical freshwater snails, aquatic gastropod mollusks in the family Pomatiopsidae. These ''Oncomelania'' snails are distantly related to the marine periwinkle, and more closely related to the small mar ...

'' Davis & Carney, 1973 - from

Lake Lindu A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

(

Lore Lindu National Park Lore Lindu National Park is a protected area of forest on the Indonesian island of Sulawesi, in the province of Central Sulawesi. The Indonesian national park is 2,180 km2 covering both lowland and montane forests (200 to 2,610 meters abov ...

Sulawesi Sulawesi (), also known as Celebes (), is an island in Indonesia. One of the four Greater Sunda Islands, and the world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Mindanao and the Sulu Ar ...

Japanese Red List Data Book (2006) recognizes also the following additional species: * ''

Oncomelania shini ''Oncomelania'' is a genus of very small tropical freshwater snails, aquatic gastropod mollusks in the family Pomatiopsidae. These ''Oncomelania'' snails are distantly related to the marine periwinkle, and more closely related to the small ...

'' - as

Vulnerable species A vulnerable species is a species which has been Conservation status, categorized by the International Union for Conservation of Nature as being threatened species, threatened with extinction unless the circumstances that are threatened species, ...

in Japan * ''

Oncomelania sakuyamai ''Oncomelania'' is a genus of very small tropical freshwater snails, aquatic gastropod mollusks in the family Pomatiopsidae. These ''Oncomelania'' snails are distantly related to the marine periwinkle, and more closely related to the small ...

'' - with no conservation status evaluated in Japan

Distribution

This genus has not yet become established in the USA, but it is considered to represent a potentially serious threat as a pest, an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

which could negatively affect agriculture, natural ecosystems, human health or commerce. Therefore, it has been suggested that this species be given top national

quarantine A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

significance in the USA.Cowie R. H., Dillon R. T., Robinson D. G. & Smith J. W. (2009). "Alien non-marine snails and slugs of priority quarantine importance in the United States: A preliminary risk assessment". ''American Malacological Bulletin'' 27: 113-132
PDF
.

Evolution

About the origin and evolution history of ''Oncomelania'', Davis (1979)Davis G. M. (1979). "The origin and evolution of the gastropod family Pomatiopsidae, with emphasis on the Mekong river Triculinae". ''

Academy of natural Sciences of Philadelphia The Academy of Natural Sciences of Drexel University, formerly the Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the Americas. It was founded in 1812, by many of the leading natura ...

'', Monograph 20: 1-120.
at Google Books
proposed a

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

n origin for the

, with rafting to mainland Asia via the

Indian Craton The geology of India is diverse. Different regions of India contain rocks belonging to different geologic periods, dating as far back as the Eoarchean Era. Some of the rocks are very deformed and altered. Other deposits include recently d ...

after break-up of Gondwanan and colonization of South-East Asia and China. It is hypothesized that ''Oncomelania'' snails, arrived in southwestern China from Indian before the second (major)

Tibetan orogeny Tibetan may mean: * of, from, or related to Tibet * Tibetan people, an ethnic group * Tibetan language: ** Classical Tibetan, the classical language used also as a contemporary written standard ** Standard Tibetan, the most widely used spoken dial ...

(2.5 Ma), then evolved and spread down their respective river systems, to mainland of China, Indonesia and Philippines. Although mutation rate calibrations using fossil data is impossible here, many studies have demonstrated the confidence that molecular data can provide reasonable estimates of divergence time. Data by Zhao et al. (2010) suggested that the two subspecies of ''

'' began to diverse as early about 2–6 Ma based on the invertebrate ITS substitution rate range. Zhao et al. (2010) did not find any strong molecular and fossil evidences about ''Oncomelania'' evolution, but the reported ''Oncomelania'' fossil found in

Guangxi Guangxi (; ; Chinese postal romanization, alternately romanized as Kwanghsi; ; za, Gvangjsih, italics=yes), officially the Guangxi Zhuang Autonomous Region (GZAR), is an Autonomous regions of China, autonomous region of the People's Republic ...

(1 Ma) by

Nils Hjalmar Odhner Nils Hjalmar Odhner (6 December 1884 – 12 June 1973) was a Swedish zoologist who studied mollusks, a malacologist. He was professor of invertebrate zoology at the Swedish Museum of Natural History, Stockholm, and a member of the Royal Swedish Ac ...

in 1930 and geological movement make this diversification time reasonable. It provides a new insight into the ''Oncomelania'' evolution history although the substitution rate needs to be verified with new fossil and molecular data in future study.

Parasites

Various ''Oncomelania'' species are significant medically, because they can serve as vectors for two serious human diseases: they can carry the

schistosomiasis Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody s ...

blood fluke

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

, and the

paragonimus ''Paragonimus'' is a genus of flukes (trematodes) and is the only genus in the monotypic family Paragonimidae. Some tens of species have been described, but they are difficult to distinguish, so it is not clear how many of the named species may b ...

lung fluke parasites. The

miracidia Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing sec ...

reproduce asexually through sporocyst stages within these

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

s, resulting in the production of many free-swimming

cercariae Trematodes are parasitic flatworms of the class ''Trematoda'', specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secr ...

.Riley S, Carabin H, Bélisle P, Joseph L, Tallo V, et al. (2008). "Multi-Host Transmission Dynamics of ''Schistosoma japonicum'' in Samar Province, the Philippines". ''

PLoS Medicine ''PLOS Medicine'' (formerly styled ''PLoS Medicine'') is a peer-reviewed weekly medical journal covering the full spectrum of the medical sciences. It began operation on October 19, 2004, as the second journal of the Public Library of Science (PLO ...

'' 5(1): e18. .

References

This article incorporates CC-BY-2.0 text from the reference and CC-BY-2.5 text from the referenceZhao Q. P., Jiang M. S., Littlewood D. T. J. & Nie P. (2010). "Distinct Genetic Diversity of ''Oncomelania hupensis'', Intermediate Host of ''Schistosoma japonicum'' in Mainland China as Revealed by ITS Sequences". '' PLoS Neglected Tropical Diseases'' 4(3): e611. . {{Taxonbar, from=Q5225925 Pomatiopsidae