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Oncomelania spp.

Diagnostic features

The shell is tall spired and some forms develop axial ribs. The aperture is reflected and bears an external varix.

Classification

Oncomelania  

Class Gastropoda

Subclass Caenogastropoda

Order Littorinimorpha

Superfamily Truncatelloidea

Family Pomatiopsidae

Subfamily: Pomatiopsinae

Genus Oncomelania Gredler, 1881

Type species: Oncomelania hupensis Gredler, 1881.

Original reference: Gredler, V. (1881). Zur Conchylien- Fauna von China. Jahrb. Deutsch. malakoz. Ges. 8: 110-132.

Type locality:  U-tschang-fu, China (found in Yangtze River drainage).

Biology and ecology

This is a seasonally amphibious species which lives in lakes, rivers, marshes and rice paddies. Sexes are separate, with males (5mm length) smaller than females (6mm length). O. hupensis  start to lay eggs within 2 to 3 months of copulation. Adulthood is reached 1 to 2 months after hatching.

Distribution

This subspecies we have chosen to illustrate occurs in the Philippines. Several other subspecies of O. hupensis occur in other parts of Asia (China, Taiwan) (see below).

Notes

These freshwater snails are of medical significance as it can serve as a vector for the blood fluke Schistosoma japonicum that causes schistosomiasis and the lung fluke parasite Paragonimus.

Several species of Oncomelania are recognised including:

O. hupensis Gredler, 1881. This is often treated as a polytypic species with several subspecies: O. h. quadrasi (Möllendorff, 1895) (Philippines) and O. h. hupensis and several others from China and Taiwan.

O. h. quadrasi is sometimes recognised as a distinct species. There are others that are usually treated as separate species including O. minima Bartsch, 1936 and two other species from Japan, and O. lindoensis Davis & Carney, 1973 from Lake Lindu, Sulawesi.

Species of Oncomelania have not yet been recorded from Australia but it is mentioned here in the event it could reach this country.

Oncomelania is closely related to Pomatiopsis from North America.

Further reading

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 Monographs 20: 1-120.

Davis, G. M., Zhang Y., Guo, Y. H. and Spolsky, C. M. (1995). Population genetics and systematic status of Oncomelania hupensis (Gastropoda: Pomatiopsidae) throughout China. Malacologia 37: 133–156.

Garcia, R. G. (1972). Tolerance of Oncomelania hupensis quadrasi to varying concentrations of dissolved oxygen and organic pollution. Bulletin of the World Health Organization 47: 59.

Hope, M. & McManus, D. P. (1994). Genetic variation in geographically isolated populations and subspecies of Oncomelania hupensis determined by a PCR-based RFLP method. Acta Tropica 57: 75-82.

Legaspino, R. T., Metillo, E. B., & Claveria, F. G. (2014). Distribution of Oncomelania quadrasi (Mollendorf 1895) and prevalence of infected snails in schistosomiasis endemic villages of Kapatagan and Lala, Lanao del Norte, Philippines. International Journal of Ecology and Conservation 11: 87-109.

Li Hsü, S. Y. & Hsü, H. F. (1960). Infectivity of the Philippine strain of Schistosoma japonicum in Oncomelania hupensis, O. formosana and O. nosophora. The Journal of parasitology 46: 793-796.

Ng, T.H., Tan, S.K., Wong, W.H., Meier, R., Chan, S-Y., Tan, H.H. and Yeo, D.C.J. 2016. Molluscs for Sale: Assessment of Freshwater Gastropods and Bivalves in the Ornamental Pet Trade. PLOS One. DOI:10.1371/journal.pone.0161130.

Wilke, T., Davis, G. M., Cui-E, C., Xiao-Nung, Z., Peng, Z. X., Yi, Z. & Spolsky, C. M. (2000). Oncomelania hupensis (Gastropoda: Rissooidea) in eastern China: molecular phylogeny, population structure, and ecology. Acta Tropica 77: 215-227.

Wilke, T., Davis, G. M., Qiu, D. C. & Spear, R. C. (2006). Extreme mitochondrial sequence diversity in the intermediate schistosomiasis host Oncomelania hupensis robertsoni: another case of ancestral polymorphism? Malacologia 48: 143-157.

Zhao, 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: e611 (611-619).