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Pomacea Perry, 1810

Diagnostic features

Large to very large globose smooth shells, sutures channelled (Pomacea canaliculata) or with the top of the whorl shouldered and flat at the suture (Pomacea diffusa). Shells umbilicate with unthickened lip. Uniform yellow to olive green with darker spiral bands. Interior of aperture orange to yellow. Operculate, with concentric operculum.

Animal with distinctive head-foot; snout uniquely with a pair of distal, long, tentacle-like processes; cephalic tentacles very long. A long 'siphon' is also present.

Classification

Pomacea Perry, 1810

Class Gastropoda

Subclass Caenogastropoda

Order Architaenioglossa

Superfamily Ampullaroidea

Family Ampullariidae

Type species: Pomacea maculata Perry, 1810

Original reference: Perry, G. 1810-1811. Arcana; or the Museum of Natural History, 84 pls., unnumbered with associated text. Issued in monthly parts, pls.[1-48] in 1810, [49-84] in 1811. Stratford, London.

Type locality: Rio Parana, Argentina.

Biology and ecology

Amphibious, on sediment and weeds etc. Lays pink coloured egg masses on plants etc. above the waterline.

Distribution

Native to North and South America but some species have been introduced around the world through the aquarium trade (Pomacea diffusa) and as a food source (Pomacea canaliculata). Pomacea diffusa has been reported from the Ross River in Townsville in NE Queensland, and from freshwater waterbodies in the greater Brisbane area, Ipswich and Urangan near Maryborough in SE Queensland. 

Notes

This genus is widely known in the aquarium trade through the so-called mystery snail, Pomacea diffusa. In countries such as the Philippines, Hawaii and parts of SE Asia, the species Pomacea canaliculata (Lamarck) is a serious pest of rice crops. Introduction of this species to the wild could result in a serious pest problem. Any sightings of this species in the wild should be reported to the Biosecurity authority or to the Australian Museum Malacology Section.

Two south Asian ampullariid species of the genus Pila have sometimes been intercepted by Australian Biosecurity – they are Pila ampullacea (Linnaeus, 1758) and Pila globosa (Swainson, 1822).

The genus Pila differs from Pomacea in the following respects:

The shells of Pila tend to have less elevated and less pointed (blunt) spires compared to Pomacea

Pila species both have rounded whorl shoulders with slightly indented sutures. The whorl shoulders of Pomacea diffusa are flat topped while the whorl shoulders of P. canaliculata are rounded with deeply indented sutures.

Pila ampullacea has a narrow to almost closed umbilicus while Pila globosa has an open, large and deep umbilicus. Both Pomacea species have an open and deep umbilicus.  

The operculum of Pila is horny on the outside and calcified on the inside while in Pomacea the whole operculum is horny.

The siphon (breathing tube) of Pila is shorter than that of Pomacea

The eggs of Pila are white and calcareous and laid above the water line on banks and mudflats in shallow depressions, while Pomacea eggs are soft and pink and laid on plants and upright surfaces just above the waterline.

Pila species aestivate by burying in mud during the dry season while Pomacea do not.

Pila are well adapted to living in ephemeral waterbodies while Pomacea generally inhabit permanent freshwater areas.

Pila originate from south Asia and Africa while Pomacea comes from the Americas.

Pila are an important food source in South Asia while Pomacea are generally not eaten.

Pila are generally not considered pest species while Pomacea canaliculata is a major crop pest.

Further reading

Cowie, R. H. (2002). Apple Snails (Ampullariidae) as Agricultural Pests: their Biology, Impacts and Management. Pp. 145-192 in G. M. Barker. Molluscs as Crop Pests. Wallingford, UK, CAB International.

Cowie, R. H. (2005). The Golden Apple Snail: Pomacea species including Pomacea canaliculata (Lamarck, 1822) (Gastropoda: Ampullariidae). Diagnostic standard. Report to Plant Health Australia. 38 p. http://www.planthealthaustralia.com.au/wp-content/uploads/2013/03/Golden-apple-snail-DP-2005.pdf

Cowie, R. H. & Thiengo, S. C. (2003). The Apple Snails of the Americas (Mollusca: Gastropoda: Ampullariidae: Asolene, Felipponea, Marisa, Pomacea, Pomella): A nomenclatural and type catalogue. Malacologia 45: 41-100.

Mochida, O. (1991). Spread of freshwater Pomacea snails (Pilidae, Mollusca) from Argentina to Asia. Micronesica Supplement 3: 51-62.

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.

Perera, G. & Walls, J. G. (1996). Apple snails in the aquarium. T.F.H. Publications, Inc., Neptune City, New Jersey.

Simone, L. R. L., 2004. Comparative morphology and phylogeny of representatives of the superfamilies of architaenioglossans and the Annulariidae (Mollusca, Caenogastropoda). Arquivos do Museu National 62: 387-504.

The Apple Snail website: http://www.applesnail.net