Synonyms for Pomacea (Perry 1810) are Ampullarius (Lamarck
1799) and Conchylium (Cuvier 1816).
The New World genus Pomacea inhabits a large geographical area from the southern of the USA to the La Plata Bassin in Argentina.
Over 100 species are described in the genus Pomacea since 1758. However, the validity of many species is doubtfull and in reality the number of species is much lower. The problem with the taxonomy in Pomacea is thea most species descriptions are based on only a few shells, without a decent detailed anatomical study to descriminate between species. Also the authors often did not take in account the geographical distribution and possible variability within on a single species. A good example of this is the flagellata complex: over 30 species have been described, while nowadays, they are all considered to be varieties of a single species, eventually with 4 sub-species.
Many authors attempted to reduce the number valid species and tried to reclassify similar species into single species. At present, about 50 nominal species are known, but even this number is likely higher than the actuall number in the field. The inevitable question here is: "How do you define a species?". In the old-style conchology, it was not uncommon to classify every variation as a new species. This completely neglects species variability and genetic relationships.
Current insights in genetics, evolution and species variability require an new approach in which new techniques are used to address the classification of the Pomacea genus. This implies the use of DNA and chromosome studies, comparing internal morphology, interbreeding experiments, immunological test and a more statistical based analysis of available data.
The newest insights reduce the number of actuall species and subdivides the Pomacea genus in several clades. Within these clades, several groups are recognized, consisting of species that are very similar and might eventually turn out to be a single species. Below is an overview of the new classification of the Pomacea genus. Keep in mind that this is a hypothesis and is subject to changes.
One of teh lmost striking changes are the recognition that Pomacea bridgesii actually consist of two different species: Pomacea bridgesii (Reeve, 1856) and diffusa (Blume, 1957). This is based on mitochondrial DNA analysis. The effect of this changes is that the common spike-topped apple snail in the aquarium trade should now be considered to be Pomacea diffusa (Blume, 1957).
|Genus||sub-genus||Species or species clade|
|Pomacea||effusa||glauca clade||Pomacea (effusa) glauca (Linné, 1758)|
|Pomacea (effusa) cumingi (Reeve, 1843)|
|pomacea||canaliculata - insularum clade||Pomacea (pomacea) canaliculata (Lamarck, 1819)|
|Pomacea (pomacea) insularum (D'Orbigny, 1839)|
|Pomacea (pomacea) lineata (Spix, 1827)|
|Pomacea (pomacea) gigas / maculata (Perry, 1810)|
|flagellata clade||Pomacea (pomacea) flagellata (Say, 1827)|
|Pomacea (pomacea) livescens (Reeve, 1856)|
|Pomacea (pomacea) erogata (Fisher & Crosse, 1890)|
|Pomacea (pomacea) dysoni (Hanley, 1854)|
|diffusa (bridgesii) - haustrum clade||Pomacea (pomacea) diffusa (Blume, 1957)|
|Pomacea (pomacea) bridgesii (Reeve, 1856)|
|Pomacea (pomacea) haustrum (Reeve, 1856)|
|Pomacea (pomacea) scalaris (D'Orbigny, 1835)|
|Pomacea (pomacea) columellaris (Gould, 1848)|
|Pomacea (Pomacea) decussate (Moricand)|
|Pomacea (pomacea) paludosa (Say, 1829)|
|Pomacea (pomacea) catamarcensis (Sowerby, 1874)|
|Pomacea (pomacea) cyclostoma (Spix, 1827)|
|Pomacea (pomacea) papyracea (Spix, 1827)|
|Pomacea (pomacea) hanleyi (Reeve, 1856)|
|Pomacea (pomacea) urceus (Müller, 1774)|
For a good review articles about the taxonomy of the Pomacea canaliculata groups, check out these references:
Want to identify an apple snail of the Pomacea genus?
There is no complete identification guide available in the literature.
Keep in mind that many species described, might be different forms of a single species. Many descriptions of species are based solely on only a few, empty shells. Colour, banding and shell surface (rough, smooth etc.) are no good identification points as these might vary a lot within a single species. An example of this variation of shell colour can be seen at the Pomacea canaliculata pictures. The height of the spine/body whorl isn't a reliable determinant (especially when having only a few snails available) either as this can differ as well within one species.
For the snails of the Pomacea canaliculata group, it's quite hard to distinguish the species as the external differences are subtle and the variation within species is high. A possible way do distinguish these snails is the colour of the eggs*:
|Pomacea (pomacea) canaliculata (Lamarck, 1819)||Bright orange|
|Pomacea (pomacea) insularum (D'Orbigny, 1839)||Pink|
|Pomacea (pomacea) lineata (Spix, 1827)||Pink|
|Pomacea (pomacea) doliodes (Reeve, 1856)||Pink|
|Pomacea (pomacea) haustrum (Reeve, 1856)||Green|
|Pomacea (pomacea) gigas / maculata (Perry, 1810)||Green|
* This is based on reported egg colours, and it could well be that even the egg colour varies withing one species. Also the food composition, the development stage of the eggs and the humidity of the air can affect the egg colour.
Species according the 'old' classification system:
Synonyms are marked light-grey, doubtfull and uncertain species are marked grey.
Characteristics of the genus Pomacea:
|Shell:||surface:||smooth to rough (growth lines), sometimes malleation|
|shape:||cone-shaped, ovoid to almost discoidal|
|umbilicus:||narrow to wide|
|colour:||yellow, dark brown to almost black, with or without spiral bands|
|Body:||head (cephalic) tentacles:||long|
|breathing siphon:||long (2.5 times body length)|
|colour:||grey to yellow-grey with or without darker spots|
|Eggs:||above the waterline|
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