Pomacea (pomacea) bridgesii (Reeve, 1856) Synonym (obsolete): Ampullarius australis

Pomacea bridgesii is known in two varieties in the wild, which could turn out to be two different species. The rare Pomacea bridgesii bridgesii subspecies (Reeve, 1856), which is only known from the Rio Grande, Reyes River at Beni (bridges) and the Pomacea bridgesii diffusa subspecies (Blume, 1957), which inhabits almost the entire Amazon river system.
Pomacea bridgesii bridgesii is rather large (65mm shell height and more), while Pomacea bridgesii effusa is much smaller, has a much more pronounced spire and a darker shell colour. The bridgesii snails, available in the aquarium trade are Pomacea bridgesii effusa snails and eventually this these snails could turn out to be Pomacea effusa instead of a subspecies from Pomacea bridgesii.

Pomacea bridgesi or Pomacea bridgesii?
In the original description of this Pomacea species, Reeve (Conchologica Iconica, X, plate 3. August 1856) appearantly intented to name the snail as "the ampullaria from Bridges" or "Bridges's ampullaria". Because species are given a Latin name, Bridges was seemingly translated to bridgesius prior to conjugation and thus the name became: "Ampullaria bridgesii".

Shell: The shell of this apple snails species has about 5 to 6 whorls. The most obvious characteristic of the shell are the square shoulders (flat at the top of the whorls) and almost 90° sutures. The shell opening (aperture) is large and oval, the umbilicus is large and deep.
The size of the shell varies from 40-50 mm wide and 45-65 mm high. The spire is high and sharp, hance the often used name: spike-topped apple snail.
The colour varies from yellow, green to brown, with or without dark spiral bands (a lot of variations exists). Due to cultivated mutations white and blue variations are obtained in recent years. The yellow variation is well known in the aquarium trade as the golden mystery snail. This variation was originally generated in Florida (U.S.A.) and has then spread in the aquarium trade. The white variations are sometimes called the ivory snail in the aquarium world.

'Shell colour genes' section (interactive page to learn more about the colour genes in Pomacea bridgesii.

Interactive 3D-models (Java): - Pomacea bridgesii shell

Operculum: The operculum is moderately thick and corneous. The structure is concentric with the nucleus near the centre of the shell. The colour of the operculum varies from light to dark brown. The operculum can be retracted in the aperture (shell opening). 
Body: As with the shell, many variations exist: from light yellow (cultivated) to almost black with yellow spots on the mouth.

Shell of a dark wild-form Pomacea bridgesii snail.	Shell of a dark wild-form Pomacea bridgesii snail, back view.	Almost white variant of Pomacea bridgesii, also called the ivory snail.
Shell and operculum, young snail. Note the 90° sutures and flat upper part of the whorls, typical of Pomacea bridgesii.	Shell of Pomacea bridgesii, view of the inside to illustrate the shell construction.	Pomacea bridgesii, yellow (golden) variant. Note the flat top of the whorls.
Yellow-black apple snail (Pomacea bridgesii). This colour variant lacks the brown colour of the shell, so the yellow base colour shines through.	Blue apple snail (Pomacea bridgesii). The shell is in fact white, but the black body of the snail shines through as blue.	Pomacea bridgesii variant with banded (brown) shell.
Red-yellow variety of Pomacea bridgesii. This colour variant lacks the yellow base colour of the shell, so the purple-reddish bands are left without their yellow pigment, which normally makes the brown.	Pomacea bridgesii, wildtype colours.

Eggs: The pale pink to reddish eggs are deposited above the waterline and are closely attached to each other. Their size varies from 2.20 to 3.5 mm (0.5 to 0.9 inch) diameter. An average egg-clutch contains 200 to 600 eggs.

Eggs, Pomacea bridgesii, 3 days old.

Young Pomacea brigesii snails. (picture not licenced under creative commons)

Food: Prefers dead and rotting plants and artificial foods like fish food; doesn't eat healthy plants unless no other food is available. This makes the Pomacea bridgesii snail a good choice for planted aquaria.
Behaviour: moderately amphibious animal; relatively inactive during the day; can often be found on the bottom where it's searching for food or remains hidden in the mud; most activity during the night.
Distribution: Pomacea bridgesii effusa: Widely distributed throughout the Amazon river system (Bolivia, Brazil, Paraguay and Peru). Pomacea bridgesii bridgesii: rare species only reported at Rio Grande, Reyes River at Beni.
In the 1960s Pomacea bridgesii effusa has been introduced to Hawaii and in the 1980s it has spread to south-east Asia. In the early 1980's Pomacea bridgesii effusa established in Florida, USA.
Common in the aquarium trade, especially the yellow variation.
Similar to: Pomacea bridgesii looks similar to more Pomacea scalaris, to which it's probably close related to. In Pomacea scalaris, the shell shoulder is much more angulated, in such extent that it almost carinated. Pomacea scalaris lives more to the south (Argentina and South Brasil). However Reeve (1856) described Bolivia as habitat of Pomacea scalaris as well.
It could make sense to group Pomacea bridgesii and Pomacea scalaris into one group as T. Pain already did 1960.

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