Apple Snail

Ampullariidae, common name the apple snails, is a family of large freshwater snails, aquatic gastropod mollusks with a gill and an operculum. This family is in the superfamily Ampullarioidea and is the type family of that superfamily.[4]

The Ampullariidae are unusual because they have both a gill and a lung, the mantle cavity being divided in order to separate the two types of respiratory structures. This adaptation allows these snails to be amphibious.

Apple snails are exceptionally well adapted to tropical regions characterized by periods of drought alternating with periods of high rainfall. This adaptation is reflected in their life style; they are moderately amphibious. They have an operculum which enables the snail to seal the shell entrance to prevent drying out while they are buried in the mud during dry periods.

One of the more typical adaptations of apple snails is the branchial respiration. The snail has a system comparable to the gills of a fish (at the right side of the snail body) to breathe under water as well as a lung (at the left side of the body) to respirate air. This lung/gill combination expands the action radius of the snail in search for food. It is part of the snail's natural behaviour to leave the water when the food supply below the surface becomes inadequate.

Pomacea canaliculata eggs.

Several apple snail genera (Pomacea, Pila and Asolene/Pomella) deposit eggs above the waterline in calcareous clutches. This remarkable strategy of aquatic snails protects the eggs against predation by fish and other aquatic inhabitants. Another anti-predator adaptation in the apple snail genera Pomacea and Pila, is the tubular siphon, used to breathe air while submerged, reducing vulnerability to attacking birds. The apple snail's usual enemies are the birds Limpkin and Snail Kite.

Apple snails inhabit various ecosystems: ponds, swamps and rivers. Although they occasionally leave the water, they spend most of their time under water. Unlike the pulmonate snail families, apple snails are not hermaphroditic, but gonochoristic; i.e. they have separate genders. 

       

Apple snails are popular aquarium pets because of their attractive appearance and size. When properly cared for, some apple snail species can reach 15 cm (5.9 in) diameter. Apple snails include species that are the biggest living freshwater snails on Earth.

The most common apple snail in aquarium shops is Pomacea bridgesii, also called Pomacea diffusa, (the spike-topped apple snail). This species comes in different colours from brown to albino or yellow and even blue, purple, pink, and jade, with or without banding. Another common apple snail is Pomacea canaliculata; this snail is bigger, rounder and is more likely to eat aquatic plants, which makes it less suitable for most aquaria. This species can also have different shell and body colours. The "giant ramshorn snail" (Marisa cornuarietis) although not always recognized as an apple snail due to its discoidal shape, is also a popular aquatic pet. Occasionally, the Florida apple snail (Pomacea paludosa) is found in the aquarium trade and these are often collected in the wild from ditches and ponds in Florida. The giant Pomacea maculata is rarely used as an aquarium species.

Apple snails are often sold under the name "golden (ivory, blue, black...) mystery snail" and they are given incorrect names like Ampullarius for the genus instead of Pomacea and wrong species names like gigas instead of maculata.

These snails sometimes become inactive (especially when first introduced to a new tank, probably from the stress of moving from one habitat to another), and may not move for several days, but once the snail is acclimated it becomes active again.