Habitat Top
Apple snails inhabit a wide range of ecosystems from swamps, ditches and ponds to lakes and rivers. Not every species has similar preferences. However, most apple snails prefer lentic waters above turbulent water (rivers). Click here to see a photograph of the natural habitat of Pomacea canaliculata (province of Buenos Aires, Argentina).
The lung/gills combination reflects an adaptation to oxygen poor water conditions often present in swamps and shallow water. Oxigen is reduced by to decay of organic materials like dead vegetation and high temperatures. Their lung prove very useful to survive in these harsh conditions.
The shell door (operculum) / lung combination increases the ability to survive periods of drought not uncommon in swamps and small ponds in dry seasons. The snails bury themselves into the substrate decrease their metabolism and enter a period of aestivation. Some genera like Felipponea and Asolene in South America and some Pila species in Asia have thick and heavy shells as adaptation to streaming habitats.
One thing all apple snail have in common: the need (sub-)tropical temperatures (also see the map at the species section). No Ampullarriidae species survives in area's were the temperature drops below 10°C in the winter months.
Respiration isn't the only function of the lung, it also enables the snails to adjust the buoyancy level (floating level). Without a filled lung, the gracious movements of the snails under water would be impossible. The weight of the shell would let them sink to the bottem like a stone. When the oxygen tension of the water drops and the snails are forced to use aerial respiration, apple snails often start to float to remain at the surface.
Food
Apple snails are not selective and eat almost everything available in their environment. In general they prefer soft and digestible vegetation. Tougher plants and algae are consumed as long as they are able to grasp pieces of with their radula (rasp tongue). Although the radular system is nearly identical throughout the different species, some have stronger and larger teeth on the radula than others. The species with thin and small teeth (like Pomacea diffusa) are unable to penetrate the tougher vegetation and specialise in death and soft plants. When there is not enough food available in the water, apple snails can profit from their amphibian life style to leave the water in search for food.