Key to Australian Freshwater and Terrestrial Invertebrates

Phylum Mollusca
Class Gastropoda
Informal group Architaenioglossa
Superfamily Ampullarioidea
Family Ampullariidae

Common names: apple snails, ampullariids

Overview

Ampullariidae, the only extant family in the superfamily Ampullarioidea, are large amphibious freshwater snails. Ampullariids have the mantle cavity divided to separate the two types of respiratory structures: gills to breathe under water (at the right side of the snail body) and a lung to respirate air (at the left side of the body). They have a calcareous operculum that is typically circular. The eyes are borne on slightly raised ocular peduncles at the bases of the cephalic (head) tentacles. Ampullariids are the biggest freshwater snails with the largest species growing up to 15 cm in diameter. Shells are globose and may or may not be banded and are typically dull green to brown in colour, however specimens may range in colour from black, brown or grey to white, yellow, blue and green.

Distribution and diversity

Ampullariidae are tropical and subtropical snails that occur in the Americas, the West Indies Africa, and Asia. The family is divided in 7 (or 10, depending of the classification followed) genera with around 120 species. However, it is very likely that new research will considerably reduce the number of species. Ampullariidae are not native to the Australasia region but two invasive New World species are present in Queensland and northern Western Australia: Pomacea bridgesi and P. canaliculata, with the latter also invasive across the South Pacific.

Life cycle

Sexes are separate and fertilisation is internal. Depending on the species, females either lay gelatinous egg masses in the water on plants or stones while others deposit eggs above the waterline in calcareous clutches on the stem of emergent aquatic vegetation, a trunk, a rock or on the ground from which juvenile snails hatch. Some species have an aestivation period, hiding in the mud.

Feeding

Ampullariidae are opportunistic generalist feeders generally preferring soft and digestible vegetation but will also consume tougher plants and algae. They will also scavenge dead and rotting plant material and dead animals such as fish, frogs, crustaceans and insects. Many species are also known to predate on other snails and the aquatic eggs of fish, frogs and snails. When the food supply below the surface becomes inadequate Ampullariids, due to their lung/gill respiration, can leave the water in search for food.

Ecology

Ampullariidae occur in temporary and still or slow-moving permanent water bodies such as ponds, ditches, swamps, rivers and lakes. They are typically submerged, often amongst vegetation or buried in soft sediments near water margins and the surface. They can endure harsh environmental conditions, such as low water levels, extreme temperatures or lack of food, by burying themselves in the sediment and closing their operculum. The lung/gill combination also enables ampullariids to survive out of water or in low oxygen conditions typical of swamps and shallow water. The larger, brightly coloured Pomacea spp. are popular freshwater aquarium pets (�golden�, �apple� or �mystery snails�). Pomacea canaliculata is ranked in the top 100 of the world�s worst invasive species. Over the last 20 years it has become a serious rice pest in south-eastern Asia and there are similar concerns for Australian rice growers. The snail also alters the diversity and function of invaded natural wetlands.

Pomacea bridgesii, an introduced species in Australia
Image credit: Felipe Miguel
used under a Creative Commons Attribution-NonCommercial-ShareAlike license

Pomacea bridgesii, an introduced species in Australia, showing the radula
Image credit: bored-now
used under a Creative Commons Attribution-NonCommercial-NoDerivs license