Family Pilidae

2008/07/20 07:24:27.805 GMT-4

The Pilidae are a tropical family. The Pilidae [synonym Ampullariidae] are peculiar because they have both gills and lung, the mantle cavity being divided to separate the two types of respiratory structures. Basically aquatic snails, the lung probably arose because of the snails' habitats - living in shallow water habitats that dry out for part of the year. Pilid snails have a siphon for taking in air when submerged.

Because of their relatively large size, pilid snails serve as human food in much of their area of distribution. Because they are often preferred to be eaten raw, they mediate a serious disease in Southeast Asia, angiostrongyliasis or eosinophilic meningoencephalitis, caused by the rat lung worm (Angiostrongylus cantonensis).

Pila ampulacea, from Thailand.

Pomacea paludosa. The common name for pilids such as those from the genera Pila and Pomacea is "apple snails." They get this name because of their size, globosity and often green color similar to many apples.

Pomacea canaliculata from Thailand. Pomacea canaliculata is a freshwater snail native to Argentina. It was transported to Asia as a proposed food source because it reproduces much faster than the local Apple Snails, species of the genus Pila. However, the local Asians, not liking the taste and consistency of Pomacea meat, preferring Pila instead, discarded their Pomatia snails into local ditches, streams and ponds. Unfortunately, Pomacea is a voracious eater of young rice seedlings, whereas Pila is not. So far there is no control for Pomacea in Asia.

The snail shown here is in the process of laying eggs, which have a distinctive pink color. Both Pomatia and Pila lay their eggs out of water. The eggs of Pila are white.

Pomacea canaliculata is yellow in color (both shell and animal), but its common name in Asia comes from it being called the "golden snail" by the Philippine government when they introduced it - "gold in your own back yard," referring to the cottage industry they had hoped to initiate.

A closer view of Pomacea canaliculata laying eggs. The shell of this specimen is covered with a black pond-water deposit.

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Lanistes sp., from Egypt.The great majority of the gastropods are dextral, i.e., the shells and underlying viscera coil to the right. A few families, genera and species are sinistral (coil to the left). Lanistes is a sinistral genus in an otherwise dextral family. Note the very long, thin tentacles, the thin, elongated anterior foot corners, and the eye on a short peduncle.

Marisa is a discoidal genus in an otherwise higher-spired family. Seen here is the spire view of the shell. This South American species has been used in the Western Hemisphere and on the African continent in attempts at biological control of snail hosts of human trematodes.

This is an apertural view, showing the discoidal nature of the species. Note the concentric operculum closing the shell aperture.

2008/07/20 07:25:13.318 GMT-4