Effects of submersion and aerial exposure on clutches and hatchlings of Pomacea canaliculata (Gastropoda: Ampullariidae).

PIZANI, NATALIA; ESTEBENET, ALEJANDRA; MARTÍN, PABLO

American Malacological Bulletin

American Malacological Society

Año: 2005 vol. 20 p. 55 - 63

Pomacea canaliculata is a neotropical freshwater snail that has invaded many countries around the world, becoming a serious pest of rice and a menace to native snails. In southern Pampas (Argentina) from early spring to late fall females deposit aerial clutches composed of hundreds of calcareous eggs on emergent substrates. Local bodies of water undergo frequently fluctuations in water level, resulting in extensive submersion of clutches or dropping of hatchlings out of water. The effects of aerial exposure on hatchlings and of submersion on development were analyzed experimentally. The submersion of the egg masses of P. canaliculata increased the duration of development up to approximately 50% and caused a decrease of up to 32% in hatching rate. The calcareous capsule, large size, and dense packaging of eggs probably impede an adequate oxygen supply to embryos when submersed or may interfere with the hatching mechanism. The embryos were unable to develop completely and to hatch under water. Submersion frequently caused the disintegration of newly laid clutches and the premature hatching of eggs in late stages of development, resulting in hatchlings with underdeveloped bodies. Aerial exposure of hatchlings, under conditions similar to those occurring in the field in midsummer, killed 99% after only four days, irrespective of the presence or absence of moist soil. During droughts of several consecutive years recruitment could be seriously affected.