Conchological variation in Pomacea canaliculata and other South American Ampullariidae (Caenogastropoda, Architaenioglossa).

Pomacea canaliculata (Lamarck, 1822) is a freshwater snail belonging to the family Ampullariidae, a taxon that includes Asian, African and American species collectively known as apple snails. P. canaliculata ranges from the Amazonas Basin (Brazil) to Tandilia and Ventania Mountain systems (Buenos Aires province, Argentina) and is the most widely studied snail in Argentina, being the object of different morphological, anatomical, ecological, embryological and taxonomical studies (Catalán et al., 2002; Castro-Vazquez et al., 2002; Estebenet and Martín, 2002; Cazzaniga, 2002; Heras and Pollero, 2002). International concern about P. canaliculata rose enormously when it became established as a serious rice pest in Asia (Cowie, 2002). Asian pest managers were very much troubled with the identification of the invading apple snails (Wada, 1997), a task seriously complicated by the multiple origin of invaders and their great morphological and ecophysiological variability (Cowie, 2002; Estebenet and Martín, 2002, 2003; Martín and Estebenet, 2002). Although already recognized by d’Orbigny (1835-1846), the wide conchological variation of P. canaliculata has been seldom quantitatively studied and most studies on the subject were performed in a restricted area (Buenos Aires province) in the southern area of its natural distribution (Cazzaniga, 1990; Estebenet, 1998; Estebenet and Martín, 2003). The shell of P. canaliculata has been described as globose to subglobose, with a low spire and an oval aperture; the color of the shell is brown-green, showing several dark spiral bands of variable width and transverse growth lines (Castellanos and Fernández, 1976). The operculum is corneous with concentric growth lines around an excentric nucleus. Most of these traits, and many others, show a great influence of ontogenetic, sexual, genetic and ecophenotypic components, which give place to an important intraand interpopulation variation. The aims of our study are to describe and analyze the variation and the origin of P. canaliculata shell traits, and to compare them with the information available for other Neotropical Ampullariids, focusing mainly on quantitative or experimental studies. ✝ Deceased October 1 2005