Colonization of Fresh Waters in the Republic of South Africa by Lymnaea columella Say (Mollusca : Gastropoda)

Lymnaea (Pseudosuccinea) columella Say 1817, described from specimens probably obtained in the vicinity of Philadelphia1, is widely distributed in still and slow-flowing waters in the eastern United States of America, Mexico, Central America, Cuba and the northern and central regions of South America1,2. Fossil specimens are known from the Pleistocene of North America, and another species of the sub-genus has been described from the Pliocene of the same region3. L. columella is believed to have been introduced by human agency, probably with aquatic plants, into Puerto Rico, Tenerife, South Africa and many European countries4.