title: Biogeography and karyotypes of freshwater planarians (Platyhelminthes, Tricladida, Paludicola) in southern Brazil.
abstract: In the Tricladida (Platyhelminthes), the incidence of different biotypes identified by several ploidy levels is very common. Planarians collected in the State of Rio Grande do Sul were identified using cytogenetics. Different species distributions were observed with respect to Rio Grande do Sul's geomorphology, which could have been caused by their different microhabitats. Girardia tigrina and G. anderlani consisted of diploid and triploid individuals, whereas G. schubarti showed diploids, triploids, and mixoploids; for all these species, individuals of different ploidies were sympatric. Only for diploid G. anderlani were B chromosomes observed. These B chromosomes seem to have an irregular segregational behavior during mitosis, and possibly also during meiosis. However the processes (e.g., selection, mutation) of maintaining 2n, 3n, and 2n/3n individuals within natural populations of G. schubarti remain to be clarified.
authors.affiliation: Programa de Pós-Graduação em Genética e Biologia Molecular. Universidade Federal do Rio Grande do Sul, Porto Alegre-RS, Brasil. tanisek@cbiot.ufrgs.br
authors.forename: Tanise
authors.initials: T
authors.lastname: Knakievicz
authors.forename: Adriana Helena
authors.initials: AH
authors.lastname: Lau
authors.forename: Daniel
authors.initials: D
authors.lastname: Prá
authors.forename: Bernardo
authors.initials: B
authors.lastname: Erdtmann
mesh_terms: D000818:Animals; D001938:Brazil; D002875:Chromosomes / Q000737:chemistry*; D019143:Evolution, Molecular; D005618:Fresh Water; D007621:Karyotyping; D010932:Planarians / Q000145:classification* / Q000235:genetics*; D011003:Ploidies