Abstract
The karyotypes of four species of freshwater triclads of the genus Girardia (Platyhelminthes), i.e. G. schubarti, G. tigrina, G. anderlani, and G. biapertura, from populations of different localities of the Rio Grande do Sul State, in southern Brazil, were analyzed. The karyotype of G. biapertura is presented for the first time. Three basic complements of 4, 8, and 9 chromosomes were found. Diploids, triploids, or mixoploids (2n/3n) specimens were frequently detected in these populations. The basic chromosomal complement of n=9 was verified in two different species (G. biapertura and G. anderlani), presenting a large acrocentric chromosome which is rare in the family Dugesiidae. An intra and interspecific chromosomal variability was also detected and its evolutionary implications are discussed.
Highlights
Systematic cytogenetic research concerning species of the genus Girardia (Dugesiidae) in south Brazil date from the 1970’s (Pereira, 1970; Kawakatsu et al, 1981, 1983, 1984)
From the six known species occurring in the Brazilian southern region, only Girardia schubarti (Marcus, 1946), Girardia tigrina (Girard, 1850), and Girardia anderlani (Kawakatsu and Hauser, 1983) were studied from a cytogenetic point of view (Pereira, 1970; Kawakatsu et al, 1981, 1983, 1984)
The purpose of this research was to analyze the karyological components of four freshwater planarian species from the northeast region of the Rio Grande do Sul State, (Southern Brazil), with the objective to recognize chromosome morphology including inter and intra species variability
Summary
Systematic cytogenetic research concerning species of the genus Girardia (Dugesiidae) in south Brazil date from the 1970’s (Pereira, 1970; Kawakatsu et al, 1981, 1983, 1984). From the six known species occurring in the Brazilian southern region, only Girardia schubarti (Marcus, 1946), Girardia tigrina (Girard, 1850), and Girardia anderlani (Kawakatsu and Hauser, 1983) were studied from a cytogenetic point of view (Pereira, 1970; Kawakatsu et al, 1981, 1983, 1984). Except for the data on a few populations of G. schubarti (Kawakatsu et al, 1984), little is known about the intraspecific cytogenetic variability in Brazilian Dugesiidae. Biol., 67(4, Suppl.): 951-955, 2007 known and the method used in earlier studies for chromosome dispersion (“squash” method) did not yield the best results to analyze the chromosome morphology
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