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Nucleolar organizer region in three species of the genus Biomphalaria(Mollusca, Gastropoda)

Toshie Kawano; Luiz Carlos Gomes Simões; Lurdes Foresti de Almeida Toledo

Departamento de Biologia, Instituto de Biociências, Universidade de São Paulo, Caixa Postal 11461, Cidade Universitária, 05499 São Paulo, SP, Brasil. Send correspondence to L.C.G.S.

ABSTRACT

The karyotypes of three species of the genus Biomphalaria (B. glabrata, B. tenagophila and B. straminea) were analyzed comparatively. The three species have the same diploid chromosome number, 2n = 36. The results obtained were compared to those previously obtained by different authors.
In the present paper, the chromosomes were classified as follows on the basis of centro-mere position: B. glabrata and B. tenagophila, 12 metacentric pairs, 4 submetacentric pairs and 2 subtelocentric pairs; B. straminea, 13 metacentric pairs, 3 submetacentric pairs and 2 subtelocentric pairs.
The nucleolus organizer regions (NORs), identified by silver staining, were located on chromosome pair number 11 in all three species.

Keywords: nucleolar; species; Biomphalaria.

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