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J. Biotec. Biodivers. v. 5, N.2: pp. 140-147 May 2014
Figure 4 - Chromosomal distribution of the nucleolar organizer regions (NORs) on metaphase spreads of Mimus saturninus : (a) Conventional Giemsa staining; (b) Silver staining. Arrows show onemicrochromosomepair bearing NORs.
It is possible to suggest that Mimus saturninus has a plesiomorphic state in relation to the ancestral birds karyotype because the NOR- bearing is expressed in just one pair of microchromosome. This hypothesis is based on the fact that in Gallus gallus NOR-bearing corresponds to only one microchromosme pair (Ladjali-Mohammedi et al. 1999) as seen in the studied species considered Paleognathas, such as Rhea americana , Crypturellus tataupa , Tinamus solitarius , Pterocnemia pennata and Eudromia elegans (Gunski and Giannoni1998, Garnero et al. 2006, Nishida-Umehara et al. 2007). Some species from Passeriformes order also show this characteristic, as Tangara cayana (Correia et al. 2009), Furnarius rufus and Turdus albicollis (unpublished data). On the other hand, some species of this order show a derived characteristic of NORs, for example, Sittasomus griseicapillus and Lepidocolaptes angustirostris have one pair of macrochromosome bearing NORs and Pheucticus aureoventris has two pairs of microchromosomes (Barbosa et al. 2013; Ledesma et al. 2006).
In conclusion, our results showed a similarity in the diploid number between the two species of the Mimidae family described so far, however, there are some differences between pairs of macrochromosomes. The data presented here contribute to the understanding of karyotype evolution and the evolutionary state of this group related to the ancestral bird karyotype. Certainly, it is necessary to study classical
cytogenetic in other species of the Mimidae family in order to check if the NOR-bearing is a plesiomorphic state shared among this group.
ACKNOWLEDGMENTS
Authors would like to thank PROPESQ/UNIPAMPA for financial support and CAPES for the scholarships to Rafael kretschmer, and the staff of the research group "Animal Genetic Diversity" for the technical support.
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