Abstract
Karyotypic characteristics of the microcrustacean Artemia franciscana Kellog 1906, introduced to the salt lakes on the northeastern coast of Brazil in the 1970s, were investigated by conventional staining, C banding, restriction endonucleases (EcoRI, PstI and KpnI) and Ag-NORs. The karyotype consisted of 42 chromosomes and secondary constrictions were observed on some pairs. Large heterochromatic blocks were found distributed in the telomere portion of most of the chromosomes. Digestion with PstI and KpnI showed a similar pattern to that obtained by C banding. Preparations treated with EcoRI revealed intense action in the heterochromatic regions indicating the presence of restriction sites. Multiple Ag-NORs were shown associated to heterochromatic blocks. These data presented here no identified modifications that might have occurred after the geographic isolation of this stock and examine the evolutionary modifications in the karyotype of this group. Keywords : Chromosome banding; brine shrimp; crustacean cytogenetics.
Highlights
Cytogenetic aspects of Crustacea have triggered less interest than in the other Arthropod groups, such as the Insecta (LAZZARETTO; LIBERTINI, 1985)
In this study we describe the A. franciscana karyotype sampled in the Northeast of Brazil, using the Ag-NORS technique to identify the number and position of the ribosomal sites, and C banding and treatment with the restriction endonucleases EcoRI and AluI to characterize the distribution and the qualitative patterns of the heterochromatic regions
The nucleoli organizer regions were identified by the Ag-NORs method (HOWELL; BLACK, 1980) while the C banding followed methodology proposed by Sumner (1972)
Summary
Cytogenetic aspects of Crustacea have triggered less interest than in the other Arthropod groups, such as the Insecta (LAZZARETTO; LIBERTINI, 1985). This condition is partly due to technical difficulties in accessing the chromosome of species. The Artemia genus is taxonomically referred to as an group of sibling species and superspecies reproductively isolated (GIL et al, 1998), consisting of five gonochoristic species A. franciscana Kellog, 1906 (found in the Americas), A. persimilis Piccinelli and Prosdocimi, 1968 (found only in Argentina), A. salina (Linnaeus, 1758) Leach, 1819 (found in Europe and North Africa), A. urmiana Günther, 1900 (in Lake Urmia, Iran) and A. monica Verrill, 1869 found in Mono Lake, California, USA (BOWEN et al, 1985). In the Americas, A. franciscana is the most intensely studied and exploited species. This species was first introduced in Macau, Rio
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