Abstract
Cytogenetic studies were performed on two sympatric species of Characidium, C. gomesi and C. cf. zebra, from the Grande River basin, Minas Gerais State, Brazil. Although both species had a chromosome number of 50 with a karyotype exclusively consisting of meta- and submetacentric chromosomes, interspecific diversity was detected concerning the size of the two first chromosome pairs of the karyotypes. Active nucleolus organizer regions (NORs) were located at the terminal position on the long arm of the 17th pair of C. gomesi and at subterminal position on the long arm of the 23rd pair of C. cf. zebra. For both species the fluorochrome CMA3 stained only the NOR-bearing pair of chromosomes. The heterochromatin pattern also showed some differentiation between these species restricted to the centromeric or pericentromeric region of C. cf. zebra and practically absent in C. gomesi. These data are discussed concerning chromosome diversification in this fish group.
Highlights
IntroductionThe genus Characidium (family Crenuchidae) is made up of small fish which rarely exceed a standard length of 10 cm and which usually occur in small headwater streams
The genus Characidium is made up of small fish which rarely exceed a standard length of 10 cm and which usually occur in small headwater streams
A cytogenetic survey was performed on two sympatric Characidium species: 14 female and 6 male (n = 20) Characidium gomesi and 10 female and 3 male (n = 13) Characidium cf. zebra collected in the Machado River at 22°04.471’ S; 46°02.810’ W near the town of São João da Mata in the Brazilian State of Minas Gerais
Summary
The genus Characidium (family Crenuchidae) is made up of small fish which rarely exceed a standard length of 10 cm and which usually occur in small headwater streams. The genus Characidium is the most cytogenetically studied Crenuchidae genera, with cytogenetic data being available on five Characidium cf zebra populations (Miyazawa and Galetti-Jr., 1994; Maistro et al, 1998a; Centofante et al, 2001), one population published as Characidium cf fasciatum and reidentified as Characidium sp. (Miyazawa and Galetti-Jr., 1994); two populations of Characidium gomesi, Send correspondence to Edson Luis Maistro.
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