A cytogenetic analysis of Loricaria cataphracta revealed a diploid number of 2n = 64 chromosomes, distributed as 12 metacentric + 8 submetacentric + 2 subtelocentric + 42 acrocentric, with a fundamental number of 86. Analysis of the nucleolus organizing region (NOR) using silver nitrate impregnation and fluorescence in situ hybridization (18S rDNA probe) techniques showed intra-population chromosomal polymorphism that could be classified into five different patterns (I to V), involving four pairs of chromosomes (8, 9, 12, and 13).
Scaptotrigona xanthotricha has a wide geographic distribution in the Brazilian Atlantic rainforest. One population from southeast and two from northeast Brazil were analyzed and were found to have chromosome polymorphisms. Although the chromosome number 2n = 34 is conserved in this species, karyotypic analysis revealed clear differences between the three populations. Congruent and ubiquitous multiple nucleolus organizer regions, heterochromatin and CMA3-positive blocks were found.
We made a cytogenetic study of the fish Rhamdia quelen collected from the Bodoquena Plateau, an isolated national park region in Mato Grosso do Sul State, Brazil. The diploid number was 2n = 58, with 36 metacentric + 16 submetacentric + 6 subtelocentric chromosomes. We found one to three B chromosomes, which were metacentric and submetacentric and of medium size, showing both intra- and interindividual variation. The nucleolus organizer region (NOR) was located in the terminal region of the short arm of submetacentric pair 20.