Corresponding author: Ana Lúcia Dias (
Academic editor: S. Grozeva
In the present work, six curimatid species were analyzed:
B chromosomes, also known as supernumerary or accessory chromosomes, are additional dispensable chromosomes present in some individuals of some populations in some species. They have probably originated from the A complement, but followed their own evolutionary paths, being found in different groups of both animals and plants (
The irregular behavior of this chromosome type in mitosis and in meiosis causes it to accumulate selfishly in the germ line of many species, producing a non-Mendelian segregation with transmission rates higher than those yielded by the chromosomes of the A complement (
In freshwater Neotropical fish, the occurrence of B chromosomes has been reported in 61 species, distributed in 16 families of seven different orders and in distinct hydrographic basins, according with the revision accomplished by
The first work to record the presence of the B chromosome in the family
The current study examines the frequency, behavior and distribution of B microchromosomes in mitotic and meiotic cells in six fish species of the family
Six species of the family
Species analysed, collection sites and hydrographic basins.
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1♀, 1♂ | Saco da Alemoa River, Eldorado do Sul, RS, Brazil / |
Laguna dos Patos Hydrographic System |
2♀, 9♂ | Capivara stream, Barra do Ribeiro, RS, Brazil / |
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2♀, 3♂ | Capivara stream, Barra do Ribeiro, RS, Brazil / |
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1♀, 10♂ | Agronomic Experiment Station of UFRGS’s Dam, Eldorado do Sul, RS, Brazil / |
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1♀, 1♂ | Forquetinha River, Canudos do Vale, RS, Brazil / |
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2♀, 5♂ | Tres Bocas stream, Londrina, PR, Brazil / |
Paranapanema River |
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3♂ | Tres Bocas stream, Londrina, PR, Brazil / |
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2♂ | Pavão stream, Sertanópolis, PR, Brazil | ||
4♀, 8♂ | Jacutinga River, Londrina, PR, Brazil / |
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1♀, 5♂ | Água dos Patos River, Iepê, SP, Brazil / |
Mitotic chromosomes were obtained by direct preparation removing the anterior kidney, according to
All samples analyzed showed a diploid number of 54 meta-submetacentric chromosomes (m-sm) and a fundamental number (FN) equal to 108 (
Somatic metaphases:
One B microchromosome was observed in all populations studied, with variation in the number and frequency among them (
B microchromosome frequency in somatic cells of the curimatids from Laguna dos Patos Hydrographic System/RS.
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Saco da Alemoa River | 149 | ♀ | 22 | 2 | 24 |
150 | ♂ | 3 | 0 | 3 | ||
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Capivara stream | 748 | ♀ | 3 | 1 | 4 | |
752 | ♂ | 4 | 1 | 5w | ||
755 | ♀ | 17 | 0 | 17 | ||
777 | ♂ | 42 | 1 | 43 | ||
780 | ♂ | 12 | 0 | 12 | ||
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Capivara stream | 580 | ♂ | 2 | 0 | 2 |
753 | ♀ | 25 | 3 | 28 | ||
758 | ♀ | 23 | 0 | 23 | ||
778 | ♂ | 8 | 1 | 9 | ||
779 | ♂ | 22 | 0 | 22 | ||
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Agronomic Experiment Station of UFRGS’s Dam | 784 | ♂ | 4 | 0 | 4 |
786 | ♀ | 5 | 0 | 5 | ||
787 | ♂ | 6 | 0 | 6 | ||
788 | ♂ | 36 | 1 | 37 | ||
789 | ♂ | 10 | 0 | 10 | ||
790 | ♂ | 8 | 0 | 8 | ||
791 | ♂ | 7 | 2 | 9 | ||
792 | ♂ | 3 | 0 | 3 | ||
793 | ♂ | 2 | 0 | 2 | ||
794 | ♂ | 6 | 0 | 6 | ||
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Forquetinha River | 857 | ♀ | 55 | 3 | 58 |
996 | ♂ | 3 | 2 | 5 | ||
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B microchromosome frequency in somatic cells of the curimatids from Paranapanema River basin.
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Tres Bocas stream | 2656 | ♂ | 5 | 0 | 0 | 5 |
3815 | ♂ | 18 | 0 | 0 | 18 | ||
3909 | ♀ | 8 | 0 | 0 | 8 | ||
3992 | ♀ | 46 | 3 | 1 | 50 | ||
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Pavão stream | 3277 | ♂ | 3 | 2 | 0 | 5 |
3278 | ♂ | 8 | 0 | 0 | 8 | ||
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Água dos Patos River | 3393 | ♀ | 40 | 8 | 0 | 48 | |
3407 | ♂ | 18 | 0 | 0 | 18 | ||
3408 | ♂ | 11 | 2 | 1 | 14 | ||
3409 | ♂ | 21 | 0 | 0 | 21 | ||
3411 | ♂ | 22 | 0 | 0 | 22 | ||
3745 | ♂ | 5 | 0 | 0 | 5 | ||
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Jacutinga River | 3453 | ♀ | 15 | 2 | 1 | 18 | |
3454 | ♀ | 22 | 0 | 0 | 22 | ||
3461 | ♂ | 14 | 0 | 0 | 14 | ||
3462 | ♂ | 20 | 0 | 0 | 20 | ||
3465 | ♂ | 23 | 1 | 0 | 24 | ||
3862 | ♀ | 6 | 0 | 0 | 6 | ||
3986 | ♂ | 2 | 0 | 0 | 2 | ||
3987 | ♂ | 5 | 0 | 0 | 5 | ||
3991 | ♂ | 4 | 0 | 0 | 4 | ||
3993 | ♀ | 3 | 0 | 0 | 3 | ||
4046 | ♂ | 8 | 0 | 0 | 8 | ||
4049 | ♂ | 4 | 10 | 0 | 14 | ||
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Of the total number of somatic cells with B microchromosomes analyzed in six species of Curimatids, there was a variation from 3.3% in
In the Paranapanema River basin, the population of the
Specimens of
The B microchromosome was observed in four species of curimatids collected from different populations:
Cytogenetic date of differents species of curimatids (2n: diploid number; FN: number fundamental; Bs: supernumerary chromosomes).
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54 | 108 | - | - | 3, 15 |
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54 | 108 | - | - | 3, 15 |
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54 | 108 | - | - | 3 |
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56 | 112 | - | - | 3 |
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54 | 108 | - | - | 3 |
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54 | 108 | - | - | 3 |
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54 | 108 | - | - | 8, 12 |
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54 | 108 | - | - | 15 |
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54 | 108 | - | - | 2 |
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54 | 108 | - | - | 3 |
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46 | 46 | - | - | 8 |
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54 | 108 | - | - | 6, 15 |
54 | 108 | - | - | 2 | |
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54 | 108 | 0 - 1 | Micro | 15 |
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54 | 108 | 0 - 4 | Micro | 1, 2, 7, 9, 13, 14, 16, 17,18 |
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54 | 108 | - | - | 2, 15 |
54 | 108 | - | - | 2 | |
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54 | 108 | 0 - 1 | Micro | 11, 12, 18 |
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54 | 108 | - | - | 2 |
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54 | 108 | 0 - 1 | Micro | 2, 12, 18 |
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58 | 116 | - | - | 12, 15 |
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54 | 108 | 0 - 1 | Micro | 18 |
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102 | 106 | - | - | 4 |
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56 | 112 | - | - | 4 |
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54 | 108 | - | - | 4 |
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102 | 106 | - | - | 12 |
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54 | 108 | - | - | 15 |
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54 | 108 | - | - | 8, 12 |
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54 | 108 | - | - | 3 |
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54 | 108 | - | - | 15 |
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54 | 108 | 0 - 1 | Micro | 18 |
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54 | 108 | - | - | 8, 12 |
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54 | 108 | - | - | 2, 12 |
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54 | 108 | - | - | 2 |
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54 | 108 | - | - | 15 |
54 | 108 | - | - | 10 | |
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54 | 108 | 0 - 2 | Micro | 2, 5, 13, 14, 15, 17,18 |
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54 | 108 | - | - | 3 |
The analysis of meiotic cells in
Meiotic cells:
Meiotic cells:
In both types of cell division, the number of cells without B microchromosomes was greater than number of cells with B microchromosomes in the species of
In others groups of fishes with B-chromosomes meiotic analysis has been performed in order to understand the behavior of this chromosome, as in
The meiotic data presented in this study are the first for
According
There are two hypotheses that could explain the origin of B chromosomes in
The results obtained in this study provides more information about the occurrence of B microchromosomes in the curimatids, confirming its presence in
The authors are grateful to CNPq for fellowships, to Dr. Luiz R. Malabarba for the identification of the studied species from the Laguna dos Patos Hydrographic System/RS and MSc Larissa Bettin Pires and Fábio H. Takagui for assistance in the construction of maps.