Abstract Among the Neotropical fish fauna, suckermouth armored catfishes (Hypostomus - Loricariidae) stands out as one of the most difficult groups to diagnose morphologically. So the use of different molecular markers, as is the case of cytogenetics, has been fundamental for a precise identification of some species. In the present study, we characterize the karyotypes of two allopatric Hypostomus spiniger populations, using classical and molecular cytogenetic methods. This species was described by Hensel (1870) but later synonymized with Hypostomus commersoni, and recently it was again recognized as a valid species. Taking to account this taxonomic problematic, the aim of this study is to determine chromosomal characters that may be useful to validate the taxonomic status of H. spiniger and to complement its diagnosis in relation to H. commersoni populations. The karyotype of H. spiniger is composed by 66 chromosomes (10m+16sm+14st+26a), few heterochromatin and a multiple nucleolar organizer regions (NORs) system. Despite, the currently geographic isolation among the samples collected in Forquetinha River (Patos Lagoon basin) and Quadros Lagoon (Tramandaí River basin), both shared the same karyotypic structure, this cytogenetic evidence, suggest that both populations belongs to the same species. Additionally, our results clearly distinguish H. spiniger from H. commersoni populations collected along the Paraná River basin, that exhibited 2n=68 chromosomes and several divergences in heterochromatin and NORs pattern. In sum, the present study reinforces the valid status of H. spiniger and demonstrated the importance of basic cytogenetic analysis to understand conflictuous taxonomic matters.

Abstract Doradinae (Siluriformes: Doradidae) is the most species-rich subfamily among thorny catfishes, encompassing over 77 valid species, found mainly in Amazon and Platina hydrographic basins. Here, we analyzed seven Doradinae species using combined methods (e.g., cytogenetic tools and Mesquite ancestral reconstruction software) in order to scrutinize the processes that mediated the karyotype diversification in this subfamily. Our ancestral reconstruction recovered that 2n=58 chromosomes and simple nucleolar organizer regions (NOR) are ancestral features only for Wertheimerinae and the most clades of Doradinae. Some exceptions were found in Trachydoras paraguayensis (2n=56), Trachydoras steindachneri (2n=60), Ossancora punctata (2n=66) and Platydoras hancockii whose karyotypes showed a multiple NOR system. The large thorny catfishes, such as Pterodoras granulosus, Oxydoras niger and Centrodoras brachiatus share several karyotype features, with subtle variations only regarding their heterochromatin distribution. On the other hand, a remarkable karyotypic variability has been reported in the fimbriate barbells thorny catfishes. These two contrasting karyoevolution trajectories emerged from a complex interaction between chromosome rearrangements (e.g., inversions and Robertsonian translocations) and mechanisms of heterochromatin dispersion. Moreover, we believe that biological features, such as microhabitats preferences, populational size, low vagility and migratory behavior played a key role during the origin and maintenance of chromosome diversity in Doradinae subfamily.

Abstract The genera Cichlasoma and Gymnogeophagus belong to the subfamily Cichlinae, the only one in Neotropical cichlids. Cichlasoma dimerus, C. paranaense, C. portalegrense, Gymnogeophagus rhabdotus, and G. lacustris were collected at different points in the Paranapanema and Paraguay basins and the Lagoon of Patos hydrographic system. In addition to conventional analysis, CMA3 fluorochrome staining, and FISH with 18S rDNA probe were performed. All species had a diploid number equal to 48, with interand intraspecific differences in karyotype formulae. All species presented a single AgNOR site, except G. rhabdotus and the C. paranaense population of the Paranapanema River, which revealed more than one pair of nucleolar chromosomes. AgNORs were coincident to 18S rDNA and CMA3. Heterochromatin was distributed in the pericentromeric chromosomal regions and coincident with NORs. For the first time, this work shows cytogenetic data for C. portalegrense, G. lacustris, and G. rhabdotus. Although some results reinforce the idea of conservative chromosome evolution of 2n in Cichlinae, interspecific and populational variations observed confirm that chromosomal rearrangements affect the microstructural karyotype diversification in this group of fish.

Abstract Crenicichla is the largest genus in the Cichlidae family in South America. The genus includes 100 valid species that are popularly known in Brazil as jacundás or joaninhas and are widely distributed in rivers east of the Andes. Cytogenetic analyses were carried out on seven species in this genus. All species showed a diploid number of 48 with interspecific differences in karyotype formulas and AgNORs located in interstitial position on the short arm of the largest metacentric pair, except for the two populations from C. britskii. Population A showed terminal markings on the long arm of the fifth pair of the complement, and population B showed up to two marked chromosome pairs. FISH with an 18S rDNA probe was coincident with AgNORs and CMA3, except for pair 6 from population B of C. britskii that did not presented positive CMA3 sites. This work presents first cytogenetic data for C. haroldoi, C. maculata, and C. punctata, and the results show karyotypic patterns similar to those in the literature. However, the diversity found in populations of C. britskii represents new information about the evolution of the karyotype of the Cichlidae family, which has been conservative. Furthermore, the data could assist in phylogenetic studies of Crenicichla.

Análises citogenéticas foram realizadas em Astyanax jacuhiensis do lago Guaíba, Brasil. O número diplóide foi 50, sendo o cariótipo composto por 8m+30sm+4st+8a cromossomos, NF = 92. As regiões organizadoras de nucléolos (AgNORs) foram observadas em 2 a 5 cromossomos, evidenciando uma variação intra e interindividual nesta espécie. O par sm 8 foi constantemente detectado com NORs nos braços curtos, mostrando um heteromorfismo de tamanho entre os homólogos. Entretanto, a hibridação in situ fluorescente (FISH) com sonda de DNAr 18S, localizou cístrons ribossômicos apenas no par 8, confirmando o heteromorfismo de tamanho entre os homólogos. O bandamento C revelou a presença de bandas discretas de heterocromatina na região pericentromérica da maioria dos cromossomos, além de algumas bandas mais evidentes intersticiais, bem como na região terminal dos braços curtos do par 8. A associação de BC+CMA3 evidenciou marcações fluorescentes mais discretas em diferentes cromossomos e uma forte marcação terminal no par 8, confirmando vários sítios de heterocromatina GC-rica nessa espécie. Nossos resultados fornecem a primeira descrição do cariótipo de Astyanax jacuhiensis, apresentando semelhanças em relação ao cariótipo de diferentes populações de A. altiparanae e A. bimaculatus, indicando que as características cromossômicas são muito semelhantes para estas três espécies.

Cytogenetic analyses were performed in Astyanax jacuhiensis from lago Guaíba, Brazil. The diploid number was 50, with a karyotype composed of 8m+30sm+4st+8a chromosomes, FN = 92. The AgNORs were observed in 2 to 5 chromosomes, with intra- and interindividual variation. The sm pair 8 observed always carried NORs on the short arms, presenting size heteromorphism between homologous. Fluorescence in situ hybridization (FISH) with an 18S rDNA probe only confirmed the location of ribosomal cistrons in the sm pair 8, and heteromorphism of these regions between the homologous chromosomes. C-banding revealed the occurrence of weak C-positive heterochromatin in the pericentromeric regions of several chromosomes, in addition to more evident bands interstitially located on some chromosome pairs and in the terminal region of the short arms in pair 8. C-banding plus CMA3 revealed light fluorescent signals in different chromosomes of the karyotype, with a strong terminal site in pair 8, indicating the occurrence of several GC-rich heterochromatic regions in this species. Our results provide the first description of the Astyanax jacuhiensis karyotype, showing karyotype similarities when compared to various populations of A. altiparanae and A. bimaculatus, indicating that chromosomal features are very similar for these three species.

Karyotypes of seventeen Hoplias malabaricus specimens, collected in the fish culture station of UNOPAR (University of Northern Paraná), were analyzed. The station is in the Claro River system in the Tibagi River basin. Two distinct and coexistent karyotype forms (cytotypes) were identified, comprising either 42 chromosomes (cytotype A) or 40 chromosomes (cytotype C), both presenting metacentric and submetacentric chromosomes. In two specimens, one male and one female, it was not possible to characterize a modal diploid number because different cell lines were observed, with a predominance of 2n=41 and 2n=42 chromosomes at a frequency of 38.24% and 41.12%, respectively. The karyotype with 2n=41 showed some putative monosomic and trisomic chromosomes, while the karyotype with 2n=42 showed 21 chromosomal pairs, similar to cytotype A. RAPD analysis showed that these two specimens have the same band pro file of cytotype A (Nei's genetic identity=92%), discarding a possible hybridization between both cytotypes and supporting the mosaicism hypothesis. These findings corroborate the isolation between cytotypes A and C.

O gênero Astyanax é destacado entre os Characiformes, pelo grande número de espécies encontradas e a ampla distribuição geográfica. Neste trabalho, foram analisados citogeneticamente espécimes de Astyanax laticeps do sistema da laguna do Patos. O número diplóide observado foi de 2n = 50 cromossomos distribuídos em 6m+16sm+16st+12a (NF= 88), sem diferenças entre machos e fêmeas. Foram observados poucos blocos de heterocromatina, além de três bandas-C mais conspícuas, correspondentes às NORs, confirmado pela coloração com nitrado de prata,CMA3, FISH, e coloração negativa ao DAPI. Estas regiões foram localizadas em um cromossomo subtelocêntrico de tamanho médio e em um par subtelocêntrico grande, provavelmente devido a deleção desta região em um dos cromossomos homólogos, ou por eventos de transposição entre eles

The genus Astyanax is prominent among Characiformes, due to the large number of species found and its wide geographic distribution. In this work, Astyanax laticeps specimens from the laguna dos Patos system were cytogenetically analyzed. A diploid number of 2n = 50 chromosomes distributed into 6m+16sm+16st+12a (FN = 88) was found, without differences between males and females. A few small heterochromatin blocks were observed, besides three more conspicuous C-bands, corresponding to NORs, as confirmed by silver nitrate and CMA3 staining, FISH, and DAPI negative staining. These regions were located in a medium-sized subtelocentric and in a large subtelocentric chromosomal pair, probably because of a deletion of this region in one homologous chromosome, or due to a transposition event between them.

Exemplares de Parapimelodus nigribarbis e Pimelodus maculatus coletados na bacia do rio Guaíba, Porto Alegre, Rio Grande do Sul, foram analisados citogeneticamente. As duas espécies apresentaram um número diplóide de 56 cromossomos, com P. nigribarbis mostrando um cariótipo de 20m + 20sm + 4st + 12a, NF igual a 100; e P. maculatus com 24m + 20sm + 6st + 6a e NF igual 106. As NORs foram evidenciadas em apenas um par de cromossomos subtelocêntricos, na região terminal do braço longo, nas duas espécies estudadas, sendo coincidentes com a banda C e CMA3; o DAPI nestas regiões se mostrou negativo. Parapimelodus nigribarbis apresentou um maior número de bandas heterocromáticas do que P. maculatus, distribuídas principalmente em regiões terminais, sendo observada nesta última espécie uma banda intersticial no braço curto do primeiro par metacêntrico. Banda C + CMA3 evidenciou em P. nigribarbis e P. maculatus a heterocromatina associada à NOR rica em GC, sendo encontrada na primeira espécie outras regiões fluorescentes. Com banda C + DAPI várias regiões cromossômicas foram observadas nas duas espécies, inclusive a porção intersticial encontrada em P. maculatus, revelando que a heterocromatina possui uma maior quantidade de regiões AT ricas em sua composição.

A cytogenetic study was conducted on specimens of Parapimelodus nigribarbis and Pimelodus maculatus collected in the lago Guaíba drainage, Porto Alegre, Rio Grande do Sul, Brazil. The two species had a diploid number of 56 chromosomes, with P. nigribarbis showing a karyotype of 20m + 20sm + 4st + 12a with FN of 100, and P. maculatus showing a karyotype of 24m + 20sm + 6st + 6a with FN of 106. NORs were demonstrated in both species in only one pair of subtelocentric chromosomes, in the terminal region of the long arm, which was coincident with C- banding and CMA3 staining, while DAPI staining was negative in these regions. Parapimelodus nigribarbis had a greater number of heterochromatic bands than did P. maculatus, which were distributed mainly in the terminal regions, where the latter species showed an interstitial band on the short arm of the first metacentric pair. C-banding plus CMA3 demonstrated heterochromatin that was associated with GC-rich NORs in both P. nigribarbis and P. maculatus, although other fluorescent regions were also observed in the former species. With C-banding plus DAPI, various chromosomal regions were stained in the two species, along with interstitial staining in P. maculatus, indicating that heterochromatin contained a greater quantity of AT-rich regions.

A cytogenetic analysis of thirteen specimens of Bryconamericus aff. Iheringii revealed a diploid number of 52 chromosomes and a karyotype of 8M+22SM+10ST+12A with a fundamental number (FN) of 92. The nucleolus organizer regions (NORs) were studied by means of AgNO3 and CMA3 staining as well as by FISH using an 18S rDNA probe. NORs were found to be located at the terminal position on the short arm of the submetacentric chromosome pair. C-banding showed strong telomeric and centromeric staining in the majority of the chromosomes, and a similar pattern was observed after treatment with AluI restriction enzyme