Characterization of repetitive DNA on the genome of the marsh rat Holochilus nanus (Cricetidae: Sigmodontinae).

Repetitive DNA are sequences repeated hundreds or thousands of times and an abundant part of eukaryotic genomes. SatDNA represents the majority of the repetitive sequences, followed by transposable elements. The species Holochilus nanus (HNA) belongs to the rodent tribe Oryzomyini, the most taxonomically diverse of Sigmodontinae subfamily. Cytogenetic studies on Oryzomyini reflect such diversity by revealing an exceptional range of karyotype variability. However, little is known about the repetitive DNA content and its involvement in chromosomal diversification of these species. In the search for a more detailed understanding about the composition of repetitive DNA on the genome of HNA and other species of Oryzomyini, we employed a combination of bioinformatic, cytogenetic and molecular techniques to characterize the repetitive DNA content of these species. RepeatExplorer analysis showed that almost half of repetitive content of HNA genome are composed by Long Terminal Repeats and a less significant portion are composed by Short Interspersed Nuclear Elements and Long Interspersed Nuclear Elements. RepeatMasker showed that more than 30% of HNA genome are composed by repetitive sequences, with two main waves of repetitive element insertion. It was also possible to identify a satellite DNA sequence present in the centromeric region of Oryzomyini species, and a repetitive sequence enriched on the long arm of HNA X chromosome. Also, comparative analysis between HNA genome with and without B chromosome did not evidence any repeat element enriched on the supernumerary, suggesting that B chromosome of HNA is composed by a fraction of repeats from all the genome.

Causes and consequences of DNA content variation in Zea / Causas y consecuencias de la variación del contenido de ADN en Zea

ABSTRACT Cytogenetic evidence indicates that Zea, which comprises maize (Z. mays ssp. mays) and its wild relatives, is an allopolyploid genus. Our research group has carried out numerous cytogenetic studies on Zea species, mainly focused on native Argentinian and Bolivian maize landraces. We found a wide inter- and intraspecific genome size variation in the genus, with mean 2C-values ranging between 4.20 and 11.36 pg. For the maize landraces studied here, it varied between 4.20 and 6.75 pg. The objectives of this work are to analyze the causes of genome size variation and to discuss their adaptive value in Zea. This variation is mainly attributed to differences in the heterochromatin located in the knobs and to the amount of interspersed DNA from retrotransposons. Polymorphisms in presence or absence of B-chromosomes (Bs) and the population frequency of Bs are also a source of genome size variation, with doses ranging between one and eight in the landraces analyzed here. Correlation analysis revealed that the percentage of heterochromatin is positively correlated with genome size. In addition, populations cultivated at higher altitudes, which are known to be precocious, have smaller genome sizes than do those growing at lower altitudes. This information, together with the positive correlation observed between the length of the vegetative cycle and the percentage of heterochromatin, led us to propose that it has an adaptive role. On the other hand, the negative relationship found between Bs and heterochromatic knobs allowed us to propose the existence of an intragenomic conflict between these elements. We hypothesize that an optimal nucleotype may have resulted from such intranuclear conflict, where genome adjustments led to a suitable length of the vegetative cycle for maize landraces growing across altitudinal clines.

RESUMEN La evidencia citogenética indica que el género Zea, el maíz (Z. mays ssp. mays) y sus parientes silvestres, posee un origen alopoliploide. Nuestro grupo de investigación ha realizado numerosos estudios en especies de Zea, principalmente en maíces nativos de Argentina y Bolivia. En este género, hallamos una amplia variación inter e intraespecífica en el tamaño del genoma, con valores 2C medios que oscilan entre 4,20 y 11,36 pg. El valor 2C medio de los maíces nativos estudiados varió entre 4,20 y 6,75 pg. Los objetivos de este trabajo son analizar las causas de la variación del tamaño del genoma en Zea y discutir su valor adaptativo. Esta variación se atribuye principalmente a las diferencias en la heterocromatina de los knobs y en la cantidad de ADN intercalado de los retrotransposones. Otras fuentes de variación son los polimorfismos para presencia/ausencia de cromosomas B (Bs) y para la frecuencia poblacional de Bs en las razas analizadas, con dosis que oscilan entre uno y ocho Bs. El porcentaje de heterocromatina se correlaciona positivamente con el tamaño del genoma. Las poblaciones cultivadas en altitudes altas, que son precoces, tienen tamaños de genoma más pequeños que las que crecen en bajas altitudes. Esta información, junto con la correlación positiva observada entre la duración del ciclo vegetativo y el porcentaje de heterocromatina, nos llevó a proponer el rol adaptativo de la heterocromatina. Por otro lado, la relación negativa encontrada entre Bs y knobs heterocromáticos nos permitió proponer la existencia de un conflicto intragenómico entre estos elementos. Hipotetizamos que de este conflicto intranuclear habría resultado el nucleotipo óptimo, donde ajustes genómicos condujeron a una duración adecuada del ciclo vegetativo en las razas de maíz que crecen a lo largo de clines altitudinales.

Diversity of the repetitive DNA fraction in Cestrum, the genus with the largest genomes within Solanaceae.

BACKGROUND: Cestrum species present large genomes (2 C = ~ 24 pg), a high occurrence of B chromosomes and great diversity in heterochromatin bands. Despite this diversity, karyotypes maintain the chromosome number 2n = 16 (except when they present B chromosomes), and a relative similarity in chromosome morphology and symmetry. To deepen our knowledge of the Cestrum genome composition, low-coverage sequencing data of C. strigilatum and C. elegans were compared, including cytogenomic analyses of seven species. METHODS AND RESULTS: Bioinformatics analyses showed retrotransposons comprising more than 70% of the repetitive fraction, followed by DNA transposons (~ 17%), but FISH assays using retrotransposon probes revealed inconspicuous and scattered signals. The four satellite DNA families here analyzed represented approximately 2.48% of the C. strigilatum dataset, and these sequences were used as probes in FISH assays. Hybridization signals were colocalized with all AT- and GC-rich sequences associated with heterochromatin, including AT-rich Cold-Sensitive Regions (CSRs). Although satellite probes hybridized in almost all tested species, a satDNA family named CsSat49 was highlighted because it predominates in centromeric regions. CONCLUSIONS: Data suggest that the satDNA fraction is conserved in the genus, although there is variation in the number of FISH signals between karyotypes. Except to the absence of FISH signals with probes CsSat1 and CsSat72 in two species, the other satellites occurred in species of different phylogenetic clades. Some satDNA sequences have been detected in the B chromosomes, indicating that they are rich in preexisting sequences in the chromosomes of the A complement. This comparative study provides an important advance in the knowledge on genome organization and heterochromatin composition in Cestrum, especially on the distribution of satellite fractions between species and their importance for the B chromosome composition.

Sex-Dependent Inheritance of B Chromosomes in Psalidodon paranae (Teleostei, Characiformes) Revealed by Directed Crossings.

B chromosomes are additional dispensable elements to the standard chromosomal set of an organism. In most cases, their transmission differs from Mendelian patterns, leading to their accumulation or extinction. The present study aimed to describe, for the first time, the transmission pattern of B chromosome in a population of Psalidodon paranae through directed crosses, as well as to analyze the populational dynamics of B chromosome. Our results revealed the possible elimination of B chromosome in crossings where only females were B-carriers, with a mean transmission rate (kB) of 0.149; however, kB was significantly higher in crossings involving male B-carriers (kB = 0.328-0.450). Moreover, we observed an increase in the frequency of B chromosomes in the natural population of P. paranae in the last two decades. These apparently contradictory results can make sense if the B chromosome provides adaptive advantages to their carriers. Here, we observed a differential transmission of B chromosomes in each sex of parental individuals, with higher transmission rates in crossing involving males B-carriers, in addition to describe the temporal changes of B chromosome frequency in P. paranae.

Intragenomic Conflict between Knob Heterochromatin and B Chromosomes Is the Key to Understand Genome Size Variation along Altitudinal Clines in Maize.

In maize, we studied the causes of genome size variation and their correlates with cultivation altitude that suggests the existence of adaptive clines. To discuss the biological role of the genome size variation, we focused on Bolivian maize landraces growing along a broad altitudinal range. These were analyzed together with previously studied populations from altitudinal clines of Northwestern Argentina (NWA). Bolivian populations exhibited numerical polymorphism for B chromosomes (Bs) (from 1 to 5), with frequencies varying from 16.6 to 81.8 and being positively correlated with cultivation altitude. The 2C values of individuals 0B (A-DNA) ranged between 4.73 and 7.71 pg, with 58.33% of variation. The heterochromatic knobs, detected by DAPI staining, were more numerous and larger in individuals 0B than in those with higher doses of Bs. Bolivian and NWA landraces exhibited the same pattern of A-DNA downsizing and fewer and smaller knobs with increasing cultivation altitude, suggesting a mechanistic link among heterochromatin, genome size and phenology. The negative association between the two types of supernumerary DNA (knob heterochromatin and Bs), mainly responsible for the genome size variation, may be considered as an example of intragenomic conflict. It could be postulated that the optimal nucleotype is the result of such conflict, where genome adjustment may lead to an appropriate length of the vegetative cycle for maize landraces growing across altitudinal clines.

Origin and evolution of highly polymorphic rDNA sites in Alstroemeria longistaminea (Alstroemeriaceae) and related species.

Alstroemeria (Alstroemeriaceae) displays a conserved and highly asymmetric karyotype, where most rDNA sites can be properly recognized by the size and morphology of the chromosomes. We analyzed the intraspecific variation of rDNA sites in A. longistaminea and compared with their distribution in other species (A. caryophyllaea and A. piauhyensis) and a representative of a sister genus, Bomarea edulis. All three species of Alstroemeria presented 2n = 16, and one to six B chromosomes were found in some individuals of A. longistaminea. There was a set of 12 conserved rDNA sites (four 5S and eight 35S) and up to 11 variable sites. B chromosomes were almost entirely covered by 35S signals, coupled with tiny 5S sites. Noteworthy, most rDNA sites found in A. caryophyllaea and A. piauhyensis were localized in chromosome positions similar to those in A. longistaminea, suggesting the existence of conserved hotspots for rDNA accumulation. Some of these hotspots were absent in Chilean Alstromeria as well in B. edulis. We propose that insertions of rDNA sequences on chromosomes do not occur randomly but rather on preferential sites or hotspots for insertions. The maintenance of these arrays, however, may be favored/constrained by different factors, resulting in stable or polymorphic sites.

Long-term persistence of supernumerary B chromosomes in multiple species of Astyanax fish.

BACKGROUND: Eukaryote genomes frequently harbor supernumerary B chromosomes in addition to the "standard" A chromosome set. B chromosomes are thought to arise as byproducts of genome rearrangements and have mostly been considered intraspecific oddities. However, their evolutionary transcendence beyond species level has remained untested. RESULTS: Here we reveal that the large metacentric B chromosomes reported in several fish species of the genus Astyanax arose in a common ancestor at least 4 million years ago. We generated transcriptomes of A. scabripinnis and A. paranae 0B and 1B individuals and used these assemblies as a reference for mapping all gDNA and RNA libraries to quantify coverage differences between B-lacking and B-carrying genomes. We show that the B chromosomes of A. scabripinnis and A. paranae share 19 protein-coding genes, of which 14 and 11 were also present in the B chromosomes of A. bockmanni and A. fasciatus, respectively. Our search for B-specific single-nucleotide polymorphisms (SNPs) identified the presence of B-derived transcripts in B-carrying ovaries, 80% of which belonged to nobox, a gene involved in oogenesis regulation. Importantly, the B chromosome nobox paralog is expressed > 30× more than the A chromosome paralog. This indicates that the normal regulation of this gene is altered in B-carrying females, which could potentially facilitate B inheritance at higher rates than Mendelian law prediction. CONCLUSIONS: Taken together, our results demonstrate the long-term survival of B chromosomes despite their lack of regular pairing and segregation during meiosis and that they can endure episodes of population divergence leading to species formation.

IGS sequences in Cestrum present AT- and GC-rich conserved domains, with strong regulatory potential for 5S rDNA.

The 35S and 5S ribosomal DNA (rDNA) organized in thousands of copies in genomes, have been widely used in numerous comparative cytogenetic studies. Nevertheless, several questions related to the diversity and organization of regulatory motifs in 5S rDNA remain to be addressed. The 5S rDNA unit is composed of a conserved 120 bp length coding region and an intergenic spacer (IGS) containing potential regulatory motifs (Poly-T, AT-rich and GC-rich) differing in number, redundancy and position along the IGS. The Cestrum species (Solanaceae) have large genomes (about 10 pg/1C) and conserved 2n = 16 karyotypes. Strikingly, these genomes show high diversity of heterochromatin distribution, variability in 35S rDNA loci and the occurrence of B chromosomes. However, the 5S rDNA loci are highly conserved in the proximal region of chromosome 8. Comparison of seventy-one IGS sequences in plants revealed several conserved motifs with potential regulatory function. The AT- and GC-rich domains appeared highly conserved in Cestrum chromosomes. The 5S genic and the GC-rich IGS probe produced FISH signals in both A (pair 8) and B chromosomes. The GC-rich domain presented a strong potential for regulation because it may be associated with CpG islands organization, as well as to hairpin and loop organization. Another interesting aspect was the ability of AT- and GC-rich motifs to produce non-heterochromatic CMA/DAPI signals. While the length of the 5S rDNA IGS region varied in size between the Cestrum species, the individual sequence motifs seem to be conserved suggesting their regulatory function. The most striking feature was the conserved GC-rich domain in Cestrum, which is recognized as a signature trait of the proximal region of chromosome pair 8.

Comparative Cytogenetics of Omophoita abbreviata and O. aequinoctialis (Coleoptera, Chrysomelidae, Alticini) from the Adolpho Ducke Forest Reserve in Brazilian Amazonia: Intrapopulation Variation in Karyotypes.

The chromosomes of 2 flea beetle species from central Amazonia, Omophoita abbreviata and O. aequinoctialis (Alticini), were investigated through analysis of meiotic and mitotic cells. These species belong to the subtribe Oedionychina, a taxon that has unique cytogenetic features, such as giant sex chromosomes which are aligned at a distance during meiosis I (asynaptic). O. abbreviata and O. aequinoctialis have a meiotic formula of 10II + X + y, which is predominant in this subtribe. While the species of the genus Omophoita possess a relatively stable karyotype, a typical feature for Oedionychina, the present study identified inter- and intrapopulational variation in chromosome morphology, constitutive heterochromatin, and the presence and number of B chromosomes in O. aequinoctialis. In addition, FISH mapping of telomeric sequences revealed signals in the collochores, raising several questions on the chromosomal evolution in this group.

Are cytological parameters of maize landraces (Zea mays ssp. mays) adapted along an altitudinal cline?

The Northwestern Argentina (NWA) highland region is one of the southernmost areas of native maize cultivation. We studied variations of different cytological parameters, such as DNA contents, presence/absence of B chromosomes (Bs), and number and sequence composition of heterochromatic knobs in ten accessions of four maize landraces growing along a broad altitudinal cline in NWA. The aim of this work was to assess variations in cytological parameters and their relationship with the crop altitude of cultivation, in an adaptive context. The A-DNA content of the A chromosome complements showed 40% of difference between the lowest (4.5 pg) and the highest (6.3 pg) 2C value. This variation could be attributed to differences in number and size of heterochromatic knobs. Fluorescent in situ hybridization studies revealed the sequence composition of each knob, with a higher proportion of knobs composed of 180-bp repeats rather than TR-1 repeats, in all accessions. We also found numerical polymorphisms and the highest frequency of Bs reported in maize to this date. These results lead us to propose that the frequencies and doses of Bs are influenced by the landrace genotypical make-up. The Bs might be maintained in higher frequencies in those accessions having lower heterochromatin content, so as to preserve an optimal nucleotype. Furthermore, selective forces acting along the altitudinal gradient might be modulating the cytological parameters studied, as suggested by the significant correlations found among them.

Contributions to the cytogenetics of the Neotropical fish fauna.

Brazilian fish cytogenetics started as early as the seventies in three pioneering research groups, located at the Universidade Estadual Paulista (UNESP, Botucatu, SP), Universidade Federal de São Carlos (UFSCar, São Carlos, SP) and Universidade de São Paulo (USP, São Paulo, SP). Investigations that have been conducted in these groups led to the discovery of a huge chromosomal and genomic biodiversity among Neotropical fishes. Besides, they also provided the expansion of this research area, with the genesis of several other South American research groups, in view of a number of dissertations and doctoral theses developed over years. The current authors were encouraged to make their thesis catalog accessible from a public source, in order to share informations on the taxa and subject matter analyzed. Some of the key contributions to evolutionary fish cytogenetics are also being highligthed.

Origin of B chromosomes in Characidium alipioi (Characiformes, Crenuchidae) and its relationship with supernumerary chromosomes in other Characidium species.

B chromosomes are apparently dispensable components found in the genomes of many species that are mainly composed of repetitive DNA sequences. Among the numerous questions concerning B chromosomes, the origin of these elements has been widely studied. To date, supernumerary chromosomes have been identified in approximately 60 species of fish, including species of the genus Characidium Reinhardt, 1867 in which these elements appear to have independently originated. In this study, we used molecular cytogenetic techniques to investigate the origin of B chromosomes in a population of Characidium alipioi Travassos, 1955 and determine their relationship with the extra chromosomes of other species of the genus. The results showed that the B chromosomes of Characidium alipioi had an intraspecific origin, apparently originated independently in relation to the B chromosomes of Characidium gomesi Travassos, 1956 Characidium pterostictum Gomes, 1947 and Characidium oiticicai Travassos, 1967, since they do not share specific DNA sequences, as well as their possible ancestral chromosomes and belong to different phylogenetic clades. The shared sequences between the supernumerary chromosomes and the autosommal sm pair indicate the origin of these chromosomes.

Variability and evolutionary implications of repetitive DNA dynamics in genome of Astyanax scabripinnis (Teleostei, Characidae).

DNA sequences of multiple copies help in understanding evolutionary mechanisms, genomic structures and karyotype differentiation. The current study investigates the organization and distribution of different repetitive DNA in the standard complement and B chromosomes in Astyanax scabripinnis (Jenyns, 1842) chromosomes from three allopatric populations in Campos do Jordão region, São Paulo State, Brazil. The location of microsatellite sequences showed different chromosome distribution between Lavrinha Farm Stream (LFS) and Lake of Pedalinho (LP) populations. However, the karyotype of these populations basically followed the pattern of dispersed distribution in the A complement, conspicuous in telomeric/interstitial regions and preferential accumulation in the B chromosome. The B chromosome showed heterogeneous location of microsatellite probes CA, CAC and GA. The H3 and H4 histone genes were isolated from the total genome of the species and then the chromosomal mapping was performed by fluorescence in situ hybridization (FISH). The FISH signals showed high similarity for the probes H3 and H4 mapping in genomes of the populations analyzed. The sequences (GATA) n revealed a sex-specific trend between the chromosomal location in males and females at (LFS) and (LP) populations. Although species that comprise the Astyanax scabripinnis complex do not have morphologically differentiated sex chromosomes, the preferential GATA location - sex-associated - may represent a sex chromosome in differentiation.

Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae) / Diversidade Cariotípica entre três espécies do gênero Astyanax (Characiformes, Characidae)

Abstract The group Incertae sedis within the Characidae family currently includes 88 genera, previously included in the subfamily Tetragonopterinae. Among them is the genus Astyanax comprising a group of species with similar morphology and widely distributed in the Neotropics. Thus, the present study aimed to analyze the karyotype diversity in Astyanax species from different watersheds by conventional Giemsa staining, C-banding and fluorescence in situ hybridization (FISH rDNA 18S) probe.specimens of Astyanax aff. paranae belonging to the scabripinnis complex, Astyanax asunsionensis and Astyanax aff. bimaculatus were analyzed. Two sympatric karyomorphs were observed in Astyanax.aff paranae, one of them having2n=48andthe other one with 2n=50 chromosomes. Other population of this same species also presented 2n=50 chromosomes, but differing in the karyotype formula and with macro supernumerary chromosome found in 100% of the cells in about 80%of females analyzed. Two population of A. asuncionensis and one population of Astyanax. aff. bimaculatus, also showed a diploid number of 50 chromosomes, but also differing in their karyotype formulas. Therefore, A. asuncionensis was also characterized by intraspecific chromosome diversity. The C-banding analysis was able to demonstrate a distinctable to demonstrate a distinct pattern of heterochromatin differing A. asuncionensis from Astyanax aff. paranae and Astyanax aff. bimaculatus. The supernumerary chromosome of Astyanax aff. paranae proved completely heterochromatic. Only Astyanax.aff. bimaculatus multiple showed multiple sites of nucleolar organizing regions. The other species were characterized by having a simple system of NOR. These data contributes to the know ledge of the existing biodiversity in our fish fauna, here highlighted by the inter- and intraspecific chromosomal diversity in the genus Astyanax.(AU)

Resumo O grupo Incertae sedis, dentro da família Characidae inclui atualmente 88 gêneros, anteriormente incluídos na subfamília Tetragonopterinae. Dentre eles encontra-se o gênero Astyanax que compreende um grupo de espécies com morfologia similar e com ampla distribuição na região Neotropical. Assim, o presente estudo teve como objetivo analisar a diversidade cariotípica em espécies de Astyanax de diferentes bacias hidrográficas, através da coloração convencional com Giemsa, bandeamento C e hibridização fluorescente in situ (FISH com rDNA 18S). Exemplares de Astyanax aff. paranae, pertencentes ao complexo scabripinnis; Astyanax asunsionensise Astyanax aff. bimaculatus foram analisados. Dois cariomorfos foram observados em A. aff. paranae, um deles com 2n=48 cromossomos e outro com 2n=50 cromossomos. Outra população apresentou 2n=50 cromossomos, ambas diferindo na fórmula cariotípica e um cromossomo supranumerário encontrado em 100% das células, em aproximadamente 80% das fêmeas analisadas. Populações de A.asunsionensis e uma população de Astyanax aff. Bimaculatus também mostraram número diplóide de 50 cromossomos, mas diferindo em suas fórmulas cariotípicas. Portanto, A. asuncionensis foi também caracterizado por uma diversidade cariotípica intraespecífica. As análises de bandeamento C foi capaz de demonstrar um padrão distinto de heterocromatina, diferindo A. asuncionensis de A.aff. paranae e A. aff. bimaculatus. O cromossomo supranumerário de Astyanax aff. paranae mostrou-se completamente heterocromático. Apenas Astyanax aff. bimaculatus mostrou múltiplos sítios de regiões organizadoras de nucléolo(NORs). As outras espécies foram caraterizadas por apresentar um sistema simples de NOR. Estes dados contribuem para o conhecimento da existência de biodiversidade em nossa fauna de peixes, aqui em destaque pela diversidade cromossômica inter e intraespecífica no gênero Astyanax.(AU)

Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae) / Diversidade Cariotípica entre três espécies do gênero Astyanax (Characiformes, Characidae)

Abstract The group Incertae sedis within the Characidae family currently includes 88 genera, previously included in the subfamily Tetragonopterinae. Among them is the genus Astyanax comprising a group of species with similar morphology and widely distributed in the Neotropics. Thus, the present study aimed to analyze the karyotype diversity in Astyanax species from different watersheds by conventional Giemsa staining, C-banding and fluorescence in situ hybridization (FISH rDNA 18S) probe.specimens of Astyanax aff. paranae belonging to the “scabripinnis complex”, Astyanax asunsionensis and Astyanax aff. bimaculatus were analyzed”. Two sympatric karyomorphs were observed in Astyanax.aff paranae, one of them having2n=48andthe other one with 2n=50 chromosomes. Other population of this same species also presented 2n=50 chromosomes, but differing in the karyotype formula and with macro supernumerary chromosome found in 100% of the cells in about 80%of females analyzed. Two population of A. asuncionensis and one population of Astyanax. aff. bimaculatus, also showed a diploid number of 50 chromosomes, but also differing in their karyotype formulas. Therefore, A. asuncionensis was also characterized by intraspecific chromosome diversity. The C-banding analysis was able to demonstrate a distinctable to demonstrate a distinct pattern of heterochromatin differing A. asuncionensis from Astyanax aff. paranae and Astyanax aff. bimaculatus. The supernumerary chromosome of Astyanax aff. paranae proved completely heterochromatic. Only Astyanax.aff. bimaculatus multiple showed multiple sites of nucleolar organizing regions. The other species were characterized by having a simple system of NOR. These data contributes to the know ledge of the existing biodiversity in our fish fauna, here highlighted by the inter- and intraspecific chromosomal diversity in the genus Astyanax.

Resumo O grupo Incertae sedis, dentro da família Characidae inclui atualmente 88 gêneros, anteriormente incluídos na subfamília Tetragonopterinae. Dentre eles encontra-se o gênero Astyanax que compreende um grupo de espécies com morfologia similar e com ampla distribuição na região Neotropical. Assim, o presente estudo teve como objetivo analisar a diversidade cariotípica em espécies de Astyanax de diferentes bacias hidrográficas, através da coloração convencional com Giemsa, bandeamento C e hibridização fluorescente in situ (FISH com rDNA 18S). Exemplares de Astyanax aff. paranae, pertencentes ao “complexo scabripinnis”; Astyanax asunsionensise Astyanax aff. bimaculatus foram analisados. Dois cariomorfos foram observados em A. aff. paranae, um deles com 2n=48 cromossomos e outro com 2n=50 cromossomos. Outra população apresentou 2n=50 cromossomos, ambas diferindo na fórmula cariotípica e um cromossomo supranumerário encontrado em 100% das células, em aproximadamente 80% das fêmeas analisadas. Populações de A.asunsionensis e uma população de Astyanax aff. Bimaculatus também mostraram número diplóide de 50 cromossomos, mas diferindo em suas fórmulas cariotípicas. Portanto, A. asuncionensis foi também caracterizado por uma diversidade cariotípica intraespecífica. As análises de bandeamento C foi capaz de demonstrar um padrão distinto de heterocromatina, diferindo A. asuncionensis de A.aff. paranae e A. aff. bimaculatus. O cromossomo supranumerário de Astyanax aff. paranae mostrou-se completamente heterocromático. Apenas Astyanax aff. bimaculatus mostrou múltiplos sítios de regiões organizadoras de nucléolo(NORs). As outras espécies foram caraterizadas por apresentar um sistema simples de NOR. Estes dados contribuem para o conhecimento da existência de biodiversidade em nossa fauna de peixes, aqui em destaque pela diversidade cromossômica inter e intraespecífica no gênero Astyanax.

Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae)

Abstract The group Incertae sedis within the Characidae family currently includes 88 genera, previously included in the subfamily Tetragonopterinae. Among them is the genus Astyanax comprising a group of species with similar morphology and widely distributed in the Neotropics. Thus, the present study aimed to analyze the karyotype diversity in Astyanax species from different watersheds by conventional Giemsa staining, C-banding and fluorescence in situ hybridization (FISH rDNA 18S) probe.specimens of Astyanax aff. paranae belonging to the scabripinnis complex, Astyanax asunsionensis and Astyanax aff. bimaculatus were analyzed. Two sympatric karyomorphs were observed in Astyanax.aff paranae, one of them having2n=48andthe other one with 2n=50 chromosomes. Other population of this same species also presented 2n=50 chromosomes, but differing in the karyotype formula and with macro supernumerary chromosome found in 100% of the cells in about 80%of females analyzed. Two population of A. asuncionensis and one population of Astyanax. aff. bimaculatus, also showed a diploid number of 50 chromosomes, but also differing in their karyotype formulas. Therefore, A. asuncionensis was also characterized by intraspecific chromosome diversity. The C-banding analysis was able to demonstrate a distinctable to demonstrate a distinct pattern of heterochromatin differing A. asuncionensis from Astyanax aff. paranae and Astyanax aff. bimaculatus. The supernumerary chromosome of Astyanax aff. paranae proved completely heterochromatic. Only Astyanax.aff. bimaculatus multiple showed multiple sites of nucleolar organizing regions. The other species were characterized by having a simple system of NOR. These data contributes to the know ledge of the existing biodiversity in our fish fauna, here highlighted by the inter- and intraspecific chromosomal diversity in the genus Astyanax.

Resumo O grupo Incertae sedis, dentro da família Characidae inclui atualmente 88 gêneros, anteriormente incluídos na subfamília Tetragonopterinae. Dentre eles encontra-se o gênero Astyanax que compreende um grupo de espécies com morfologia similar e com ampla distribuição na região Neotropical. Assim, o presente estudo teve como objetivo analisar a diversidade cariotípica em espécies de Astyanax de diferentes bacias hidrográficas, através da coloração convencional com Giemsa, bandeamento C e hibridização fluorescente in situ (FISH com rDNA 18S). Exemplares de Astyanax aff. paranae, pertencentes ao complexo scabripinnis; Astyanax asunsionensise Astyanax aff. bimaculatus foram analisados. Dois cariomorfos foram observados em A. aff. paranae, um deles com 2n=48 cromossomos e outro com 2n=50 cromossomos. Outra população apresentou 2n=50 cromossomos, ambas diferindo na fórmula cariotípica e um cromossomo supranumerário encontrado em 100% das células, em aproximadamente 80% das fêmeas analisadas. Populações de A.asunsionensis e uma população de Astyanax aff. Bimaculatus também mostraram número diplóide de 50 cromossomos, mas diferindo em suas fórmulas cariotípicas. Portanto, A. asuncionensis foi também caracterizado por uma diversidade cariotípica intraespecífica. As análises de bandeamento C foi capaz de demonstrar um padrão distinto de heterocromatina, diferindo A. asuncionensis de A.aff. paranae e A. aff. bimaculatus. O cromossomo supranumerário de Astyanax aff. paranae mostrou-se completamente heterocromático. Apenas Astyanax aff. bimaculatus mostrou múltiplos sítios de regiões organizadoras de nucléolo(NORs). As outras espécies foram caraterizadas por apresentar um sistema simples de NOR. Estes dados contribuem para o conhecimento da existência de biodiversidade em nossa fauna de peixes, aqui em destaque pela diversidade cromossômica inter e intraespecífica no gênero Astyanax.

Cytogenetic analyses using C-banding and DAPI/CMA3 staining of four populations of the maize weevil Sitophiluszeamais Motschulsky, 1855 (Coleoptera, Curculionidae).

Cytogenetic data avalaible for the maize weevil Sitophiluszeamais Motschulsky, 1855 (Coleoptera: Curculionidae), one of the most destructive pests of stored cereal grains, are controversial. Earlier studies focused on single populations and emphasized chromosome number and sex determination system. In this paper, the karyotypes of four populations of Sitophiluszeamais were characterized by conventional staining, C-banding and sequential staining with the fluorochromes chromomycin-A3/4-6-diamidino-2-phenylindole (CMA3/DAPI). The analyses of metaphases obtained from the cerebral ganglia of last instar larvae and the testes of adults showed that the species had 2n = 22 chromosomes, with 10 autosomal pairs and a sex chromosome pair (XX in females and Xyp in males). Chromosome number, however, ranged from 2n = 22 to 26 due to the presence of 0-4 supernumerary chromosomes in individuals from the populations of Viçosa, Unai and Porto Alegre. With the exception of the Y chromosome, which was dot-like, all other chromosomes of this species were metacentric, including the supernumeraries. The heterochromatin was present in the centromeric regions of all autosomes and in the centromere of the X chromosome. The B chromosomes were partially or totally heterochromatic, and the Y chromosome was euchromatic. The heterochromatic regions were labeled with C-banding and DAPI, which showed that they were rich in AT base pairs.

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) from Northeast Paraguay.

Chromosome counts and karyotypes of two species of Chrysolaena H. Robinson 1988 are presented in this paper. Mitotic analysis revealed that both taxa have x=10, a basic chromosome number considered characteristic of the genus. The chromosome number and the karyotype of Chrysolaena cristobaliana are reported for the first time, as well as a new cytotype and the karyotype of Chrysolaena sceptrum. Chrysolaena cristobaliana showed heptaploid cytotype with 2n=7x=70 and a karyotype composed of 46 m + 24 sm chromosomes. On the other hand, Chrysolaena sceptrum presented tetraploid cytotype with 2n=4x=40 and a karyotype with 30 m + 10 sm chromosomes. Accessory chromosomes were observed in cells of both species. The chromosome analysis showed that these species differ in the chromosome number and the total chromosome length, although they showed similar chromosome morphology and asymmetry indexes. The results support the use of chromosome data in taxonomic treatments of the American members of the tribe Vernonieae.

Cytogenetic description of the Amazonian brown brocket Mazama nemorivaga (Artiodactyla, Cervidae).

The Amazonian brown brocket Mazama nemorivaga (Cuvier, 1817) is a small to medium-sized deer from the Amazon rainforest and ecotones. The first karyotype described was 2n=67 to 69 + 2-7 B and FN= 69-72, in which all chromosomes were acrocentric and the X chromosome was the only submetacentric chromosome. However, important aspects of the species chromosome evolution were not resolved because of the lack of information on chromosome banding. The G-banding pattern of Mazama nemorivaga karyotype showed the presence of an XX/XY1Y2 sex chromosome system as a product of an X-autosome tandem fusion, which results in a basic 2n=68, FN=70 in females and 2n= 69, FN=70 in males. The fact that this karyotype only differs from that of Capreolus capreolus pygargus (Pallas, 1771; 2n=70, FN=72+B) by X-autosome tandem fusion may corroborate the basal condition of Mazama nemorivaga and its proximity to the ancestral karyotype of the American Odocoileini. A derived karyotype 2n=67, XY1Y2, FN=70 + 3B from the Brazilian state of Mato Grosso (the western Amazon) may be evidence of differentiation between western and eastern populations.

First record of supernumerary (B) chromosomes in electric fish (Gymnotiformes) and the karyotype structure of three species of the same order from the upper Paraná River basin.

Cytogenetic studies were performed on the species Apteronotus prope albifrons Linnaeus, 1766, Rhamphichthys hahni Meinken, 1937 and Brachyhypopomus gauderio Giora & Malabarba, 2009, collected in the upper Paraná River floodplain, Porto Rico (PR), Brazil. Apteronotus prope albifrons showed a diploid number of 2n=24 chromosomes for both sexes and a karyotype formula of 14m+2sm+2st+6a (FN=42). Besides the standard karyotype, three specimens had one to three extra microchromosomes with inter- and intra-individual variations, which suggested the occurrence of B chromosomes in the species. The chromosomal data of Rhamphichthys hahni, described here for the first time, consists of 50 chromosomes and a formula comprised of 20m+24sm+6a (FN=94). Brachyhypopomus gauderio specimens demonstrated 2n=42 chromosomes infemales, all acrocentric, and 2n=41 chromosomes in males, with 40 acrocentric and 1 medium-sized metacentric chromosome. These differences concern with a multiple system of sexchromosome determination X1X1X2X2/X1X2Y (FN=42) in Brachyhypopomus gauderio. The analysis of nucleolar organizer regions by Ag-NOR and FISH 18S banding revealed a simple NOR system in Apteronotus prope albifrons and Rhamphichthys hahni and a multiple NOR system in Brachyhypopomus gauderio, that is unusual for Gymnotiformes fishes. Constitutive heterochromatin was mainly found in the pericentromere region in most of the chromosomes of the three species, although each species had its own peculiarities. The B chromosomes in Apteronotus prope albifrons demonstrated heterochromatin positioned in the centromeric and telomeric regions whereas Rhamphichthys hahni presented conspicuous blocks of heterochromatin on the long arms in three submetacentric pairs. Brachyhypopomus gauderio showed blocks of heterochromatin on the long arm in the interstitial and telomere positions. The finding of B chromosomes in Apteronotus prope albifrons represents the first description of these elements in the Gymnotiformes order. Although the karyotype of this species is similar with that described for populations in the Amazon basin, the presence of B chromosomes could represent a specific characteristic of this population. A comparative analysis of karyotypes of Rhamphichthys hahni with other species of the genus showed a relatively conservative structure suggesting 2n=50 as a common number in this group. The karyotype of Brachyhypopomus gauderio, a new species, provides an important reference for future chromosome studies of the Brachyhypopmus Mago-Lecia, 1994, and it might be also significant for cytotaxonomy in this group. The cytogenetic data also demonstrate the need of more comparative cytogenetic studies in the families of the highly diversified and taxonomically difficult complex Gymnotiformes.