Chromosomal rearrangements played an important role in the speciation of rice rats of genus Cerradomys (Rodentia, Sigmodontinae, Oryzomyini)

Rodents of the genus Cerradomys belong to tribe Oryzomyini, one of the most diverse and speciose groups in Sigmodontinae (Rodentia, Cricetidae). The speciation process in Cerradomys is associated with chromosomal rearrangements and biogeographic dynamics in South America during the Pleistocene era. As the morphological, molecular and karyotypic aspects of Myomorpha rodents do not evolve at the same rate, we strategically employed karyotypic characters for the construction of chromosomal phylogeny to investigate whether phylogenetic relationships using chromosomal data corroborate the radiation of Cerradomys taxa recovered by molecular phylogeny. Comparative chromosome painting using Hylaeamys megacephalus (HME) whole chromosome probes in C. langguthi (CLA), Cerradomys scotii (CSC), C. subflavus (CSU) and C. vivoi (CVI) shows that karyotypic variability is due to 16 fusion events, 2 fission events, 10 pericentric inversions and 1 centromeric repositioning, plus amplification of constitutive heterochromatin in the short arms of the X chromosomes of CSC and CLA. The chromosomal phylogeny obtained by Maximum Parsimony analysis retrieved Cerradomys as a monophyletic group with 97% support (bootstrap), with CSC as the sister to the other species, followed by a ramification into two clades (69% of branch support), the first comprising CLA and the other branch including CVI and CSU. We integrated the chromosome painting analysis of Eumuroida rodents investigated by HME and Mus musculus (MMU) probes and identified several syntenic blocks shared among representatives of Cricetidae and Muridae. The Cerradomys genus underwent an extensive karyotypic evolutionary process, with multiple rearrangements that shaped extant karyotypes. The chromosomal phylogeny corroborates the phylogenetic relationships proposed by molecular analysis and indicates that karyotypic diversity is associated with species radiation. Three syntenic blocks were identified as part of the ancestral Eumuroida karyotype (AEK): MMU 7/19 (AEK 1), MMU 14 (AEK 10) and MMU 12 (AEK 11). Besides, MMU 5/10 (HME 18/2/24) and MMU 8/13 (HME 22/5/11) should be considered as signatures for Cricetidae, while MMU 5/9/14, 5/7/19, 5 and 8/17 for Sigmodontinae.

Chromosomal organization of multigene families and meiotic analysis in species of Loricariidae (Siluriformes) from Brazilian Amazon, with description of a new cytotype for genus Spatuloricaria

In the Amazon, some species of Loricariidae are at risk of extinction due to habitat loss and overexploitation by the ornamental fish market. Cytogenetic data related to the karyotype and meiotic cycle can contribute to understanding the reproductive biology and help management and conservation programs of these fish. Additionally, chromosomal mapping of repetitive DNA in Loricariidae may aid comparative genomic studies in this family. However, cytogenetics analysis is limited in Amazonian locariids. In this study, chromosomal mapping of multigenic families was performed in Scobinancistrus aureatus, Scobinancistrus pariolispos and Spatuloricaria sp. Meiotic analyzes were performed in Hypancistrus zebra and Hypancistrus sp. "pão". Results showed new karyotype for Spatuloricaria sp. (2n=66, NF=82, 50m-10sm-6m). Distinct patterns of chromosomal organization of histone H1, histone H3 and snDNA U2 genes were registered in the karyotypes of the studied species, proving to be an excellent cytotaxonomic tool. Hypotheses to explain the evolutionary dynamics of these sequences in studied Loricariidae were proposed. Regarding H. zebra and H. sp. "pão", we describe the events related to synapse and transcriptional activity during the meiotic cycle, which in both species showed 26 fully synapsed bivalents, with high gene expression only during zygotene and pachytene. Both Hypancistrus species could be used may be models for evaluating changes in spermatogenesis of Loricariidae.

Genetic diversity analysis in the Brazilian Amazon reveals a new evolutionary lineage and new karyotype for the genus Mesomys (Rodentia, Echimyidae, Eumysopinae)

Morphological, molecular and chromosomal studies in the genera Lonchothrix and Mesomys have contributed to a better understanding of taxonomic design, phylogenetic relationships and karyotypic patterns. Recent molecular investigations have shown a yet undescribed diversity, suggesting that these taxa are even more diverse than previously assumed. Furthermore, some authors have questioned the limits of geographic distribution in the Amazon region for the species M. hispidus and M. stimulax. In this sense, the current study sought to understand the karyotypic evolution and geographic limits of the genus Mesomys, based on classical (G- and C-banding) and molecular cytogenetic analysis (FISH using rDNA 18S and telomeric probes) and through the sequencing of mitochondrial genes Cytochrome b (Cytb) and Cytochrome Oxidase-Subunit I (CO using phylogeny, species delimitation and time of divergence, from samples of different locations in the Brazilian Amazon. The species M. stimulax and Mesomys sp. presented 2n = 60/FN = 110, while M. hispidus presented 2n = 60/FN = 112, hitherto unpublished. Molecular dating showed that Mesomys diversification occurred during the Plio-Pleistocene period, with M. occultus diverging at around 5.1 Ma, followed by Mesomys sp. (4.1 Ma) and, more recently, the separation between M. hispidus and M. stimulax (3.5 Ma). The ABGD and ASAP species delimiters support the formation of 7 and 8 potential species of the genus Mesomys, respectively. Furthermore, in both analyzes Mesomys sp. was recovered as a valid species. Our multidisciplinary approach involving karyotypic, molecular and biogeographic analysis is the first performed in Mesomys, with the description of a new karyotype for M. hispidus, a new independent lineage for the genus and new distribution data for M. hispidus and M. stimulax.

Mechanisms of Karyotypic Diversification in Ancistrus (Siluriformes, Loricariidae): Inferences from Repetitive Sequence Analysis

Ancistrus is a highly diverse neotropical fish genus that exhibits extensive chromosomal variability, encompassing karyotypic morphology, diploid chromosome number (2n = 34-54), and the evolution of various types of sex chromosome systems. Robertsonian rearrangements related to unstable chromosomal sites are here described. Here, the karyotypes of two Ancistrus species were comparatively analyzed using classical cytogenetic techniques, in addition to isolation, cloning, sequencing, molecular characterization, and fluorescence in situ hybridization of repetitive sequences (i.e., 18S and 5S rDNA; U1, U2, and U5 snDNA; and telomere sequences). The species analyzed here have different karyotypes: Ancistrus sp. 1 (2n = 38, XX/XY) and Ancistrus cirrhosus (2n = 34, no heteromorphic sex chromosomes). Comparative mapping showed different organizations for the analyzed repetitive sequences: 18S and U1 sequences occurred in a single site in all populations of the analyzed species, while 5S and U2 sequences could occur in single or multiple sites. A sequencing analysis confirmed the identities of the U1, U2, and U5 snDNA sequences. Additionally, a syntenic condition for U2-U5 snDNA was found in Ancistrus. In a comparative analysis, the sequences of rDNA and U snDNA showed inter- and intraspecific chromosomal diversification. The occurrence of Robertsonian rearrangements and other dispersal mechanisms of repetitive sequences are discussed.

Cytotoxicity and Genotoxicity Evaluation of Zanthoxylum rhoifolium Lam and In Silico Studies of Its Alkaloids

The alkaloids isolated from Zanthoxylum rhoifolium have demonstrated great pharmacological potential; however, the toxic profiles of these extracts and fractions are still not well elucidated. This study evaluated the toxicity of the ethanol extract (EEZR) and neutral (FNZR) and alkaloid (FAZR) fractions. Chemical characterization was performed by chromatographic methods: thin-layer chromatography (TLC) and high-performance liquid chromatography coupled with diode array detection (HPLC-DAD). The cytotoxicity of the samples was evaluated in human hepatocellular carcinoma (HepG2) cells using the cell viability method (MTT) and mutagenicity by the Allium cepa assay (ACA). Alkaloids isolated from the species were selected for toxicity prediction using preADMET and PROTOX. The molecular docking of the topoisomerase II protein (TOPOII) was used to investigate the mechanism of cell damage. In the EEZR, FNZR, and FAZR, the presence of alkaloids was detected in TCL and HPLC-DAD analyses. These samples showed a 50% inhibitory concentration (IC₅₀) greater than 400 μg/mL in HepG2 cells. In ACA, time- and concentration-dependent changes were observed, with a significant reduction in the mitotic index and an increase in chromosomal aberrations for all samples. Nuclear sprouts and a micronucleus of the positive control (PC) were observed at 10 µg/mL and in the FAZR at 30 µg/mL; a chromosomal bridge in FNZR was observed at 105 µg/mL, CP at a concentration of 40 µg/mL, and nuclear bud and mitotic abnormalities in the EEZR were observed at 170 µg/mL. The alkaloids with a benzophenanthridine were selected for the in silico study, as structural alterations demonstrated certain toxic effects. Molecular docking with topo II demonstrated that all alkaloids bind to the protein. In summary, the fractionation of Z. rhoifolium did not interfere with toxicity; it seems that alkaloids with a benzophenanthridine nucleus may be involved in this toxicity.

The Potential of DHA as Cancer Therapy Strategies: A Narrative Review of In Vitro Cytotoxicity Trials

Docosahexaenoic acid (DHA), also known as omega-3 (n-3) polyunsaturated fatty acid (PUFA), is a natural compound that has demonstrated pharmacological activity against several malignant neoplasms. Available cancer treatments cause side effects, affect healthy cells, reduce the quality of life of patients and may cause resistance to antineoplastics. For these reasons, the search for new therapies is continuous. This narrative review aimed to compile information on in vitro experiments that study the cytotoxic effect of DHA or molecules derived from DHA in tumor and nontumor cells. This was performed to highlight the potential of DHA as a strategy for cancer therapy and to gather information, which will help researchers plan experimental designs and develop research to discover effective therapies against cancer. In addition, studies were presented that demonstrate the dose of DHA that can treat patients with cancer. Thus, a search was conducted for articles on the SCOPUS and Web of Science platforms, published until 2022, that analyzed the action of DHA against breast, lung, colorectal, prostate, stomach and liver cancers. Cytotoxic effects were observed in tumor and nontumor cell lines, and these results varied with the type of cell line studied, drug concentration, incubation time and treatment combination, i.e., with DHA alone, combined with other drugs and with molecules derived from DHA. In patients with cancer, in all analyzed studies, DHA intake was associated with eicosapentaenoic acid (EPA) and/or proteins to aid chemotherapy, and with this procedure, tumor reduction, chemotherapy tolerance and muscle mass gain were obtained. This work contributes to the community by demonstrating the possible applicability of DHA in the pharmaceutical area of oncological therapies.

Chromosomal Mapping of the Histone Multigene Family and U2 snRNA in Hypancistrus Species (Siluriformes, Loricariidae) from the Brazilian Amazon

Loricariidae (Siluriformes) comprises ∼1026 species of neotropical fish, being considered the most diverse among the Siluriformes. Studies on repetitive DNA sequences have provided important data on the evolution of the genomes of members of this family, especially of the Hypostominae subfamily. In this study, the chromosomal mapping of the histone multigene family and U2 snRNA was performed in two species belonging to the Hypancistrus genus, Hypancistrus sp. "pão" (2n = 52, 22m + 18sm +12st) and Hypancistrus zebra (2n = 52, 16m + 20sm +16st). The presence of dispersed signals of histones H2A, H2B, H3, and H4 in the karyotype of both species, with each sequence displaying a varied level of accumulation and dispersion of these sequences between them was observed; in addition, U2 snDNA probe only showed positive results in H. zebra, which present this multigene in the terminal region of three chromosomal pairs. The obtained results resemble data already analyzed in the literature, in which the action of transposable elements interfere in the organization of these multigene families, in addition to other evolutionary processes that shape the evolution of the genome, such as circular or ectopic recombination. This study also shows that the dispersion of the multigene histone family is quite complex, and from this, these data serve as a point of discussion for the evolutionary processes that occur in the Hypancistrus karyotype.

Ancestral chromosomal signatures of Paenungulata (Afroteria) reveal the karyotype of Amazonian manatee (Trichechus inunguis, Sirenia: Trichechidae) as the oldest among American manatees

BACKGROUND

Chromosomal painting in manatees has clarified questions about the rapid evolution of sirenians within the Paenungulata clade. Further cytogenetic studies in Afrotherian species may provide information about their evolutionary dynamics, revealing important insights into the ancestral karyotype in the clade representatives. The karyotype of Trichechus inunguis (TIN, Amazonian manatee) was investigated by chromosome painting, using probes from Trichechus manatus latirostris (TML, Florida manatee) to analyze the homeologies between these sirenians.

RESULTS

A high similarity was found between these species, with 31 homologous segments in TIN, nineteen of which are whole autosomes, besides the X and Y sex chromosomes. Four chromosomes from TML (4, 6, 8, and 9) resulted in two hybridization signals, totaling eight acrocentrics in the TIN karyotype. This study confirmed in TIN the chromosomal associations of Homo sapiens (HSA) shared in Afrotheria, such as the 5/21 synteny, and in the Paenungulata clade with the syntenies HSA 2/3, 8/22, and 18/19, in addition to the absence of HSA 4/8 common in eutherian ancestral karyotype (EAK).

CONCLUSIONS

TIN shares more conserved chromosomal signals with the Paenungulata Ancestral Karyotype (APK, 2n = 58) than Procavia capensis (Hyracoidea), Loxodonta africana (Proboscidea) and TML (Sirenia), where TML presents less conserved signals with APK, demonstrating that its karyotype is the most derived among the representatives of Paenungulata. The chromosomal changes that evolved from APK to the T. manatus and T. inunguis karyotypes (7 and 4 changes, respectively) are more substantial within the Trichechus genus compared to other paenungulates. Among these species, T. inunguis presents conserved traits of APK in the American manatee genus. Consequently, the karyotype of T. manatus is more derived than that of T. inunguis.

Chromosome painting and phylogenetic analysis suggest that the genus Lophostoma (Chiroptera, Phyllostomidae) is paraphyletic

The subfamily Phyllostominae (Chiroptera, Phyllostomidae) comprises 10 genera of Microchiroptera bats from the Neotropics. The taxonomy of this group is controversial due to incongruities in the phylogenetic relationships evident from different datasets. The genus Lophostoma currently includes eight species whose phylogenetic relationships have not been resolved. Integrative analyzes including morphological, molecular and chromosomal data are powerful tools to investigate the phylogenetics of organisms, particularly if obtained by chromosomal painting. In the present work we performed comparative genomic mapping of three species of Lophostoma (L. brasiliense 2n = 30, L. carrikeri 2n = 26 and L. schulzi 2n = 26), by chromosome painting using whole chromosome probes from Phyllostomus hastatus and Carollia brevicauda; this included mapping interstitial telomeric sites. The karyotype of L. schulzi (LSC) is a new cytotype. The species L. brasiliense and L. carrikeri showed interstitial telomeric sequences that probably resulted from expansions of repetitive sequences near pericentromeric regions. The addition of chromosomal painting data from other species of Phyllostominae allowed phylogeny construction by maximum parsimony, and the determination that the genera of this subfamily are monophyletic, and that the genus Lophostoma is paraphyletic. Additionally, a review of the taxonomic status of LSC is suggested to determine if this species should be reclassified as part of the genus Tonatia.

Chromosomal Diversification in Pseudacanthicus Species (Loricariidae, Hypostominae) Revealed by Comparative Mapping of Repetitive Sequences

Simple Summary

The fishes of the Loricariidae family have a huge genetic diversity, mainly involving variations in the number and shape of chromosomes. The recognition of the species genus Pseudacanthicus is complex due to the large diversity of forms and limited knowledge of their genetic diversity. In this study, the karyotypes of three Pseudacanthicus species were comparatively analyzed using classical and molecular methods. They presented the same diploid number, but with different compositions of repetitive DNA sequences. Such information can be useful for the recognition of distinct species, in addition to providing important insights into the real biodiversity of this important group of Neotropical fish.

Abstract

Pseudacanthicus is a genus of Neotropical fish with eight valid species, in addition to numerous lineages not formally identified. It occurs along the Amazon and Tocantins River basins, in Suriname and in the Guiana shield. There are no karyotypic data in the literature for species of this genus. Here, the karyotypes of three Pseudacanthicus species (P. spinosus, P. leopardus and Pseudacanthicus sp.) were comparatively analyzed by classical cytogenetics and fluorescence in situ hybridization using 18S and 5S rDNA probes, U2 snDNA and telomeric sequences. The analyzed species presented 52 chromosomes and KF = 18 m + 34 sm. Constitutive heterochromatin occurred in blocks on a few chromosomes. The 18S rDNA occurred in a single pair; interestingly, P. leopardus presented only one locus of this sequence in its diploid genome. The 5S rDNA sequence occurred in only one pair in P. leopardus, and in multiple sites in Pseudacanthicus sp. and P. spinosus. The snDNA U2 occurred in only one pair in all analyzed species. Telomeric sequences did not show interstitial sites. Although Pseudacanthicus species share the same 2n and KF, repetitive sequence analysis revealed karyotypic diversity among these species. The occurrence of DNA double-strand breaks related to fragile sites, unequal crossing over and transpositions is proposed as the mechanism of karyotypic diversification, suggesting that the conservation of the karyotypic macrostructure is only apparent in this group of fish.

Kinetic Activity of Chromosomes and Expression of Recombination Genes in Achiasmatic Meiosis of Tityus (Archaeotityus) Scorpions

Several species of Tityus (Scorpiones, Buthidae) present multi-chromosomal meiotic associations and failures in the synaptic process, originated from reciprocal translocations. Holocentric chromosomes and achiasmatic meiosis in males are present in all members of this genus. In the present study, we investigated synapse dynamics, transcriptional silencing by γH2AX, and meiotic microtubule association in bivalents and a quadrivalent of the scorpion Tityus maranhensis. Additionally, we performed RT-PCR to verify the expression of mismatch repair enzymes involved in crossing-over formation in Tityus silvestris gonads. The quadrivalent association in T. maranhensis showed delay in the synaptic process and long asynaptic regions during pachytene. In this species, γH2AX was recorded only at the chromosome ends during early stages of prophase I; in metaphase I, bivalents and quadrivalents of T. maranhensis exhibited binding to microtubules along their entire length, while in metaphase II/anaphase II transition, spindle fibers interacted only with telomeric regions. Regarding T. silvestris, genes involved in the recombination process were transcribed in ovaries, testes and embryos, without significant difference between these tissues. The expression of these genes during T. silvestris achiasmatic meiosis is discussed in the present study. The absence of meiotic inactivation by γH2AX and holo/telokinetic behavior of the chromosomes are important factors for the maintenance of the quadrivalent in T. maranhensis and the normal continuation of the meiotic cycle in this species.

Chromosomal painting in Charadrius collaris Vieillot, 1818 and Vanellus chilensis Molina, 1782 and an analysis of chromosomal signatures in Charadriiformes

Charadriiformes represent one of the largest orders of birds; members of this order are diverse in morphology, behavior and reproduction, making them an excellent model for studying evolution. It is accepted that the avian putative ancestral karyotype, with 2n = 80, remains conserved for about 100 million years. So far, only a few species of Charadriiformes have been studied using molecular cytogenetics. Here, we performed chromosome painting on metphase chromosomes of two species of Charadriidae, Charadrius collaris and Vanellus chilensis, with whole chromosome paint probes from Burhinus oedicnemus. Charadrius collaris has a diploid number of 76, with both sex chromosomes being submetacentric. In V. chilensi a diploid number of 78 was identified, and the Z chromosome is submetacentric. Chromosome painting suggests that chromosome conservation is a characteristic common to the family Charadriidae. The results allowed a comparative analysis between the three suborders of Charadriiformes and the order Gruiformes using chromosome rearrangements to understand phylogenetic relationships between species and karyotypic evolution. However, the comparative analysis between the Charadriiformes suborders so far has not revealed any shared rearrangements, indicating that each suborder follows an independent evolutionary path, as previously proposed. Likewise, although the orders Charadriiformes and Gruiformes are placed on sister branches, they do not share any signature chromosomal rearrangements.

The emergence of a new sex-system (XX/XY1Y2) suggests a species complex in the "monotypic" rodent Oecomys auyantepui (Rodentia, Sigmodontinae)

X-autosome translocation (XY₁Y₂) has been reported in distinct groups of vertebrates suggesting that the rise of a multiple sex system within a species may act as a reproductive barrier and lead to speciation. The viability of this system has been linked with repetitive sequences located between sex and autosomal portions of the translocation. Herein, we investigate Oecomys auyantepui, using chromosome banding and Fluorescence In Situ Hybridization with telomeric and Hylaeamys megacephalus whole-chromosome probes, and phylogenetic reconstruction using mtDNA and nuDNA sequences. We describe an amended karyotype for O. auyantepui (2n = 64♀65♂/FNa = 84) and report for the first time a multiple sex system (XX/XY₁Y₂) in Oryzomyini rodents. Molecular data recovered O. auyantepui as a monophyletic taxon with high support and cytogenetic data indicate that O. auyantepui may exist in two lineages recognized by distinct sex systems. The Neo-X exhibits repetitive sequences located between sex and autosomal portions, which would act as a boundary between these two segments. The G-banding comparisons of the Neo-X chromosomes of other Sigmodontinae taxa revealed a similar banding pattern, suggesting that the autosomal segment in the Neo-X can be shared among the Sigmodontinae lineages with a XY₁Y₂ sex system.

Chromosome Painting in Gymnotus carapo "Catalão" (Gymnotiformes, Teleostei): Dynamics of Chromosomal Rearrangements in Cryptic Species

The genus Gymnotus is a large monophyletic group of freshwater weakly-electric fishes, with wide distribution in Central and South America. It has 46 valid species divided into six subgenera (Gymnotus, Tijax, Tigre, Lamontianus, Tigrinus and Pantherus) with large chromosome plasticity and diploid numbers (2n) ranging from 34 to 54. Within this rich diversity, there is controversy about whether Gymnotus (Gymnotus) carapo species is a single widespread species or a complex of cryptic species. Cytogenetic studies show different diploid numbers for G. carapo species, ranging from 40 to 54 chromosomes with varied karyotypes found even between populations sharing the same 2n. Whole chromosome painting has been used in studies on fish species and recently has been used for tracking the chromosomal evolution of Gymnotus and assisting in its cytotaxonomy. Comparative genomic mapping using chromosome painting has shown more complex rearrangements in Gymnotus carapo than shown in previous studies by classical cytogenetics. These studies demonstrate that multiple chromosome pairs are involved in its chromosomal reorganization, suggesting the presence of a complex of cryptic species due to a post zygotic barrier. In the present study, metaphase chromosomes of G. carapo occidentalis "catalão" (GCC, 2n = 40, 30m/sm+10st/a) from the Catalão Lake, Amazonas, Brazil, were hybridized with whole chromosome probes derived from the chromosomes of G. carapo (GCA, 2n = 42, 30m/sm+12st/a). The results reveal chromosome rearrangements and a high number of repetitive DNA sites. Of the 12 pairs of G. carapo chromosomes that could be individually identified (GCA 1-3, 6, 7, 9, 14, 16 and 18-21), 8 pairs (GCA 1, 2, 6, 7, 9, 14, 20, 21) had homeology conserved in GCC. Of the GCA pairs that are grouped (GCA [4, 8], [5, 17], [10, 11] and [12, 13, 15]), most kept the number of signals in GCC (GCA [5, 17], [10, 11] and [12, 13, 15]). The remaining chromosomes are rearranged in the GCC karyotype. Analysis of both populations of the G. carapo cytotypes shows extensive karyotype reorganization. Along with previous studies, this suggests that the different cytotypes analyzed here may represent different species and supports the hypothesis that G. carapo is not a single widespread species, but a group of cryptic species.

Chromosomal Diversification in Ancistrus Species (Siluriformes: Loricariidae) Inferred From Repetitive Sequence Analysis

The Ancistrus genus has extensive chromosomal diversity among species, including heteromorphic sex chromosomes occurrence. However, studies have been shown that chromosomal diversity may still be underestimated. Repetitive sequences represent a large part of eukaryotic genomes, associated with mechanisms of karyotypic diversification, including sex chromosomes evolution. This study analyzed the karyotype diversification of two Ancistrus species (Ancistrus sp. 1 and Ancistrus sp. 2) from the Amazon region by classical and molecular chromosomal markers. Conventional chromosome bands and fluorescence in situ hybridization using probes 18S and 5S rDNA, besides (CA)n, (CG)n, (GA)n, (CAC)n, (CAG)n, (CAT)n, (GAA)n, (GAC)n, (TAA)n, and (TTAGGG)n in tandem repeats were determined on the karyotypes. Ancistrus sp. 1 and Ancistrus sp. 2 presented karyotypes with 2n = 38 (20 m + 14sm+4st, XX/XY) and 2n = 34 (20 m + 14sm, without heteromorphic sex chromosomes), respectively. Robertsonian rearrangements can explain the diploid number difference. C-bands occurred in pericentromeric regions in some chromosomes, and a single 18S rDNA locus occurred in both species. The 5S rDNA showed variation in the number of loci between species karyotypes, suggesting the occurrence of unstable sites and rearrangements associated with these sequences in Ancistrus. The microsatellite mapping evidenced distinct patterns of organization between the two analyzed species, occurring mainly in the sex chromosomes in Ancistrus sp. 1, and in the centromeric and pericentromeric regions of chromosomes m/sm in Ancistrus sp. 2. These data shows the extensive chromosomal diversity of repetitive sequences in Ancistrus, which were involved in Robertsonian rearrangements and sex chromosomes differentiation.

Comparative Cytogenetics Analysis Among Peckoltia Species (Siluriformes, Loricariidae): Insights on Karyotype Evolution and Biogeography in the Amazon Region

Peckoltia is widely distributed genus in the Amazon and Orinoco basins and the Guiana Shield, containing 18 valid species, and distinct morphotypes still needing description in the scientific literature due to its great taxonomic complexity. This study performed a comparative chromosomal analysis of two undescribed Peckoltia species (Peckoltia sp. 3 Jarumã and Peckoltia sp. 4 Caripetuba) from the Brazilian Amazon using conventional chromosome bands methods and in situ localization of the repetitive DNA (5S and 18S rRNA and U1 snRNA genes and telomeric sequences). Both species presented 2n = 52 but differed in their karyotype formula, probably due to inversions or translocations. The nucleolus organizer regions (NORs) showed distal location on a probably homeologous submetacentric pair in both species, besides an extra signal in a subtelocentric chromosome in Peckoltia sp. 4 Caripetuba. Heterochromatin occurred in large blocks, with different distributions in the species. The mapping of the 18S and 5S rDNA, and U1 snDNA showed differences in locations and number of sites. No interstitial telomeric sites were detected using the (TTAGGG)n probes. Despite 2n conservationism in Peckoltia species, the results showed variation in karyotype formulas, chromosomal bands, and locations of repetitive sites, demonstrating great chromosomal diversity. A proposal for Peckoltia karyotype evolution was inferred in this study based on the diversity of location and number of chromosomal markers analyzed. A comparative analysis with other Peckoltia karyotypes described in the literature, their biogeography patterns, and molecular phylogeny led to the hypothesis that the derived karyotype was raised in the left bank of the Amazon River.

Archolaemus janeae (Gymnotiformes, Teleostei): First insights into karyotype and repetitive DNA distribution in two populations of the Amazon

Archolaemus, one of the five genera of Neotropical freshwater fish of the family Sternopygidae (Gymnotiformes), was long considered a monotypic genus represented by Archolaemus blax. Currently, it consists of six species, most of them occurring in the Amazon region. There are no cytogenetic data for species of this genus. In the present study, we used classical cytogenetics (conventional staining and C-banding) and molecular cytogenetics (probes of telomeric sequences and multigenic families 18S rDNA, 5S rDNA, and U2 snDNA) to study the karyotype of Archolaemus janeae from Xingu and Tapajós rivers in the state of Pará (Brazil). The results showed that the two populations have identical karyotypes with 46 chromosomes: four submetacentric and 42 acrocentric (2n = 46; 4m/sm + 42a). Constitutive heterochromatin occurs in the centromeric region of all chromosomes, in addition to small bands in the interstitial and distal regions of some pairs. The 18S rDNA occurs in the distal region of the short arm of pair 2; the 5S rDNA occurs in five chromosome pairs; and the U2 snDNA sequence occurs in chromosome pairs 3, 6, and 13. No interstitial telomeric sequence was observed. These results show karyotypic similarity between the studied populations suggesting the existence of a single species and are of great importance as a reference for future cytotaxonomic studies of the genus.

Comparative genomic mapping reveals mechanisms of chromosome diversification in Rhipidomys species (Rodentia, Thomasomyini) and syntenic relationship between species of Sigmodontinae

Rhipidomys (Sigmodontinae, Thomasomyini) has 25 recognized species, with a wide distribution ranging from eastern Panama to northern Argentina. Cytogenetic data has been described for 13 species with 12 of them having 2n = 44 with a high level of autosomal fundamental number (FN) variation, ranging from 46 to 80, assigned to pericentric inversions. The species are grouped in groups with low FN (46–52) and high FN (72–80). In this work the karyotypes of Rhipidomys emiliae (2n = 44, FN = 50) and Rhipidomys mastacalis (2n = 44, FN = 74), were studied by classical cytogenetics and by fluorescence in situ hybridization using telomeric and whole chromosome probes (chromosome painting) of Hylaeamys megacephalus (HME). Chromosome painting revealed homology between 36 segments of REM and 37 of RMA. We tested the hypothesis that pericentric inversions are the predominant chromosomal rearrangements responsible for karyotypic divergence between these species, as proposed in literature. Our results show that the genomic diversification between the karyotypes of the two species resulted from translocations, centromeric repositioning and pericentric inversions. The chromosomal evolution in Rhipidomys was associated with karyotypical orthoselection. The HME probes revealed that seven syntenic probably ancestral blocks for Sigmodontinae are present in Rhipidomys. An additional syntenic block described here is suggested as part of the subfamily ancestral karyotype. We also define five synapomorphies that can be used as chromosomal signatures for Rhipidomys.

New karyotype for Mesomys stimulax (Rodentia, Echimyidae) from the Brazilian Amazon: A case for species complex?

Mesomys Wagner, 1845 (Rodentia, Echimyidae, Eumysopinae) currently has four recognized species, three of which occur in Brazil: Mesomys hispidus (probably a species complex), M. occultus, and M. stimulax. Mesomys leniceps is found in montane forests of northern Peru. Mesomys stimulax, the focus of the present study, has a distribution that is restricted to the central and eastern Amazonia south of the Amazon River, extending from the left bank of the Tapajós River to the right bank of the Tocantins River, and south to the southeast portion of Pará State. The genus presents karyotypes with diploid number 2n = 60 and Fundamental Number (FN) = 116 for M. hispidus and M. stimulax, and 2n = 42, FN = 54 for M. occultus. We studied the karyotype of a female specimen of M. stimulax collected from the Tapirapé-Aquiri National Forest, Marabá, Pará, Brazil, in the Xingu/Tocantins interfluvium. The obtained karyotype (2n = 60 and FN = 110) differs from that described in the literature for both M. stimulax and M. hispidus by exhibiting more biarmed chromosomes, probably due to pericentric inversions and/or centromeric repositioning, and exhibiting differences in the amount and distribution of constitutive heterochromatin (CH). These results suggest that, similar to what has already been proposed for M. hispidus, M. stimulax may represent a species complex and/or cryptic species. The mechanisms of chromosomal diversification in Mesomys and the biogeographic implications are discussed reinforcing the need for broad systematic review for Mesomys.

Bioactive Compounds and Evaluation of Antioxidant, Cytotoxic and Cytoprotective Effects of Murici Pulp Extracts (Byrsonima crassifolia) Obtained by Supercritical Extraction in HepG2 Cells Treated with H2O2

The use of clean technologies in the development of bioactive plant extracts has been encouraged, but it is necessary to verify the cytotoxicity and cytoprotection for food and pharmaceutical applications. Therefore, the objective of this work was to obtain the experimental data of the supercritical sequential extraction of murici pulp, to determine the main bioactive compounds obtained and to evaluate the possible cytotoxicity and cytoprotection of the extracts in models of HepG2 cells treated with H2O2. The murici pulp was subjected to sequential extraction with supercritical CO2 and CO2+ethanol, at 343.15 K, and 22, 32, and 49 MPa. Higher extraction yields were obtained at 49 MPa. The oil presented lutein (224.77 µg/g), oleic, palmitic, and linoleic, as the main fatty acids, and POLi (17.63%), POO (15.84%), PPO (13.63%), and LiOO (10.26%), as the main triglycerides. The ethanolic extract presented lutein (242.16 µg/g), phenolic compounds (20.63 mg GAE/g), and flavonoids (0.65 mg QE/g). The ethanolic extract showed greater antioxidant activity (122.61 and 17.14 µmol TE/g) than oil (43.48 and 6.04 µmol TE/g). Both extracts did not show cytotoxicity and only murici oil showed a cytoprotective effect. Despite this, the results qualify both extracts for food/pharmaceutical applications.

Andiroba oil and nanoemulsion (Carapa guianensis Aublet) reduce lesion severity caused by the antineoplastic agent doxorubicin in mice

Doxorubicin (DOX) is an anthracycline antibiotic used in the fight against many types of cancer. Although it is quite effective for this purpose, its clinical use is limited by its severe side effects, highlighting the relevance of efforts to identify substances that act to minimize these effects. In this work, we sought to verify the ability of andiroba oil (AO) and a nanoemulsion of andiroba oil (AN) to lessen the side effects of DOX. The animals were separated into 7 groups with 6 animals each: mice treated with AO (2000 mg/kg), AN (2000 mg/kg), the antineoplastic agent DOX (40 mg/kg), AO+DOX, AN+DOX and solvent controls was used of negative control (corn oil and nanoemulsion surfactant). AO and AN were administered for 14 consecutive days orally by gavage and on the 13th day, applied DOX by intraperitoneal route (i.p.), in order to evaluate the protective potential of andiroba. The animals were euthanized on the 15th day. Hematological, biochemical, histological, and immunohistochemical parameters were analyzed. Andiroba reduced several aspects of the severity of lesions caused by DOX, decreasing hematotoxicity and the severity of histological changes in the liver and kidneys, and reducing the frequency of apoptotic cell death. In many cases, AN showed greater efficacy than AO alone, reflecting the feasibility of using this nanotechnology to improve the pharmacokinetics of lipid compounds in the body. The study sheds new light on the therapeutic benefits of andiroba and suggests new ways for investigating how the quantity and quality of lipid compounds affect exposed organisms.

Analysis of multiple chromosomal rearrangements in the genome of Willisornis vidua using BAC-FISH and chromosome painting on a supposed conserved karyotype

BACKGROUND

Thamnophilidae birds are the result of a monophyletic radiation of insectivorous Passeriformes. They are a diverse group of 225 species and 45 genera and occur in lowlands and lower montane forests of Neotropics. Despite the large degree of diversity seen in this family, just four species of Thamnophilidae have been karyotyped with a diploid number ranging from 76 to 82 chromosomes. The karyotypic relationships within and between Thamnophilidae and another Passeriformes therefore remain poorly understood. Recent studies have identified the occurrence of intrachromosomal rearrangements in Passeriformes using in silico data and molecular cytogenetic tools. These results demonstrate that intrachromosomal rearrangements are more common in birds than previously thought and are likely to contribute to speciation events. With this in mind, we investigate the apparently conserved karyotype of Willisornis vidua, the Xingu Scale-backed Antbird, using a combination of molecular cytogenetic techniques including chromosome painting with probes derived from Gallus gallus (chicken) and Burhinus oedicnemus (stone curlew), combined with Bacterial Artificial Chromosome (BAC) probes derived from the same species. The goal was to investigate the occurrence of rearrangements in an apparently conserved karyotype in order to understand the evolutionary history and taxonomy of this species. In total, 78 BAC probes from the Gallus gallus and Taeniopygia guttata (the Zebra Finch) BAC libraries were tested, of which 40 were derived from Gallus gallus macrochromosomes 1-8, and 38 from microchromosomes 9-28.

RESULTS

The karyotype is similar to typical Passeriformes karyotypes, with a diploid number of 2n = 80. Our chromosome painting results show that most of the Gallus gallus chromosomes are conserved, except GGA-1, 2 and 4, with some rearrangements identified among macro- and microchromosomes. BAC mapping revealed many intrachromosomal rearrangements, mainly inversions, when comparing Willisornis vidua karyotype with Gallus gallus, and corroborates the fissions revealed by chromosome painting.

CONCLUSIONS

Willisornis vidua presents multiple chromosomal rearrangements despite having a supposed conservative karyotype, demonstrating that our approach using a combination of FISH tools provides a higher resolution than previously obtained by chromosome painting alone. We also show that populations of Willisornis vidua appear conserved from a cytogenetic perspective, despite significant phylogeographic structure.

Chromosomal painting of the sandpiper (Actitis macularius) detects several fissions for the Scolopacidae family (Charadriiformes)

Background

The Scolopacidae family (Suborder Scolopaci, Charadriiformes) is composed of sandpipers and snipes; these birds are long-distance migrants that show great diversity in their behavior and habitat use. Cytogenetic studies in the Scolopacidae family show the highest diploid numbers for order Charadriiformes. This work analyzes for the first time the karyotype of Actitis macularius by classic cytogenetics and chromosome painting.

Results

The species has a diploid number of 92, composed mostly of telocentric pairs. This high 2n is greater than the proposed 80 for the avian ancestral putative karyotype (a common feature among Scolopaci), suggesting that fission rearrangements have formed smaller macrochromosomes and microchromosomes. Fluorescence in situ hybridization using Burhinus oedicnemus whole chromosome probes confirmed the fissions in pairs 1, 2, 3, 4 and 6 of macrochromosomes.

Conclusion

Comparative analysis with other species of Charadriiformes studied by chromosome painting together with the molecular phylogenies for the order allowed us to raise hypotheses about the chromosomal evolution in suborder Scolopaci. From this, we can establish a clear idea of how chromosomal evolution occurred in this suborder.

Karyotypic divergence reveals that diversity in the Oecomys paricola complex (Rodentia, Sigmodontinae) from eastern Amazonia is higher than previously thought

The genus Oecomys (Rodentia, Sigmodontinae) is distributed from southern Central America to southeastern Brazil in South America. It currently comprises 18 species, but multidisciplinary approaches such as karyotypic, morphological and molecular studies have shown that there is a greater diversity within some lineages than others. In particular, it has been proposed that O. paricola constitutes a species complex with three evolutionary units, which have been called the northern, eastern and western clades. Aiming to clarify the taxonomic status of O. paricola and determine the relevant chromosomal rearrangements, we investigated the karyotypes of samples from eastern Amazonia by chromosomal banding and FISH with Hylaeamys megacephalus (HME) whole-chromosome probes. We detected three cytotypes for O. paricola: A (OPA-A; 2n = 72, FN = 75), B (OPA-B; 2n = 70, FN = 75) and C (OPA-C; 2n = 70, FN = 72). Comparative chromosome painting showed that fusions/fissions, translocations and pericentric inversions or centromeric repositioning were responsible for the karyotypic divergence. We also detected exclusive chromosomal signatures that can be used as phylogenetic markers. Our analysis of karyotypic and distribution information indicates that OPA-A, OPA-B and OPA-C are three distinct species that belong to the eastern clade, with sympatry occurring between two of them, and that the “paricola group” is more diverse than was previously thought.

Lethal and sublethal exposure of Hemichromis bimaculatus (Gill, 1862) to malachite green and possible implications for ornamental fish

Malachite green (MG) is a triphenylmethane dye that is widely used in aquaculture as a fungicide, bactericide, ectoparasiticide, and antiprotozoal. There is great debate regarding the potential for this compound to trigger adverse effects. Here, we review the previous findings and then evaluate the lethal and sublethal effects of MG in the species Hemichromis bimaculatus (jewelfish). The lethal concentration for 50% of the fish in 96 h was 1 mg/L. We observed a dose-dependent increase in the percentage of fish mortality as well as physical and behavioral changes. We further found that the highest tested sublethal dose significantly increased the DNA damage index identified using the comet assay (74.97 ± 13.8 at a significant level of P < 0.05 for the 0.75 mg/L concentration), but did not significantly alter the results of the micronucleus test. Although our results suggest that MG confers risks on exposed fish, the findings were significant only at the highest exposure concentration (0.75 mg/L). At lower concentrations (0.25 mg/L and 0.5 mg/L), no adverse effect was observed. The maximum MG concentration recommended for use in ornamental fish farming is 0.2 mg/L. Therefore, our results suggest that, specifically for the parameters analyzed in this work, MG does not have any adverse effect when users strictly adhere to the recommended concentration criteria for ornamental fish.

Karyotypic diversity within the genus Makalata (Echimyidae: Echimyinae) of Brazilian Amazon: Chromosomal evidence for multiple species

The genus Makalata is a taxonomically complex group of rodents on which few cytogenetic studies have been performed. Most of the published karyotypes were described based only on conventional chromosome staining. Here, we studied the karyotypes of Makalata from two Brazilian Amazonian states, Amapá and Pará, by Giemsa-staining, G- and C-banding, AgNO3-staining and FISH with 18S rDNA and telomeric sequences probes. We observed 2n = 66/FN = 124 in the Pará state population in Makalata sp; and 2n = 72/FN = 128 in the Amapá state population in M. didelphoides. Multiple chromosome rearrangements may have given rise to these karyotypes, which differ significantly from each other and from those reported in the literature. The chromosomal differences among the described Makalata karyotypes can act as a barrier to gene flow; since they are also associated with geographic barriers (e.g., rivers) and numerous molecular differences, they could be seen as evidence for reproductive isolation of populations from genus Makalata. Our data suggest that the genus is chromosomally diverse and the karyotypes may belong to different species. These karyotypes may prove useful as taxonomic markers for these rodents.

Evolutionary insights in Amazonian turtles (Testudines, Podocnemididae): co-location of 5S rDNA and U2 snRNA and wide distribution of Tc1/Mariner

Eukaryotic genomes exhibit substantial accumulation of repetitive DNA sequences. These sequences can participate in chromosomal reorganization events and undergo molecular cooption to interfere with the function and evolution of genomes. In turtles, repetitive DNA sequences appear to be accumulated at probable break points and may participate in events such as non-homologous recombination and chromosomal rearrangements. In this study, repeated sequences of 5S rDNA, U2 snRNA and Tc1/Mariner transposons were amplified from the genomes of the turtles, Podocnemis expansa and Podocnemis unifilis, and mapped by fluorescence in situ hybridization. Our data confirm the 2n=28 chromosomes for these species (the second lowest 2n in the order Testudines). We observe high conservation of the co-located 5S rDNA and U2 snRNA genes on a small chromosome pair (pair 13), and surmise that this represents the ancestral condition. Our analysis reveals a wide distribution of the Tc1/Mariner transposons and we discuss how the mobility of these transposons can act on karyotypic reorganization events (contributing to the 2n decrease of those species). Our data add new information for the order Testudines and provide important insights into the dynamics and organization of these sequences in the chelonian genomes.

Molecular cytogenetics characterization of Rhinoclemmys punctularia (Testudines, Geoemydidae) and description of a Gypsy-H3 association in its genome

The wide variation found in the size of eukaryotic genomes is largely related to the accumulation of repetitive sequences. Studies show that these sequences can go through an evolutionary process (molecular co-optation) and acquire new genomic functions. Cytogenetic studies reveal a wide karyotypic variation between chelonians (order Testudines) (2n = 26-68), attributed mainly to the number of microchromosomes. The study of repetitive DNAs has the potential to provide data on the dynamics of these sequences, and how they influence the organization of the genome. Here, we reveal the first in situ mapping data of 45S rDNA, histone H3 genes, and telomeric sequences, for a species of the genus Rhinoclemmys, R. punctularia. The karyotype described here for R. punctularia is different from previous reports for the diploid complement of this species, with differences probably attributable to centric fissions and pericentric inversions or centromere repositioning. The 45S rDNA are on a single chromosome pair (like in other turtles), telomeric sequences are in terminal position on all the chromosomes, and histone H3 is dispersed in low copy number, with clusters in pericentromeric regions of three chromosome pairs. We report on the presence of a Gypsy retrotransposon insert located within H3 histone of R. punctularia, and the H3 region sequenced contained the open reading frame of the histone sequence. Comparative modeling revealed a functional pattern for the protein, thus suggesting that the Gypsy element might have been recruited for new functions in the genome of this species.

Chromosomal phylogeny and comparative chromosome painting among Neacomys species (Rodentia, Sigmodontinae) from eastern Amazonia

BACKGROUND

The Neacomys genus is predominantly found in the Amazon region, and belongs to the most diverse tribe of the Sigmodontinae subfamily (Rodentia, Cricetidae, Oryzomyini). The systematics of this genus and questions about its diversity and range have been investigated by morphological, molecular (Cytb and COI sequences) and karyotype analysis (classic cytogenetics and chromosome painting), which have revealed candidate species and new distribution areas. Here we analyzed four species of Neacomys by chromosome painting with Hylaeamys megacephalus (HME) whole-chromosome probes, and compared the results with two previously studied Neacomys species and with other taxa from Oryzomyini and Akodontini tribes that have been hybridized with HME probes. Maximum Parsimony (MP) analyses were performed with the PAUP and T.N.T. software packages, using a non-additive (unordered) multi-state character matrix, based on chromosomal morphology, number and syntenic blocks. We also compared the chromosomal phylogeny obtained in this study with molecular topologies (Cytb and COI) that included eastern Amazonian species of Neacomys, to define the phylogenetic relationships of these taxa.

RESULTS

The comparative chromosome painting analysis of the seven karyotypes of the six species of Neacomys shows that their diversity is due to 17 fusion/fission events and one translocation, pericentric inversions in four syntenic blocks, and constitutive heterochromatin (CH) amplification/deletion of six syntenic autosomal blocks plus the X chromosome. The chromosomal phylogeny is consistent with the molecular relationships of species of Neacomys. We describe new karyotypes and expand the distribution area for species from eastern Amazonia and detect complex rearrangements by chromosome painting among the karyotypes.

CONCLUSIONS

Our phylogeny reflects the molecular relationships of the Akodontini and Oryzomyini taxa and supports the monophyly of Neacomys. This work presents new insights about the chromosomal evolution of this group, and we conclude that the karyotypic divergence is in accord with phylogenetic relationships.

Karyoevolution of Crenicichla heckel 1840 (Cichlidae, Perciformes): a process mediated by inversions

Crenicichla (Cichliformes, Cichlidae) present a highly conserved diploid number 2n=48 with fundamental numbers varying between 52 and 62. We analyzed four species in order to investigate the role of repetitive DNA in chromosome evolution in the genus. Crenicichla johanna, Crenicichla cf. saxatilis and Crenicichla cf. regani have 2n=48 (8 m/sm and 40st/a) and FN=56, while Crenicichla sp. ‘Xingu I’ has 2n=48 (48 st/a) and FN=48. Different patterns of constitutive heterochromatin distribution were observed including pericentric, interstitial and whole arm C bands. A single chromosome bears 18S rDNA clusters in most species, except C. johanna, where population variation exists in terms of the quantity and distribution of clusters and their association with interstitial telomeric sequences. All species showed hybridization of 5S rDNA sequences in an interstitial region on an acrocentric chromosome pair. The karyotypic differences and maintenance of the diploid number supports chromosome evolution mediated by inversions in Crenicichla. The telomeric and 18S rDNA sequence association in various chromosomes of C. johanna are proposed to represent hotspots for breakage, favoring intra-chromosomal rearrangements. The results suggest that repetitive sequences can contribute to microstructural cytogenetic diversity in Crenicichla.

Summary: This paper has a great importance for understanding karyotype evolutionary dynamics in neotropical freshwater fish, focusing on repetitive DNA and the role of inversions in Crenicichla.

Meiosis in the scorpion Tityus silvestris: new insights into achiasmatic chromosomes

Achiasmatic male meiosis in scorpions is characterized by a high frequency of gaps, asynaptic regions and multivalent associations. Here, we performed an immunocytogenetic analysis to investigate recombination, and synapsis and chromatin-remodeling events during meiosis of the scorpion Tityus silvestris Our results demonstrate that the synaptonemal complex (SC) begins its organization in the zygotene stage and persists until metaphase I. The advancement of the synaptic process is related to the epigenetic modification histone H3 lysine 27 trimethylation (H3K27m3). The distribution and dynamics patterns of variant γH2AX and recombinase Rad51 during achiasmatic meiosis suggests formation and repair of DNA double-strand breaks (DSBs) during early stages of prophase I. The epigenetic modifications, histone H3 lysine 4 trimethylation (H3K4m3) and histone H3 lysine 9 acetylation (H3K9ac), showed a dispersed distribution along the bivalents, suggesting that transcriptional activity is maintained constitutively during prophase I. However, H3K9ac modifications are absent in constitutive heterochromatin carrying the 45S rDNA in pachytene and post-pachytene stages. Collectively, our data demonstrate that T. silvestris exhibits adaptations to the achiasmatic mode, and suggest that epigenetic modifications may act in the regulation of these mechanisms to favor the normal continuation of meiosis in this scorpion.

First cytogenetic information for Lonchothrix emiliae and taxonomic implications for the genus taxa Lonchothrix + Mesomys (Rodentia, Echimyidae, Eumysopinae)

The taxonomic identification of Lonchothrix emiliae (Rodentia, Echimyidae, Eumysopinae) is problematic because of the overlap of morphological characters with its sister clade represented by species in the genus Mesomys which, like L. emiliae, is distributed throughout the Amazonian biome. Cytogenetic studies reported the karyotype of L. emiliae as 2n = 60/FN = 116, but this karyotype and samples were later designated as M. hispidus. To evaluate the karyotype diversity of Lonchothrix and Mesomys, and to provide data useful as karyological diagnostic characters, in the present study we made a comparative analysis of specimens of L. emiliae and M. stimulax collected from two Brazilian Amazonian localities, using C-banding, G-banding, FISH using rDNA 45S and telomeric probes, and Cytochrome-b (Cytb) sequences. The results indicate that L. emiliae has 2n = 64♀, 65♂/FN = 124 and a multiple sexual system (XX/XY₁Y₂), while M. stimulax has 2n = 60/FN = 116. The Neo-X system found in L. emiliae also occurs in two Proechimys species, but cytogenetic analysis indicated an independent origin for these systems. The rDNA 45S analysis showed interstitial signals at one autosomal pair for each species, while an ITS found in L. emiliae was not coincident with the NOR. The molecular analysis confirmed Lonchothrix and Mesomys are sister genera, and the high level of intraspecific genetic divergence (7.1%) in M. stimulax suggests that it may be a species complex.

Identification of two independent X-autosome translocations in closely related mammalian (Proechimys) species

Multiple sex chromosome systems have been described for several mammalian orders, with different species from the same genus sharing the same system (e.g., X₁X₂Y or XY₁Y₂). This is important because the translocated autosome may be influenced by the evolution of the recipient sex chromosome, and this may be related to speciation. It is often thought that the translocation of an autosome to a sex chromosome may share a common origin among phylogenetically related species. However, the neo-X chromosomes of Proechimys goeldii (2n = 24♀, 25♂/NFa = 42) and Proechimys gr. goeldii (2n = 16♀, 17♂/NFa = 14) have distinct sizes and morphologies that have made it difficult to determine whether they have the same or different origins. This study investigates the origins of the XY₁Y₂ sex chromosome determination system in P. goeldii (PGO) and P. gr. goeldii (PGG) and elucidates the chromosomal rearrangements in this low-diploid-number group of Proechimys species. Toward this end, we produced whole-chromosome probes for P. roberti (PRO; 2n = 30♂/NFa = 54) and P. goeldii (2n = 25♂/NFa = 42) and used them in comparative chromosomal mapping. Our analysis reveals that multiple translocations and inversions are responsible for the karyotype diversity of these species, with only three whole-chromosomes conserved between PRO and PGO and eight between PGO and PGG. Our data indicate that multiple sex chromosome systems have originated twice in Proechimys. As small populations are prone to the fixation of chromosomal rearrangements, we speculate that biological features of Rodentia contribute to this fixation. We also highlight the potential of these rodents as a model for studying sex chromosome evolution.

Chromosome painting in Glyphorynchus spirurus (Vieillot, 1819) detects a new fission in Passeriformes

Glyphorynchus spirurus (GSP), also called the Wedge-billed Woodcreeper (Furnariidae) has an extensive distribution in the Americas, including the Atlantic coast of Brazil. Nevertheless, there is no information about its karyotype or genome organization. To contribute to the knowledge of chromosomal evolution in Passeriformes we analysed the karyotype of Glyphorynchus spirurus by classic and molecular cytogenetics methods. We show that Glyphorynchus spirurus has a 2n = 80 karyotype with a fundamental number (FN) of 84, similar to the avian putative ancestral karyotype (PAK). Glyphorynchus spirurus pair 1 was heteromorphic in the Tapajós population whereby the short arms varied in sizes, possibly due to a pericentric inversion, as described in other Furnariidae birds. FISH with the Histone H5 probe revealed a signal in the pericentromeric region of G. spirurus chromosome 5 and rDNA 18S showed interstitial signal in GSP-1. Chromosome painting with Gallus gallus (GGA) macrochromosomes 1-9 probes showed disruption of chromosome syntenies of GGA-1, 2 and 4 by fission in Glyphorynchus spirurus. Our results confirm that the GGA1 centric fission is a synapomorphic character for the phylogenetic branch composed of Strigiformes, Passeriformes, Columbiformes and Falconiformes. On the other hand, the GGA-2 fission is reported here for the first time in Passeriformes. Chromosome painting with BOE whole chromosome probes confirmed these rearrangements in Glyphorynchus spirurus revealed by Gallus gallus 1-9 probes, in addition to enabling the establishment of genome-wide homology map.

Particular Chromosomal Distribution of Microsatellites in Five Species of the Genus Gymnotus (Teleostei, Gymnotiformes)

Microsatellites show great abundance in eukaryotic genomes, although distinct chromosomal distribution patterns might be observed, from small dispersed signals to strong clustered motifs. In Neotropical fishes, the chromosome mapping of distinct microsatellites was employed several times to uncover the origin and evolution of sex and supernumerary chromosomes, whereas a detailed comparative analysis considering different motifs at the chromosomal level is scarce. Here, we report the chromosomal location of several simple sequence repeats (SSRs) in distinct electric knife fishes showing variable diploid chromosome numbers to unveil the structural organization of several microsatellite motifs in distinct Gymnotus species. Our results showed that some SSRs are scattered throughout the genomes, whereas others are particularly clustered displaying intense genomic compartmentalization. Interestingly, the motifs CA, GA, and GAG exhibited a band-like pattern of hybridization, useful for the identification of homologous chromosomes. Finally, the colocalization of SSRs with multigene families is probably related to the association of microsatellites with gene spacers in this case.

Physical mapping of repetitive DNA suggests 2n reduction in Amazon turtles Podocnemis (Testudines: Podocnemididae)

Cytogenetic studies show that there is great karyotypic diversity in order Testudines (2n = 26-68), and that this may be mainly attributed to the presence/absence of microchromosomes. Members of the Podocnemididae family have the smallest diploid numbers of this order (2n = 26-28), which may be a derived condition of the group. Diverse studies suggest that repetitive-DNA-rich sites generally act as hotspots for double-strand breaks and chromosomal reorganization. In this context, we used fluorescent in situ hybridization (FISH) to map telomeric sequences (TTAGGG)n, 45S rDNA, and the genes encoding histones H1 and H3 in two species of genus Podocnemis. We also observed conservation of the 45S rDNA and H1 histone sequences (probable case of conserved synteny), but multiple conserved and non-conserved clusters of H3 genes, which colocalized with the interstitial telomeric sequences in the Podocnemis genome. Our results suggest that fusions have occurred between macro and microchromosomes or between microchromosomes, leading to the observed reduction in diploid number in the family Podocnemididae.

Chromosomal evolution and phylogeny in the Nullicauda group (Chiroptera, Phyllostomidae): evidence from multidirectional chromosome painting

BACKGROUND

The family Phyllostomidae (Chiroptera) shows wide morphological, molecular and cytogenetic variation; many disagreements regarding its phylogeny and taxonomy remains to be resolved. In this study, we use chromosome painting with whole chromosome probes from the Phyllostomidae Phyllostomus hastatus and Carollia brevicauda to determine the rearrangements among several genera of the Nullicauda group (subfamilies Gliphonycterinae, Carolliinae, Rhinophyllinae and Stenodermatinae).

RESULTS

These data, when compared with previously published chromosome homology maps, allow the construction of a phylogeny comparable to those previously obtained by morphological and molecular analysis. Our phylogeny is largely in agreement with that proposed with molecular data, both on relationships between the subfamilies and among genera; it confirms, for instance, that Carollia and Rhinophylla, previously considered as part of the same subfamily are, in fact, distant genera.

CONCLUSIONS

The occurrence of the karyotype considered ancestral for this family in several different branches suggests that the diversification of Phyllostomidae into many subfamilies has occurred in a short period of time. Finally, the comparison with published maps using human whole chromosome probes allows us to track some syntenic associations prior to the emergence of this family.

Synaptic behavior of Leptodactylus pentadactylus (Anura: Leptodactylidae) by immunolocalization of proteins

Most species of the genus Leptodactylus share similar karyotypes, with 2n=22 and NF=44. The species L. pentadactylus presents a multivalent in its karyotype, resulting from multiple translocations, forming a ring chromosome during meiosis I. In this study analyzed the meiotic behavior of L. pentadactylus, from Brazilian Amazonia, through immunoprotein markers. Testicular tissues of an adult male were collected and analyzed by immunofluorescence microscopy, using antibodies to detect the following meiotic proteins: SMC3, component of chromosomal axis, and responsible for cohesion between sister chromatids; ?-H2AX in a protein marker of meiotic silencing of unsynapsed chromatin (MSUC). The results showed that: in leptotene, SMC3 and ?-H2AX mark fuzzy segments throughout all the chromatin; in the zygotene; regions that start synapses are intensely marked by ?-H2AX; in turn, with the advancement of the synapse at the end of the zygotene, ?-H2AX markings expand evenly in the chromatin; in pachytene, the synapsis remains incomplete, and several asynaptic regions were noted, with ?-H2AX markings more intense on synapsed regions of chromosomes involved or not in multivalent links; in diplotene, the synaptonemal complex is disorganized, SMC3 cohesin is present on partially decondensed, chromatin, and ?-H2AX markings are present only in some regions; in diakinesis, SMC3 maintains the same pattern of diplotene, however, ?-H2AX markings are quite reduced. The results of meiotic behavior of L. pentadactylus show asynaptic axes in pachytene, which probably do not present homology with each other, corresponding to segments that suffered multiple rearrangements. SMC3 pattern and reduction of ?-H2AX markings in diplotene, suggest decondensation of chromatin, with reactivation of transcription in chromosomal handles. The absence of ?-H2AX markings in diakinesis show that the rearranged chromosomes of L. pentadactylus do not compromise the spermatogenesis of the animal, ensuring its meiotic dynamic and fertility. 

Filogenética de morcegos nectarívoros (Phyllostomidae: Lonchophyllinae) baseada em pintura cromossômica multidirecional (ZOO-FISH), com a descrição de dois novos citótipos para o gênero monotípico Hsunycteris

A subfamília Lonchophyllinae foi recentemente dividida em duas tribos, Lonchophyllini e Hsunycterini. Lonchophyllini abriga os gêneros Lionycteris Lonchophylla, Platalina e Xeronycteris. Hsunycterini abriga o gênero Hsunycteris, que, além de abrigar vários citótipos diferentes, também possui elevados níveis de divergência genética entre táxons coespecíficos, sugerindo que a sua diversidade está subestimada. A citogenética clássica, atrelada ao uso da pintura cromossômica multidirecional, permite comparações mais detalhadas entre os taxa e a identificação de rearranjos entre espécies e/ou gêneros, permitindo assim uma boa resolução de questões filogenéticas. Neste contexto, o presente estudo verifica a existência de possíveis variações cromossômicas intrapopulacionais atribuídas à H. thomasi através dos bandeamentos cromossômicos, como também investigar as relações evolutivas desta subfamília através da reconstrução filogenética baseada em pintura cromossômica multidirecional (ZOO-FISH), utilizando sondas de cromossomos totais de Carollia brevicauda e Phyllostomus hastatus. As análises filogenéticas foram realizadas utilizando métodos cladísticos baseados no critério de parcimônia, com o auxílio do software PAUP. Utilizamos como grupo externo as subfamílias Desmodontinae e Macrotinae, visando estabelecer um mapeamento cromossômico comparativo entre os gêneros Hsunycteris, Lionycteris e Lonchophylla. Os resultados encontrados sugerem que os representantes da tribo Lonchophyllini (Lionycteris e Lonchophylla) estão intimamente relacionados, baseados nos dados cromossômicos (clássicos e moleculares), compartilhando a mesma morfologia cromossômica, número diploide (2n = 28), número fundamental (FN = 50) e associações sintênicas (PHA 1p/5p/3p, PHA 1q/8inv e PHA 5q/12p/9q). Observamos a presença de variação intraespecífica em Hsunycteris thomasi, com 2n variando entre 30 a 36 cromossomos e NF variando de 38 a 48. Além disso descrevemos dois novos citótipos, 2n=36/NF=46 e 2n=34/NF=48. As associações sintênicas que apoiam o clado Hsunycterini são PHA10/13p, PHA14/4/14 e inversão em PHA11. Os processos responsáveis pela diversificação cariotípica desta subfamília seriam translocações (Lonchophyllini), fusões e fissões (Hsunycterini). As associações sintênicas PHA5/3, PHA14/4 e inversão em PHA8 podem ser consideradas como assinatura cromossômica que define a subfamília Lonchophyllinae. A nossa proposta filogenética mostra-se bem apoiada, congruente com a topologia molecular recente sobre a relação das tribos como taxa irmã, bem como a monofilia de Lonchophyllinae.

Mapeamento cromossômico do elemento transponível A REX 1 no gênero Peckoltia (Siluriformes, Loricariidae)

O gênero Peckoltia (Hypostominae) possui 20 espécies descritas, com dados citogenéticos disponíveis para apenas três. Estudos de elementos transponíveis (TE) vêm auxiliando na compreensão da evolução genômica de alguns grupos de peixes. Análises comparativas do mapeamentoto físico por hibridização in situ fluorescente (FISH) do TE Rex 1 foram realizadas em quatro espécies do gênero Peckoltia: P. oligospila, P. multispinis, P. sabaji e P. vittata coletadas na região Amazônica. As quatro espécies apresentam cariótipos constituídos por 52 cromossomos com a formulas cariotípicas (FC) de 38m/sm+14st para P. oligospila e P. sabaji, de 28m/sm+24st para P. multispinis e 36m/sm+16st/a para P. vittata. A localização dos sítios de rDNA 5S é divergente entre as quatro espécies. A maioria dos sítios de rDNA têm uma localização terminal, com exceção de um sítio de rDNA 5S que está localizado na região proximal em P. vittata. Os resultados mostram uma distribuição dispersa de Rex 1 ao longo dos genomas, tanto em regiões heterocromáticas quanto eucromáticas. Sugerimos que, a distribuição de Rex 1 em regiões heterocromáticas pode estar relacionada a um processo de regulação desses elementos, visando evitar uma propagação excessiva no genoma, uma vez que a presença da heterocromatina pode regular a expressão e a dispersão destes sem alterar a sequência nucleotídica. No entanto, a posição deste TE em regiões eucromáticas parece ter uma importância na evolução genômica das espécies de Peckoltia. Estes elementos, por se inserirem em regiões eucromáticas, podem gerar mutações, afetar níveis de expressão genética e padrões de recombinação de DNA, além de interferir na organização da arquitetura genômica. A ocorrência de sítios de rDNA 5S sintênicos aos sítios de Rex 1 nas  espécies analisadas, já foram evidenciadas em outras espécies. Assim, loci ribossômicos são nichos importantes para a manutenção de elementos móveis que, por sua vez, podem atuar como mecanismos de transposição do rDNA no genoma. Essas informações podem explicar as diferenças estruturais nos cariótipos das espécies P. oligospila, P. multispinis, P. sabaji e P. vittata refletidas pelas FCs.

Pintura cromossômica em Gymnotus arapaima com sonda e cromossomo total de Gymnotus carapo (Gymnotiformes, Gymnotidae)

O gênero Gymnotus é um dos gêneros mais especiosos (40 espécies) e mais amplamente distribuídos nas águas continentais da América do Sul, com maior ocorrência na bacia amazônica, onde varias espécies ocorrem em simpatria. A citogenética tem sido uma importante ferramenta na citotaxinomia e na elucidação dos processos evolutivos no gênero, que possui uma diversidade cariotípica elevada, sendo os cariótipos espécie-específicos, mesmo nas espécies que possuem o mesmo número diploide e são um fator de isolamento reprodutivo pré-zigotico nas espécies em simpatria. Cromossomos metafásicos de Gymnotus arapaima (GAR, 2n=44, FC: 24 m/sm + 20 st/a) foram hibridizados com sondas de cromossomo total de Gymnotus carapo (GCA, 2n=42). A sonda da região 1 (GCA 20) hibridizou um único cromossomo, o GAR 19, portador da NOR. As sondas da região 2 (GCA 1, 2, 3 e 16) hibridizaram os cromossomos de GAR: 1, 2, 14 e 18 e 21, o braço curto do par 4 e braço curto e uma parte do braço longo do par 13. As da região 3 (GCA 4, 5, 6, 7, 8, 17, 18, 19) hibridizaram os cromossomos de GAR 3, 5, 6, 5, 16, 20 e 22, o braço longo do par 4 e parte do braço longo do par 13. As da região 4 (GCA 9 – 15 e 21) hibridizaram os cromossomo 7-12 e 17. Até a presente análise pelo menos 3 pares (GAR 1, 16 e 20) se encontram conservados em relação ao cariótipo de GCA, enquanto outros encontram-se fragmentados e/ou fusionados. A pintura cromossômica em Gymnotus é uma ferramenta recente que, como observado no cariotipo analisado e em trabalhos anteriores, vem mostrando que os rearranjos cromossômicos no gênero são numerosos e o processo evolutivo dinâmico.

Citogenética comparativa entre espécies do gênero Peckoltia (Siluriformes: Loricariidae)

Loricariidae é uma das mais especiosas famílias dentro da ordem Siluriformes, possuindo cerca de 800 espécies válidas. O gênero Peckoltia (Loricariidae, Hypostominae), atualmente contém 19 espécies válidas, apresentando status taxonômico confuso. O objetivo deste trabalho foi analisar comparativamente os cariótipos das espécies Peckoltia cf. braueri e Peckoltia sp., coletadas no município Abaetetuba – PA por métodos clássicos (coloração convencional e bandeamento C) e Hibridização in situ Fluorescente com sondas de rDNA 18S, 5S e telomérica. As espécies compartilham o 2n=52 cromossomos, mas diferem nas fórmulas cariotípicas. P. cf. braueri apresentou 20m + 24sm + 8st/a, enquanto P. sp. apresentou 26m + 14sm + 12st/a. O bandeamento C revelou grandes blocos heterocromáticos distribuídos em cromossomos submetacêntricos nas duas espécies. Diferenças da quantidade e distribuição de heterocromatina foram observadas nos cromossomos 24 de P. cf. braueri e 21 de P. sp., sugerindo a ocorrência de rearranjos cromossômicos dos tipos inversão paracêntrica e translocação. As hibridizações com sondas de rDNA 18S e 5S revelaram diferenças na localização e número de sítios entre os cariótipos analisados. Peckoltia cf. braueri apresentou sítios múltiplos de rDNA 5S em posição distal do par 11q e homólogo do par 24q, o rDNA 18S apresentou marcações simples em região distal do par 11q. Peckoltia sp. apresentou sítios simples de rDNA 5S em posição intersticial do par 1p, enquanto o rDNA 18S apresentou sítios múltiplos em região distal do par 11q e homólogo do par 21q. Essas diferenças na distribuição dos genes de rDNA possivelmente está relacionada a dinâmica evolutiva dessas sequências, provavelmente associadas a elementos transponíveis. A hibridização das sondas teloméricas revelaram sítios distais nos cromossomos, nas duas espécies, não sendo evidenciadas sequências intersticiais. Sugerimos que a distribuição de heterocromatina representa um bom marcador para análises evolutivas nas espécies de Peckoltia, podendo ser útil na identificação de rearranjos cromossômicos e de suas consequências na diferenciação cariotípica entre espécies relacionadas. Além disso, o mapeamento de rDNA representa uma ferramenta poderosa para estudo da evolução cromossômica em peixes do gênero Peckoltia.

Genômica comparativa entre Cerradomys scotti e Cerradomys subflavus por pintura cromossômica

O gênero Cerradomys apresenta atualmente 8 espécies, todas com cariótipos básicos descritos. Essas espécies apresentam grande variação cromossômica, com número diploide variando de 2n=46 em Cerradomys langguthi a 2n=60 em C. akroai. Neste trabalho estudamos comparativamente os cariótipos de Cerradomys scotti (CSC) e Cerradomys subflavus (CSU) por bandeamntos G, C e pintura cromossômica utilizando sondas cromossomos totais de Hylaeamys megacephalus (HME: 2n=54, NFa=62). Analisamos 3 exemplares de C. scotti (1 macho e 2 fêmeas) coletados nos estados de Mato Grosso e Minas Gerais e 3 exemplares de C. subflavus (2 machos e 1 fêmea) coletados no estado de Minas Gerais. C. scotti apresenta 2n=58 e NFa=70, sendo composto por 7 pares de dois braços e 21 pares acrocêntricos, o X é submetacêntrico grande e o Y é submetacêntrico médio. C. subflavus apresenta 2n=54 e NFa=62, sendo composto por 5 pares de dois braços e 21 pares acrocêntricos, o X é acrocêntrico grande e o Y é acrocêntrico pequeno. A Heterocromatina Constitutiva foi observada na região pericentromérica em todos os pares autossômicos, nas duas espécies. As FISHs (Hibridização in situ fluorescente) com as sondas de HME revelaram 36 segmentos de homologia no cariótipo de CSC e 6 associações sintênicas: HME19/7/[9,10] (CSC1), HEM21/6 (CSC2), HME12/[9,10] (CSC4), HME[13,22]/20 (CSC7), HME19/14/19/[13,22] (CSC8) e HME[16,17]/11 (HME10). No cariótipo de CSU, as FISHs revelaram 39 segmentos de homologia e 6 associações sintênicas: HEM6/21/8/1 (CSU1), HME 3/14/7/[9,10] (CSU2), HME15/12/[9,10] (CSU3), HME[13,22]/20 (CSU4), HME[16,17]/11 (CSU5) e HME14/19 (CSU9). O mapeamento genômico comparativo mostra que as duas espécies compartilham 4 associações sintênicas (HME 7/[9,10], HME12/[9,10], HME[13,22]/20 e HME14/19) das quais, somente a associação HME[13,22]/20 é compartilhada sem modificações; as demais formam blocos sintênicos diferentes nas duas espécies. Estes resultados demonstram que as duas espécies de Cerradomys apresentam cariótipos muito reorganizados entre si e ambos, em relação a HME. Rearranjos cromossômicos como translocações, inversões e fusões/fissões diferenciam o cariótipo das duas espécies. Análises nas demais espécies do gênero permitirão uma melhor compreensão dos mecanismos de rearranjos cromossômicos envolvidos na diferenciação das espécies de Cerradomys.

Marcadores protéicos de sinapse e dinâmica de quebras de DNA programadas em meiose aquiasmática do Escorpião T. silvestris (Scorpiones: Buthidae)

Análises meióticas realizadas em escorpiões Buthidae, por microscopia óptica e eletrônica, demonstraram bivalentes holocinéticos, heterosinápticos e com ausência de quiasmas e nódulos de recombinação durante a meiose do macho. No presente estudo analisamos o mecanismo sináptico e a dinâmica de quebras programadas de cadeias de DNA na meiose do butídeo Tityus silvestris por imunofluorescência. Preparações meióticas fixadas em paraformaldeído 2%, foram submetidas à imunodetecção com anticorpos primários anti-SMC3 e anti-?H2AX, bem como Imuno-FISH com sonda telomérica de artrópodes (TTAGG) e anti-SMC3. Nossos resultados demonstraram que o cariótipo de Tityus silvestris apresenta 2n = 24, com morfologia holocêntrica e ausência de cromossomos sexuais heteromórficos. Imuno-FISH com sonda telomérica e anti-SMC3 (que detecta eixos axiais/laterais do complexo sinaptonêmico) permitiu analisar a progressão da sinapse neste escorpião: em leptóteno, a coesina SMC3 apresenta-se na forma de pontuações e curtos filamentos; no início do zigóteno, cromossomos são organizados em configuração bouquet, e a sinapse inicia-se a partir das regiões teloméricas; em paquítenos iniciais, gaps foram observados ao longo de alguns complexos sinaptonêmicos; em paquítenos tardios, a sinapse completa-se, permitindo individualizar os 12 bivalentes; finalmente, em células pós-paquitênicas, o eixo SMC3 localiza-se centralmente ao longo de cada bivalente até Metáfase I. Em relação aos eventos iniciais do processo de recombinação, quebras de cadeias duplas de DNA (evidenciadas por ?H2AX) iniciam-se em núcleos pré-leptóteno. A variante histônica ?H2AX é localizada sobre eixo SMC3, distribuindo-se de acordo com o avanço da sinapse em zigóteno e desaparecendo no final do Paquíteno. Nossos resultados mostraram que na meiose de T. silvestris, formação de quebras programadas de DNA ocorrem antes do início da sinapse, diferindo do padrão observado em Drosophila melanogaster e C. elegans. A ocorrência de ?H2AX durante a meiose aquiasmática deste escorpião sugere que quebras de cadeia dupla de DNA durante a prófase I, sejam reperadas por um mecanismo distinto ao da recombinação homóloga. Finalmente, apesar da aparente ausência de recombinação, o reparo de quebras de DNA programadas é necessário para o progresso normal da meiose em T. silvestris.

Evolução cromossômica em morcegos neotropicais da Subfamília Glossophaginae, tribo Choeronycterini (Chiroptera, Phyllostomidae)

Estudos recentes revelaram que a evolução molecular da tribo Choeronycterini (Glossophaginae) está entre as mais rápidas da família Phyllostomidae. A elucidação dos rearranjos cromossômicos por mapeamento genômico comparativo usando pintura cromossômica multidirecional, pode mostrar como a evolução cromossômica desta tribo ocorreu, seguindo ou não a rápida evolução molecular destes táxons. Além disso, devido a diversidade de espécies e cromossomos de morcegos filostomídeos da região Neotropical, é importante a investigação de possíveis variações intraespecíficas. O presente trabalho objetiva realizar estudos de evolução cromossômica por meio de citogenética clássica e molecular em Anoura geoffroyi (AGE), Anoura caudifer (ACA) e Choeroniscus minor (CMI) provenientes da Amazônia e Mata Atlântica. Cromossomos metafásicos obtidos a partir da medula óssea foram submetidos a bandeamentos G e C, Hibridização in situ Fluorescente (FISH) com sondas de cromossomos totais de Phyllostomus hastatus (PHA) e Carollia brevicauda (CBR). Os dados obtidos no presente trabalho são parciais, onde AGE e ACA apresentaram 2n=30, NF=54 e 56 respectivamente. CMI apresentou 2n=24, NF=44. A pintura cromossômica multidirecional usando sondas de PHA e CBR revelaram 28 e 30 segmentos conservados respectivamente em AGE. Foram hibridizadas até o presente momento 13 sondas de PHA e 11 sondas de CBR em ACA, tendo sido encontrados 21 segmentos conservados para ambas sondas. A pintura cromossômica parcial de CMI revelou 15 e 16 segmentos sintênicos de PHA e CBR, respectivamente. Os cariótipos de AGE e ACA diferem apenas por uma inversão no par 14, corroborando o conservadorismo cromossômico para o gênero Anoura. Dados da literatura mostram que os espécimes de CMI da Amazônia apresentam 2n=20 e NF=36. Assim o cariótipo do presente trabalho é inédito para esta espécie, além de ser o primeiro cariótipo de um espécime macho. A análise parcial da pintura cromossômica mostra que a associação PHA 11/12 está presente nas três espécies analisadas, podendo ser uma assinatura cromossômica para tribo. O estudo comparativo das diferentes espécies estudadas com os dados disponíveis na literatura poderá elucidar os rearranjos cromossômicos envolvidos na diferenciação cariotípica do grupo, além de fornecer caracteres citogenéticos para construção de filogenias consistentes.

Primeira descrição cariotípica para Lonchothrix emiliae (Rodentia, Echimyidae, Eumysopinae), com diagnóstico de sistema sexual cromossômico múltiplo

A família Echimyidae é conhecida como o grupo mais diversos dos roedores Hystricognathi sul-americanos. Variam de pequeno a médio porte e possuem diversificados hábitos de vida. O gênero Lonchothrix é monotípico (L. emiliae) e possui distribuição do baixo rio Madeira ao baixo rio Xingu e apenas ao sul do rio Amazonas. A identificação taxonômica de L. emiliae é confusa, devido a similaridades morfológicas com seu gênero irmão, Mesomys. Neste sentido, o único cariótipo previamente descrito para L. emiliae foi posteriormente associado à Mesomys hispidus (2n=60/NF=116). A partir de quatro amostras (uma fêmea e três machos) provenientes dos municípios de Juruti-PA e Parintis-AM, foram realizados bandeamentos cromossômicos G, C e FISH com sondas de rDNA 45S e telomérica em L. emiliae. A análise citogenética em L. emiliae mostrou cariótipo com 2n=64?/65? e NF=124, apresentando sistema sexual do tipo múltiplo. Os bandeamentos G e C possibilitaram a identificação dos homólogos e a classificação morfológica dos cromossomos, sendo todos os autossomos meta/submetacêntricos. O sexual X é submetacêntrico médio e os Y1 e Y2 são acrocêntricos pequenos. A heterocromatina constitutiva está distribuída na região centromérica de todos os autossomos e nos sexuais X e Y2; o sexual Y1 apresentou-se praticamente todo heterocromático. A FISH com sonda de rDNA 45S apresentou marcação na região intersticial do sexual X, com dois sinais na fêmea e um no macho. FISH com sonda telomérica apresentou marcação na região distal de todos os cromossomos; o par 4, adicionalmente, apresentou marcação na região pericentromérica. A ITS encontrada no par 4 pode ser um resquício de um rearranjo cromossômico do tipo fusão (comuns entre os Echimyidae), ou amplificação de sequências similares às teloméricas presentes na heterocromatina constitutiva, como sugerido para o gênero Proechimys (Echimyidae). O sistema sexual do tipo múltiplo (XX/XY1Y2) é devido a uma translocação autossomo/sexual. Assim, o presente trabalho apresenta os primeiros dados cariotípicos para L. emiliae, bem como descreve o sistema sexual do tipo múltiplo para esta espécie.

Evolução cromossômica e filogenia no grupo nullicauda (Chiroptera, Phyllostomidae): Evidências a partir de pintura cromossômica multidirecional

A família Phyllostomidae (Chiroptera) apresenta ampla variação morfológica, molecular e citogenética, havendo discordâncias na literatura com relação à sua filogenia e nos vários níveis taxonômicos. No presente trabalho utilizamos pintura cromossômica multidirecional com sondas de cromossomo total das espécies de Phyllostomidae, Phyllostomushastatus e Carolliabrevicauda para determinar os rearranjos ocorridos entre diversos gêneros desta família que compõem o grupo Nullicauda (subfamílias Gliphonycterinae, Carolliinae, Rhinophyllinae e Stenodermatinae). Estes dados puderam ser comparados com mapeamentos já publicados, permitindo assim a construção de uma filogenia comparável com aquelas obtidas anteriormente por análise morfológica e molecular. Nossa filogenia está de acordo em grande parte com aquela proposta com dados moleculares, tanto no que se refere às relações entre as subfamílias como na relação entre os gêneros, confirmando por exemplo que Carollia e Rhinophylla, previamente considerados como parte da mesma subfamília, na verdade são gêneros filogenéticas distantes. Observou-se também a recorrência do cariótipo considerado ancestral para esta família em vários ramos, sugerindo que a diversificação de Phyllostomidae nas suas várias subfamílias ocorreu em um período curto de tempo. Finalmente, a comparação com dados publicados de sondas de cromossomos totais humanas permitiu estabelecer alguns grupos sintênicos anteriores ao surgimento desta família.