RESUMO
Xenarthra-a superorder of placental mammals endemic to the Neotropics-is represented by armadillos, anteaters, and sloths. Considering their long history in the Americas, extant xenarthrans represent an important group for understanding the impact of past environmental changes on species diversification and serve key ecological functions as ecosystem engineers. Unfortunately, most wild xenarthran populations are at risk, due primarily to anthropogenic activities, necessitating urgent conservation efforts. Moreover, the paucity of information on some species has rendered population estimation and, consequently, conservation management challenging. In addition, relatively few groups are researching this superorder, perhaps because fieldwork with armadillos, anteaters, or sloths and their captive care are challenging tasks. Nevertheless, dedicated research and efforts to ensure the long-term conservation of these animals are deemed essential. In this context, cryobanks are a practical approach for breeding and maintaining genetic diversity in wildlife, and they are important tools for assisting and improving both ex situ and in situ conservation strategies. Therefore, cryopreservation of biological resources may be a promising strategy for conserving xenarthrans. Specifically, semen cryopreservation, which has already been applied in some species, may be the most effective strategy for this group. The present article provides an overview of ex situ conservation of xenarthrans, which will contribute to the development and implementation of additional strategies for protecting these unique mammals.
Assuntos
Bichos-Preguiça , Xenarthra , Gravidez , Animais , Feminino , Xenarthra/genética , Bichos-Preguiça/genética , Tatus/genética , Vermilingua , Ecossistema , Placenta , MamíferosRESUMO
Although mammals of the superorder Xenarthra are considered hosts of a wide range of zoonotic agents, works aiming at investigating the role of these animals as hosts for bacteria with zoonotic potential are rare. The present study aimed to investigate the occurrence and molecularly characterize Coxiella burnetii and haemoplasma (haemotropic mycoplasmas) DNA in blood and spleen samples from 397 free-living Xenarthra mammals (233 sloths, 107 anteaters and 57 armadillos) in five Brazilian states (Mato Grosso do Sul, São Paulo, Pará, Rondônia and Rio Grande do Sul). All biological samples from Xenarthra were negative in the qPCR for Coxiella burnetii based on the IS1111 gene. The absence of C. burnetii DNA in blood and spleen samples from Xenarthra suggests that these mammals may not act as possible hosts for this agent in the locations studied. When performed conventional PCR assays for the endogenous (gapdh) mammalian gene, 386 samples were positive. When screened by molecular assays based on the 16S rRNA gene of haemoplasmas, 81 samples were positive, of which 15.54% (60/386) were positive by conventional PCR and 5.44% (21/386) were positive by real-time PCR; three samples were positive in both assays. Of these, 39.74% (31/78) were also positive for the 23S rRNA gene and 7.69% (6/78) for the haemoplasma RNAse P gene. Among the samples positive for haemoplasmas, 25.64% (20/78) were obtained from anteaters (Tamandua tetradactyla and Myrmecophaga tridactyla), 39.74% (31/78) from sloths (Bradypus tridactylus, Bradypus sp. and Choloepus sp.) 34.61% (27/78) from armadillos (Priodontes maximus, Euphractus sexcinctus and Dasypus novemcinctus). A haemoplasma 16S rRNA sequence closely related and showing high identity (99.7%) to Mycoplasma wenyonii was detected, for the first time, in B. tridactylus. Based on the low identity and phylogenetic positioning of 16S rRNA and 23S rRNA sequences of haemoplasmas detected in anteaters and armadillos, the present study showed, for the first time, the occurrence of putative new Candidatus haemotropic Mycoplasma spp. ("Candidatus Mycoplasma haematotetradactyla" and "Candidatus Mycoplasma haematomaximus") in Xenarthra mammals from Brazil.
Assuntos
Coxiella burnetii , Infecções por Mycoplasma , Mycoplasma , Bichos-Preguiça , Xenarthra , Animais , Tatus/genética , Brasil/epidemiologia , Coxiella burnetii/genética , DNA , Mycoplasma/genética , Infecções por Mycoplasma/epidemiologia , Infecções por Mycoplasma/microbiologia , Infecções por Mycoplasma/veterinária , Filogenia , RNA Ribossômico 16S/genética , RNA Ribossômico 23S , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Ribonuclease P/genéticaRESUMO
The development of agro-ecosystems in the pastures of the Pampean Region has substantially modified their structure and functioning. Many wild mammal populations in the Argentinean Pampas face habitat loss and/or fragmentation due to human activities, resulting in harmful genetic effects. The screaming hairy armadillo (Chaetophractus vellerosus) is a species considered an indicator of the state of preservation of the environments it inhabits. However, very little information is available about its mating system in the wild. In this sense, an isolated population of the screaming hairy armadillo in the northeast of Buenos Aires Province, which is separated from the main distribution area of the species by about 500 km, requires special attention. Genetic studies that analyzed social behavior and mating systems in Xenarthra are scarce but necessary to establish conservation actions for the isolated screaming hairy armadillo population under study. Thus, we analyzed the existence of a possible social organization in the species, together with its mating system, using a set of previously characterized microsatellites. Our results showed a complex scenario for the dispersal and mating system in this C. vellerosus population. Males disperse and females have a philopatric tendency with some degree of dispersal. This strategy, in combination with a polygynous-polyandrous mating system, could enhance genetic variability in this small and isolated population. In addition, no evidence of social organization was found.
Assuntos
Tatus/fisiologia , Comportamento Animal/fisiologia , Preferência de Acasalamento Animal/fisiologia , Reprodução/fisiologia , Animais , Tatus/genética , Ecossistema , Feminino , Hierarquia Social , Humanos , Masculino , Repetições de Microssatélites/genética , População , Reprodução/genéticaRESUMO
Little is known about phylogeography of armadillo species native to southern South America. In this study we describe the phylogeography of the screaming hairy armadillo Chaetophractus vellerosus, discuss previous hypothesis about the origin of its disjunct distribution and propose an alternative one, based on novel information on genetic variability. Variation of partial sequences of mitochondrial DNA Control Region (CR) from 73 individuals from 23 localities were analyzed to carry out a phylogeographic analysis using neutrality tests, mismatch distribution, median-joining (MJ) network and paleontological records. We found 17 polymorphic sites resulting in 15 haplotypes. Two new geographic records that expand known distribution of the species are presented; one of them links the distributions of recently synonimized species C. nationi and C. vellerosus. Screaming hairy armadillo phylogeographic pattern can be addressed as category V of Avise: common widespread linages plus closely related lineages confined to one or a few nearby locales each. The older linages are distributed in the north-central area of the species distribution range in Argentina (i.e. ancestral area of distribution). C. vellerosus seems to be a low vagility species that expanded, and probably is expanding, its distribution range while presents signs of genetic structuring in central areas. To explain the disjunct distribution, a hypothesis of extinction of the species in intermediate areas due to quaternary climatic shift to more humid conditions was proposed. We offer an alternative explanation: long distance colonization, based on null genetic variability, paleontological record and evidence of alternance of cold/arid and temperate/humid climatic periods during the last million years in southern South America.
Assuntos
Tatus/genética , Clima , Animais , DNA Mitocondrial , Extinção Biológica , Haplótipos , Umidade , Periodicidade , Filogeografia , América do SulRESUMO
The screaming hairy armadillo (Chaetophractus vellerosus) is a mammal species containing disjunct and isolated populations. In order to assess the effect of habitat fragmentation and geographic isolation, we developed seven new microsatellite loci isolated from low-coverage genome shotgun sequencing data for this species. Among these loci, six microsatellites were found to be polymorphic with 8-26 alleles per locus detected across 69 samples analyzed from a relictual population of the species located in the northeast of the Buenos Aires Province (Argentina). Mean allelic richness and polymorphic information content were 15 and 0.75, with observed and expected heterozygosities ranging from 0.40 to 0.67 and 0.58 to 0.90, respectively. All loci showed departures from Hardy-Weinberg equilibrium. The analysis of population structure in this relictual population revealed three groups of individuals that are genetically differentiated. These newly developed microsatellites will constitute a very useful tool for the estimation of genetic diversity and structure, population dynamics, social structure, parentage and mating system in this little-studied armadillo species. Such genetic data will be particularly helpful for the development of conservation strategies for this isolated population and also for the endangered Bolivian populations previously recognized as a distinct species (Chaetophractus nationi).
Assuntos
Tatus/genética , Loci Gênicos , Genética Populacional , Repetições de Microssatélites , Animais , Argentina , GeografiaRESUMO
Karyotype and cytotype variations for the large hairy armadillo (Chaetophractus villosus) were studied throughout the species' Argentine distribution. Peripheral blood lymphocyte cultures of 421 animals were used to obtain mitotic metaphases. Preparations were subjected to conventional staining, G- and C-banding, and FISH involving a telomeric probe. Meiotic analysis was performed on testis material from 10 adults. Spermatocytes were examined for synaptonemal complexes in microspreads. The karyotype (2n = 60 XX/XY; FN = 84 without XY) showed an autosomal complement of 6 metacentric and 7 submetacentric chromosomes; the remainder was acrocentric. The X chromosome was submetacentric and the Y acrocentric. Centromeric C+ marks were observed in all chromosomes except pair 16. Three NOR signals were detected in 6q, 12p, and 26p. Two chromosomal rearrangements were characterized in chromosome pair 1 a pericentric inversion seen in the material from Jacinto Aráuz, General Madariaga and Pellegrini and a deletion in the material from Loma Verde. Interstitial telomeric signals were observed in chromosome pairs 4, 12, 16, and 26. Pachytene spermatocyte analysis confirmed the basic chromosome number and morphologies observed in mitotic karyotypes. The evolution of C. villosus involved chromosomal rearrangements as recorded for other species of its superorder. The present results establish the basis for the cytogenetic characterization of this species.
Assuntos
Tatus/genética , Deleção Cromossômica , Inversão Cromossômica , Animais , Argentina , Células Cultivadas , Bandeamento Cromossômico/veterinária , Cromossomos de Mamíferos/genética , Feminino , Variação Genética , Hibridização in Situ Fluorescente/veterinária , Cariótipo , Linfócitos/citologia , Masculino , Meiose/genética , Mitose/genética , Espermatócitos/citologia , Complexo Sinaptonêmico/genéticaRESUMO
A variety of host immunogenetic factors appear to influence both an individual's susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.
Assuntos
Animais , Camundongos , Animais Geneticamente Modificados , Tatus/genética , Modelos Animais de Doenças , Fenômenos Imunogenéticos/imunologia , Hanseníase/genética , Hanseníase/imunologia , Mycobacterium leprae , Camundongos/genética , Tatus/microbiologia , Mycobacterium leprae/genética , Mycobacterium leprae/imunologiaRESUMO
Three xenarthrans species Chaetophractus villosus, Chaetophractus vellerosus, and Zaedyus pichiy have been used for the analysis of the structure, behavior, and immunochemical features of the XY body during pachytene. In all these species, the sex chromosomes form an XY body easily identifiable in thin sections by the special and regular packing of the chromatin fibers of the internal region of the XY body ("differential" regions) and those of the peripheral region (synaptic region). Spermatocyte spreads show a complete synapsis between the X- and the Y-axis, which lasts up to the end of pachytene. From the early pachytene substages to the late ones, the X-axis develops prominent branches, which in late pachytene span the synaptic region. Synapsis is regular as shown by SYCP1 labeling. Axial development is followed by SYCP3 labeling and in the asynaptic region of the X-axis by BRCA1. Gamma-H2AX labels exclusively the differential (asynaptic) region of the X chromosome. A single focus is labeled by MLH1 in the synaptic region. The location of this MLH1 focus spans from 0.3 to 1.6 µm from the telomere in the analyzed xenarthrans, covering approximately half of the Y-axis length. It is concluded that xenarthrans, as basal placental mammals, harbor the largest pseudoautosomal regions of presently analyzed mammals, and shows the typical features of meiotic sex chromosome inactivation (MSCI).
Assuntos
Tatus/genética , Montagem e Desmontagem da Cromatina , Pareamento Cromossômico , Recombinação Genética , Animais , Cromatina/ultraestrutura , Masculino , Cromossomos Sexuais , Espermatócitos/metabolismo , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestruturaRESUMO
A variety of host immunogenetic factors appear to influence both an individual's susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.
Assuntos
Animais Geneticamente Modificados , Tatus/genética , Modelos Animais de Doenças , Fenômenos Imunogenéticos/imunologia , Hanseníase/genética , Hanseníase/imunologia , Camundongos/genética , Mycobacterium leprae , Animais , Tatus/microbiologia , Camundongos/imunologia , Mycobacterium leprae/genética , Mycobacterium leprae/imunologiaRESUMO
Fairy armadillos or pichiciegos (Xenarthra, Dasypodidae) are among the most elusive mammals. Due to their subterranean and nocturnal lifestyle, their basic biology and evolutionary history remain virtually unknown. Two distinct species with allopatric distributions are recognized: Chlamyphorus truncatus is restricted to central Argentina, while Calyptophractus retusus occurs in the Gran Chaco of Argentina, Paraguay, and Bolivia. To test their monophyly and resolve their phylogenetic affinities within armadillos, we obtained sequence data from modern and museum specimens for two mitochondrial genes (12S RNA [MT-RNR1] and NADH dehydrogenase 1 [MT-ND1]) and two nuclear exons (breast cancer 1 early onset exon 11 [BRCA1] and von Willebrand factor exon 28 [VWF]). Phylogenetic analyses provided a reference phylogeny and timescale for living xenarthran genera. Our results reveal monophyletic pichiciegos as members of a major armadillo subfamily (Chlamyphorinae). Their strictly fossorial lifestyle probably evolved as a response to the Oligocene aridification that occurred in South America after their divergence from Tolypeutinae around 32 million years ago (Mya). The ancient divergence date (â¼17Mya) for separation between the two species supports their taxonomic classification into distinct genera. The synchronicity with Middle Miocene marine incursions along the Paraná river basin suggests a vicariant origin for pichiciegos by the disruption of their ancestral range. Their phylogenetic distinctiveness and rarity in the wild argue in favor of high conservation priority.
Assuntos
Tatus/genética , Evolução Biológica , Genes Mitocondriais , Especiação Genética , Filogenia , Animais , Tatus/classificação , Teorema de Bayes , Complexo I de Transporte de Elétrons/genética , Éxons , Genes BRCA1 , Filogeografia , Ribonucleotídeo Redutases/genética , Análise de Sequência de DNA , América do Sul , Fator de von Willebrand/genéticaRESUMO
We unite genetic data with a robust test of niche divergence to test the hypothesis that patterns of gene flow between two lineages of the nine-banded armadillo are influenced by their climatic niches. We collected Geographical Information System (GIS) data on climate using locality information from 111 individuals from two lineages that had associated genetic material. We tested whether niches of these lineages were more conserved or divergent than the background environments of their geographic ranges and found evidence for niche conservatism on two axes and no evidence for divergence on any axis. To address the role of niche similarity in gene flow, we genotyped the 111 individuals at five microsatellite loci and tested whether admixed individuals tended to be located in parts of multidimensional environmental space (E-space) shared between the two lineages. We observed an asymmetrical pattern of overlap, in which the West lineage's E-space was almost completely included inside East lineage's E-space. Genetic admixture levels were significantly higher in the West lineage and, for both lineages, in shared portions of E-space. This suggests that niche similarity can facilitate gene flow among disjunct groups with moderate-to-good dispersal capabilities, contrasting with the prevailing view of niche conservatism as a diversifying force.
Assuntos
Tatus/genética , Fluxo Gênico , Variação Genética , Animais , Tatus/fisiologia , Evolução Biológica , Clima , DNA Mitocondrial/genética , Ecossistema , Genótipo , Sistemas de Informação Geográfica , México , Repetições de Microssatélites , Modelos Biológicos , Filogenia , Dinâmica PopulacionalRESUMO
The cingulates of the mammalian order Xenarthra present a typical case of disagreement between molecular and morphological phylogenetic studies. We report here the discovery of two new skulls from the Late Oligocene Salla Beds of Bolivia (approx. 26 Ma), which are the oldest known well-preserved cranial remains of the group. A new taxon is described: Kuntinaru boliviensis gen. et sp. nov. A phylogenetic analysis clusters K. boliviensis together with the armadillo subfamily Tolypeutinae. These skulls document an early spotty occurrence for the Tolypeutinae at 26 Ma, in agreement with the temporal predictions of previous molecular studies. The fossil record of tolypeutines is now characterized by a unique occurrence in the Late Oligocene, and a subsequent 12 Myr lack in the fossil record. It is noteworthy that the tolypeutines remain decidedly marginal in the Late Palaeogene and Early Neogene deposits, whereas other cingulate groups diversify. Also, the anatomical phylogenetic analysis herein, which includes K. boliviensis, is congruent with recent molecular phylogenetic analyses. Kuntinaru boliviensis is the oldest confident calibration point available for the whole Cingulata.
Assuntos
Tatus/anatomia & histologia , Tatus/genética , Evolução Biológica , Fósseis , Crânio/anatomia & histologia , Xenarthra/anatomia & histologia , Animais , Bolívia , Filogenia , Xenarthra/genéticaRESUMO
We report a phylogeographic study of Chaetophractus villosus populations in Argentina. Control Region (CR) sequences (484 bp) were obtained for 76 C. villosus from 20 locations across the species whole distribution range. Seventeen new haplotypes were identified. The highest genetic variation and the earliest fossils were found in the Pampean Region, thus appearing as the most probable area of origin of the species. A general pattern of Contiguous Range Expansion (CRE) was revealed by Nested Clade Analysis (NCA) supported by mismatch analysis and Fu's test. The Pampean Region would have been the pre-expansion area, while Patagonia would have been the main dispersal route of contiguous expansion, possibly after the Pleistocenic glaciations.
Assuntos
Tatus/genética , Evolução Molecular , Genética Populacional , Filogenia , Animais , Argentina , Tatus/classificação , DNA Mitocondrial/genética , Fósseis , Variação Genética , Geografia , Haplótipos , Análise de Sequência de DNARESUMO
Para este estudo foi sequenciado o gene mitocondrial Citocromo b (1140pb) em amostras de ADN de 12 exemplares de Euphractus sexcinctus e 67 exemplares de Dasypus novemcinctus. Análises filogenéticas (distância, máxima parcimônia e máxima vesossimilhança) e populacionais (median-joining) foram realizadas com objetivo de estudar a variação genética e a filogeografica destas duas espécies. Também foi avaliada a posição filogenética de outros Dasypodidae (Dasypus kappleri, Cabassous unicinctus, C. tatouay e Tolypeutes tricinctus). Os resultados confirmaram a monofilia de Dasypodidae, Dasypodinae, Euphractinae e Tolypeutinae, assim como a relação maior entre as duas últimas sub-famílias. Em E. sexcinctus foram identificados 11 haplótipos e em D. novemcinctus 49. As análises mostraram o alto polimorfismo do gene Citocromo b, a falta de estruturação genética das populações, uma baixa divergência genética (distância p) entre os haplótipos e mostraram que o Rio São Francisco não constitui uma barreira ao fluxo gênico nestas duas espécies, uma vez que o mesmo haplótipo ocorreu em suas duas margens. Três haplótipos de E. sexcinctus formaram em todas as análises um grupo que se distribui na região da Caatinga do extremo nordeste do Brasil, ao norte do Rio São Francisco. As análises mostraram quatro grupos entre os haplótipos de D. novemcinctus (49 deste estudo e 26 do Genbank), com uma clara separação entre o haplótipo norte-americano de todos os demais sul-americanos. Entre os sul-americanos existem três grupos, um formado por 65 haplótipos que se distribuem no Brasil, Argentina e Paraguai. Os outros dois grupos são menores, um ocorrendo na região Norte do Brasil (Amazonas e Pará) com três haplótipos e outro formado por seis haplótipos que ocorrem na Bahia, Rio de Janeiro e Rondônia. Embora suas características morfológicas sejam compatíveis com as descrições de D. novemcinctus, exemplares destes dois últimos grupos mostraram diferenças morfológicas em seus crânios...
DNA samples of 12 specimens of Euphractus sexcinctus and 67 specimens of Dasypys novemcinctus had the mitochondrial gene Cytochrome b (1140pb) amplified and sequenced. Phylogenetic (distance, maximum parsimony and maximum likelihood) and population (median-joining) analyses were carried out in order to study the genetic variation and phylogeography of these two species. It was also assessed the phylogenetic position of other Dasypodidae: Dasypus kappleri, Cabassous unicinctus, C. tatouay and Tolypeutes tricinctus. The results confirmed the monophyly of Dasypodidae, Dasypodinae, Euphractinae and Tolypeutinae, as well as the relationship between the two largest sub-families. In E. sexcinctus 11 haplotypes and in D. novemcinctus 49, were identified. The analyses showed the high polymorphism of the gene Cytochrome b, a lack of population genetic structure, a low genetic divergence (p distance) between haplotypes and that Rio São Francisco is not a barrier to gene flow in these two species, once the same haplotype occur in both margins. Three haplotypes of E. sexcinctus formed, in all analyses, a group that is distributed in the region of Caatinga, the extreme northeastern Brazil, north of Rio São Francisco. Analyses were congruent in showing four groups among D. novemcinctus haplotypes (49 of this study and 26 of Genbank), with a clear separation between United States haplotype and all other South American ones. Among South American haplotypes there are three groups, one is formed by 65 haplotypes distributed in Brazil, Argentina and Paraguay. The other two groups are smaller, one occurring in northern Brazil (Para and Amazonas) with three haplotypes, and another formed by six haplotypes occurring in Bahia, Rio de Janeiro and Rondônia. Although morphologic characteristics are compatible with the descriptions of D. novemcinctus, the latter two groups showed some morphologic differentiation in their skulls that corroborate molecular data and suggest...
Assuntos
Animais , Filogeografia , Citocromos b/análise , DNA Mitocondrial/análise , Variação Genética , Filogenia , Polimorfismo Genético , Especificidade da Espécie , Tatus/genéticaRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete SC karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombination nodule (RN) is located in the region of the SC nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the SC length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells, and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC.
Assuntos
Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Animais , Argentina , Evolução Biológica , Troca Genética , Cariotipagem , Masculino , Especificidade da Espécie , Espermatócitos/ultraestruturaRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete se karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombi-nation nodule (RN) is located in the region of the se nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the se length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells , and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC
Assuntos
Masculino , Animais , Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Argentina , Meiose , Xenarthra/anatomia & histologia , Xenarthra/genéticaRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete se karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombi-nation nodule (RN) is located in the region of the se nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the se length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells , and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC(AU)
Assuntos
Masculino , Animais , Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Argentina , Xenarthra/anatomia & histologia , Xenarthra/genética , MeioseRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete se karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombi-nation nodule (RN) is located in the region of the se nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the se length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells , and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC(AU)
Assuntos
Masculino , Animais , Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Argentina , Xenarthra/anatomia & histologia , Xenarthra/genética , MeioseRESUMO
The distribution of the vertebrate telomeric sequence (TTAGGG)(n) in four species of armadillos (Dasypodidae, Xenarthra), i.e. Chaetophractus villosus (2n = 60), Chaetophractus vellerosus (2n = 62), Dasypus hybridus (2n = 64) and Zaedyus pichiy (2n = 62) was examined by FISH with a peptide nucleic acid (PNA) probe. Besides the expected telomeric hybridization, interstitial (centromeric) locations of the (TTAGGG)n sequence were observed in one chromosome pair of Chaetophractus vellerosus and Zaedyus pichiy, suggesting chromosome fusion of ancestral chromosomes occurring during the evolution of Dasypodidae. In addition, all the species analysed showed one to four apparently telocentric chromosomes, exhibiting only two telomeric signals. However, the immunodetection study of kinetochore proteins on synaptonemal complex spreads from C. villosus showed that the apparently telocentric chromosomes have a tiny short arm that can be resolved only in the more elongated pachytene bivalents. This finding suggests that none of the species of armadillos possess true telocentric chromosomes. Our present results support a reduction in the diploid number by fusion of acrocentrics with loss of chromosome material as a tendency in Dasypodidae.