Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Xenarthra”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1992

The functional morphology of xenarthrous vertebrae in the armadillo Dasypus novemcinctus (Mammalia, Xenarthra).

In order to assess the mechanical properties of xenarthrous vertebrae, and to evaluate the role of xenarthrae as fossorial adaptations, in vitro bending tests were performed on posterior thoracic and lumbar vertebral segments excised from specimens of the armadillo Dasypus novemcinctus and the opossum Didelphis virginiana, the latter being used to represent the primitive mammalian condition. The columns of the two species were subjected to dorsal, ventral, and lateral bending, as well as torsion, in order to determine their stiffness in each of these directions. During these tests, bone strains in the centra of selected vertebrae were determined using rosette strain gages. Overall stiffness of the armadillo backbone at physiologically relevant displacement levels was significantly higher than that of the opossum for both dorsal and lateral bending. The two species also exhibited significant differences in angular displacement of individual vertebrae and in vertebral strain magnitudes and orientations in these two directions. No significant differences were observed when the columns of the two species were subjected to torsion or to ventral bending. Our results suggest that some, but not all, of the mechanical differences between the two species are due to the presence of xenarthrae. For example, removal of the xenarthrae from selected vertebrae (L2-L4) changes strain orientation and shear, but not strain magnitudes. Comparisons with functional data from other digging mammals indicate that the modified mechanical properties of the Dasypus column are consistent with an interpretation of xenarthrae as digging adaptations and lend support to the idea that the order Xenarthra represents an early offshoot of placental mammals specialized for fossoriality.

Animals↗
PubMed2005

Genome sizes in afrotheria, xenarthra, euarchontoglires, and laurasiatheria.

Topical literature and Web site databases provide genome sizes for approximately 4,000 animal species, invertebrates and vertebrates, 330 of which are mammals. We provide the genome size for 67 mammalian species, including 51 never reported before. Knowledge of genome size facilitates sequencing projects. The data presented here encompassed 5 Metatheria (order Didelphimorphia) and 62 Eutheria: 15 Xenarthra, 24 Euarchontoglires (Rodentia), as well as 23 Laurasiatheria (22 Chiroptera and 1 species from Perissodactyla). Already available karyotypes supplement the haploid nuclear DNA contents of the respective species. Thus, we established the first comprehensive set of genome size measurements for 15 Xenarthra species (armadillos) and for 12 house-mouse species; each group was previously represented by only one species. The Xenarthra exhibited much larger genomes than the modal 3 pg DNA known for mammals. Within the genus Mus, genome sizes varied between 2.98 pg and 3.68 pg. The 22 bat species we measured support the low 2.63 pg modal value for Chiroptera. In general, the genomes of Euarchontoglires and Laurasiatheria were found being smaller than those of (Afrotheria and) Xenarthra. Interspecific variation in genome sizes is discussed with particular attention to repetitive elements, which probably promoted the adaptation of extant mammals to their environment.

Animals↗
PubMed2006

The ancestral eutherian karyotype is present in Xenarthra.

Molecular studies have led recently to the proposal of a new super-ordinal arrangement of the 18 extant Eutherian orders. From the four proposed super-orders, Afrotheria and Xenarthra were considered the most basal. Chromosome-painting studies with human probes in these two mammalian groups are thus key in the quest to establish the ancestral Eutherian karyotype. Although a reasonable amount of chromosome-painting data with human probes have already been obtained for Afrotheria, no Xenarthra species has been thoroughly analyzed with this approach. We hybridized human chromosome probes to metaphases of species (Dasypus novemcinctus, Tamandua tetradactyla, and Choloepus hoffmanii) representing three of the four Xenarthra families. Our data allowed us to review the current hypotheses for the ancestral Eutherian karyotype, which range from 2n = 44 to 2n = 48. One of the species studied, the two-toed sloth C. hoffmanii (2n = 50), showed a chromosome complement strikingly similar to the proposed 2n = 48 ancestral Eutherian karyotype, strongly reinforcing it.

Animals↗
PubMed1997

Phylogenetic analyses of mitochondrial DNA suggest a sister group relationship between Xenarthra (Edentata) and Ferungulates.

Phylogenetic analysis of 12 protein-coding genes from complete mitochondrial DNA (mtDNA) molecules of various mammals including a xenarthran representative, the armadillo (Dasypus novemcinctus), showed that the order Xenarthra (Edentata) is a sister group to the ferungulates (carnivores, perissodactyls, artiodactyls, cetaceans). Morphological and previous molecular analyses have placed the Xenarthra basal to other extant eutherians. The present findings are in striking contrast with that understanding. The results suggest that Xenarthra and ferungulates separated about 86 MYA.

Amino Acid Sequence↗
PubMed2005

Low rate of genomic repatterning in Xenarthra inferred from chromosome painting data.

Comparative cytogenetic studies on Xenarthra, one of the most basal mammalian clades in the Placentalia, are virtually absent, being restricted largely to descriptions of conventional karyotypes and diploid numbers. We present a molecular cytogenetic comparison of chromosomes from the two-toed (Choloepus didactylus, 2n = 65) and three-toed sloth species (Bradypus tridactylus, 2n = 52), an anteater (Tamandua tetradactyla, 2n = 54) which, together with some data on the six-banded armadillo (Euphractus sexcinctus, 2n = 58), collectively represent all the major xenarthran lineages. Our results, based on interspecific chromosome painting using flow-sorted two-toed sloth chromosomes as painting probes, show the sloth species to be karyotypically closely related but markedly different from the anteater. We also test the synteny disruptions and segmental associations identified within Pilosa (anteaters and sloths) against the chromosomes of the six-banded armadillo as outgroup taxon. We could thus polarize the 35 non-ambiguously identified chromosomal changes characterizing the evolution of the anteater and sloth genomes and map these to a published sequence-based phylogeny for the group. These data suggest a low rate of genomic repatterning when placed in the context of divergence estimates based on molecular and fossil data. Finally, our results provide a glimpse of a likely ancestral karyotype for the extant Xenarthra, a pivotal group for understanding eutherian genome evolution.

Animals↗
PubMed2004

LINE-1 distribution in Afrotheria and Xenarthra: implications for understanding the evolution of LINE-1 in eutherian genomes.

Long interspersed nuclear elements (LINEs) comprise about 21% of the human genome (of which L1 is most abundant) and are preferentially accumulated in AT-rich regions, as well as the X and Y chromosomes. Most knowledge of L1 distribution in mammals is restricted to human and mouse. Here we report the first investigation of L1 distribution in the genomes of a wide variety of eutherian mammals, including species in the two basal clades, Afrotheria and Xenarthra. Our results show L1 accumulation on the X of all eutherian mammals, an observation consistent with an ancestral involvement of these elements in the X-inactivation process (the Lyon repeat hypothesis). Surprisingly, conspicuous accumulation of L1 in AT-rich regions of the genome was not observed in any species outside of Euarchontoglires (represented by human, mouse and rabbit). Although several features were common to most species investigated, our comprehensive survey shows that the patterns observed in human and mouse are, in many aspects, far from typical for all mammals. We discuss these findings with reference to models that have previously been proposed to explain the AT distribution bias of L1 in human and mouse, and how this relates to the evolution of these elements in other eutherian genomes.

Animals↗
PubMed2005

Chromosomal localization of the telomeric (TTAGGG)n sequence in four species of Armadillo (Dasypodidae) from Argentina: an approach to explaining karyotype evolution in the Xenarthra.

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.

Animals↗
PubMed1989

The primary structure of pale-throated three-toed sloth (Bradypus tridactylus, Xenarthra) hemoglobin.

The hemoglobin of the Pale-Throated Three-Toed Sloth (Bradypus tridactylus, Xenarthra) was separated into two components (ratio 4:1) with identical amino-acid analyses for the alpha- and beta-chains. The primary structures of both chains from the major component are given. They could be isolated by chromatography on carboxymethyl cellulose CM-52. The sequences have been determined by automatic Edman degradation of the native chains and their tryptic peptides. The comparison with human hemoglobin showed 27 substitutions in the alpha-chains and 33 in the beta-chains. In the alpha-chains one amino-acid exchange involves an alpha 1/beta 1-contact. In the beta-chains two heme- and four alpha 1/beta 1-contacts are substituted. The hemoglobin of the Sloth is compared to that of the Nine-Banded Armadillo (Dasypus novemcinctus), another representative of the order Xenerthra.

Amino Acid Sequence↗
PubMed2006

Osteoderm morphology and development in the nine-banded armadillo, Dasypus novemcinctus (Mammalia, Xenarthra, Cingulata).

Among modern mammals, armadillos (Xenarthra, Cingulata) are the only group that possesses osteoderms, bony inclusions within the integument. Along the body, osteoderms are organized into five discrete assemblages: the head, pectoral, banded, pelvic, and tail shields. The pectoral, banded, and pelvic shields articulate to form the carapace. We examined osteoderm skeletogenesis in the armadillo Dasypus novemcinctus using serial and whole-mount histochemistry. Compared with the rest of the skeleton, osteoderms have a delayed onset of development. Skeletogenesis begins as condensations of osteoblasts secreting osteoid, localized within the papillary layer of the dermis. Osteoderm formation is asynchronous both within each shield and across the body. The first osteoderms to mineralize are situated within the pectoral shield of the carapace, followed by elements within the banded, head, pelvic, and tail shields. In general, within each shield ossification begins craniomedially and proceeds caudally and laterally, except over the head, where the earliest elements form over the frontal and parietal bones. The absence of cartilage precursors indicates that osteoderms are dermal elements, possibly related to the all-encompassing vertebrate dermal skeleton (exoskeleton). The mode of development of D. novemcinctus osteoderms is unlike that described for squamate osteoderms, which arise via bone metaplasia, and instead is comparable with intramembranously derived elements of the skull.

Animals↗
PubMed2003

Molecular systematics of armadillos (Xenarthra, Dasypodidae): contribution of maximum likelihood and Bayesian analyses of mitochondrial and nuclear genes.

The 30 living species of armadillos, anteaters, and sloths (Mammalia: Xenarthra) represent one of the three major clades of placentals. Armadillos (Cingulata: Dasypodidae) are the earliest and most speciose xenarthran lineage with 21 described species. The question of their tricky phylogeny was here studied by adding two mitochondrial genes (NADH dehydrogenase subunit 1 [ND1] and 12S ribosomal RNA [12S rRNA]) to the three protein-coding nuclear genes (alpha2B adrenergic receptor [ADRA2B], breast cancer susceptibility exon 11 [BRCA1], and von Willebrand factor exon 28 [VWF]) yielding a total of 6869 aligned nucleotide sites for thirteen xenarthran species. The two mitochondrial genes were characterized by marked excesses of transitions over transversions-with a strong bias toward CT transitions for the 12S rRNA-and exhibited two- to fivefold faster evolutionary rates than the fastest nuclear gene (ADRA2B). Maximum likelihood and Bayesian phylogenetic analyses supported the monophyly of Dasypodinae, Tolypeutinae, and Euphractinae, with the latter two armadillo subfamilies strongly clustering together. Conflicting branching points between individual genes involved relationships within the subfamilies Tolypeutinae and Euphractinae. Owing to a greater number of informative sites, the overall concatenation favored the mitochondrial topology with the classical grouping of Cabassous and Priodontes within Tolypeutinae, and a close relationship between Euphractus and Chaetophractus within Euphractinae. However, low statistical support values associated with almost equal distributions of apomorphies among alternatives suggested that two parallel events of rapid speciation occurred within these two armadillo subfamilies.

Animals↗
PubMed1999

Armadillos exhibit less genetic polymorphism in North America than in South America: nuclear and mitochondrial data confirm a founder effect in Dasypus novemcinctus (Xenarthra).

Heterozygosity at eight nuclear enzymatic loci and mitochondrial DNA control region (D-loop) sequence polymorphism was compared between North and South American nine-banded armadillos (Dasypus novemcinctus: Xenarthra, Dasypodidae). All markers revealed a striking genetic homogeneity amongst Texas, Louisiana, and Mississippi individuals, vs. the usual level of polymorphism for the French Guiana population. This may reflect a founder effect during colonization of North America. Occurrence of polymorphism in the D-loop microsatellite motif of North American armadillos suggests a recent recovery of mitochondrial variability. Phylogeographic analyses using Dasypus kappleri as outgroup provides evidence for a clear separation between North and South American control region haplotypes.

Animals↗
PubMed2004

A study of platelets in the armadillo chaetophractus villosus (xenarthra, dasypodidae).

Nothing is known about haemostasis in Xenarthra, a widely distributed Order of American mammalians. Chaetophractus villosus, a member of the Dasypodidae family of this group, which is easily adapted to captivity, is of growing interest for biomedical research. In this work, we studied platelet number, MPV, ultrastructure of the platelets by SEM and TEM, and aggregation responses to ADP and ristocetin in this species. Blood samples were obtained by cardiac puncture in 20 anaesthetised animals. Platelet count and MPV were evaluated at the beginning and at the end of a 3-year experimental period, to detect possible variations related to time of captivity. SEM and TEM were done by routine methods adapted to the material, and aggregation response to ADP and ristocetin were evaluated by the Born method. The parameters studied did not show any sex-related differences, nor did the platelet count change during captivity. Nevertheless, MPV decreased during this period. Platelets were ultrastructurally similar to those of other mammals and human beings and responded to proven agonists. Data provided in this study will contribute to the understanding of the haemostatic process in this species.

Animals↗
PubMed1985

Evolutionary trends of the histological pattern in the teeth of Edentata (Xenarthra).

In a comparative study of the dental structure of Edentata, the central tissue was identified as a modified orthodentine, except in the Glyptodontidae where an osteodentine was found. Some evolutionary trends of the tissues in these teeth may have been related with the extinction of ground sloths. Comparative studies of the tissues in mammalian teeth seem to be good tests for systematics.

Animals↗
PubMedDate not supplied

Coccidia of Brazilian mammals: Eimeria corticulata n. sp. (Apicomplexa: Eimeriidae) from the anteater Tamandua tetradactyla (Xenarthra: Myrmecophagidae) and Eimeria zygodontomyis n. sp. from the cane mouse Zygodontomys lasiurus (Rodentia: Cricetidae).

Feces from a specimen of Tamandua tetradactyla (Linn.) from Portel, Pará State, north Brazil, contained two different coccidial oocysts; one identified as Eimeria tamanduae Lainson 1968, and the other as a new species, described here as Eimeria corticulata n. sp. Oocysts of E. corticulata are ellipsoidal, 37.4 x 30.4 (31.2-43.7 x 23.7-35.0) microns, shape index (length/width) 1.2 (1.0-1.5). Oocyst wall 2.5-3.7 microns thick and composed of two layers; an outer thick, brown-yellow one with radial striations, and a thin inner smooth one: no visible micropyle. Oocyst residuum a large globule of about 10.7 x 10.3 microns, usually accompanied by a number of smaller attached globules. Sporocysts ellipsoidal, 21.0 x 11.0 (20.0-22.5 x 10.0-12.5) microns, with a conspicuous Stieda body; shape index 1.9 (1.6-2.2). Sporocyst residuum a small number of scattered granules: sporozoites 18.7 x 5.0 microns, with a large posterior refractile body. Eimeria zygodontomyis n. sp. is described in feces from Zygodontomys lasiurus (Lund) from the Serra dos Carajás, Pará. Oocysts ellipsoidal to cylindrical, 16.5 x 12.0 (13.7-18.7 x 11.2-12.3) microns, shape index 1.4 (1.2-1.5). Wall colorless, smooth, single-layered and about 0.6 micron thick: no micropyle. No oocyst residuum, but a polar granule of about 1.8 x 1.0 microns is sometimes present. Sporocysts ellipsoidal, 8.4 x 5.5 (7.5-8.7 x 5.0-6.2) microns, shape index 1.5 (1.4-1.7), with a thin colorless wall and a delicate Stieda body. Sporozoites enclose a compact residuum of about 2.5 x 3.7 microns.

Animals↗
PubMedDate not supplied

Coccidia of Brazilian mammals: Eimeria marajoensis N. Sp. (Apicomplexa: Eimeriidae) from the Anteater, Tamandua tetradactyla (Xenarthra: Myrmecophagidae).

Feces from a juvenile specimen of the anteater Tamandua tetradactyla from Ponta de Pedras, Marajó, Pará, northern Brazil, contained three different coccidial oocysts: Eimeria tamanduae Lainson, 1968; E. corticulata Lainson & Shaw, 1990; and a third species previously unrecorded and described here as Eimeria marajoensis n. sp. Oocysts of the latter parasite are spherical to subspherical, 13.9 +/- 1.5 x 13.4 +/- 1.4 (11.1-16.5 x 11.1-16.5) microns, shape index (length/width) 1.0 (1.0-1.2). The oocyst wall is a single, colorless layer about 0.6-1.0 microns thick with no striations or micropyle. There is no oocyst residuum, but a single, round, oval or irregularly shaped polar granule of about 0.75-2.5 microns is consistently present. The sporocysts are broadly ellipsoidal, 7.1 +/- 0.7 +/- 5.3 +/- 0.6 (6.0-8.8 x 4.0-5.7) microns, shape index 1.3 (1.2-1.5), with a delicate wall bearing minute stieda body. No sub-stieda body was visible. The sporocyst residuum consists of some 10-20 rounded granules, lying between the two slightly curved sporozoites which measure approximately 6.5 x 2.0 microns. Sporocyst refractile bodies were not discernable.

Animals↗