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1
J. Foley, William. "Marsupial Nutrition". Pacific Conservation Biology 5, n. 3 (1999): 240. http://dx.doi.org/10.1071/pc99240a.
Testo completoAbstract (sommario):
In the early 1980s advances in marsupial biology could no longer be encapsulated in a single volume such as Hugh Tyndale-Biscoe's "Life of Marsupials" and Cambridge University Press commissioned a series of monographs covering a range of different topics in marsupial biology. As it was, only three of that series were realized and among them was the ptedecessor to this book "Digestive Physiology and Nutrition of Marsupials" published in 1982. "Marsupial Nutrition" is a considerably expanded and comprehensive review of studies of nutrition and digestive physiology of Australasian and South American marsupials. In Australia, many ecologists view the limited nutrient status of our soils and vegetation as a fundamental limit to animal populations. This book explains firstly how Australian marsupials have responded to those limitations and secondly asks whether these responses are common amongst marsupials living in New Guinea and South America.
2
SOUZA ROCHA, Katarine de, Gleiciane SCHUPP DE SENA MESQUITA, Maeli Fernanda SILVA FERREIRA, Flávia de Nazaré LEITE BARROS, Renata Cecília Soares de Lima MACEDO, Elane de ARAÚJO SARAIVA, Ana Cristina MENDES-OLIVEIRA et al. "New records of Leptospira spp. in wild marsupials and a rodent in the eastern Brazilian Amazon through PCR detection". Acta Amazonica 50, n. 4 (dicembre 2020): 305–8. http://dx.doi.org/10.1590/1809-4392201903683.
Testo completoAbstract (sommario):
ABSTRACT We analyzed the presence of Leptospira spp. in liver and kidney tissue of wild marsupials and rodents trapped in a periurban forest in the eastern Brazilian Amazon. We examined 25 individuals of four marsupial and seven rodent species for the presence of the 16S rRNA gene of Leptospira in the DNA extracted from 47 liver and kidney tissue samples using PCR. We detected positive samples in 12% (3/25) of the individuals, in kidney fragments of two marsupial species (Didelphis marsupialis and Marmosops pinheiroi) and in a liver fragment of one rodent species (Echimys chrysurus). These are the first records of Leptospira spp. in M. pinheiroi and E. chrysurus and it is the first molecular survey of marsupials and rodents in the Brazilian Amazon.
3
Cifelli, Richard L., e Christian De Muizon. "Marsupial mammal from the Upper Cretaceous North Horn Formation, Central Utah". Journal of Paleontology 72, n. 3 (maggio 1998): 532–37. http://dx.doi.org/10.1017/s0022336000024306.
Testo completoAbstract (sommario):
Little is known of the non-dinosaurian fauna from the Cretaceous (Maastrichtian) part of the North Horn Formation, despite its biogeographic importance. Herein we describe a new marsupial mammal from the unit, founded on an exceptionally complete specimen of a juvenile individual, and present new information on the incisor region of early marsupials, based on comparison with complete specimens from the early Paleocene of Bolivia. Alphadon eatoni, new species, is the smallest Lancian species of the genus, and departs from a presumed marsupial morphotype in having the second lower incisor enlarged. The species is, however, primitive in lacking a “staggered” pattern to the incisor series and in having a labial mandibular foramen, and in these respects it differs from Paleocene and later marsupials. Poor representation of other taxa precludes meaningful comparison to most other North American Cretaceous marsupials, although Eodelphis, thought to be distantly related, also has an enlarged i2. Although Alphadon is characterized by many primitive features, the relative development of the incisors is not what would be predicted in a morphological antecedent to later Marsupialia.
4
Denyer, Alice L., Sophie Regnault e John R. Hutchinson. "Evolution of the patella and patelloid in marsupial mammals". PeerJ 8 (19 agosto 2020): e9760. http://dx.doi.org/10.7717/peerj.9760.
Testo completoAbstract (sommario):
The musculoskeletal system of marsupial mammals has numerous unusual features beyond the pouch and epipubic bones. One example is the widespread absence or reduction (to a fibrous “patelloid”) of the patella (“kneecap”) sesamoid bone, but prior studies with coarse sampling indicated complex patterns of evolution of this absence or reduction. Here, we conducted an in-depth investigation into the form of the patella of extant marsupial species and used the assembled dataset to reconstruct the likely pattern of evolution of the marsupial patella. Critical assessment of the available literature was followed by examination and imaging of museum specimens, as well as CT scanning and histological examination of dissected wet specimens. Our results, from sampling about 19% of extant marsupial species-level diversity, include new images and descriptions of the fibrocartilaginous patelloid in Thylacinus cynocephalus (the thylacine or “marsupial wolf”) and other marsupials as well as the ossified patella in Notoryctes ‘marsupial moles’, Caenolestes shrew opossums, bandicoots and bilbies. We found novel evidence of an ossified patella in one specimen of Macropus rufogriseus (Bennett’s wallaby), with hints of similar variation in other species. It remains uncertain whether such ossifications are ontogenetic variation, unusual individual variation, pathological or otherwise, but future studies must continue to be conscious of variation in metatherian patellar sesamoid morphology. Our evolutionary reconstructions using our assembled data vary, too, depending on the reconstruction algorithm used. A maximum likelihood algorithm favours ancestral fibrocartilaginous “patelloid” for crown clade Marsupialia and independent origins of ossified patellae in extinct sparassodonts, peramelids, notoryctids and caenolestids. A maximum parsimony algorithm favours ancestral ossified patella for the clade [Marsupialia + sparassodonts] and subsequent reductions into fibrocartilage in didelphids, dasyuromorphs and diprotodonts; but this result changed to agree more with the maximum likelihood results if the character state reconstructions were ordered. Thus, there is substantial homoplasy in marsupial patellae regardless of the evolutionary algorithm adopted. We contend that the most plausible inference, however, is that metatherians independently ossified their patellae at least three times in their evolution. Furthermore, the variability of the patellar state we observed, even within single species (e.g. M. rufogriseus), is fascinating and warrants further investigation, especially as it hints at developmental plasticity that might have been harnessed in marsupial evolution to drive the complex patterns inferred here.
5
Kirsch, John A. W., Mark S. Springer e François-Joseph Lapointe. "DNA-hybridisation Studies of Marsupials and their Implications for Metatherian Classification". Australian Journal of Zoology 45, n. 3 (1997): 211. http://dx.doi.org/10.1071/zo96030.
Testo completoAbstract (sommario):
We review past DNA-hybridisation studies of marsupials and present a reanalysis of the data, utilising results from our and additional studies to formulate and rationalise a new classification of Marsupialia. In the reanalysis, 13 individual DNA-hybridisation matrices, many lacking some pairwise comparisons, were sutured in stages to provide the basis for generating a tree of 101 marsupials plus an outgroup eutherian; a fourteenth matrix provided data for a tree including eight additional eutherians and a monotreme. Validation was achieved by jackknifing on taxa for each matrix as well as on tables combining two or more matrices generated during assembly of the 102-taxon data set. The results are consistent with most conclusions from the individual studies and dramatise the unevenness of hierarchical levels in current classifications of marsupials. In particular, the affinities of the American marsupial Dromiciops gliroides with, and the distinctness of marsupial bandicoots from, Australasian metatherians are reaffirmed, while opossums are shown to be as internally divergent as are most members of the order Diprotodontia. Calibration of the 102-taxon tree and dating of the major dichotomies suggest that no extant marsupial lineage originated before the latest Cretaceous, and that all of them together with most South American and all Australasian fossils should be recognised as a monophyletic group contrasting with a largely Laurasian (if possibly paraphyletic) taxon. These inferences, together with the details of the phylogeny, mandate that the misleading ‘Australian’ v. ‘American’ distinction be abandoned, even as a geographic convenience.
6
Deakin, Janine E. "Marsupial X chromosome inactivation: past, present and future". Australian Journal of Zoology 61, n. 1 (2013): 13. http://dx.doi.org/10.1071/zo12113.
Testo completoAbstract (sommario):
Marsupial and eutherian mammals inactivate one X chromosome in female somatic cells in what is thought to be a means of compensating for the unbalanced X chromosome dosage between XX females and XY males. The hypothesis of X chromosome inactivation (XCI) was first published by Mary Lyon just over 50 years ago, with the discovery of XCI in marsupials occurring a decade later. However, we are still piecing together the evolutionary origins of this fascinating epigenetic mechanism. From the very first studies on marsupial X inactivation, it was apparent that, although there were some similarities between marsupial and eutherian XCI, there were also some striking differences. For instance, the paternally derived X was found to be preferentially silenced in marsupials, although the silencing was often incomplete, which was in contrast to the random and more tightly controlled inactivation of the X chromosome in eutherians. Many of these earlier studies used isozymes to study the activity of just a few genes in marsupials. The sequencing of several marsupial genomes and the advent of molecular cytogenetic techniques have facilitated more in-depth studies into marsupial X chromosome inactivation and allowed more detailed comparisons of the features of XCI to be made. Several important findings have come from such comparisons, among which is the absence of the XIST gene in marsupials, a non-coding RNA gene with a critical role in eutherian XCI, and the discovery of the marsupial RSX gene, which appears to perform a similar role to XIST. Here I review the history of marsupial XCI studies, the latest advances that have been made and the impact they have had towards unravelling the evolution of XCI in mammals.
7
Wright, Jonathan C., e Anne Yoshizawa. "Ionic Composition and Ion Provisioning in Marsupial Fluid of Terrestrial Isopods (Isopoda, Oniscidea)". Crustaceana 84, n. 11 (2011): 1307–24. http://dx.doi.org/10.1163/156854011x594803.
Testo completoAbstract (sommario):
AbstractThe marsupium of the primarily terrestrial isopod sub-order Oniscidea is modified from the basal marine design and represents one of the key evolutionary innovations enabling the invasion of land habitats. In the Ligiidae, the marsupial chamber is provisioned with water from the external environment via a capillary channel formed from the apposed 6th and 7th pereiopods. The other oniscidean families possess a 'closed' marsupium, isolated from the pleural water-conducting system and provisioned with water and ions by sternal cotyledons. How these different modes of fluid provisioning influence the ionic composition of marsupial fluid and its osmotic and ionic relationship to the haemolymph remains essentially unstudied. We analysed the ionic composition (Na+, K+, Ca2+, Cl–, pH) of marsupial fluid and haemolymph in 4 species of Oniscidea: Ligia occidentalis (Ligiidae), Ligidium lapetum (Ligiidae), Alloniscus perconvexus (Alloniscidae), and Armadillidium vulgare (Armadillidiidae). In all four species, ion concentrations show a broad similarity between marsupial fluid and haemolymph, but with elevated potassium concentrations in the 'closed'-marsupium species. The sternal integument of Armadillidium vulgare is permeable to inulin and the volume of the combined marsupial fluid and haemolymph is not significantly enlarged compared to the haemolymph of non-gravid females. Accordingly, the 'closed' marsupium of A. vulgare can be viewed as a functional subdivision of the haemolymph space. In Ligidium lapetum, marsupial water is derived from external freshwater sources, but marsupial fluid [Na+] and [Cl–]are actually significantly higher than haemolymph values. This species thus possesses an effective means of ion provisioning, paralleling that seen in the 'closed' marsupial species.
8
Belov, Katherine, Robert D. Miller, Julie M. Old e Lauren J. Young. "Marsupial immunology bounding ahead". Australian Journal of Zoology 61, n. 1 (2013): 24. http://dx.doi.org/10.1071/zo12111.
Testo completoAbstract (sommario):
Marsupial immune responses were previously touted as ‘primitive’ but we now know that the marsupial immune system is complex and on par with that of eutherian mammals. In this manuscript we review the field of marsupial immunology, focusing on basic anatomy, developmental immunology, immunogenetics and evolution. We concentrate on advances to our understanding of marsupial immune gene architecture, made possible by the recent sequencing of the opossum, tammar wallaby and Tasmanian devil genomes. Characterisation of immune gene sequences now paves the way for the development of immunological assays that will allow us to more accurately study health and disease in marsupials.
9
Price, Gilbert J., Kyle J. Ferguson, Gregory E. Webb, Yue-xing Feng, Pennilyn Higgins, Ai Duc Nguyen, Jian-xin Zhao, Renaud Joannes-Boyau e Julien Louys. "Seasonal migration of marsupial megafauna in Pleistocene Sahul (Australia–New Guinea)". Proceedings of the Royal Society B: Biological Sciences 284, n. 1863 (27 settembre 2017): 20170785. http://dx.doi.org/10.1098/rspb.2017.0785.
Testo completoAbstract (sommario):
Seasonal two-way migration is an ecological phenomenon observed in a wide range of large-bodied placental mammals, but is conspicuously absent in all modern marsupials. Most extant marsupials are typically smaller in body size in comparison to their migratory placental cousins, possibly limiting their potential to undertake long-distance seasonal migrations. But what about earlier, now-extinct giant marsupial megafauna? Here we present new geochemical analyses which show that the largest of the extinct marsupial herbivores, the enormous wombat-like Diprotodon optatum , undertook seasonal, two-way latitudinal migration in eastern Sahul (Pleistocene Australia–New Guinea). Our data infer that this giant marsupial had the potential to perform round-trip journeys of as much as 200 km annually, which is reminiscent of modern East African mammal migrations. These findings provide, to our knowledge, the first evidence for repetitive seasonal migration in any metatherian (including marsupials), living or extinct, and point to an ecological phenomenon absent from the continent since the Late Pleistocene.
10
Cockburn, A. "Sex-Ratio Variation in Marsupials". Australian Journal of Zoology 37, n. 3 (1989): 467. http://dx.doi.org/10.1071/zo9890467.
Testo completoAbstract (sommario):
Many marsupials produce sex ratios biased towards male or female young. In several cases these changes are comfortably accommodated in the existing theory of sex allocation. Local resource competition and the Trivers-Willard hypothesis have been usefully applied to several data sets, and preliminary experimental work has supported the main tenets of theory. By contrast, several data sets lack explanation, and provide challenges to theoreticians. The high frequency of bias in marsupials does not result from data-dredging, as bias is usually reported in descriptive accounts of marsupial reproduction, without recourse to any theoretical or mechanistic explanations. It is not possible to distinguish whether the marsupial mode of reproduction is well suited to manipulate sex allocation, or whether it facilitates measurement of biased sex allocation. As for most eutherians and birds, the mechanism of prenatal sex allocation is unknown for any marsupial. However, the current interest in sex-determining mechanisms in marsupials suggests a profitable avenue for collaboration between geneticists, physiologists and evolutionary ecologists.
11
Sherwin, WB, e ND Murray. "Population and Conservation Genetics of Marsupials". Australian Journal of Zoology 37, n. 3 (1989): 161. http://dx.doi.org/10.1071/zo9890161.
Testo completoAbstract (sommario):
This article summarises current knowledge of marsupial population genetics, and discusses its relevance to the conservation of marsupial species. It has been suggested that there is much lower genetic variation within marsupial populations than in eutherian mammals. This trend is not evident in the electrophoretic data summarised here. However, genetic differentiation between populations, subspecies, and species of marsupials appears to be slightly lower than comparable values for eutherians. Genetic estimates of migration between populations are scarce at present, but show values that are comparable with eutherians. Some studies of marsupial population genetics have used non-electrophoretic characteristics, or have addressed the possibility of selection on the characters analysed. Although few, these studies indicate the suitability of marsupials for such investigations. Recent debate over the theories and applications of conservation genetics has made it clear that more research is required on individual species. Given the record of extinction of marsupials in the last 200 years, it is important to test the applicability of these theories to individual marsupial species. Several examples are discussed emphasising the need for ecological studies that estimate the effective number of reproducing individuals per generation. This figure, called the effective size, is the corner- stone of conservation genetics theory, being an important determinant of both the rate of loss of variation between individuals, and the rate of inbreeding. The effective size of the mainland population of the eastern barred bandicoot, Perameles gunnii, appears to be only about one-tenth of its census number. This result is comparable with estimates made in other vertebrates, and demonstrates that many marsupial species which appear to have an adequate census size on ecological grounds may face genetic problems resulting from small effective size.
12
Pevsner, Spencer K., David M. Grossnickle e Zhe-Xi Luo. "The functional diversity of marsupial limbs is influenced by both ecology and developmental constraint". Biological Journal of the Linnean Society 135, n. 3 (4 gennaio 2022): 569–85. http://dx.doi.org/10.1093/biolinnean/blab168.
Testo completoAbstract (sommario):
Abstract Extant marsupials are less ecologically diverse than placentals, and this is reflected by placentals exhibiting a greater diversity of locomotor modes, including powered flight and fully aquatic swimming. One proposed explanation for this discrepancy is that the development of more disparate marsupial forelimbs is prevented by the neonate’s crawl to the pouch, which requires precocious forelimb development for climbing adaptations. To test predictions of this Developmental Constraint Hypothesis (DCH), we pursue a comparative morphometric study on osteological traits of mammalian limbs, with an emphasis on functional differentiation of marsupial limbs among locomotor modes. We apply multivariate analyses to a large dataset of limb metrics and a diverse sample of mammals, with the placental sample limited to taxa whose locomotor modes are exhibited in marsupials. Overall, we do not find consistent evidence in support of the DCH. Diprotodontia serves as an exception, with comparisons of their forelimbs to hind limbs supporting the DCH. Our results suggest that developmental constraints on marsupial forelimbs may have limited marsupial diversity to some degree. Despite this, the marsupial locomotor groups show unexpectedly high levels of morphological differentiation relative to placentals of the same locomotor modes, indicating that ecological functions may overcome developmental constraints on a macroevolutionary scale.
13
Deakin, Janine E., e Sally Potter. "Marsupial chromosomics: bridging the gap between genomes and chromosomes". Reproduction, Fertility and Development 31, n. 7 (2019): 1189. http://dx.doi.org/10.1071/rd18201.
Testo completoAbstract (sommario):
Marsupials have unique features that make them particularly interesting to study, and sequencing of marsupial genomes is helping to understand their evolution. A decade ago, it was a huge feat to sequence the first marsupial genome. Now, the advances in sequencing technology have made the sequencing of many more marsupial genomes possible. However, the DNA sequence is only one component of the structures it is packaged into: chromosomes. Knowing the arrangement of the DNA sequence on each chromosome is essential for a genome assembly to be used to its full potential. The importance of combining sequence information with cytogenetics has previously been demonstrated for rapidly evolving regions of the genome, such as the sex chromosomes, as well as for reconstructing the ancestral marsupial karyotype and understanding the chromosome rearrangements involved in the Tasmanian devil facial tumour disease. Despite the recent advances in sequencing technology assisting in genome assembly, physical anchoring of the sequence to chromosomes is required to achieve a chromosome-level assembly. Once chromosome-level assemblies are achieved for more marsupials, we will be able to investigate changes in the packaging and interactions between chromosomes to gain an understanding of the role genome architecture has played during marsupial evolution.
14
Tojima, Sayaka, Hidaka Anetai, Kaito Koike, Saori Anetai, Kounosuke Tokita, Chris Leigh e Jaliya Kumaratilake. "Gross anatomy of the gluteal and posterior thigh muscles in koalas based on their innervations". PLOS ONE 17, n. 9 (14 settembre 2022): e0261805. http://dx.doi.org/10.1371/journal.pone.0261805.
Testo completoAbstract (sommario):
Morphological and functional comparison of convergently-evolved traits in marsupials and eutherians is an important aspect of studying adaptive divergence in mammals. However, the anatomy of marsupials has been particularly difficult to evaluate for multiple reasons. First, previous studies on marsupial anatomy are often uniformly old and non-exhaustive. Second, muscle identification was historically based on muscle attachment sites, but attachment sites have since been declared insufficient for muscle identification due to extensive interspecific variation. For example, different names have been used for muscles that are now thought to be equivalent among several different species, which causes confusion. Therefore, descriptions of marsupial muscles have been inconsistent among previous studies, and their anatomical knowledge itself needs updating. In this study, the koala was selected as the representative marsupial, in part because koala locomotion may comprise primate (eutherian)-like and marsupial-like mechanics, making it an interesting phylogenetic group for studying adaptive divergence in mammals. Gross dissection of the lower limb muscles (the gluteal and the posterior thigh regions) was performed to permit precise muscle identification. We first resolved discrepancies among previous studies by identifying muscles according to their innervation; this recent, more reliable technique is based on the ontogenetic origin of the muscle, and it allows for comparison with other taxa (i.e., eutherians). We compared our findings with those of other marsupials and arboreal primates and identified traits common to both arboreal primates and marsupials as well as muscle morphological features unique to koalas.
15
Hayman, DL. "Marsupial Cytogenetics". Australian Journal of Zoology 37, n. 3 (1989): 331. http://dx.doi.org/10.1071/zo9890331.
Testo completoAbstract (sommario):
This review includes a list of the chromosome numbers of marsupials and a summary of the main features of chromosome evolution in this group of mammals. Special topics discussed include sex chromosome mosaicism, the size of the marsupial X chromosome, X chromosomes and nucleolar organisers, complex sex chromosome systems, repeated DNA sequences and aspects of meiosis.
16
Kumar, Satish, Erica M. De Leon, Jose Granados, Deanne J. Whitworth e John L. VandeBerg. "Monodelphis domestica Induced Pluripotent Stem Cells Reveal Metatherian Pluripotency Architecture". International Journal of Molecular Sciences 23, n. 20 (20 ottobre 2022): 12623. http://dx.doi.org/10.3390/ijms232012623.
Testo completoAbstract (sommario):
Marsupials have been a powerful comparative model to understand mammalian biology. However, because of the unique characteristics of their embryology, marsupial pluripotency architecture remains to be fully understood, and nobody has succeeded in developing embryonic stem cells (ESCs) from any marsupial species. We have developed an integration-free iPSC reprogramming method and established validated iPSCs from two inbred strains of a marsupial, Monodelphis domestica. The monoiPSCs showed a significant (6181 DE-genes) and highly uniform (r2 [95% CI] = 0.973 ± 0.007) resetting of the cellular transcriptome and were similar to eutherian ESCs and iPSCs in their overall transcriptomic profiles. However, monoiPSCs showed unique regulatory architecture of the core pluripotency transcription factors and were more like marsupial epiblasts. Our results suggest that POU5F1 and the splice-variant-specific expression of POU5F3 synergistically regulate the opossum pluripotency gene network. It is plausible that POU5F1, POU5F3 splice variant XM_016427856.1, and SOX2 form a self-regulatory network. NANOG expression, however, was specific to monoiPSCs and epiblasts. Furthermore, POU5F1 was highly expressed in trophectoderm cells, whereas all other pluripotency transcription factors were significantly downregulated, suggesting that the regulatory architecture of core pluripotency genes of marsupials may be distinct from that of eutherians.
17
McKenzie, LM, e DW Cooper. "Low MHC class II variability in a marsupial". Reproduction, Fertility and Development 6, n. 6 (1994): 721. http://dx.doi.org/10.1071/rd9940721.
Testo completoAbstract (sommario):
The major histocompatibility complex (MHC) loci have been shown to be highly polymorphic in most eutherian ('placental') species studied. Several hypotheses have been advanced for the maintenance of this exceptional level of genetic variation, one of which suggests that it is necessary for successful eutherian reproduction. Marsupials (metatherians) and eutherians are the only two groups of viviparous mammals, but their modes of reproduction are quite distinct. Although marsupials have placentae, they are generally shorter lived and less invasive than in eutherians. Other investigations have shown that genetic variation at marsupial MHC class I loci is probably high. Weak or non-existent mixed lymphocyte culture responses previously reported in several marsupial species have suggested a lack of class II variation. Data have therefore been collected on the level of restriction fragment length polymorphism at MHC class II beta-chain encoding loci of a marsupial, Macropus eugenii (the tammar wallaby). This level is shown to be low, between the level of MHC variation found in cheetahs and a population of lions with a restricted genetic base. Attention is drawn to the need to collect more data on the level of class II variability in both eutherians and marsupials, and to the potential of marsupials for understanding the relation, if any, between mode of reproduction and MHC variability.
18
Tyndale-Biscoe, C. H. "Australasian marsupials - to cherish and to hold". Reproduction, Fertility and Development 13, n. 8 (2001): 477. http://dx.doi.org/10.1071/rd01079.
Testo completoAbstract (sommario):
Considerable interchange of mammals between South America and Australasia occurred during the first half of the Tertiary, including the presence of placental mammals in Australia. This challenges the old assumption that the marsupial radiation in Australia was made possible by the absence of placental competition, and suggests that two properties of marsupial organization may have favoured their survival in the increasingly arid climates that developed after the separation of Australasia from Antarctica. The basal metabolic rates of marsupials are about 70% of equivalent placentals, so their maintenance requirements for energy, nitrogen and water are lower, whereas their field metabolic rates are about the same, which means that they have a greater metabolic scope to call on when active. This may have given marsupials an advantage in semi-arid environments. The lengthy and complex lactation of marsupials enables the female to exploit limited resources over an extended period without compromising the survival of the young. Both these properties of marsupials enabled them to survive the double constraints of low fertility soils and the uncertain climate of Australia throughout the Tertiary. The arrival of people was followed first by the extinction of the large marsupials and, much later, by the wholesale decline or extinction of the small-to-medium sized species. The common factor in both extinctions may have been the constraints of marsupial reproduction.
19
Deakin, Janine E. "Marsupial Genome Sequences: Providing Insight into Evolution and Disease". Scientifica 2012 (2012): 1–22. http://dx.doi.org/10.6064/2012/543176.
Testo completoAbstract (sommario):
Marsupials (metatherians), with their position in vertebrate phylogeny and their unique biological features, have been studied for many years by a dedicated group of researchers, but it has only been since the sequencing of the first marsupial genome that their value has been more widely recognised. We now have genome sequences for three distantly related marsupial species (the grey short-tailed opossum, the tammar wallaby, and Tasmanian devil), with the promise of many more genomes to be sequenced in the near future, making this a particularly exciting time in marsupial genomics. The emergence of a transmissible cancer, which is obliterating the Tasmanian devil population, has increased the importance of obtaining and analysing marsupial genome sequence for understanding such diseases as well as for conservation efforts. In addition, these genome sequences have facilitated studies aimed at answering questions regarding gene and genome evolution and provided insight into the evolution of epigenetic mechanisms. Here I highlight the major advances in our understanding of evolution and disease, facilitated by marsupial genome projects, and speculate on the future contributions to be made by such sequences.
20
Churcher, C. S. "Dental functional morphology in the marsupial sabre-tooth Thylacosmilus atrox (Thylacosmilidae) compared to that of the felid sabre-tooths." Australian Mammalogy 8, n. 4 (1 ottobre 1985): 201–20. http://dx.doi.org/10.1071/am85020.
Testo completoAbstract (sommario):
The South American Middle to Late Pliocene fauna of Argentina included the borhyaenid marsupials Thylacosmilus atrox and Notosmilus pattersoni, the latter known only from a single Late Pliocene occurrence. Thylacosmilus atrox has been interpreted as a marsupial with a carnivorous specialisation convergent on the fissipede and machairodont sabre-tooths of Eurasia, Africa and North America. Thylacosmilus atrox superficially resembles placental sabre-tooths in general conformation but also shows remarkable divergences, some of which are attributable to its marsupial ancestry.
21
Kasai, Fumio, Patricia C. M. O'Brien, Jorge C. Pereira e Malcolm A. Ferguson-Smith. "Marsupial chromosome DNA content and genome size assessed from flow karyotypes: invariable low autosomal GC content". Royal Society Open Science 5, n. 8 (agosto 2018): 171539. http://dx.doi.org/10.1098/rsos.171539.
Testo completoAbstract (sommario):
Extensive chromosome homologies revealed by cross-species chromosome painting between marsupials have suggested a high level of genome conservation during evolution. Surprisingly, it has been reported that marsupial genome sizes vary by more than 1.2 Gb between species. We have shown previously that individual chromosome sizes and GC content can be measured in flow karyotypes, and have applied this method to compare four marsupial species. Chromosome sizes and GC content were calculated for the grey short-tailed opossum (2 n = 18), tammar wallaby (2 n = 16), Tasmanian devil (2 n = 14) and fat-tailed dunnart (2 n = 14), resulting in genome sizes of 3.41, 3.31, 3.17 and 3.25 Gb, respectively. The findings under the same conditions allow a comparison between the four species, indicating that the genomes of these four species are 1–8% larger than human. We show that marsupial genomes are characterized by a low GC content invariable between autosomes and distinct from the higher GC content of the marsupial × chromosome.
22
Ralston, GB. "Proteins of Marsupial Erythrocyte Membranes". Australian Journal of Biological Sciences 38, n. 1 (1985): 121. http://dx.doi.org/10.1071/bi9850121.
Testo completoAbstract (sommario):
The proteins of erythrocyte membranes from the red kangaroo, western grey kangaroo, eastern grey wallaroo (euro), red-necked wallaby, Tammar wallaby, and brush-tail possum have been fractionated on acrylamide gels in the presence of sodium dodecyl sulfate. The pattern of proteins was remarkably similar between the different marsupial species. The pattern of Coomassie blue-staining proteins in the membranes of these species was also very similar to that of the human erythrocyte membrane. However, the glycoproteins in the marsupial erythrocyte membranes were markedly less conspicuous than those of the human erythrocyte membrane. Furthermore, the mobilities of the glycoproteins from the marsupials were different from those of the human erythrocyte membrane.
23
Koenigswald von, Wighart, e Francisco Goin. "Enamel differentiation in South American marsupials and a comparison of placental and marsupial enamel". Palaeontographica Abteilung A 255, n. 4-6 (31 gennaio 2000): 129–68. http://dx.doi.org/10.1127/pala/255/2000/129.
Testo completo
24
Stannard, Hayley J., Robert D. Miller e Julie M. Old. "Marsupial and monotreme milk—a review of its nutrient and immune properties". PeerJ 8 (23 giugno 2020): e9335. http://dx.doi.org/10.7717/peerj.9335.
Testo completoAbstract (sommario):
All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother’s milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes.
25
Dörner, Marion, Markus Altmann, Svante Pääbo e Mario Mörl. "Evidence for Import of a Lysyl-tRNA into Marsupial Mitochondria". Molecular Biology of the Cell 12, n. 9 (settembre 2001): 2688–98. http://dx.doi.org/10.1091/mbc.12.9.2688.
Testo completoAbstract (sommario):
The mitochondrial tRNA gene for lysine was analyzed in 11 different marsupial mammals. Whereas its location is conserved when compared with other vertebrate mitochondrial genomes, its primary sequence and inferred secondary structure are highly unusual and variable. For example, eight species lack the expected anticodon. Because the corresponding transcripts are not altered by any RNA-editing mechanism, the lysyl-tRNA gene seems to represent a mitochondrial pseudogene. Purification of marsupial mitochondria and in vitro aminoacylation of isolated tRNAs with lysine, followed by analysis of aminoacylated tRNAs, show that a nuclear-encoded tRNALys is associated with marsupial mitochondria. We conclude that a functional tRNALys encoded in the nuclear genome is imported into mitochondria in marsupials. Thus, tRNA import is not restricted to plant, yeast, and protozoan mitochondria but also occurs also in mammals.
26
Griffiths, M., e N. G. Simms. "Observations on the anatomy of mammary glands in two species of conilurine rodent (Muridae: Hydromyinae) and in an opossum (Marsupialia: Didelphidae)." Australian Mammalogy 16, n. 1 (1993): 9. http://dx.doi.org/10.1071/am93002.
Testo completoAbstract (sommario):
The pups of Pseudomys nanus and P. australis are attached to their mothers' teats for extended periods of time, analogous to the situation encountered in pouchless marsupials. The structures in the mammary glands involved in facilitating prolonged attachment are different in the two rodent species and both kinds are different from those in marsupial glands including those of Monodelphis domestica, the subject of the present study. In P. nanus, the teats are anchored to postero-ventrally directed, tubular diverticula of the body wall. In P. australis there are no diverticula. However, support for the mammary glands and teats is afforded by the body wall, in the form of two well-developed fan-shaped muscles dorsal to the mammary glands in conjunction with a broad lamina of connective tissue, smooth and striated muscle situated between the skin of the belly and the mammary glands. In M. domestica, the teats are anchored to swathes of striated voluntary muscle, derived from the ilio-marsupialis muscles which pass ventrally through the secretory parenchyma to be inserted onto the bases of the teats. Since this musculature has not been observed in the mammary glands of any eutherians so far studied, nor in those of Monotremata, it is put that it is a character unique to the Marsupialia.
27
Moore, HD. "Gamete biology of the new world marsupial, the grey short-tailed opossum, Monodelphis domestica". Reproduction, Fertility and Development 8, n. 4 (1996): 605. http://dx.doi.org/10.1071/rd9960605.
Testo completoAbstract (sommario):
Mammalian gametes undergo a series of functional and developmental changes that culminate in fertilization. In order to appreciate the necessity for such complex processes as sperm maturation, capacitation and the intimate sperm-egg interactions leading to gamete fusion, it is important to understand how gametes may have evolved. In this respect, marsupials are particularly relevant since they exhibit features reminiscent of both non-mammalian vertebrates and eutherian mammals. The grey short-tailed opossum, Monodelphis domestica, is a New World marsupial from Brazil. It breeds well under laboratory conditions and is an excellent animal model to investigate marsupial gamete biology. As in other American marsupials, the spermatozoa of the opossum form pairs in the epididymis. Here, a number of studies carried out in this laboratory, related to sperm maturation, capacitation and fertilization in M. domestica, are reviewed and the gamete biology in this species is compared with what is known in other marsupials and eutherian mammals.
28
Westerman, M. "Phylogenetic-Relationships of the Marsupial Mole, Notoryctes-Typhlops (Marsupialia, Notoryctidae)". Australian Journal of Zoology 39, n. 5 (1991): 529. http://dx.doi.org/10.1071/zo9910529.
Testo completoAbstract (sommario):
The phylogenetic position of the marsupial mole, Notorcytes typhlops, has been difficult to ascertain with morphological characters because of its highly specialised fossorial lifestyle. On the basis of serological data, Kirsch (1977b) suggested that this species was sufficiently different from other marsupials to warrant placing it in its own suborder. Using the DNA-DNA hybridisation technique on single-copy DNA to assess sequence differences over the entire genome, I confirm that N. typhlops is not closely related to any other marsupial family, and warrants placement in its own order.
29
Renfree, Marilyn B. "Society for Reproductive Biology Founders' Lecture 2006 Life in the pouch: womb with a view". Reproduction, Fertility and Development 18, n. 7 (2006): 721. http://dx.doi.org/10.1071/rd06072.
Testo completoAbstract (sommario):
Marsupials give birth to an undeveloped altricial young after a relatively short gestation period, but have a long and sophisticated lactation with the young usually developing in a pouch. Their viviparous mode of reproduction trades placentation for lactation, exchanging the umbilical cord for the teat. The special adaptations that marsupials have developed provide us with unique insights into the evolution of all mammalian reproduction. Marsupials hold many mammalian reproductive ‘records’, for example they have the shortest known gestation but the longest embryonic diapause, the smallest neonate but the longest sperm. They have contributed to our knowledge of many mammalian reproductive events including embryonic diapause and development, birth behaviour, sex determination, sexual differentiation, lactation and seasonal breeding. Because marsupials have been genetically isolated from eutherian mammals for over 125 million years, sequencing of the genome of two marsupial species has made comparative genomic biology an exciting and important new area of investigation. This review will show how the study of marsupials has widened our understanding of mammalian reproduction and development, highlighting some mechanisms that are so fundamental that they are shared by all today’s marsupial and eutherian mammals.
30
Withers, P. C., G. G. Thompson e R. S. Seymour. "Metabolic physiology of the north-western marsupial mole, Notoryctes caurinus (Marsupialia : Notoryctidae)". Australian Journal of Zoology 48, n. 3 (2000): 241. http://dx.doi.org/10.1071/zo99073.
Testo completoAbstract (sommario):
We studied the thermal and metabolic physiology of a single specimen of the north-western marsupial mole, Notoryctes caurinus, an almost completely fossorial Australian marsupial, and compared it with the morphologically convergent Namib desert golden mole, Eremitalpa granti namibensis. This was the first study of any aspect of the physiology of this rare marsupial. Mean body mass of the marsupial mole was 34 g. Body temperature (Tb) was low and labile, ranging from 22.7 to 30.8˚C over a range of ambient temperature (Ta) from 15 to 30˚C. The highest Tb of 30.8˚C was significantly lower than expected for a marsupial of this body mass. Metabolic rate varied with Ta in an attenuated fashion for an endotherm, because of the labile Tb. Basal metabolic rate (BMR) was 0.63 mL O2 g–1 h–1, at a Ta of 30˚C. This was lower than expected for a 34-g marsupial, but was not different from expected for a marsupial when corrected to a Tb of 35˚C (0.94 mL O2 g–1 h–1). Evaporative water loss increased from 0.8 mg g–1 h–1 at 15˚C to 3.7 at 30˚C. Wet thermal conductance was 0.2 mL O2 g–1 h–1 ˚C–1 at 15˚C and 0.6 at 25˚C; these values were higher than expected for a marsupial. The net metabolic cost of transport (NCOT) for running (0.0022 mL O2 g–1 m–1 at a mean velocity of 484 m h–1) was similar to expected values for walking and running mammals. The NCOT for sand-swimming (0.124 mL O2 g–1 m–1 at a mean velocity of 7.6 m h–1) was substantially higher, and at a much lower velocity than for running, but was similar to NCOT for sand-swimming by the Namib golden mole. We conclude that the marsupial mole differs in some aspects of thermal and metabolic physiology from other marsupials, most likely reflecting its almost completely fossorial existence.
31
Renfree, MB. "Monotreme and marsupial reproduction". Reproduction, Fertility and Development 7, n. 5 (1995): 1003. http://dx.doi.org/10.1071/rd9951003.
Testo completoAbstract (sommario):
Marsupials were regarded as curiosities by their early European discoverers, animals to be wondered at. Monotremes were even more surprising; the platypus was such an amalgam of characters that it was thought to be a hoax. They were recognized very early as mammals that could make a major contribution to our understanding of reproductive processes, and work on marsupials at the turn of the century was much in evidence. It is, however, only in the past two decades, and especially in the past few years that marsupial research has regained this position. There is no doubt that future research will strengthen this contribution, but we are faced with serious conservation questions that must be solved if we are to maintain these wonderful animals as a resource for future generations.
32
Green, Brian, Jim Merchant e Keith Newgrain. "Milk Composition in the Eastern Quoll, Dasyurus viverrinus (Marsupialia : Dasyuridae)". Australian Journal of Biological Sciences 40, n. 4 (1987): 379. http://dx.doi.org/10.1071/bi9870379.
Testo completoAbstract (sommario):
The milk constituents of Dasyurus viverrinus, a carnivorous marsupial, exhibited major quantitative and qualitative changes during the course of lactation. The milk produced in the early stages of lactation was dilute, about 13-16070 (w/w) solids before 3 weeks with carbohydrate representing the major fraction. In the latter stages of lactation the milk was concentrated, around 30% solids, and lipid was the predominant fraction. Palmitic acid was the major fatty acid present in early-stage milk but oleic acid became predominant in milk after 10 weeks post-partum. The changes in milk composition in D. viverrinus were similar to those described for the milks of herbivorous marsupials which therefore suggests that this pattern may be uniform throughout the Marsupialia.
33
Lapointe, FJ, e JAW Kirsch. "Construction And Verification Of A Large Phylogeny Of Marsupials". Australian Mammalogy 23, n. 1 (2001): 9. http://dx.doi.org/10.1071/am01009.
Testo completoAbstract (sommario):
Much of the controversy over marsupial phylogeny at higher-categorical levels stems from the piecemeal nature of the contributing studies or the paucity of taxonomic representation in many of them. Yet the problems of constructing large phylogenies are manyfold, involving the initial generation of the data as well as their efficient analysis. Often unaddressed, also, is the need to validate extremely large data sets and trees. Many of these problems can be ameliorated by treating the data as distances (or generating distances directly). We show that, contrary to the assertions of many protagonists in the total-evidence versus consensus debate, the validated data and pathlength (tree) matrices usually give very similar results, although a few additional unstable nodes may be found when the results of internal and external validations are themselves combined in a global-congruence test. Here we illustrate our protocols with a 109-taxon data set, representing combination of marsupial DNA-hybridisation data with similar information on a series of outgroups. Phylogenetically, the results affirm the marsupial groupings we have previously found, and suggest but do not unambiguously support a nearer relationship of monotremes than placentals to marsupials. This paper represents the first attempt to validate the tree of 101 marsupials presented earlier.
34
Rodger, JC. "Prefertilization gamete maturation events in marsupials". Reproduction, Fertility and Development 6, n. 4 (1994): 473. http://dx.doi.org/10.1071/rd9940473.
Testo completoAbstract (sommario):
Despite many fundamental similarities between the gametes of marsupials and placental mammals, the regulation and timing of prefertilization gamete maturation are quite different. The marsupial acrosome is remarkably stable and an acrosome reaction (AR) is not induced by reagent effective for the sperm of placental mammals. The ultrastructure of the marsupial sperm AR is essentially similar to that of placental mammals, however, whether an equatorial segment (ES) persists to serve as the site of sperm-egg membrane fusion is unclear. Diacylglycerol induction of the AR suggests that the sperm of Australian species lack an ES, yet an ES-like region appears to be involved in fertilization in the opossum Monodelphis. The marsupial oocyte, unlike those of placentals, continues to grow throughout follicular life and major cytoplasmic maturation events occur late in oocyte development. Cortical granules only become evident shortly before ovulation and mature dark granules may only appear after ovulation. Further, the zona pellucida (ZP) changes in character and function during the peri-ovulatory period. In vitro fertilization has been achieved for an opossum but not for any Australian marsupial, owing to failure of sperm-ZP binding. Requirement for a sperm maturation process is likely, but capacitation treatments used for placental sperm in vitro have been ineffective. Since it is now feasible to experimentally manipulate marsupial gametes in vitro major advances in our understanding of their function can be expected.
35
Graves, Jennifer A. Marshall. "Marsupial genomics meet marsupial reproduction". Reproduction, Fertility and Development 31, n. 7 (2019): 1181. http://dx.doi.org/10.1071/rd18234.
Testo completoAbstract (sommario):
We came from very different backgrounds, with different skills and interests. Marilyn Renfree was recognised as ‘a giant of marsupial embryology’; I had spent my working life studying genes and chromosomes. We teamed up out of mutual respect (awe on my side) to form, with Des Cooper, the ARC Centre of Excellence in Kangaroo Genomics. This is the story of how our collaboration came to be, and what it has produced for our knowledge of some of the world’s most remarkable animals.
36
Fidler, Andrew E., Andrea H. Western, Nicole Griffith, Lynne Selwood, Vicki Stent e Kenneth P. McNatty. "Production of a biologically active recombinant marsupial growth factor using the methylotrophic yeast Pichia pastoris". Reproduction, Fertility and Development 14, n. 6 (2002): 327. http://dx.doi.org/10.1071/rd02040.
Testo completoAbstract (sommario):
The cytokine stem cell factor (SCF) and its interaction with its receptor c-kit plays an important role in the development of germ cells in eutherians. To investigate the putative roles of the SCF/c-kit system in marsupials, recombinant Australian brushtail possum (Trichosurus vulpecula) SCF was purified after secretion by the methylotrophic yeast Pichia pastoris. The purification procedure utilized Ni2+ affinity chromatography with a poly-histidine tag engineered onto the C-terminus of the recombinant SCF. The recombinant possum SCF had a molecular weight of 48 kDa, as determined by sodium dodecyl sulphate–polyacrylamide gel electrophoresis, and was biologically active with respect to its ability to maintain and induce proliferation of marsupial primordial germ cells in vitro. Furthermore, the recombinant possum SCF stimulated proliferation of the cell line TF1 and this bioactivity could be inhibited using an antibody directed against recombinant mouse SCF. This source of biologically active marsupial SCF may prove useful in future studies of marsupial development.
37
Taggart, D. A., D. Schultz e P. D. Temple-Smith. "Development and Application of Assisted Reproductive Technologies in Marsupials: Their Value for Conservation of Rock-wallabies." Australian Mammalogy 19, n. 2 (1996): 183. http://dx.doi.org/10.1071/am97183.
Testo completoAbstract (sommario):
Assisted reproductive technology is used routinely in management to treat infertility and in domestic species in basic husbandry. In eutherian mammals application of this technology is also well established in wildlife conservation programs. The development and application of this technology in marsupials, however, is a relatively new field. The reproductive techniques currently available for marsupial studies, their benefits and implications for conservation are discussed in order to remove any previous misconceptions and provide an insight into how these techniques might be applied. The potential of this technology for maintaining genetic variability and enhancing reproductive output of threatened marsupial species is highlighted, with particular reference to the conservation of rock wallabies.
38
Mate, KE. "Cytoplasmic maturation of the marsupial oocyte during the periovulatory period". Reproduction, Fertility and Development 8, n. 4 (1996): 509. http://dx.doi.org/10.1071/rd9960509.
Testo completoAbstract (sommario):
During the period immediately before ovulation, the oocytes of most eutherian and marsupial mammals complete the first meiotic maturation division and extrude the first polar body. In marsupials, this phase of nuclear maturation is accompanied by an increase in size of the egg and maturation of cytoplasmic components. Oocytes from at least four marsupial species, Trichosurus vulpecula, Macropus eugenii, Bettongia penicillata and Monodelphis domestica, continue to grow after formation of the follicular antrum and, although the rate of growth slows in larger follicles, it continues into the period immediately before ovulation. The basis of this growth is unknown but may include accumulation of fluid and/or yolk-like material. Maturational changes within the cytoplasm of the oocyte also occur during the periovulatory period, including the accumulation of cortical granules. Differences in the structure of the zona pellucida are also evident between follicular and ovulated eggs; these differences are suggestive of compression of the zona pellucida, but may involve the addition of extra material. These findings suggest that the marsupial oocyte may not achieve complete cytoplasmic maturity until after ovulation; however, their relevance to fertilization and embryonic development require further investigation. Like those of eutherian mammals, marsupial oocytes undergo spontaneous nuclear maturation once removed from the follicular environment, suggesting a basically similar control system. It is not known whether the preovulatory cytoplasmic changes seen in marsupial oocytes matured in vivo also occur during maturation in vitro.
39
Marcondes, Carlos Brisola, João Carlos Pinto Dias, Leonardo A. Guedes, Antenor N. Ferraz Filho, Vera L. C. C. Rodrigues e Delosmar D. Mendonça. "Estudo epidemiológico de fontes de alimentação sangüínea dos triatomíneos da fazenda aroeira (Catolé do Rocha, Paraíba) e circunvizinhanças". Revista da Sociedade Brasileira de Medicina Tropical 24, n. 3 (settembre 1991): 137–40. http://dx.doi.org/10.1590/s0037-86821991000300002.
Testo completoAbstract (sommario):
Analisamos a fonte de alimentação sangüínea de 94 triatomíneos (51 Triatoma brasiliensis, 42 T. pseudomaculata e um Rhodnius neglectus) da Fazenda Aroeira, no Município de Catolé do Rocha, no Estado da Paraíba, e de quatro localidades próximas. Observamos positividade para marsupial, homem e ave, respectivamente, de 39,7 , 6,2 e 23,0%. Três insetos da Fazenda Aroeira, positivos para Trypanosoma cruzi, foram positivos para marsupial, só um deles também para outro mamífero. Os marsupiais são a mais importante fonte de T. cruzi para os insetos da área e estes têm pouco contato com o homem.
40
Soderquist, TR, e CR Dickman. "A Technique for Marking Marsupial Pouch Young With Fluorescent Pigment Tattoos". Wildlife Research 15, n. 5 (1988): 561. http://dx.doi.org/10.1071/wr9880561.
Testo completoAbstract (sommario):
Small quantities of fluorescent pigments were tattooed into the pinnae of pouch young Dasyurus geoffroii and Isoodon obesulus (Marsupialia), and into the pinnae of 5-day-old Mus rnusculus (Rodentia). The tattoos contrasted sharply with natural skin pigmentation when scanned with a UV light. Of 11 pigments tested, Flare 610 pigments were the most persistent, remaining visible for a minimum of 6 months. The technique facilitates rapid, cheap and reliable marking of marsupial pouch young, and should be generally applicable for determining filial relationships in a wide range of marsupial species.
41
Jolly, SE, GA Morriss, S. Scobie e PE Cowan. "Composition of Milk of the Common Brushtail Possum, Trichosurus Vulpecula (Marsupialia: Phalangeridae): Concentrations of Elements". Australian Journal of Zoology 44, n. 5 (1996): 479. http://dx.doi.org/10.1071/zo9960479.
Testo completoAbstract (sommario):
The concentrations of 11 elements (calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sodium, strontium, sulphur and zinc) were measured in milk samples collected from 193 lactating brushtail possums, Trichosurus vulpecula, at all stages of lactation. Most elements showed patterns of change during lactation similar to those of other marsupials. The most marked changes occurred at about 80-120 days, when the growth rate of the pouch young increased and developmental changes took place, such as eye opening and fur growth. Compared with eutherians, copper and iron concentrations were high in possum milk, as in other marsupials, but zinc levels were exceptionally high. Strontium and manganese levels, not measured before in marsupial milk, were considerably higher than levels reported in eutherian milk. In contrast to eutherian mammals, marsupial young must be supplied with large quantities of minerals in the milk as almost all growth and development occurs after birth, and possum young are entirely dependent on milk supplied by the mother for about the first 100 days.
42
Cowan, PE. "Changes in milk composition during lactation in the common brushtail possum, Trichosurus vulpecula (Marsupialia: Phalangeridae)". Reproduction, Fertility and Development 1, n. 4 (1989): 325. http://dx.doi.org/10.1071/rd9890325.
Testo completoAbstract (sommario):
The milk constituents of Trichosurus vulpecula, a folivorous marsupial, showed marked quantitative and qualitative changes during the course of lactation. The milk produced in the early stages of lactation was dilute, with about 9-13% (w/w) solids during the first 3 weeks, comprising mostly carbohydrate and protein (35-40%). At 20 weeks, about three-quarters of the way through lactation, the milk was much more concentrated, about 28% solids, with lipid the predominant fraction (30-35%), after a marked decline in carbohydrate content (20-25%). Concentrations of the electrolytes sodium and potassium also underwent marked changes. The changes in milk composition of T. vulpecula during the first three-quarters of lactation were similar to those described for a range of herbivorous, insectivorous and carnivorous marsupials. In the last quarter of lactation, however, brushtail possum milk maintained a relatively stable composition, with higher levels of carbohydrate and lower levels of lipid than for other marsupials. There appears to be a uniform pattern of changes in milk composition throughout the Marsupialia over most of lactation, with family differences evident only in the latter stages.
43
Renfree, Marilyn B., Eleanor I. Ager, Geoff Shaw e Andrew J. Pask. "Genomic imprinting in marsupial placentation". REPRODUCTION 136, n. 5 (novembre 2008): 523–31. http://dx.doi.org/10.1530/rep-08-0264.
Testo completoAbstract (sommario):
Genomic imprinting is a widespread epigenetic phenomenon in eutherian mammals, which regulates many aspects of growth and development. Parental conflict over the degree of maternal nutrient transfer is the favoured hypothesis for the evolution of imprinting. Marsupials, like eutherian mammals, are viviparous but deliver an altricial young after a short gestation supported by a fully functional placenta, so can shed light on the evolution and time of acquisition of genomic imprinting. All orthologues of eutherian imprinted genes examined have a conserved expression in the marsupial placenta regardless of their imprint status. Differentially methylated regions (DMRs) are the most common mechanism controlling genomic imprinting in eutherian mammals, but none were found in the marsupial imprinted orthologues of IGF2 receptor (IGF2R), INS or mesoderm-specific transcript (MEST). Instead, histone modification appears to be the mechanism used to silence these genes. At least three genes in marsupials have DMRs: H19, IGF2 and PEG10. PEG10 is particularly interesting as it is derived from a retrotransposon, providing the first direct evidence that retrotransposon insertion can drive the evolution of an imprinted region and of a DMR in mammals. The insertion occurred after the prototherian–therian mammal divergence, suggesting that there may have been strong selection for the retention of imprinted regions that arose during the evolution of placentation. There is currently no evidence for genomic imprinting in the egg-laying monotreme mammals. However, since these mammals do have a short-lived placenta, imprinting appears to be correlated with viviparity but not placentation.
44
Hughes, R. Leon. "Structure of the female reproductive tract of an adult parous Tasmanian tiger, Thylacinus cynocephalus". Australian Journal of Zoology 48, n. 5 (2000): 487. http://dx.doi.org/10.1071/zo00022.
Testo completoAbstract (sommario):
The present observations on the now-extinct Thylacinus are based on the reproductive system of an adult thylacine discovered among the specimens of the Hill collection at the Hubrecht Laboratory in the Netherlands. As in other marsupials, the reproductive tract was characterised by the presence of a uterus duplex and a vaginal complex where the ureters passed dorsally over each lateral vaginal canal to enter the bladder. The lateral vaginal canals each entered a urogenital sinus that terminated in a shallow cloaca. The gross dimensions of the reproductive tract of the thylacine were greater than those of any extant dasyurid marsupial. The distance from the rostral pole of the ovaries to the most caudal extremity of the urogenital sinus measured 25 cm. The distinctive aspects of the reproductive tract included a disproportionate enlargement of the corpus uteri that is without parallel in any other marsupial species. The bodies of the right and left uteri measured 10.4 cm 1.2 cm 0.9 cm and 9.1 cm 0.8 cm 0.7 cm respectively. The rostro-caudal length of the right and left cervices measured 2.7 cm and 1.7 cm respectively. The cervical canals entered the vaginal complex by way of a thick median vaginal septum. The elongated caudal component of the vaginal culs-de-sac lacked a median vaginal septum. As in other dasyurid marsupials, the lateral vaginae and associated vaginal complex were of diminutive proportions in relation to the typical marsupial pattern. The histology of the tract was remarkably good for tissue preserved since 1902 and indicated that the tissues were free of pathological changes. A characteristic marsupial pattern of ovarian folliculogenesis was evident where all but a thin peripheral zone of the cytoplasm of the primary oocyte became vacuolated during the pre-antral stage of ovarian follicle development.
45
Cooper, W. James, e Scott J. Steppan. "Developmental constraint on the evolution of marsupial forelimb morphology". Australian Journal of Zoology 58, n. 1 (2010): 1. http://dx.doi.org/10.1071/zo09102.
Testo completoAbstract (sommario):
Compared with the placental mammals, marsupials are born at an almost embryonic stage, but nearly all of these neonates immediately climb or crawl to one of their mother’s teats using precociously developed forelimbs. Marsupial adults also exhibit limited forelimb shape diversity relative to the members of their sister group. That the functional requirements of this natal climb have imposed a developmental constraint on marsupial forelimb evolution represents a compelling and widely accepted hypothesis, yet its resulting predictions for the comparative patterns of mammal limb shape diversity have never been tested. In order to perform such tests we conducted extensive taxonomic sampling of mammal limb morphology (including fossil specimens), and then examined these data using morphometric methods, non-parametric analyses of anatomical disparity, and phylogenetic comparative analyses of evolutionary rates. Our results strongly support the constraint hypothesis, and indicate that the highly significant differences between marsupial and placental forelimb shape diversity has been strongly influenced by different rates of morphological evolution among the distal forelimb elements in these two important mammal lineages.
46
Renfree, M. B., S. R. Frankenberg e C. Freyer. "054. TROPHOBLAST, PLACENTA AND EARLY EMBRYO: HOW THE MARSUPIAL DEVELOPS". Reproduction, Fertility and Development 22, n. 9 (2010): 15. http://dx.doi.org/10.1071/srb10abs054.
Testo completoAbstract (sommario):
In marsupials, the blastocyst forms as a single cell layer of cells. The marsupial blastocyst has no inner cell mass, so the 80–100 cell tammar embryo remains in diapause as a unilaminar blastocyst. All marsupials have a unilaminar stage, but what is unusual is that in the tammar the total cessation of cell division and cell metabolism lasts for 11 months each year. Marsupials are placental mammals. The yolk sac forms the definitive placenta up to birth. Only very few marsupials, such as the bandicoot, have a chorio-allantoic placenta, which supplements the placental functions of the yolk sac. However, the understanding how the unilaminar layer of trophoblast cells of the diapausing blastocyst become specified into placental and embryonic tissues has been an ongoing puzzle. To identify genes that do become differentially expressed in tammar development, we targeted the stage of the earliest appearance of the embryonic disc, at which the remainder of the blastocyst is then defined as trophoblast, as well as early cleavage stages. Intriguingly, we found no evidence for early differential expression of the canonical pluripotency genes POU5F1, SOX2 and NANOG, or of CDX2. By contrast, we found overt differential expression of GATA3, the closely related gene GATA2, and FGF4. This expression profile suggests that in the tammar, mechanisms regulating trophoblast- and pluriblast-specific expression of POU5F1, SOX2, NANOG and CDX2 are temporally secondary to those regulating GATA2 & -3 and FGF4 expression. Together, our results may signify the evolution of alternative mechanisms of early lineage specification in marsupials, or alternatively reveal a general hierarchy of signalling mechanisms that are masked in the relatively rapid and ‘compressed’ development of mice. The results of our ongoing study have important implications for understanding not only marsupial stem cells but the early development of all therian mammals.
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Bernard, S. L., D. L. Luchtel, R. W. Glenny e S. Lakshminarayan. "Bronchial circulation in the marsupial opossum, Didelphis marsupialis". Respiration Physiology 105, n. 1-2 (agosto 1996): 77–83. http://dx.doi.org/10.1016/0034-5687(96)00027-8.
Testo completo
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Singh, Devika, Dan Sun, Andrew G. King, David E. Alquezar-Planas, Rebecca N. Johnson, David Alvarez-Ponce e Soojin V. Yi. "Koala methylomes reveal divergent and conserved DNA methylation signatures of X chromosome regulation". Proceedings of the Royal Society B: Biological Sciences 288, n. 1945 (24 febbraio 2021): 20202244. http://dx.doi.org/10.1098/rspb.2020.2244.
Testo completoAbstract (sommario):
X chromosome inactivation (XCI) mediated by differential DNA methylation between sexes is an iconic example of epigenetic regulation. Although XCI is shared between eutherians and marsupials, the role of DNA methylation in marsupial XCI remains contested. Here, we examine genome-wide signatures of DNA methylation across fives tissues from a male and female koala ( Phascolarctos cinereus ), and present the first whole-genome, multi-tissue marsupial ‘methylome atlas’. Using these novel data, we elucidate divergent versus common features of representative marsupial and eutherian DNA methylation. First, tissue-specific differential DNA methylation in koalas primarily occurs in gene bodies. Second, females show significant global reduction (hypomethylation) of X chromosome DNA methylation compared to males. We show that this pattern is also observed in eutherians. Third, on average, promoter DNA methylation shows little difference between male and female koala X chromosomes, a pattern distinct from that of eutherians. Fourth, the sex-specific DNA methylation landscape upstream of Rsx , the primary lnc RNA associated with marsupial XCI, is consistent with the epigenetic regulation of female-specific (and presumably inactive X chromosome-specific) expression. Finally, we use the prominent female X chromosome hypomethylation and classify 98 previously unplaced scaffolds as X-linked, contributing an additional 14.6 Mb (21.5%) to genomic data annotated as the koala X chromosome. Our work demonstrates evolutionarily divergent pathways leading to functionally conserved patterns of XCI in two deep branches of mammals.
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Miller, Robert D., Hilary Grabe e George H. Rosenberg. "VH Repertoire of a Marsupial (Monodelphis domestica)". Journal of Immunology 160, n. 1 (1 gennaio 1998): 259–65. http://dx.doi.org/10.4049/jimmunol.160.1.259.
Testo completoAbstract (sommario):
Abstract When contrasted with information available for placental mammals, very little is known about the development of immunocompetence in marsupials. Marsupials, however, provide interesting immunology problems, since most appear to be born at a stage of development much less mature than that of placental mammals. To further understand the marsupial immune system, the Ig repertoire of the short-tailed opossum, Monodelphis domestica, was characterized. The majority of the VH clones were isolated in an unbiased manner by screening a spleen cDNA phage library, using C region probes, or anchored PCR, using C region-specific primers paired with vector specific primers. Analysis of 54 unique VH sequences from this marsupial revealed the presence of two VH families in the expressed Ig repertoire. The larger family, which contributed the majority of the clones identified, appears to be derived from 10 to 12 germline VH segments. The second family of clones is derived from a single germline VH. Both VH families are related to the group III sequences described in other vertebrates. Unusual codon bias differences between the two families may result in very different patterns of somatic mutation within the opossum Ig repertoire.
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Renfree, M. B., E. S. Robinson, R. V. Short e J. L. Vandeberg. "Mammary glands in male marsupials: I. Primordia in neonatal opossums Didelphis virginiana and Monodelphis domestica". Development 110, n. 2 (1 ottobre 1990): 385–90. http://dx.doi.org/10.1242/dev.110.2.385.
Testo completoAbstract (sommario):
Neonates of the American didelphid marsupials Didelphis virginiana and Monodelphis domestica were sexed by karyotype and histologically examined on the day of birth. Mammary anlagen were found in both sexes of both species, but the neonatal males had less than one-third of the full female complement of mammary glands. Male neonates of both species also had paired scrotal bulges anterior to the genital tubercle but these were never present in females, once again raising the question of whether the pouch and scrotum are homologous structures. Mammary anlagen are not found in male neonates of the Australian marsupial species so far studied, which suggests a dichotomy in the control of some aspects of sexual differentiation in the two marsupial lineages.