Letteratura scientifica selezionata sul tema "Dasyurus viverrinus"

There has been disagreement for more than 100 years concerning the presence or absence of deciduous and successional third premolars in the dentition of the Australian dasyurid marsupial Dasyurus viverrinus as well as in other species of the genus Dasyurus. Most authors during the 19th and 20th centuries have considered the missing premolar in Dasyurus to be the third premolar family in both jaws, in part because of the reduction in size of the third deciduous premolar in many other genera of dasyurids. While other authors, found “the deciduous premolar to be constantly present in the young mammary foetus as a small and precociously calcified vestigial tooth”. However, the fate of this deciduous tooth, and its possible successor in later developmental stages, was never described; and the vestigial dp3 and its possible successor were assumed to undergo absorption during foetal life. With access to later developmental stages of Dasyurus viverrinus, via the extensive collections of Professor J.P. Hill, we present new evidence for the later development of dP3 and P3 in both jaws, the probable eruption of the successional P3 in both jaws and evidence that dP2 is the missing tooth in both jaws of this dasyurid species.

The spermatozoa of most marsupials lack nuclear stabilising disulfide-bonded protamines found in eutherian mammals. However, disulfide stabilisation has been observed in the acrosome of macropodid (Macropus eugenii) and phalangerid (Trichosurus vulpecula) marsupials. As a result this organelle, which is normally fragile in eutherian mammals, is robust and able to withstand physical and chemical challenge in these marsupials. The present study examined acrosomal characteristics of the spermatozoa of three dasyurid marsupials; the fat-tailed dunnart (Sminthopsis crassicaudata), eastern quoll (Dasyurus viverrinus) and northern quoll (Dasyurus hallucatus). In all species examined Bryan’s staining demonstrated that significant acrosomal loss occurred following physical challenge with osmotic stress, cryopreservation without cryoprotectant and exposure to detergent (Triton-X). Bromobimane staining indicated that the acrosomes of dasyurids lacked stabilising disulfide bonds. As reported for the wallaby and possum, calcium ionophore (A23187) did not induce the acrosome reaction-like exocytosis in dasyurid spermatozoa but treatment with diacylglycerol (DiC8) caused significant acrosome loss at concentrations similar to those effective for other marsupials. The present study found that the spermatozoa of dasyurids are more sensitive to physical challenge than the previously-studied marsupials and we suggest that this is due to the absence of acrosomal stabilising disulfide bonds.

Metaphase chromosomes (2n = 14) from D. viverrinus were analysed by flow cytometry and flow sorted into six homogeneous groups. Relative chromosomal DNA contents and distribution frequencies of the groups corresponded closely with values for the karyotype obtained by conventional methods.

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.

The tolerances to sodium fluoroacetate (1080) were estimated for Dasyurus geoffroii (LD*50, ca. 7.5 mg 1080 kg-1), D. hallucatus (ca. 7.5 mg kg-1), Antechinus flavipes (ca. 11.0 mg kg-1) and Phascogale calura (ca. 17.5 mg kg-1) from Western Australia and comparisons were made with D. viverrinus (ca. 1.5 mg kg-1) and A. flavipes (ca. 3.5 mg kg-1) from south-eastern Australia. The species from Western Australia have had evolutionary exposure to naturally occurring fluoroacetate and were more tolerant to the toxin than dasyurids from south-eastern Australia, Presumably, they have acquired this tolerance through feeding on prey which had fed on plants containing fluoroacetate.

The quolls are among the largest of the remaining carnivorous marsupials in the Australasian region, and thus occupy an important ecological niche as top predators and scavengers. All quolls are currently in decline and threatened to some degree yet the application of molecular information to the conservation and management of quolls has been unexplored until now. In this thesis I use two independent and highly variable genetic marker systems, the mitochondrial DNA (mtDNA) control region and nuclear microsatellites, to explore various aspects of conservation genetics relevant to the management of quolls. These aspects include an examination of the phylogenetic or evolutionary relationships among all six species of quolls, an examination of the genetic diversity within populations and the degree of differentiation between populations of the four Australian species of quolls, and the definition of units for conservation within these species. The development of suitable nuclear markers was a vital first step in defining levels of genetic variability and differentiation within and between the different populations and species. These markers proved to be highly variable and provided a wealth of information of relevance to the conservation of these species, and will be extremely useful in further studies. The use of the mtDNA control region for phylogenetic analyses was a novel approach to examining this question in quolls and also proved to be highly informative. Results from these phylogenetic analyses highlight the necessity of 1) examining more than one exemplar of each species, as well as 2) finally bringing some consensus to the question of the evolutionary relationships among quolls. Results show that northern quolls form the earliest split from all other quolls and that western quolls are closely related to the two New Guinean species. Furthermore, there is evidence for distinct lineages within species, corresponding to geographically separate or isolated populations. Levels of genetic variability within populations were examined using the microsatellites developed previously. Genetic variation was significantly higher in western quolls than in any other species. This was surprising given the long term and widespread decline of this species. There were also significant differences between populations within species in the level of genetic variability. Low levels of variability were usually found in small or captive bred populations or populations in severe decline. Genetic differentiation between populations was also explored using microsatellites. Significant differentiation in allele frequency distributions was found between most pairwise population comparisons, indicating that each of these populations forms a separate management unit (MU) for conservation purposes. One notable exception was found among populations of tiger quolls from a highly localized area in the Barrington Tops region of New South Wales. Using microsatellites, these populations were not significantly subdivided and thus appeared to be one MU. Using mtDNA, however, these populations were significantly subdivided and thus should be considered separate MUs. Differences in the way these two genetic markers are inherited (mtDNA is maternally inherited, microsatellites are biparentally inherited) provides a clue as to the social structure and organization of these cryptic nocturnal species. Consequently, the use of different genetic marker systems shows that there is sex-biased migration within this species. Finally, the degree of genetic differentiation observed within tiger quolls does not conform to the currently recognized subspecific categories within this species. The major genetic split occurs between the Tasmanian and mainland populations of tiger quolls, not between Dasyurus maculatus maculatus and D. m. gracilis. Thus, the Tasmanian and mainland populations form two distinct evolutionarily significant units (ESUs) for conservation purposes, and I propose that the Tasmanian populations should be elevated to the subspecific status to account for this.

The Eastern quoll, Dasyurus viverrinus, is one of the larger members of the family Dasyuridae and is found only in Tasmania. The quoll has a short breeding period with mating occupying two to three weeks of every year. Males display seasonal cycles of body weight and testes size. Both parameters are maximal prior to breeding then decline during and after mating. LH and testosterone concentrations fluctuate at basal levels for much of the year. A gradual rise in LH and testosterone occurs in April, two to three months before breeding. This probably functions to initiate spermatogenesis and to prepare the gonads and accessory glands for reproduction. Male quoll produce a peak in LH (mean 13.9 ng per ml) and testosterone (mean 5.0 ng per ml) during the mating period. This peak coincides with maximimi number of animals in the area and is associated with an increase in activity and mobility of males at this time. The highest testosterone level occurs just prior to mating and declines during copulation. By the time the young are born, approximately 19 days after copulation, most males have basal levels of hormones. Juvenile quoll increase in weight with age and have comparatively high levels of LH and testosterone when entering the population after weaning. These levels may be associated with the processes of maturation and also with agonistic behaviour encountered during dispersal. LH, progesterone and prolactin secretion in the female quoll conform to the patterns shown by other marsupials. LH and progesterone levels are highest near the time of oestrus and ovulation while prolactin concentration increases throughout the lactation period. The endocrine cycles and pouch development of pregnant and non-pregnant females appear to be similar. Experimental evidence suggests that photoperiod is the likely proximate cue regulating the breeding cycle of the male quoll. Males exposed to a long daylength increase in weight and have lower LH concentrations compared to control animals. Testosterone secretion and testes size appear unaffected by a change in photoperiod and may require either a longer exposure time or additional factors to influence these cycles. Males in captivity generally have lower LH and testosterone levels compared to males in the wild. The hormonal profiles of captive male quoll are related to the degree of physical contact with the female. When males are housed with females, LH and testosterone levels are significantly higher than when males are housed near, or isolated from females. A cue fi-om the female may be the stimulus initiating a peak in androgens in the male and therefore females may be responsible for the S5mchrony of the breeding cycle. Cortisol levels are significantly lower in captive animals when physical contact is prevented. There is no evidence of an androgen dependent decrease in plasma CBG during breeding nor is there any increase in free Cortisol associated with a decrease in MCBC. The breeding season did not appear to be a period of high stress nor was it characterised by major changes in plasma protein, albumin or triglyceride levels. This is consistent with the Eastern quoll being one of the long lived members of the Dasyuridae. This project proposes that the seasonal breeding activity in the male quoll is broadly regulated by photoperiod. However, the androgen rise prior to mating is triggered by additional cues, mainly from the female. The synchrony of this rise is directly related to interspecific male aggression probably involving physical interaction. High androgen levels occur just before mating, enabling males to establish their dominance and position in the social hierarchy before pairing with females. This reproductive pattern enables the Eastern quoll to intensify its reproductive effort and the relatively short, sharp rise in androgens and free cortisol does not impose immediate constraints on the life expectancy of the animal. The role of the male throughout the breeding cycle therefore contributes much to the life history classification of this species.

Tüpfelbeutelmarder gehören zu den Beuteltieren Australiens und Tasmaniens. Die Populationen in der Wildbahn sind rückläufig und werden in der International Union for Conservation of Nature (IUCN) Red List of Threatened Species™ seit dem Jahr 2016 als „endangered“ gelistet. In Zoos sind die bedrohten, nachtaktiven Tiere auch aufgrund ihrer anspruchsvollen Haltungs- und Zuchtbedingungen bisher selten zu sehen. Ziel dieser Arbeit war es relevante veterinärmedizinische Aspekte für die Haltung von Tüpfelbeutelmardern in menschlicher Obhut zusammenzutragen. Damit sollte ein besseres Verständnis zu den Haltungsansprüchen und dem medizinischen Umgang geschaffen werden, das zum Schutz dieser bedrohten Spezies beiträgt. Im Rahmen einer ausführlichen Recherche und Sichtung des durch 12 Zoologische Einrichtungen zur Verfügung gestellten Materials zwischen 2011 und 2019 und eigens durchgeführter Untersuchungen im Leipziger Zoo im Zeitraum von 2013 bis 2019 konnten wichtige Daten über die Tüpfelbeutelmarder zusammengetragen und ausgewertet werden. Hauptaugenmerk wurde dabei auf das Vorkommen bestimmter Erkrankungen und oder Neoplasien, labordiagnostische Parameter wie Hämatologie und klinische Chemie, die Häufigkeit bestimmter bakterieller und parasitärer Infektionserreger sowie Immobilisationsmethoden gelegt. Insgesamt wurden 88 pathologisch-anatomische und-histologische Befunde, 42 Blutproben, 53 bakteriologisch und 107 parasitologisch untersuchte Kotproben in die Studie einbezogen. Die deskriptive Auswertung der Daten erfolgte mit dem Programm GNU PSPP. Im Anschluss erfolgten Signifikanzprüfungen der einzelnen Variablen anhand des Tests nach Fisher, dem T-Test für unabhängige Stichproben und mit Hilfe der Berechnung einzelner Konfidenzintervalle bestimmter Neoplasie- und Erkrankungsentitäten. Das Signifikanzniveau wurde auf p<0,05 festgelegt. Zusammenfassend ließen sich bei 59% der untersuchten Tüpfelbeutelmarder eine oder mehrere Neoplasien nachweisen. Es bestand eine signifikante Korrelation zwischen dem Alter und dem Auftreten der Tumoren. Eine tierartspezifische Neoplasie konnte hingegen nicht nachgewiesen werden. Darüber hinaus wiesen 71% der Tiere eine oder mehrere Erkrankungen zum Todeszeitpunkt auf. Die Hepatitis, Nephritis und die Steatosis Hepatis waren dabei die am häufigsten dokumentierten Krankheiten. Keine der Entitäten lag allerdings als signifikante Häufung vor. Weiterhin ließ sich in Übereinstimmung mit der Literatur die Leukenzephalopathie als degenerativer Erkrankungskomplex bei 35%, der zumeist älteren Tüpfelbeutelmarder bestätigen. Die Inhalationsanästhesie erwies sich insgesamt als die zuverlässigste und sicherste Narkoseform für diese Tierart. Die mikrobiologischen Kotuntersuchungen ergaben den Verdacht einer einrichtungsspezifischen Erregerbesiedlung der Quolls, mit Clostridium perfringens, Proteus mirabilis und Escherichia coli. Wobei E. coli möglicherweise sogar als enterale Normalflora bezeichnet werden könnte. Eine ebenso einrichtungsspezifische Erregerbesiedlung ergaben die parasitologischen Kotuntersuchungen. Hier konnten vornehmlich Nematoden und Zestoden vermutlich als Darmpassanten bedingt durch die Futtertiere detektiert werden. Darüber hinaus wurden labordiagnostische Parameter etabliert, die als Orientierungshilfe zur Beurteilung des Gesundheitsstatus der Tüpfelbeutelmarder dienen können. Im Durchschnitt kann von einer Lebenserwartung der Tüpfelbeutelmarder in menschlicher Obhut von 3-4 Jahren ausgegangen werden. Die Haltungsansprüche der Tiere umfassen hauptsächlich das passende Lichtregime, vielseitig gestaltete Gehege und eine saisonal angepasste, täglich wechselnde Fütterung von Ganzkörpern. Regelmäßige Beutelkontrollen, sowie das richtige Handling durch geschulte Pfleger können darüber hinaus zur erfolgreichen Reproduktion der Eastern Quolls beitragen. Die größte veterinärmedizinische Bedeutung der Tüpfelbeutelmarderhaltung sollte der zumeist altersbedingten Ausbildung von Neoplasien und dem degenerativen Erkrankungskomplex der Leukenzephalopathie beigemessen werden. Bisher sind keine erfolgversprechenden Therapien bekannt, so dass eine engmaschige Überwachung des Allgemeinzustandes der Tiere im Sinne des Tierschutzes unbedingt anzuraten ist.

The Australian fauna has endured numerous extinctions and declines in recent history. In particular, Australian mammals have experienced disproportionately more extinctions than their overseas counterparts, with many other species now only persisting on offshore islands after disappearing from their former mainland habitats. Once widespread throughout south-eastern Australia, the eastern quoll (Dasyurus viverrinus) is now considered extinct on the mainland, with the last confirmed sighting in Sydney in 1 963 . By contrast, eastern quoll populations in Tasmania were, until recently, presumed to be relatively stable and secure. However, spotlighting survey results suggest that the species may now be undergoing rapid and continuing decline. The aim of the current study was to further investigate this suspected decline, by measuring long-term changes in eastern quoll populations at a number of sites across Tasmania, and identifying factors that could have contributed to any observed population changes. Eastern quoll populations were surveyed using live capture and release at three study sites, with three replicate surveys performed at two-monthly intervals at each site. Results from the present study were compared with historical data from previous studies at these sites to gauge the extent of any local population changes. Significant reductions of >60% were observed in the number of quolls trapped at both Cradoc and Cradle Mountain, with no eastern quolls observed during any surveys at the Buckland study site. These declines appear to meet the criteria for listing the species as endangered under the Tasmanian Threatened Species Protection Act 1995 and the IUCN Red List of Threatened Species. A range of morphometric data and biological samples was collected from captured eastern quolls to assist in identifying potential causes of decline. Population structure, body condition, reproductive output and the health and disease status of captured quolls were compared across sites and between years. Several significant trends were observed in areas such as the development and timing of key reproductive stages, changes in population demographics and shifts in coat-colour ratios. From the findings of this study, critical information gaps were identified and several hypotheses were formulated to guide the management of key threats, halt further reductions, and ideally reverse the recent declines in eastern quolls.

Diagnosing the cause of a species’ decline is one of the most challenging tasks faced by conservation practitioners. A decline in abundance may simply be part of a natural population fluctuation from which the species will recover without management intervention, or it may indicate a more concerning trajectory towards extinction. Different threats and mechanisms can operate at different temporal and spatial scales, in succession or simultaneously. Often, several threats act together to produce synergistic effects that are greater than the sum of the contributions of each threatening process in isolation. Effective conservation strategies require an understanding of the factors that threaten a species and how those factors interact. The eastern quoll (Dasyurus viverrinus) is a medium-sized carnivorous marsupial that is extinct on the Australian mainland and survives only in Tasmania. The species has declined by more than 50% in the 10 years to 2009, with no sign of recovery. The reasons for this precipitous decline are not currently understood. Population eruptions and declines have been anecdotally reported in eastern quolls since the 1800s, suggesting that the species may be sensitive to short-term variations in weather. Additionally, a recent study suggested that the decline of the Tasmanian devil (Sarcophilus harrisii) due to the spread of the Devil Facial Tumour Disease (DFTD) may have released feral cats (Felis catus) from competitive suppression. A subsequent increase in cat sightings might be linked to eastern quoll declines, possibly through mechanisms such as increased predation, competition or exposure to toxoplasmosis, the disease caused by the cat-borne coccidian parasite Toxoplasma gondii.