Добірка наукової літератури з теми "Phascolarctidae"

THE pre Holocene-Late Pleistocene record of Phascolarctos in Australia is extremely meagre. There are at least two, possibly three extinct species of Phascolarctos in addition to the extant Phascolarctos cinereus (Black 1999). P. yorkensis (syn. Cundokoala yorkensis; Black and Archer 1997) is known from the Early Pliocene Curramulka Local Fauna, South Australia (SA), and the Late Pleistocene Wellington Caves Local Fauna, New South Wales (Archer et al. 1997; Pledge 1992). P. stirtoni occurs in the Late Pleistocene Cement Mills Local Fauna, Queensland, and is known only from a partial maxilla containing P3-M2 (Bartholomai 1968, 1977). Phascolarctos material from the mid- Pleistocene Victoria Fossil Cave and Spring Cave, Naracoorte, SA, have also been referred to P. cf. stirtoni but remain undescribed (Reed and Bourne 2000; Moriarty et al. 2000). P. maris is known from a single lower molar from the Early Pliocene Sunlands Local Fauna, SA (Pledge 1987). Black (1999) cast doubt on its validity, suggesting its features may fall within the intraspecific variation of P. stirtoni. If P. maris is referable to P. stirtoni it is another South Australian instance of this species, and extends its range back to the Early Pliocene. The new phascolarctid material documented here is from the early Pleistocene Nelson Bay Local Fauna, Portland, Victoria (141o 35? E; 38o 36? S). It is therefore an important additional southern occurrence of a species larger than the living P. cinereus, and is the only pre- Late Pleistocene record of the Phascolarctidae in Victoria.

The muscles of mastication of the koala, Phascolarctos cinereus, were dissected, described, weighed and the areas of their origin and insertion were determined. In addition, the temporomandibular joint was described. The aim was to ascertain the relative contribution of those muscles to the jaw movements of the koala. The masseter and temporalis muscles were the principle group and could account for the major movements and forces generated in chewing. In contrast to other herbivorous mammals, the pterygoid muscles were small and probably exert fine motor control over the mandible and temporo- mandibular joints. The digastric and geniohyoid muscles were small, compatible with the limited gape in the animal.

The faecal microflora of four Phascolarctos cinereus kept at the Saitama Children's Zoo in Japan was investigated using 10 selective and 4 nonselec tive agar media. Total viable counts (in log form) of faecal bacteria (8.2 g of wet faeces) were significantly lower than the direct microscopic counts (11.2 g of wet faeces). Four groups of obligate anaerobes (bacteroidaceae, peptococcaceae, bifidobacteria , and clostridia) and three groups of facultative anaerobes (enterobacteria, streptococci and lactobacilli) were isolated. Dominant components of the flora were obligate anaerobes, in particular bacteroidaceae and peptococcaceae.

Wear of the premolar and molar teeth of the Koala, Phascolarctos cinereus, was studied at two localities, in central and southern Queensland respectively. Tooth wear was classified into 10 tooth wear classes (TWC). Mean ages were determined for TWCs 1- 6, ranging from 1.2 to 7.3 years. An age estimate is also given for TWC 7 (9 years), but is based on data from only one known age animal. Rate of tooth wear varied greatly between animals from the same area, but there was no difference in rate of wear between the two localities, at which diets differed (Eucalyptus tereticornis / E. microtheca versus E. populnea). TWC is useful for dividing samples of animals from P. cinereus populations into separate age classes and for giving an approximation to the age of particular animals. The correlation between age and head length of P. cinereus of known year class was examined. Head length differs between P. cinereus from year classes 0, I and 2, and may be used to place animals in this age range into a year class.

Doubly labelled water measurements in free-ranging adult koalas (9.2 kg) indicated that field metabolic rates averaged 0.434 ml CO2 g-�h-� (equivalent to 2090 kJ per animal per day, or 2.59 X basal metabolic rate). Females (7.8 kg) had significantly higher mass-specific metabolic rates than males (10.8 kg). Percentage apparent assimilation of dietary substances was 56% for dry matter, 52% for energy, 32% for nitrogen, and 66% for water. Feeding rates were about 222 g dry food per animal per day (equivalent to 510 g fresh food per animal per day) in both sexes. However, males had a higher water influx rate (475 ml per animal per day) than females (358 ml per animal per day), suggesting either that males selected more succulent food than females, or that males drank rainwater but females did not. Koalas consumed about twice as much dietary nitrogen as they required for maintenance. They maintained constant body masses, and (presumably) had balanced energy, water and nitrogen budgets during our 20-day study, while eating Eucalyptus ovata foliage. Koalas spent about 4.7 h eating, 4 min travelling, 4.8 h resting while awake and 14.5 h sleeping in a 24-h period. Their activity periods were not obviously restricted to periods of daylight or darkness, but were scattered through the 24 hours. In comparison with free-living, three-toed sloths Bradypus variegatus (4.08 kg) in central America, koalas had significantly higher mass-corrected field metabolic rates (391 kJ kg-0.75 day-� for koalas v.209 for sloths), water influx rates (69.9 ml kg-0.80 day-� for koalas v. 49.8 for sloths), and feeding rates (42.7 g dry food kg-0.75 day-� for koalas v. 21.2 for sloths). Unlike sloths, koalas did not bask in the morning sunshine, and one telemetered koala had a relatively constant body temperature over 24 h (c. 36�C), compared with daily variations between 30 and 38�C in sloths. Population food consumption (g dry food consumed ha-� day-�) was greater for koalas (681 v. 378 for sloths), and koalas consumed most of the leaf production of their preferred food species, E. ovata, which resulted in extensive defoliation of these trees. Although there is similarity in the ecological roles of koalas and sloths, their physiology and behaviour differ substantially.

Renal disease had been reported to occur at high prevalence in the koala population of the Mount Lofty Ranges in South Australia, but the cause was unclear. Kidney crystals consistent with calcium oxalate had been observed in several koalas, suggesting that oxalate nephrosis may occur. The aims of this study were to describe renal pathological changes and confirm oxalate deposition in these koalas and also to investigate possible causes of disease. Oxalate nephrosis was found in 55% of 51 captive and rescued wild koalas from the Mount Lofty population. Renal histopathological changes associated with crystals included intratubular and interstitial inflammation, tubule dilation, glomerular atrophy, tubule loss and cortical fibrosis. Renal insufficiency was confirmed in affected koalas by azotaemia in association with poorly concentrated urine, and decreasing urine specific gravity was significantly associated with increasing severity of histopathological changes. The number of males and females, and captive and rescued wild koalas showing oxalate nephrosis was similar. Age was not found to be a predisposing factor, but many koalas <2 years old were affected. Urinary crystals in all koalas with oxalate nephrosis showed an atypical morphology for calcium oxalate. Hyperoxaluria was also found, suggestive of a primary cause for disease. To investigate whether a dietary cause existed for oxalate nephrosis in koalas, oxalate concentration was measured in juvenile, semi-mature and mature leaves from manna gum (E. viminalis), red gum (E. camaldulensis), SA blue gum (E. leucoxylon) and messmate stringybark (E. obliqua) in spring. Eucalypt leaves were found to be low in oxalate overall (<1% dry weight) with occasional samples that were higher in oxalate. Mount Lofty eucalypts were found to have higher oxalate content overall than those eaten by koalas in Moggill, Queensland, where the prevalence of oxalate nephrosis is lower. To investigate whether endogenous overproduction of oxalate could occur due to an inherited liver enzyme dysfunction, similar to primary hyperoxaluria type I in humans, the activity of alanine: glyoxylate aminotransferase (AGT) was measured in liver samples. Koalas with oxalate nephrosis showed no decrease in AGT activity compared with samples from unaffected Queensland koalas, indicating normal activity of this enzyme. Water content of eucalypt leaves was also measured, since dehydration is a key risk factor for renal calcium oxalate deposition. Mount Lofty eucalypt leaves were found to be lower in moisture in autumn compared with those in Queensland, particularly juvenile and semi-mature leaves of E. obliqua and E. leucoxylon. The pathological, histopathological and clinicopathological description of oxalate nephrosis in koalas provided by this study will assist veterinarians and pathologists in the diagnosis of this disease. Investigation of the pathogenesis of oxalate nephrosis in the Mount Lofty koala population found that neither high eucalypt leaf oxalate or decreased AGT activity were the primary cause. Further research is needed, but based on the low genetic diversity of the Mount Lofty koalas, an inherited pathogenesis of oxalate nephrosis remains likely. To decrease the risk of oxalate nephrosis, water supplementation should be provided for captive and wild Mount Lofty koalas during the hot, dry summer.
Thesis (Ph.D.) -- University of Adelaide, School of Medical Sciences, 2013

Koalas are a vulnerable iconic species, for which disease is a significant threat to populations around Australia. Lymphoid neoplasia and immunomodulation in koalas have been associated with an important pathogen, koala retrovirus (KoRV). The prevalence and transmission of KoRV differs in northern koalas, from Queensland and New South Wales, compared to southern koalas, from Victoria and South Australia. Northern koalas inherit and horizontally transmit KoRV via endogenous and exogenous mechanisms, respectively with all koalas infected. Southern koalas are hypothesised to only have exogenous transmission, and within these populations the prevalence is less. Both proviral load (inserted viral genome into host DNA) and viral load (extracellular RNA viral genome) are significantly higher in northern koalas in comparison to southern koalas, representing active transcription in a greater number of cells. Mechanisms for KoRV-associated oncogenesis are still unknown, along with the prevalence of lymphoid neoplasia in the Mount Lofty Ranges population, South Australia. Increased susceptibility of disease has been inferred from studies exploring KoRV coinfection with Chlamydia pecorum, a bacterium which causes both ocular and urogenital disease in koalas. KoRV and C. pecorum are well-studied key pathogens of koalas, although the significance of another infectious agent Phascolarctid gammaherpesviruses, is unknown. Avian and human studies have shown increased incidence of neoplasia when coinfected with a retrovirus and gammaherpesvirus, but there is no current evidence for this in koalas. Association of diseases is based on a confident diagnosis of infectious agents, for which koalas in South Australia have shown variations in proviral analysis creating complexity in the diagnosis of KoRV. The KoRV viral genome consists of three genes, gag, pol and env, flanked by long terminal repeats, LTRs. The pol gene qPCR has been a standard diagnostic tool, but more investigation across multiple genome targets has shown variance in SA koala PCR and qPCR results. In this study, PCR and qPCR methods were used against two targets in the gag gene, one in the pol gene and two in the env gene. Koalas for which all proviral targets were positive were designated KoRV positive and koalas for which one gag target, pol target and env targets were negative were designated KoRV negative. There were 41.2% (89/216) KoRV positive, 56.9% (123/216) KoRV negative koalas and only 1.9% (4/216) deemed inconclusive. Viral gene expression analysed by qPCR was found to be present in 10/10 KoRV positive koalas, and absent in 5/5 KoRV negative koalas. RNAseq analysis revealed transcription of sequences homologous to terminal regions of the KoRV genome in all koalas, verified by the presence of one gag gene target in almost all (215/216) koalas tested by PCR. The presence of these regions in South Australian koalas without the presence of the full KoRV genome, suggests an endogenised retroviral element, potentially within the koala genome prior to KoRV. Lymphomic koalas showed high expression of KoRV and higher proviral loads compared to KoRV positive koalas without lymphoma. Lymphoma was found in 1.2% (3/240) of koalas and these cases were collated with previous South Australian lymphoma cases for classification. All cases had abdominal involvement, were intermediate to large cell and of non-T cell origin. RNAseq data was compared from lymphomic lymph nodes, lymph nodes from KoRV positive and lymph nodes of KoRV negative koalas. High KoRV transcription was found in lymphomic tissue, 1207 genes showed differential expression between KoRV positive koalas diagnosed with lymphoma and KoRV negative koalas and 939 genes between KoRV positive koalas diagnosed with lymphoma and KoRV positive koalas. Oncogenes MYB, MYCL and FLT3 were significantly upregulated and possible candidates in the incitement of oncogenesis. Dysregulation in IL10, and pathways associated with NF-kB also support the role of immunosuppression in lymphoma pathogenesis. Based on theories of KoRV-associated immunosuppression leading to opportunistic infections and augmentation of disease with pathogens, coinfections and comorbidities were investigated in 247 necropsied koalas. KoRV was not found to be associated with C. pecorum or disease severity. However, C. pecorum was associated with another recently discovered infectious agent, Phascolarctid gammaherpesvirus (PhaHV), and in this cohort PhaHV was associated with the presence of paraovarian cysts, regardless of chlamydial status, similar to Victorian koalas. Also, KoRV and PhaHV-2 coinfection was associated with neoplasia and warrants further investigation. Disease and infectious agents were negatively correlated with victims of road traffic accidents showing the potential importance of this group of koalas. Novel pathologies were found in this koala necropsy cohort. Pulmonary actinomycosis, a new presentation of respiratory disease of koalas, with a subset of these koalas presenting with secondary hypertrophic osteopathy, a second novel pathology in koalas. Fifteen koalas were found to have pyogranulomatous lobar pneumonia, predominantly affecting the left caudal lung lobe. Histological examination showed Splendore Hoeppli phenomenon with associated Gram-positive or Gram-variable, non-acid fast, filamentous bacteria. The pathogen was identified as a novel Actinomyces sp. and through 16S rRNA gene sequencing was closest to A. timonensis. Collaboration with other wildlife veterinarians found that two of the study koalas also presented with another undescribed pathology in koalas, hypertrophic osteopathy, found secondary to the pulmonary lesions. These discoveries highlight the necessity for ongoing necropsy studies in koalas to increase the knowledge of disease presentations in this iconic species. Overall, this thesis aimed to examine the association of disease with several pathogens, with particular focus on the association between KoRV and lymphoma. Advancements were made in recommendations for KoRV diagnosis in South Australia, gene dysregulation in KoRVassociated lymphoma, interactions with other key pathogens; C. pecorum and PhaHV, and the report of novel disease presentations. The increased knowledge of infectious disease and interaction of disease in South Australian koalas can help management strategies protecting the health and welfare of these koalas. Also, identification of dysregulated genes has increased the knowledge of oncogenesis by koala retrovirus.
Thesis (Ph.D.) -- University of Adelaide, School of Animal and Veterinary Sciences, 2021