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P A Woolley - One of the best experts on this subject based on the ideXlab platform.

  • the julia creek dunnart Sminthopsis douglasi marsupialia dasyuridae breeding of a threatened species in captivity and in wild populations
    Australian Journal of Zoology, 2015
    Co-Authors: P A Woolley
    Abstract:

    A detailed description of the methods used to house, maintain and assess the reproductive condition of captive Julia Creek dunnarts, Sminthopsis douglasi, that led to successful breeding of the species in captivity is provided. Basic features of the reproductive biology of this species of Sminthopsis have been established from observations made on captive animals. The females are polyoestrous, with a cycle length of ~28 days. Young are born 13–16 days after mating and are dependent on the mother for ~70 days. The age at which captive animals commence breeding ranged from 13 to 38 weeks (females) and 23 to 40 weeks (males). Both sexes are capable of breeding when two years old. Breeding in wild populations is seasonal and occurs over a six-month period from August to March, which encompasses the hottest and wettest time of the year. Both females and males are known to be capable of breeding in more than one season and females have the potential to rear two litters in a season. Recruitment of young to the population may be affected by heavy rainfall during the breeding season that can lead to closure of the cracks and holes in which the dunnarts shelter.

  • microsatellite markers from the julia creek dunnart Sminthopsis douglasi marsupialia dasyuridae
    Molecular Ecology Notes, 2003
    Co-Authors: Peter B S Spencer, T P Fletcher, P A Woolley
    Abstract:

    The Julia Creek dunnart (Sminthopsis douglasi) was not recognized as a distinct species until 1979. The description was based on three specimens held in museum collections and, prior to 1991, it was thought that the species might have become extinct. A few small populations are now known to exist but the species is currently listed as endangered. Here we characterize seven dinucleotide microsatellite loci with between two and nine alleles per locus and expected heterozygosities ranging from 0.53 to 0.91. These markers provide an additional approach to the study of the ecology and conservation status of the Julia Creek dunnart.

  • anatomy and physiology of the gastrointestinal tract of the julia creek dunnart Sminthopsis douglasi marsupialia dasyuridae
    Australian Journal of Zoology, 2000
    Co-Authors: I D Hume, C Smith, P A Woolley
    Abstract:

    The gastrointestinal tract of the endangered Julia Creek dunnart (Sminthopsis douglasi), the largest member of the genus Sminthopsis, consists of a simple, unilocular stomach and an intestine of relatively uniform calibre throughout. There is no hindgut caecum, in common with other Australian carnivorous marsupials. Brunner’s glands form a collar at the proximal end of the duodenum; they consist of simple uncoiled tubes at Day 45 of pouch life but are well differentiated at Day 60, before the young take their first solid food at Day 65–70. Rate of passage of digesta was measured in nine adult Julia Creek dunnarts on diets of minced meat with either mealworm larvae or adult crickets added, using pulse doses of the solute marker Co–EDTA and large (0.5–1.0 mm) particles of plant cell walls mordanted with Cr. Transit time (time of first appearance in the faeces) of both markers (P < 0.001) and mean retention time (the average time markers are retained in the tract) of the solute marker (P < 0.05) were shorter on the diet containing mealworms than the cricket diet. These results suggest that emptying of the stomach (the main site of digesta retention in carnivores) was delayed on the cricket diet, possibly because of longer digestion times as a result of a tougher exoskeleton. Comparison with other data suggests that total tract passage times increase among dasyurids as body size increases.

  • growth and development of pouch young of the stripe faced dunnart Sminthopsis macroura marsupialia dasyuridae in captivity
    Australian Journal of Zoology, 1997
    Co-Authors: L Frigo, P A Woolley
    Abstract:

    The growth and development of the stripe-faced dunnart, Sminthopsis macroura (Gould), a small insectivorous marsupial, was examined and described from birth to weaning (a period of 65–70 days). All observations and analyses were based on known-age individuals from a laboratory colony. Growth curves showing the regression of body weight, head, pes, crown–rump, tail and head+body lengths as a function of age were constructed. Relative growth was determined by calculating the instantaneous relative growth rate, k, and two major phases of growth were recognised: during Phase I (birth to about Day 54 post partum) growth rate was rapid, and during Phase II (about Day 55 to weaning) a deceleration in growth rate was apparent. Growth rate may decline because of regression of the mammary tissue associated with the commencement of weaning. No significant relationship was found between month of birth and growth rate, and preliminary evidence suggests that litters of different sizes may grow at varying rates during Phase II of the suckling period. Preserved and living specimens were used to examine the development of young from birth to weaning.

  • development of the skeleton of the stripe faced dunnart Sminthopsis macroura marsupialia dasyuridae
    Australian Journal of Zoology, 1996
    Co-Authors: L Frigo, P A Woolley
    Abstract:

    Development of the skeleton of the stripe-faced dunnart, Sminthopsis macroura (Gould), a small carnivorous marsupial, was examined in captive-bred pouch young of known age. Skeletal tissue was differentially stained with the dyes alcian blue and alizarin red to demonstrate the presence of cartilage and bone, respectively. The skeleton of the neonate is cartilaginous and ossification centres are first apparent in the skull by Day 5 post partum. The skeleton of S. macroura is well invested with bone by Day 40 of the lactation period, when the young can relinquish the nipple. The sequence of ossification is similar to that reported for other marsupials. Comparisons are made with the eutherian pattern of ossification. This study is the first published work on the ossification of a dasyurid marsupial as shown by whole-mount staining.

Bronwyn M. Mcallan - One of the best experts on this subject based on the ideXlab platform.

  • Transcriptomic changes in the pre-implantation uterus highlight histotrophic nutrition of the developing marsupial embryo
    Scientific Reports, 2018
    Co-Authors: Camilla M. Whittington, Denis O’meally, Melanie K. Laird, Katherine Belov, Michael B. Thompson, Bronwyn M. Mcallan
    Abstract:

    Early pregnancy is a critical time for successful reproduction; up to half of human pregnancies fail before the development of the definitive chorioallantoic placenta. Unlike the situation in eutherian mammals, marsupial pregnancy is characterised by a long pre-implantation period prior to the development of the short-lived placenta, making them ideal models for study of the uterine environment promoting embryonic survival pre-implantation. Here we present a transcriptomic study of pre-implantation marsupial pregnancy, and identify differentially expressed genes in the Sminthopsis crassicaudata uterus involved in metabolism and biosynthesis, transport, immunity, tissue remodelling, and uterine receptivity. Interestingly, almost one quarter of the top 50 genes that are differentially upregulated in early pregnancy are putatively involved in histotrophy, highlighting the importance of nutrient transport to the conceptus prior to the development of the placenta. This work furthers our understanding of the mechanisms underlying survival of pre-implantation embryos in the earliest live bearing ancestors of mammals.

  • Extensive production of Neospora caninum tissue cysts in a carnivorous marsupial succumbing to experimental neosporosis
    Veterinary Research, 2011
    Co-Authors: Jessica S King, Bronwyn M. Mcallan, John Ellis, Derek Spielman, Scott A. Lindsay, Lada Hůrková-hofmannová, Ashlie Hartigan, Sarwat Al-qassab, Jan Slapeta
    Abstract:

    Experimental infections of Sminthopsis crassicaudata, the fat-tailed dunnart, a carnivorous marsupial widely distributed throughout the arid and semi-arid zones of Australia, show that this species can act as an intermediate host for Neospora caninum. In contrast to existing models that develop relatively few N. caninum tissue cysts, dunnarts offer a new animal model in which active neosporosis is dominated by tissue cyst production. The results provide evidence for a sylvatic life cycle of N. caninum in Australia between marsupials and wild dogs. It establishes the foundation for an investigation of the impact and costs of neosporosis to wildlife.

  • cortical cyto and chemoarchitecture in three small australian marsupial carnivores Sminthopsis macroura antechinus stuartii and phascogale calura
    Brain Behavior and Evolution, 2008
    Co-Authors: Ken W S Ashwell, Bronwyn M. Mcallan, George Paxinos
    Abstract:

    The cyto- and chemoarchitecture of the cerebral cortex has been examined in three small (mouse-sized) polyprotodont marsupial carnivores from Australia (the stripe-faced dunnart, Sminthopsis

  • Marsupial uncoupling protein 1 sheds light on the evolution of mammalian nonshivering thermogenesis
    Physiological Genomics, 2008
    Co-Authors: Kerry Withers, Verena Hirschberg, Tobias Fromme, Peter B. Frappell, Gerhard Heldmaier, Stefan Taudien, Michael Helwig, Bronwyn M. Mcallan, Bruce T. Firth
    Abstract:

    Brown adipose tissue expressing uncoupling protein 1 (UCP1) is responsible for adaptive nonshivering thermogenesis giving eutherian mammals crucial advantage to survive the cold. The emergence of this thermogenic organ during mammalian evolution remained unknown as the identification of UCP1 in marsupials failed so far. Here, we unequivocally identify the marsupial UCP1 ortholog in a genomic library of Monodelphis domestica. In South American and Australian marsupials, UCP1 is exclusively expressed in distinct adipose tissue sites and appears to be recruited by cold exposure in the smallest species under investigation (Sminthopsis crassicaudata). Our data suggest that an archetypal brown adipose tissue was present at least 150 million yr ago allowing early mammals to produce endogenous heat in the cold, without dependence on shivering and locomotor activity.

  • lateralisation of escape responses in the stripe faced dunnart Sminthopsis macroura dasyuridae marsupialia
    Laterality, 2005
    Co-Authors: Giuseppe Lippolis, Bronwyn M. Mcallan, Wendy Westman, Lesley J Rogers
    Abstract:

    Although lateralisation has been observed in many vertebrate species, marsupials have been neglected in the study of lateralisation. We investigated the behavioural responses of the stripe-faced dunnart (Sminthopsis macroura) to a mechanical model of a snake approaching into the monocular (left and right) or the binocular visual field. The snake model was presented to 30 adult subjects. The behavioural responses and the latency to react to the stimulus were scored. Reactivity was calculated by pooling scores for retreat, startle, ears back, and orientation. Retreat tended to be the most common of these responses. Approach of the snake into the dunnarts' left monocular visual field elicited a significantly higher reactivity compared to approach into the right or binocular visual field. Half of the animals did not respond in the 60 seconds allocated when the stimulus approached on their right side, whereas only seven did not respond when the stimulus approached on the left, and ten when the stimulus was pre...

Philip C Withers - One of the best experts on this subject based on the ideXlab platform.

  • comparative thermoregulatory physiology of two dunnarts Sminthopsis macroura and Sminthopsis ooldea marsupialia dasyuridae
    Australian Journal of Zoology, 2012
    Co-Authors: Sean Tomlinson, Philip C Withers, Shane K Maloney
    Abstract:

    Metabolic rate and evaporative water loss (EWL) were measured to quantify the thermoregulatory patterns of two dasyurids, the stripe-faced dunnart (Sminthopsis macroura) and the Ooldea dunnart (S. ooldea) during acute exposure to Ta between 10 and 35°C. S. macroura maintained consistent Tb across the Ta range, whereas S. ooldea was more thermolabile. The metabolic rate of both species decreased from Ta = 10°C to BMR at Ta = 30°C. Mass-adjusted BMR at Ta = 30°C was the same for the two species, but there was no common regression of metabolic rate below the thermoneutral zone (TNZ). There was no significant difference between the species in allometrically corrected EWL at Ta = 30°C. Total EWL increased significantly at Ta = 10 and 35°C compared with the TNZ for S. macroura, but was consistent across the Ta range for S. ooldea. At any Ta below the TNZ, S. macroura required more energy per gram of body mass than S. ooldea, and had a higher EWL at the lower critical Ta. By being thermolabile S. ooldea reduced its energetic requirements and water loss at low Ta. The more constant thermoregulatory strategy of S. macroura may allow it to exploit a broad climatic envelope, albeit at the cost of higher energetic and water requirements. Since S. ooldea does not expend as much energy and water on thermoregulation this may be a response to the very low productivity, ‘hyperarid’ conditions of its central Australian distribution.

  • flexibility in thermoregulatory physiology of two dunnarts Sminthopsis macroura and Sminthopsis ooldea marsupialia dasyuridae
    The Journal of Experimental Biology, 2012
    Co-Authors: Sean Tomlinson, Philip C Withers, Shane K Maloney
    Abstract:

    SUMMARY Stripe-faced dunnarts (Sminthopsis macroura) and Ooldea dunnarts (S. ooldea) were acclimated for 2 weeks to ambient temperature (Ta) regimes of 12–22°C, 18–28°C and 25–35°C, and then measured for standard, basal (BMR) and maximum (MMR) metabolic rate using flow-through respirometry. Sminthopsis macroura maintained a stable body temperature under all experimental Ta and acclimation regimes. Although its BMR was not statistically different between the three acclimation regimes, the lower end of the thermoneutral zone (TNZ) shifted from 30°C under the 18–28°C and 12–22°C acclimation regimes to 35°C under the 25–35°C acclimation regime. MMR increased significantly at the cooler acclimation regimes. EWL increased at Ta=35°C, compared with lower Ta, in all acclimation regimes, but an increase in evaporative water loss (EWL) at Ta=10°C observed in cool acclimations did not occur at the 25–35°C regime. In contrast, S. ooldea had variable body temperature between experimental Ta in all acclimation regimes, but no acclimational shift in TNZ, which was between 30 and 35°C. Neither BMR nor MMR was affected by exposure to the three acclimation regimes. EWL did not change across Ta or with acclimation regime. Sminthopsis macroura was flexible in many aspects of its thermoregulation (involving energy and water balance) in response to thermal acclimation, presumably allowing it to balance its energy and water requirements over a broad range of climatic conditions. Sminthopsis ooldea seems to have an inflexible energetic and water balance in response to thermal acclimation, but has low nominal expenditure of either resource on thermoregulation because it thermoregulates less precisely than S. macroura. It seems that S. ooldea is adapted to a more narrow, stable climate.

  • thermal metabolic hygric and ventilatory physiology of the sandhill dunnart Sminthopsis psammophila marsupialia dasyuridae
    Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2009
    Co-Authors: Philip C Withers, Christine Cooper
    Abstract:

    We present here the first physiological data for the sandhill dunnart (Sminthopsis psammophila), the second largest (35-44 g) sminthopsine dasyurid marsupial, and report torpor for this species. Their thermoneutral body temperature (34.4 degrees C), thermolability below thermoneutrality (0.062 degrees C degrees C(-1)), and mild hyperthermia above thermoneutrality (35.5 degrees C) are typical of small dunnarts, and dasyurids. Basal metabolic rate (0.80 mL O2 g(-1) h(-1)) is as predicted from mass. Sandhill dunnarts generally conform to the Scholander-Irving model of endothermy, although metabolism increases less than expected and extrapolates to a higher than actual body temperature.Wet (0.22 mL O2 g(-1) h(-1) C(-1)) and dry (2.8 J g(-1) h(-1) degrees C(-1)) thermal conductances were as predicted. Thermoneutral evaporative water loss (1.6 mg g(-1) h(-1)) was only 54% of expected, but this is not significantly different, and more likely reflects variability in the marsupial dataset than an adaptation.Relative water economy resembles that of other small marsupials, rodents and birds, with a point of relative economy of 18 degrees C. Respiratory ventilation closely matches metabolic rate, with minute volume increased at low ambient temperatures by increased breathing rate rather than tidal volume; oxygen extraction was constant at about 17%, except during hyperthermia above the thermoneutrality. Torpor conferred significant energetic and hygric benefits. We found no evidence of deviation from allometrically- and phylogenetically-based expectations despite the sandhill dunnart's arid habitat and large (for a dunnart) body mass.

Divljan Anja - One of the best experts on this subject based on the ideXlab platform.

Bruce T. Firth - One of the best experts on this subject based on the ideXlab platform.

  • Marsupial uncoupling protein 1 sheds light on the evolution of mammalian nonshivering thermogenesis
    Physiological Genomics, 2008
    Co-Authors: Kerry Withers, Verena Hirschberg, Tobias Fromme, Peter B. Frappell, Gerhard Heldmaier, Stefan Taudien, Michael Helwig, Bronwyn M. Mcallan, Bruce T. Firth
    Abstract:

    Brown adipose tissue expressing uncoupling protein 1 (UCP1) is responsible for adaptive nonshivering thermogenesis giving eutherian mammals crucial advantage to survive the cold. The emergence of this thermogenic organ during mammalian evolution remained unknown as the identification of UCP1 in marsupials failed so far. Here, we unequivocally identify the marsupial UCP1 ortholog in a genomic library of Monodelphis domestica. In South American and Australian marsupials, UCP1 is exclusively expressed in distinct adipose tissue sites and appears to be recruited by cold exposure in the smallest species under investigation (Sminthopsis crassicaudata). Our data suggest that an archetypal brown adipose tissue was present at least 150 million yr ago allowing early mammals to produce endogenous heat in the cold, without dependence on shivering and locomotor activity.