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1
Bleicher, Sonny S., e Christopher R. Dickman. "On the landscape of fear: shelters affect foraging by dunnarts (Marsupialia, Sminthopsis spp.) in a sandridge desert environment". Journal of Mammalogy 101, n. 1 (15 febbraio 2020): 281–90. http://dx.doi.org/10.1093/jmammal/gyz195.
Testo completoAbstract (sommario):
Abstract Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing the risk of predation for small prey species. The postfire effect of predation has especially deleterious effects in Australian habitats owing to the presence of invasive mammalian predators, the red fox (Vulpes vulpes) and feral cat (Felis catus), that rapidly exploit burned habitats. Here, we investigated whether the provision of artificial shelter could alleviate the risk of predation perceived by two species of small marsupial, the dunnarts Sminthopsis hirtipes and S. youngsoni, in open postfire habitat in the sandridge system of the Simpson Desert, central Australia. We installed artificial shelters constructed from wire mesh that allowed passage of the dunnarts but not of their predators at one site, and measured and compared the perceived risk of predation by the dunnarts there with those on a control site using optimal patch-use theory (giving-up densities, GUDs). GUDs were lower near artificial shelters than away from them, and near dune crests where dunnarts typically forage, suggesting that the shelters acted as corridors for dunnarts to move up to the crests from burrows in the swales. Foraging was lower near the crest in the control plot. Two-day foraging bouts were observed in dunnart activity, with recruitment to GUD stations occurring a day earlier in the augmented shelter plot. Despite these results, the effects of the shelters were localized and not evident at the landscape scale, with GUDs reduced also in proximity to sparse natural cover in the form of regenerating spinifex grass hummocks. Mapping dunnart habitat use using the landscape of fear (LOF) framework confirmed that animals perceived safety near shelter and risk away from it. We concluded that the LOF framework can usefully assess real-time behavioral responses of animals to management interventions in situations where demographic responses take longer to occur.
2
Read, John L., Matthew J. Ward e Katherine E. Moseby. "Factors that influence trap success of sandhill dunnarts (Sminthopsis psammophila) and other small mammals in Triodia dunefields of South Australia". Australian Mammalogy 37, n. 2 (2015): 212. http://dx.doi.org/10.1071/am14020.
Testo completoAbstract (sommario):
Optimised detection and sensitivity of fauna-monitoring programs is essential for the adaptive management of threatened species. We describe the influence of trap type, trapping duration and timing on the detection rates of small vertebrates, in particular the nationally endangered sandhill dunnart (Sminthopsis psammophila) in its two primary populations in South Australia. A total of 118 and 155 sandhill dunnarts were captured from the Middleback and Yellabinna regions, respectively, from five trapping sessions between 2008 and 2012. Wide deep pitfall traps (225 mm diameter × 600–700 mm deep) captured significantly more adult sandhill dunnarts than shorter, narrower pitfalls (150 mm diameter × 500 mm deep) or Elliott traps. Deep pitfall traps also captured significantly more hopping mice (Notomys mitchellii) but smaller mammal species were equally trapable in deep or short pitfall traps. Capture rates declined through successive nights of trapping. Capture rates of sandhill dunnarts were greatest in one study region when the moon illumination was less than 40% compared with fuller moon phases but were not affected by moon illumination in the other study region. The results suggest that higher capture rates of sandhill dunnarts will be achieved when using wide, deep pitfall traps on dark nights during the first two nights of trapping. Trapping in summer detected more juvenile sandhill dunnarts than trapping in winter.
3
Haythornthwaite, Adele S. "Microhabitat use and foraging behaviour of Sminthopsis youngsoni (Marsupialia:Dasyuridae) in arid central Australia". Wildlife Research 32, n. 7 (2005): 609. http://dx.doi.org/10.1071/wr04126.
Testo completoAbstract (sommario):
In this study, fluorescent pigment tracking was used to determine the microhabitat use and foraging behaviour of a small insectivorous marsupial, Sminthopsis youngsoni (the lesser hairy-footed dunnart), in the dunefields of the Simpson Desert, south-western Queensland. In total, 25 successful trails were traced over the duration of this study, between March 1996 and April 1998. Nocturnal foraging trails were identified, then the distance travelled by the dunnart through each microhabitat type (nine in all) was measured and accumulated for each trail and compared with surrounding available microhabitats along control trails. This provided an index of selectivity of microhabitat use. Terrestrial invertebrates were collected from both actual and control trails to measure food availability. Dunnarts strongly selected open microhabitats when foraging, with the periphery of spinifex hummocks (up to 20 cm from the edge of a spinifex hummock) being favoured. Spinifex itself was avoided unless shelter was sought (i.e. immediately after release). Potential invertebrate prey captured along the actual trails travelled by dunnarts tended to occur in greater numbers and were larger than those captured along the control trails, indicating that dunnarts can accurately locate resource-rich areas in which to forage. Clearly, the foraging strategies used by this species enable it to successfully exploit patchy and unpredictable food resources, thereby ensuring its continued persistence and relative abundance in an unstable environment.
4
Langman, C., S. Orgeig e C. B. Daniels. "Alterations in composition and function of surfactant associated with torpor in Sminthopsis crassicaudata". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 271, n. 2 (1 agosto 1996): R437—R445. http://dx.doi.org/10.1152/ajpregu.1996.271.2.r437.
Testo completoAbstract (sommario):
Cold profoundly influences lung compliance in homeothermic mammals. Much of this effect has traditionally been attributed to the inactivation of the surfactant system. However, many mammals undergo large fluctuations in body temperature (heterothermic mammals). Here, the surfactant lipid composition and lung compliance of warm-active dunnarts (Sminthopsis crassicaudata) and the homeothermic mouse (Mus musculus) [body temperature (Tb) = 35-37 degrees C] were compared with those of dunnarts killed after 1,4 or 8 h of torpor (Tb < 20 degrees C). Lung compliance was measured before and after the removal of surfactant, and tissue compliance was determined by inflating the lung with saline. Relative to total phospholipid (PL), mouse surfactant contained proportionately less phosphatidylinositol but more cholesterol (Chol) and phosphatidylglycerol than that of the dunnart. Lung compliance was lower in dunnarts than in mice, consistent with an allometric effect. Surfactant levels, including total PL, Chol, and disaturated phospholipid (DSP) increased during torpor. The relative proportions of Chol and DSP increased after 4 and 8 h, respectively. In marked contrast to previous studies on the behavior of isolated lungs from homeothermic mammals, in our study the lung compliance of dunnarts remained unchanged throughout torpor. Tissue compliance decreased at 1 and 4 h of torpor, but this decrease was abolished by 8 h. It appears that the surfactant of the dunnarts counteracted the negative effect of tissue compliance at 1 and 4 h, an effect not present in homeothermic mammals. However, because lung compliance was maintained at 1 h of torpor in the absence of a compositional change in surfactant lipids, the changes in lipid composition observed at 4 and 8 h of torpor are thought to relate to functions of surfactant other than that of maintaining lung compliance.
5
Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels e David Palmer. "Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata". Journal of Applied Physiology 84, n. 1 (1 gennaio 1998): 146–56. http://dx.doi.org/10.1152/jappl.1998.84.1.146.
Testo completoAbstract (sommario):
Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels, and David Palmer. Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata. J. Appl. Physiol. 84(1): 146–156, 1998.—Torpor changes the composition of pulmonary surfactant (PS) in the dunnart Sminthopsis crassicaudata [C. Langman, S. Orgeig, and C. B. Daniels. Am. J. Physiol. 271 ( Regulatory Integrative Comp. Physiol. 40): R437–R445, 1996]. Here we investigated the surface activity of PS in vitro. Five micrograms of phospholipid per centimeter squared surface area of whole lavage (from mice or from warm-active, 4-, or 8-h torpid dunnarts) were applied dropwise onto the subphase of a Wilhelmy-Langmuir balance at 20°C and stabilized for 20 min. After 4 h of torpor, the adsorption rate increased, and equilibrium surface tension (STeq), minimal surface tension (STmin), and the %area compression required to achieve STmin decreased, compared with the warm-active group. After 8 h of torpor, STmin decreased [from 5.2 ± 0.3 to 4.1 ± 0.3 (SE) mN/m]; %area compression required to achieve STmindecreased (from 43.4 ± 1.0 to 27.4 ± 0.8); the rate of adsorption decreased; and STeqincreased (from 26.3 ± 0.5 to 38.6 ± 1.3 mN/m). ST-area isotherms of warm-active dunnarts and mice at 20°C had a shoulder on compression and a plateau on expansion. These disappeared on the isotherms of torpid dunnarts. Samples of whole lavage (from warm-active and 8-h torpor groups) containing 100 μg phospholipid/ml were studied by using a captive-bubble surfactometer at 37°C. After 8 h of torpor, STmin increased (from 6.4 ± 0.3 to 9.1 ± 0.3 mN/m) and %area compression decreased in the 2nd (from 88.6 ± 1.7 to 82.1 ± 2.0) and 3rd (from 89.1 ± 0.8 to 84.9 ± 1.8) compression-expansion cycles, compared with warm-active dunnarts. ST-area isotherms of warm-active dunnarts at 37°C did not have a shoulder on compression. This shoulder appeared on the isotherms of torpid dunnarts. In conclusion, there is a strong correlation between in vitro changes in surface activity and in vivo changes in lipid composition of PS during torpor, although static lung compliance remained unchanged (see Langman et al. cited above). Surfactant from torpid animals is more active at 20°C and less active at 37°C than that of warm-active animals, which may represent a respiratory adaptation to low body temperatures of torpid dunnarts.
6
Lang, Carol J., Anthony D. Postle, Sandra Orgeig, Fred Possmayer, Wolfgang Bernhard, Amiya K. Panda, Klaus D. Jürgens, William K. Milsom, Kaushik Nag e Christopher B. Daniels. "Dipalmitoylphosphatidylcholine is not the major surfactant phospholipid species in all mammals". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 289, n. 5 (novembre 2005): R1426—R1439. http://dx.doi.org/10.1152/ajpregu.00496.2004.
Testo completoAbstract (sommario):
Pulmonary surfactant, a complex mixture of lipids and proteins, lowers the surface tension in terminal air spaces and is crucial for lung function. Within an animal species, surfactant composition can be influenced by development, disease, respiratory rate, and/or body temperature. Here, we analyzed the composition of surfactant in three heterothermic mammals (dunnart, bat, squirrel), displaying different torpor patterns, to determine: 1) whether increases in surfactant cholesterol (Chol) and phospholipid (PL) saturation occur during long-term torpor in squirrels, as in bats and dunnarts; 2) whether surfactant proteins change during torpor; and 3) whether PL molecular species (molsp) composition is altered. In addition, we analyzed the molsp composition of a further nine mammals (including placental/marsupial and hetero-/homeothermic contrasts) to determine whether phylogeny or thermal behavior determines molsp composition in mammals. We discovered that like bats and dunnarts, surfactant Chol increases during torpor in squirrels. However, changes in PL saturation during torpor may not be universal. Torpor was accompanied by a decrease in surfactant protein A in dunnarts and squirrels, but not in bats, whereas surfactant protein B did not change in any species. Phosphatidylcholine (PC)16:0/16:0 is highly variable between mammals and is not the major PL in the wombat, dunnart, shrew, or Tasmanian devil. An inverse relationship exists between PC16:0/16:0 and two of the major fluidizing components, PC16:0/16:1 and PC16:0/14:0. The PL molsp profile of an animal species is not determined by phylogeny or thermal behavior. We conclude that there is no single PL molsp composition that functions optimally in all mammals; rather, surfactant from each animal is unique and tailored to the biology of that animal.
7
Knight, K. "DUNNARTS' DEVELOPMENT ADAPTS". Journal of Experimental Biology 215, n. 9 (11 aprile 2012): iii. http://dx.doi.org/10.1242/jeb.073072.
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Yousef, A., e L. Selwood. "Embryonic development in culture of the marsupials Antechinus stuartii (Macleay) and Sminthopsis macroura (Spencer) during preimplantation stages". Reproduction, Fertility and Development 5, n. 4 (1993): 445. http://dx.doi.org/10.1071/rd9930445.
Testo completoAbstract (sommario):
Forty-nine blastocysts from 11 brown antechinus, Antechinus stuartii, and 96 blastocysts from 17 stripe-faced dunnarts, Sminthopsis macroura, were used to develop a culture system for embryos during preimplantation stages. Blastocysts of brown antechinus were collected on Days 6-9 for unilaminar stages, Days 16-21 for bilaminar stages and Days 20 and 21 for trilaminar stages. Blastocysts of stripe-faced dunnarts were collected on Day 6 for unilaminar stages, Days 6-8 for bilaminar stages and Day 8 for trilaminar stages. Culture media were Dulbecco's modified Eagle's medium (DMEM) with 4.5% glucose and Whittingham's T6 medium both of which were supplemented with 5, 10, 12.5 and 20% fetal calf serum (FCS). Antechinus serum (5%) and bovine serum albumin (0.1%, 0.2%) were also added to some media. Human amniotic fluid (HAF) and Monomed media were also tested. Blastocysts were cultured at 35 degrees C in 5% CO2 in air. DMEM + 10% FCS and HAF supported normal development for the longest periods and over the greatest range of stages. Developmental failure of blastocysts in vitro during expansion of the unilaminar blastocyst and formation of the bilaminar blastocyst suggests that these stages may be dependent on uterine signals. When cultured in DMEM + 10% FCS, the rate of development of bilaminar and trilaminar blastocysts into organogenesis was 4 h slower than in vivo in the stripe-faced dunnart and about 6 h slower than in vivo in the brown antechinus. Embryos of stripe-faced dunnarts were cultured to within 18 h of birth.
9
Webb, Jonathan K., David Pearson e Richard Shine. "A small dasyurid predator (Sminthopsis virginiae) rapidly learns to avoid a toxic invader". Wildlife Research 38, n. 8 (2011): 726. http://dx.doi.org/10.1071/wr10206.
Testo completoAbstract (sommario):
Context Invasive species are a leading cause of extinctions, yet predicting their ecological impacts poses a formidable challenge for conservation biologists. When native predators are naïve to invaders, they may lack appropriate behaviours to deal with the invader. In northern Australia, the invasion of the highly toxic cane toad (Rhinella marina) has caused serious population declines of reptilian and mammalian predators that are ill equipped to deal with toad toxins. Cane toads recently invaded the Kimberley region of Western Australia, where they potentially threaten several species of small dasyurid predators. Aims We investigated whether red-cheeked dunnarts (Sminthopsis virginiae) attack cane toads, and if so, whether individuals subsequently learn to avoid toads as prey. Methods We quantified feeding and learning behaviours in toad-naïve red-cheeked dunnarts from the north Kimberley in Western Australia. Key results All toad-naïve dunnarts attacked toads during their first encounter. Most dunnarts bit the toad on the snout, killed it by biting the cranium, and consumed the toad snout-first, thereby initially avoiding the toad’s parotoid glands. Most dunnarts partially consumed toads before discarding them, and only one animal showed visible signs of toad poisoning. All dunnarts rapidly learnt to avoid toads as prey after one or two encounters. Predators rejected toads as prey for the duration of the study (22 days), suggesting long-term retention of the knowledge that toads are noxious. Conclusions Our results show that red-cheeked dunnarts rapidly learn to avoid cane toads as prey. Implications Our study was limited by small sample sizes, but our results suggest that small dasyurids can adapt to the cane toad invasion via taste aversion learning.
10
Woolley, P. A. "Diurnal resting sites of the nocturnal dasyurid marsupial Sminthopsis douglasi in Bladensburg National Park, Queensland". Australian Mammalogy 39, n. 1 (2017): 121. http://dx.doi.org/10.1071/am16013.
Testo completoAbstract (sommario):
An attempt has been made to determine where Julia Creek dunnarts (Sminthopsis douglasi), small nocturnal dasyurid marsupials, rest during the day under differing seasonal conditions. A short-term study was carried out in Bladensburg National Park, near the southern edge of its known distribution on the Mitchell grass downs in Queensland. Radio-collared individuals were located in cracks and holes. None of the males and females (including one with young in the pouch) were found to use the same resting site over periods of up to nine days, suggesting that they may be nomadic. Climatic factors may have affected the size of the dunnart population over the course of the study.
11
Paolino, Annalisa, Laura R. Fenlon, Peter Kozulin, Elizabeth Haines, Jonathan W. C. Lim, Linda J. Richards e Rodrigo Suárez. "Differential timing of a conserved transcriptional network underlies divergent cortical projection routes across mammalian brain evolution". Proceedings of the National Academy of Sciences 117, n. 19 (20 aprile 2020): 10554–64. http://dx.doi.org/10.1073/pnas.1922422117.
Testo completoAbstract (sommario):
A unique combination of transcription factor expression and projection neuron identity demarcates each layer of the cerebral cortex. During mouse and human cortical development, the transcription factor CTIP2 specifies neurons that project subcerebrally, while SATB2 specifies neuronal projections via the corpus callosum, a large axon tract connecting the two neocortical hemispheres that emerged exclusively in eutherian mammals. Marsupials comprise the sister taxon of eutherians but do not have a corpus callosum; their intercortical commissural neurons instead project via the anterior commissure, similar to egg-laying monotreme mammals. It remains unknown whether divergent transcriptional networks underlie these cortical wiring differences. Here, we combine birth-dating analysis, retrograde tracing, gene overexpression and knockdown, and axonal quantification to compare the functions of CTIP2 and SATB2 in neocortical development, between the eutherian mouse and the marsupial fat-tailed dunnart. We demonstrate a striking degree of structural and functional homology, whereby CTIP2 or SATB2 of either species is sufficient to promote a subcerebral or commissural fate, respectively. Remarkably, we reveal a substantial delay in the onset of developmental SATB2 expression in mice as compared to the equivalent stage in dunnarts, with premature SATB2 overexpression in mice to match that of dunnarts resulting in a marsupial-like projection fate via the anterior commissure. Our results suggest that small alterations in the timing of regulatory gene expression may underlie interspecies differences in neuronal projection fate specification.
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Cole, J. R., e D. F. Gibson. "Distribution of Stripe-faced Dunnarts Sminthopsis macroura and Desert Dunnarts S. youngsoni (Marsupialia: Dasyuridae) in the Northern Territory." Australian Mammalogy 14, n. 2 (1991): 129. http://dx.doi.org/10.1071/am91014.
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Bleicher, Sonny S., e Christopher R. Dickman. "Bust economics: foragers choose high quality habitats in lean times". PeerJ 4 (21 gennaio 2016): e1609. http://dx.doi.org/10.7717/peerj.1609.
Testo completoAbstract (sommario):
In environments where food resources are spatially variable and temporarily impoverished, consumers that encounter habitat patches with different food density should focus their foraging initially where food density is highest before they move to patches where food density is lower. Increasing missed opportunity costs should drive individuals progressively to patches with lower food density as resources in the initially high food density patches deplete. To test these expectations, we assessed the foraging decisions of two species of dasyurid marsupials (dunnarts:Sminthopsis hirtipesandS. youngsoni) during a deep drought, or bust period, in the Simpson Desert of central Australia. Dunnarts were allowed access to three patches containing different food densities using an interview chamber experiment. Both species exhibited clear preference for the high density over the lower food density patches as measured in total harvested resources. Similarly, when measuring the proportion of resources harvested within the patches, we observed a marginal preference for patches with initially high densities. Models analyzing behavioral choices at the population level found no differences in behavior between the two species, but models analyzing choices at the individual level uncovered some variation. We conclude that dunnarts can distinguish between habitat patches with different densities of food and preferentially exploit the most valuable. As our observations were made during bust conditions, experiments should be repeated during boom times to assess the foraging economics of dunnarts when environmental resources are high.
14
Wood, Philip G., Olga V. Lopatko, Sandra Orgeig, Jean M. P. Joss, Allan W. Smits e Christopher B. Daniels. "Control of pulmonary surfactant secretion: an evolutionary perspective". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, n. 3 (1 marzo 2000): R611—R619. http://dx.doi.org/10.1152/ajpregu.2000.278.3.r611.
Testo completoAbstract (sommario):
Pulmonary surfactant, a mixture consisting of phospholipids (PL) and proteins, is secreted by type II cells in the lungs of all air-breathing vertebrates. Virtually nothing is known about the factors that control the secretion of pulmonary surfactant in nonmammalian vertebrates. With the use of type II cell cultures from Australian lungfish, North American bullfrogs, and fat-tailed dunnarts, we describe the autonomic regulation of surfactant secretion among the vertebrates. ACh, but not epinephrine (Epi), stimulated total PL and disaturated PL (DSP) secretion from type II cells isolated from Australian lungfish. Both Epi and ACh stimulated PL and DSP secretion from type II cells of bullfrogs and fat-tailed dunnarts. Neither Epi nor ACh affected the secretion of cholesterol from type II cell cultures of bullfrogs or dunnarts. Pulmonary surfactant secretion may be predominantly controlled by the autonomic nervous system in nonmammalian vertebrates. The parasympathetic nervous system may predominate at lower body temperatures, stimulating surfactant secretion without elevating metabolic rate. Adrenergic influences on the surfactant system may have developed subsequent to the radiation of the tetrapods. Furthermore, ventilatory influences on the surfactant system may have arisen at the time of the evolution of the mammalian bronchoalveolar lung. Further studies using other carefully chosen species from each of the vertebrate groups are required to confirm this hypothesis.
15
Leslie, Alexandra M., Mathew Stewart, Elizabeth Price e Adam J. Munn. "Daily changes in food availability, but not long-term unpredictability, determine daily torpor-bout occurrences and frequency in stripe-faced dunnarts (Sminthopsis macroura)". Australian Journal of Zoology 63, n. 1 (2015): 12. http://dx.doi.org/10.1071/zo14058.
Testo completoAbstract (sommario):
Daily torpor, a short-term reduction in body temperature and metabolism, is an energy-saving strategy that has been interpreted as an adaptation to unpredictable resource availability. However, the effect of food-supply variability on torpor, separately from consistent food restriction, remains largely unexamined. In this study, we investigated the effect of unpredictable food availability on torpor in stripe-faced dunnarts (Sminthopsis macroura). After a control period of ad libitum feeding, dunnarts were offered 65% of their average daily ad libitum intake over 31 days, either as a constant restriction (i.e. as equal amount of food offered each day) or as an unpredictable schedule of feed offered, varied daily as 0%, 30%, 60%, 100% or 130% of ad libitum. Both feeding groups had increased torpor-bout occurrences (as a proportion of all dunnarts on a given day) and torpor-bout frequency (average number of bouts each day) when on a restricted diet compared with ad libitum feeding, but torpor frequency did not differ between the consistently restricted and unpredictably restricted groups. Most importantly, torpor occurrence and daily bout frequency by the unpredictably restricted group appeared to change in direct association with the amount of food offered on each day; torpor frequency was higher on days of low food availability. Our data do not support the interpretation that torpor is a response to unpredictable food availability per se, but rather that torpor allowed a rapid adjustment of energy expenditure to manage daily fluctuations in food availability.
16
Bishop, N., M. Bulbert, S. Carr, S. Kroker e J. Millikan. "Sonographic Analysis of Vocalisations in Captive Dunnarts, Sminthopsis crassicaudata." Australian Mammalogy 18, n. 1 (1995): 99. http://dx.doi.org/10.1071/am95099.
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Bennison, Kerrie, Christopher R. Dickman e Robert Godfree. "Habitat use and ecological observations of the Ooldea dunnart (Sminthopsis ooldea) at Uluru–Kata Tjuta National Park, Northern Territory". Australian Mammalogy 35, n. 2 (2013): 175. http://dx.doi.org/10.1071/am12048.
Testo completoAbstract (sommario):
The Ooldea dunnart (Sminthopsis ooldea) is a small (10–11 g) and poorly known dasyurid marsupial that is endemic to the central and western arid regions of Australia. Surveys carried out at Uluru–Kata Tjuta National Park, Northern Territory, from 1994 to 2010 yielded 37 captures of this elusive species, providing novel insights into its biology. Most captures were made in pitfall traps, with spring breeding confirmed by the presence of pregnant or lactating females during October and November. Animals were captured in mallee and mulga woodland and spinifex (Triodia spp.) dominated dune fields and sand plains. Capture rates were variable in most habitat types, but were relatively consistent in one site dominated by mulga (Acacia aneura). Although we found no consistent association between captures of S. ooldea and prior rainfall, fewest animals were captured in the two wettest years of the study. Ooldea dunnarts showed no clear response to fire. We suggest that mulga is a key habitat for S. ooldea, but also that the demography of this species may be shaped by biotic and/or abiotic factors that remain to be fully elucidated.
18
Woolley, P. A. "The Julia Creek dunnart, Sminthopsis douglasi (Marsupialia : Dasyuridae): breeding of a threatened species in captivity and in wild populations". Australian Journal of Zoology 63, n. 6 (2015): 411. http://dx.doi.org/10.1071/zo15056.
Testo completoAbstract (sommario):
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.
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Krajewski, Carey, Frank E. Anderson, Patricia A. Woolley e Michael Westerman. "Molecular Evidence for a Deep Clade of Dunnarts (Marsupialia: Dasyuridae: Sminthopsis)". Journal of Mammalian Evolution 19, n. 4 (13 giugno 2012): 265–76. http://dx.doi.org/10.1007/s10914-012-9204-3.
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Hume, I. D., C. Smith e P. A. Woolley. "Anatomy and physiology of the gastrointestinal tract of the Julia Creek dunnart, Sminthopsis douglasi (Marsupialia : Dasyuridae)". Australian Journal of Zoology 48, n. 5 (2000): 475. http://dx.doi.org/10.1071/zo00016.
Testo completoAbstract (sommario):
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.
21
Woolley, P. A., e S. L. Gilfillan. "Confirmation of polyoestry in captive White-footed Dunnarts, Sminthopsis leucopus (Marsupialia: Dasyuridae)." Australian Mammalogy 14, n. 2 (1991): 137. http://dx.doi.org/10.1071/am91016.
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Suárez, Rodrigo, Annalisa Paolino, Laura R. Fenlon, Laura R. Morcom, Peter Kozulin, Nyoman D. Kurniawan e Linda J. Richards. "A pan-mammalian map of interhemispheric brain connections predates the evolution of the corpus callosum". Proceedings of the National Academy of Sciences 115, n. 38 (4 settembre 2018): 9622–27. http://dx.doi.org/10.1073/pnas.1808262115.
Testo completoAbstract (sommario):
The brain of mammals differs from that of all other vertebrates, in having a six-layered neocortex that is extensively interconnected within and between hemispheres. Interhemispheric connections are conveyed through the anterior commissure in egg-laying monotremes and marsupials, whereas eutherians evolved a separate commissural tract, the corpus callosum. Although the pattern of interhemispheric connectivity via the corpus callosum is broadly shared across eutherian species, it is not known whether this pattern arose as a consequence of callosal evolution or instead corresponds to a more ancient feature of mammalian brain organization. Here we show that, despite cortical axons using an ancestral commissural route, monotremes and marsupials share features of interhemispheric connectivity with eutherians that likely predate the origin of the corpus callosum. Based on ex vivo magnetic resonance imaging and tractography, we found that connections through the anterior commissure in both fat-tailed dunnarts (Marsupialia) and duck-billed platypus (Monotremata) are spatially segregated according to cortical area topography. Moreover, cell-resolution retrograde and anterograde interhemispheric circuit mapping in dunnarts revealed several features shared with callosal circuits of eutherians. These include the layered organization of commissural neurons and terminals, a broad map of connections between similar (homotopic) regions of each hemisphere, and regions connected to different areas (heterotopic), including hyperconnected hubs along the medial and lateral borders of the cortex, such as the cingulate/motor cortex and claustrum/insula. We therefore propose that an interhemispheric connectome originated in early mammalian ancestors, predating the evolution of the corpus callosum. Because these features have been conserved throughout mammalian evolution, they likely represent key aspects of neocortical organization.
23
Tomlinson, Sean, Philip C. Withers e Shane K. Maloney. "Comparative thermoregulatory physiology of two dunnarts, Sminthopsis macroura and Sminthopsis ooldea (Marsupialia : Dasyuridae)". Australian Journal of Zoology 60, n. 1 (2012): 54. http://dx.doi.org/10.1071/zo12034.
Testo completoAbstract (sommario):
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.
24
Bonney, Kathryn R., e C. D. L. Wynne. "Visual discrimination learning and strategy behavior in the fat-tailed dunnarts ( Sminthopsis crassicaudata )." Journal of Comparative Psychology 116, n. 1 (2002): 55–62. http://dx.doi.org/10.1037/0735-7036.116.1.55.
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25
Tomlinson, S., P. C. Withers e S. K. Maloney. "Flexibility in thermoregulatory physiology of two dunnarts, Sminthopsis macroura and Sminthopsis ooldea (Marsupialia; Dasyuridae)". Journal of Experimental Biology 215, n. 13 (6 giugno 2012): 2236–46. http://dx.doi.org/10.1242/jeb.065516.
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26
Start, A. N., D. Moro, M. Adams e R. Bencini. "Dunnarts from Boullanger Island: new evidence and reassessment of a taxonomic issue with resource implications." Australian Mammalogy 28, n. 1 (2006): 51. http://dx.doi.org/10.1071/am06006.
Testo completoAbstract (sommario):
Crowther et al. (1999) described an island population of an Australian dasyurid marsupial, Sminthopsis griseoventer, as a new subspecies on molecular (allozyme) and morphological grounds despite a previously published, contradictory genetic study and evidence of sympatry with its mainland conspecific. The legitimacy of this taxonomic arrangement has implications for the allocation of scarce management resources because the new taxon could be considered 'Critically Endangered'. Samples of the original tissues from which the molecular data cited by Crowther et al. were obtained no longer exist. Therefore, salient components of that work were rerun with fresh tissue and the results used to reassess evidence that the island population warrants recognition as a subspecies. We conclude that neither the molecular nor the morphological data supports differentiation at taxonomic or evolutionarily significant levels. Nevertheless, there is a good case for recognising the island population as an important management unit. This case study emphasises the importance of sound taxonomy determined by macro and molecular characters as a prerequisite to allocating resources for conservation.
27
Paull, David C. "Refuge sites, activity and torpor in wild common dunnarts (Sminthopsis murina) in a temperate heathland". Australian Mammalogy 35, n. 2 (2013): 153. http://dx.doi.org/10.1071/am12016.
Testo completoAbstract (sommario):
This telemetric study describes patterns of movement, activity, refuge-site use and torpor in free-living Sminthopsis murina over one autumn/winter period in a warm-temperate habitat. S. murina were found to rest during the day in burrows and hollow logs. Individuals maintained several daytime refuges and foraged over several hectares each night. They were found to prefer agamid burrows where a daily temperature of 10.3–15.8°C was maintained when ambient surface temperatures varied between 3.5 and 24.6°C. Torpor was employed in 12 of 13 complete resting periods recorded. Dunnarts were found to use both long (>6 h) and short (<4 h) torpor bouts with a minimum skin temperature of 17.2–26.7°C. Typically, torpor occurred in the morning, though bouts into the afternoon were also recorded. Arousal rates from torpor were variable and were achieved by endogenous and passive means. Normothermic rest bouts tended to be short (mostly <3 h) though longer periods were recorded, with a mean resting skin temperature of 32.3 ± 0.8°C. The variable physiological responses observed in S. murina seem to follow a facultative pattern, and, along with long activity periods and their use of refuge sites, may be linked to variable invertebrate activity during cooler months.
28
Nagy, KA, AK Lee, RW Martin e MR Fleming. "Field Metabolic-Rate and Food Requirement of a Small Dasyurid Marsupial, Sminthopsis-Crassicaudata". Australian Journal of Zoology 36, n. 3 (1988): 293. http://dx.doi.org/10.1071/zo9880293.
Testo completoAbstract (sommario):
Field metabolic rates (FMRs) and rates of water flux in free-ranging fat-tailed dunnarts, Sminthopsis crassicaudata, were measured during spring (late October) using doubly labelled water. Feeding rates were estimated on the basis of water and energy fluxes. FMRs averaged 68.7 kJ d-' in adults (mean body mass= 16.6 g), and were 29.2 kJ d-' in juveniles (6.1 g). These FMRs are 6.6 times basal metabolic rate (BMR), and are much higher than the hypothetical maxima of four to five times BMR. Other dasyurid marsupials also have high FMR/BMR ratios, but so does a small petaurid marsupial. S. crassicaudata consumed 80-90% of its body mass in arthropods each day. The diet of arthropods apparently provided enough water for the animals to maintain water balance without drinking during this study.
29
Buttemer, William A., Paul G. Story, Karen J. Fildes, Russell V. Baudinette e Lee B. Astheimer. "Fenitrothion, an organophosphate, affects running endurance but not aerobic capacity in fat-tailed dunnarts (Sminthopsis crassicaudata)". Chemosphere 72, n. 9 (luglio 2008): 1315–20. http://dx.doi.org/10.1016/j.chemosphere.2008.04.054.
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STRACHAN, JESSICA, LING-YU E. CHANG, MATTHEW J. WAKEFIELD, JENNIFER A. MARSHALL GRAVES e SAMIR S. DEEB. "Cone visual pigments of the Australian marsupials, the stripe-faced and fat-tailed dunnarts: Sequence and inferred spectral properties". Visual Neuroscience 21, n. 3 (maggio 2004): 223–29. http://dx.doi.org/10.1017/s0952523804213281.
Testo completoAbstract (sommario):
Studies of color vision in marsupial mammals have been very limited. Two photoreceptor genes have been characterized from the tammar wallaby, but a third cone pigment was suggested by microspectrophotometric measurements on cone photoreceptors in two other species, including the fat-tailed dunnart, Sminthopsis crassicaudata. To determine the sequence and infer absorption maxima of the cone photoreceptor pigments of S. crassicaudata and the related stripe-faced dunnart (Sminthopsis macroura), we have used evolutionarily conserved sequences of the cone pigments of other species, including the tammar wallaby, to design primers to amplify the S. macroura and S. crassicaudata pigment sequences by the polymerase chain reaction (PCR) using genomic DNA or retinal cDNA as a template. These primers will be useful for amplifying cone opsin coding sequences from a variety of vertebrates. Amplified products were directly sequenced to determine gene structure and coding sequences. The inferred amino acid sequences of the cone visual pigments indicated that both species have middle-wave-sensitive (MWS) pigments with a predicted absorption maximum (λmax) at 530 nm, and ultraviolet-sensitive (UVS) pigments with a predicted λmax at 360 nm. The MWS pigments of the two species differ by two, and UVS by three amino acid positions. No evidence was obtained for a third cone pigment in either species.
31
Frank, A., e T. Soderquist. "The importance of refuge habitat in the local conservation of stripe-faced dunnarts Sminthopsis macroura on arid rangelands." Australian Mammalogy 27, n. 1 (2005): 75. http://dx.doi.org/10.1071/am05075.
Testo completoAbstract (sommario):
ANTHROPOGENIC change to Australian habitats accelerated rapidly during the late 1800s as sheep grazing spread across the continent. In particular, intensive grazing in arid and semi-arid regions is believed to have vastly altered vegetation communities, triggered extensive soil erosion, and reduced shelter available to small mammals, thus increasing their vulnerability to predation (Morton 1990). It is not surprising, then, that since European settlement 32 species (42%) of mammals inhabiting the arid zone of Australia have become extinct (Landsberg et al. 1997), and many others have suffered major range reductions or are currently considered widespread but rare. This faunal collapse was due to multiple factors (Burbidge and McKenzie 1989; Morton 1990), but the most consistent predictor of marsupial decline is geographic overlap with domestic sheep (Fisher et al. 2003). While overgrazing is a serious broadscale problem, the destruction of naturally occurring pockets of highquality habitat probably played a critical role in the extirpation of species that relied on refugia for survival during droughts (Morton 1990).
32
Every, Alison L., Lynne Selwood, Natalia Castano-Rodriguez, Wei Lu, Helen M. Windsor, Janet LK Wee, Agnieszka Swierczak et al. "Did transmission of Helicobacter pylori from humans cause a disease outbreak in a colony of Stripe-faced Dunnarts (Sminthopsis macroura)?" Veterinary Research 42, n. 1 (2011): 26. http://dx.doi.org/10.1186/1297-9716-42-26.
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33
Bennison, Clifford, J. Anthony Friend, Timothy Button, Harriet Mills, Cathy Lambert e Roberta Bencini. "Potential impacts of poison baiting for introduced house mice on native animals on islands in Jurien Bay, Western Australia". Wildlife Research 43, n. 1 (2016): 61. http://dx.doi.org/10.1071/wr15126.
Testo completoAbstract (sommario):
Context House mice (Mus domesticus) are present on Boullanger and Whitlock islands, Western Australia, and could potentially threaten populations of the dibbler (Parantechinus apicalis) and grey-bellied dunnart (Sminthopsis griseoventer) through competition for resources. A workshop in 2007 recommended a study to assess the feasibility of eradicating house mice from the islands by using poison baits and of the risk posed to non-target native species. Aim We aimed to assess the risk to non-target native species if poison baiting was used to eradicate house mice on Boullanger and Whitlock islands. Methods Non-toxic baits containing the bait marker rhodamine B were distributed on Boullanger Island and on the mouse free Escape Island to determine the potential for primary poisoning. Acceptance of baits by mammals was measured through sampling and analysis of whiskers, and by reptiles through observations of dye in faeces. To determine the potential for secondary exposure to poison, the response of dibblers to mouse carcasses was observed using motion-activated cameras. Bait acceptance was compared using two methods of delivery, namely, scattering in the open and delivery in polyvinyl chloride (PVC) tubes. A cafeteria experiment of bait consumption by dibblers was also undertaken using captive animals held at the Perth Zoo. Ten dibblers were offered non-toxic baits containing rhodamine B in addition to their normal meals; consumption of bait and the presence of dye in whiskers were measured. Key results Bait acceptance on the islands was high for house mice (92% of individuals) and dibblers (48%) and it was independent of bait-delivery technique. There was no evidence of bait acceptance by grey-bellied dunnarts. Dibblers may consume mice carcasses if available; however, no direct consumption of mice carcasses was observed with movement sensor cameras but one dibbler was observed removing a mouse carcass and taking it away. During the cafeteria experiment, 9 of 10 captive dibblers consumed baits. Conclusions This investigation demonstrated that dibblers consume baits readily and island populations would experience high mortality if exposed to poison baits. Poison baiting could effectively eradicate mice from Boullanger and Whitlock islands but not without mortality for dibblers. Implications Toxic baits could be used to eradicate mice from Boullanger and Whitlock islands, provided that non-target species such as dibblers were temporarily removed from the islands before the application of baits.
34
Yeo, Jia Hao, Bronwyn M. McAllan e Stuart T. Fraser. "Scanning Electron Microscopy Reveals Two Distinct Classes of Erythroblastic Island Isolated from Adult Mammalian Bone Marrow". Microscopy and Microanalysis 22, n. 2 (22 febbraio 2016): 368–78. http://dx.doi.org/10.1017/s1431927616000155.
Testo completoAbstract (sommario):
AbstractErythroblastic islands are multicellular clusters in which a central macrophage supports the development and maturation of red blood cell (erythroid) progenitors. These clusters play crucial roles in the pathogenesis observed in animal models of hematological disorders. The precise structure and function of erythroblastic islands is poorly understood. Here, we have combined scanning electron microscopy and immuno-gold labeling of surface proteins to develop a better understanding of the ultrastructure of these multicellular clusters. The erythroid-specific surface antigen Ter-119 and the transferrin receptor CD71 exhibited distinct patterns of protein sorting during erythroid cell maturation as detected by immuno-gold labeling. During electron microscopy analysis we observed two distinct classes of erythroblastic islands. The islands varied in size and morphology, and the number and type of erythroid cells interacting with the central macrophage. Assessment of femoral marrow isolated from a cavid rodent species (guinea pig,Cavis porcellus) and a marsupial carnivore species (fat-tailed dunnarts,Sminthopsis crassicaudata) showed that while the morphology of the central macrophage varied, two different types of erythroblastic islands were consistently identifiable. Our findings suggest that these two classes of erythroblastic islands are conserved in mammalian evolution and may play distinct roles in red blood cell production.
35
Elsworth, P., D. Berman e M. Brennan. "Changes in small native animal populations following control of European rabbits (Oryctolagus cuniculus) by warren ripping in the Australian arid zone". Wildlife Research 46, n. 4 (2019): 343. http://dx.doi.org/10.1071/wr18088.
Testo completoAbstract (sommario):
Context European rabbits have a great impact on native vegetation and small vertebrates in Australia. Rabbits consume vegetation and promote invasive plants and invasive predators, and compete directly and indirectly with native animals suppressing those populations. Aims We explored the changes in small native vertebrates and invertebrates following the removal of rabbits. Methods Warren ripping was undertaken on a property in south-western Queensland at four sites and the results of pitfall trapping were compared with four nearby paired control sites. Invertebrates and small mammals were counted in pitfall traps, and bird surveys were conducted in all treatment and control sites. Key results Following a rabbit-control program, we observed a four-fold increase in the number of dunnarts trapped in treatment plots, whereas no change was observed in control plots. The spring following the rabbit-control program also saw an increase in some lizards in treatment plots. Conclusions The presence of rabbits in arid-zone Australia can suppress native animal populations. Implications Many species of small native mammals and lizards rely on food sources that fluctuate greatly with environmental conditions. The presence of rabbits altering the landscape, supporting introduced predators, reducing vegetation and, therefore, insects, adds increased pressure for insectivorous species. Rabbit control through warren ripping in arid-zone Australia is an effective method to reduce rabbit numbers, and allowed for an increase in small vertebrates in treated areas.
36
Monamy, Vaughan, e Barry J. Fox. "Differential habitat use by a local population of subadult common dunnarts, Sminthopsis murina, following wildfire in coastal wet heath, New South Wales, Australia". Wildlife Research 32, n. 7 (2005): 617. http://dx.doi.org/10.1071/wr04105.
Testo completoAbstract (sommario):
Little has been published about Sminthopsis murina, a small insectivorous marsupial encountered infrequently during trapping studies. Individuals favour vegetation associations found in recently burnt heathlands and forests; however, individuals rarely remain in such areas long enough for repeated capture. We report an unusual occurrence of habitat fidelity by a dense population of subadult S. murina in coastal wet heath, New South Wales, Australia. Individuals were captured repeatedly in the first 16 months following wildfire (30 subadults trapped 154 times: recapture rate = 80%). Densities peaked 10 months after fire at 3.75 individuals ha–1. More males than females were captured (23 males, 7 females). Habitat analyses revealed differential use of regenerating coastal wet heathland by S. murina. Significantly more captures were made in areas of high soil moisture in the first six months following fire. Captures then decreased in these areas but increased where soil moisture had been lower and where vegetation had been growing more slowly. Beyond the 1995/96 breeding season, regenerating vegetation became increasingly dense and less patchy and captures of S. murina ultimately declined to zero. This paper records a rare opportunity to examine habitat preferences of a single cohort of subadult S. murina. Habitat use may have been determined by the presence of a narrow range of vegetation structure.
37
Czarny, N. A., J. I. Garnham, M. S. Harris e J. C. Rodger. "Comparison of the production, quality, and in vitro maturation capacity of oocytes from untreated cycling and intermediate phase equine serum gonadotropin-treated fat-tailed dunnarts (Sminthopsis crassicaudata)". REPRODUCTION 138, n. 1 (luglio 2009): 23–31. http://dx.doi.org/10.1530/rep-09-0064.
Testo completoAbstract (sommario):
This study describes ovarian changes during the natural and stimulated reproductive cycle of breeding (≤12 month) and retired (>12 month) fat-tailed dunnarts, Sminthopsis crassicaudata. Increased urinary cornified epithelial cells and the influx of leukocytes defined day 0, at which time the naturally cycling females had already ovulated; at day 16 females had no antral follicles, but by day 20 antral follicles had begun to develop. There was no difference between naturally cycling breeding and retired females. Females were stimulated with 1 IU equine serum gonadotropin (eSG) during the intermediate phase on day 16 and killed 3, 4, or 5 days later. Stimulation resulted in a significant increase in the number of growing antral follicles but retired females demonstrated a reduced response. Upon collection from breeding females 4 days following eSG stimulation, 100% of oocytes were at the first polar body (PB1) stage, those collected from retired females were immature upon collection but within 48 h 98.2±1.9% were cultured to the PB1 stage. The rate of ovulation was high in breeding females 5 days following stimulation but retired females were less reliable, and in both groups all oocytes were degraded. This is the first study to describe a reliable technique, involving ovarian stimulation during the intermediate phase and segregation of age groups, allowing the collection of a large number of healthy PB1 stage oocytes from S. crassicaudata. This is important for the development of further assisted reproductive techniques for this species and threatened dasyurids.
38
Haynes, JI, e GW Skidmore. "Hematology of the Dasyurid Marsupials Sminthopsis-Crassicaudata and Sminthopsis-Macroura". Australian Journal of Zoology 39, n. 2 (1991): 157. http://dx.doi.org/10.1071/zo9910157.
Testo completoAbstract (sommario):
Various haematological parameters and morphological aspects were determined for blood collected from 52 fat-tailed dunnarts, Sminthopsis crassicaudata. Compared with those of other marsupials, the erythrocyte and leukocyte counts, haemoglobin concentration and packed cell volume were low, whereas the percentage of reticulocytes (8%) was high. Differential counts revealed a sexual dimorphism for the percentage of neutrophils and lymphocytes present. Blood cell counts, including reticulocyte and differential counts, were also performed on blood from 11 animals of a closely related species, Sminthopsis macroura. For both species mature and developing blood cells from circulating blood, bone marrow, and intestinal mucosa were examined with the light and transmission electron microscope. The unusual features of peripheral blood were: the band forms of neutrophils with annular nuclei; a high percentage of hypersegmented neutrophils; the persistence of polyribosomes in many circulating red blood cells which otherwise appeared mature; the lack of basophils; the absence of eosinophils in S. crassicaudata and the rarity of these leukocytes in S. macroura. The ultrastructure of the developing and circulating blood cells was similar to that previously described for humans, except for the later stages of nuclear maturation in some neutrophils. In these cells annular nuclei developed into rings of beads that then broke to give the typical lobulated nuclei of mature neutrophils. All three types of granulocytes were found in the bone marrow. The leukocytic granules appeared slightly different from their human counterparts.
39
Story, Paul, Michael J. Hooper, Lee B. Astheimer e William A. Buttemer. "Acute oral toxicity of the organophosphorus pesticide fenitrothion to fat-tailed and stripe-faced dunnarts and its relevance for pesticide risk assessments in Australia". Environmental Toxicology and Chemistry 30, n. 5 (4 marzo 2011): 1163–69. http://dx.doi.org/10.1002/etc.478.
Testo completo
40
Yousef, A., e L. Selwood. "The type and differentiation of cells in vitro from unilaminar and bilaminar blastocysts of two marsupials, Antechinus stuartii and Sminthopsis macroura". Reproduction, Fertility and Development 8, n. 4 (1996): 743. http://dx.doi.org/10.1071/rd9960743.
Testo completoAbstract (sommario):
The type and ability to differentiate in vitro of cells found in blastocysts of two marsupials were examined. Thirteen unilaminar blastocysts on Day 7 to Day 12 of gestation and 24 bilaminar blastocysts on Day 16 and Day 18 of gestation were collected from 11 brown antechinus, Antechinus stuartii. A total of of 77 unilaminar blastocysts on Day 5 and Day 6 of gestation and a total of 61 bilaminar blastocysts on Day 6 and Day 7 of gestation were collected from 40 stripe-faced dunnarts, Sminthopsis macroura. Pluriblast and trophoblast cells, confined to separate hemispheres, were found in unilaminar and bilaminar blastocysts, establishing that the blastocyst epithelium was not a protoderm. Hypoblast cells were found only in bilaminar blastocysts. Pluriblast and hypoblast cells did not differentiate or proliferate in up to eight weeks in culture. A small number of trophoblast cells transformed to a multinucleate state but the remainder did not proliferate or differentiate further. The presence of murine leukaemia inhibitory factor or medium conditioned by exposure to marsupial fibroblast feeder layer was not required for the maintenance of an undifferentiated state. Differentiation, proliferation and attachment of cells were not influenced by the presence of the yolk mass or the egg coats in culture. The time taken for attachment of dissociated cells varied significantly between cultures with no substrate and with collagen, fibronectin or laminin (P = 0.001, ANOVA) but did not vary significantly between substrates. The substrates did not influence the state of differentiation of the cells.
41
Garrett, Andrew, Virginia Lannigan, Nathanael J. Yates, Jennifer Rodger e Wilhelmina Mulders. "Physiological and anatomical investigation of the auditory brainstem in the Fat-tailed dunnart (Sminthopsis crassicaudata)". PeerJ 7 (30 settembre 2019): e7773. http://dx.doi.org/10.7717/peerj.7773.
Testo completoAbstract (sommario):
The fat-tailed dunnart (Sminthopsis crassicaudata) is a small (10–20 g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5 ms) tone pips at a range of frequencies (4–47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fat-tailed dunnart.
42
Gardner, DK, L. Selwood e M. Lane. "Nutrient uptake and culture of Sminthopsis macroura (stripe-faced dunnart) embryos". Reproduction, Fertility and Development 8, n. 4 (1996): 685. http://dx.doi.org/10.1071/rd9960685.
Testo completoAbstract (sommario):
Glucose and pyruvate uptake by individual embryos were measured in a marsupial species (stripe-faced dunnart) and a eutherian species (mouse). At each stage of development, nutrient uptake by the dunnart embryo was around an order of magnitude greater than that of the mouse embryo. The pattern of glucose uptake by the dunnart embryo was not like that for any eutherian embryo, all of which have a low glucose uptake before the blastocyst stage. Rather, in the dunnart embryo there was a significant increase in glucose uptake after the third cleavage division, increasing from 13.6 pmol embryo h-1 at the 4-cell stage to 34.9 pmol embryo h-1 by the 8-cell stage. This increase in glucose uptake before blastocyst formation may be attributed to an increased energy demand associated with the movement of cells within the dunnart embryo. Using a new culture system, it was possible to culture 66% of dunnart embryos at the 2-4-cell stage and 80% of those at the 8-16-cell stage to the unilaminar blastocyst stage. Embryos cultured from the 2-cell to the 4-cell stage were retarded by around 12 h when they reached the blastocyst stage. Developmental retardation was also reflected in the pattern of nutrient uptake, which lagged behind that of embryos developed in vivo. The present study has shown that it is possible to culture the early marsupial embryo to the blastocyst stage in a serum-free culture system, while concomitantly quantifying embryonic nutrient requirements. Such an approach is essential for species where there is a paucity of material for study.
43
Taggart, DA, CM Leigh, VR Steele, WG Breed, PD Temple-Smith e J. Phelan. "Effect of cooling and cryopreservation on sperm motility and morphology of several species of marsupial". Reproduction, Fertility and Development 8, n. 4 (1996): 673. http://dx.doi.org/10.1071/rd9960673.
Testo completoAbstract (sommario):
The effects of long-term cooling and freezing on sperm motility are described for six marsupial species: the fat-tailed dunnart, koala, brushtail possum, long-footed potoroo, northern brown bandicoot and ring-tailed possum. The effects of up to eight days of cooling at 4 degrees C on the motility of dunnart spermatozoa and the effect of cryopreservation on spermatozoa of the other species were determined. The cryoprotectant used was a Tris-citrate-fructose-egg yolk-glycerol diluent. The percentage and rating of sperm motility, and sperm structure, as determined by light microscopy, were investigated. Sperm motility in the fat-tailed dunnart was retained for up to six days when cooled to 4 degrees C, suggesting that sperm from this species have some degree of tolerance to cold shock. After this time, however, the percentage of motile spermatozoa and their motility rating declined. In all species except the fat-tailed dunnart, reinitiation of motility following cryopreservation occurred across a range of glycerol concentrations (4-17%). Cryoprotectant containing 6% and/or 8% glycerol resulted in little change of motility rating or of the percentage of live sperm after thawing, although there was some decline in the percentage of motile sperm. The unusual structural and motility characteristics of dunnart spermatozoa may account for the lack of success of sperm cryopreservation in this species.
44
ARRESE, C. A., J. RODGER, L. D. BEAZLEY e J. SHAND. "Topographies of retinal cone photoreceptors in two Australian marsupials". Visual Neuroscience 20, n. 3 (maggio 2003): 307–11. http://dx.doi.org/10.1017/s0952523803203096.
Testo completoAbstract (sommario):
Microspectrophotometry indicates the presence of at least three cone visual pigments in two Australian marsupials, the fat-tailed dunnart (Sminthopsis crassicaudata) and honey possum (Tarsipes rostratus). Here we have examined the distribution of cone types using antisera, JH455 and JH492, that recognize short-wavelength-sensitive (SWS) and medium-to-long-wavelength-sensitive (M/LWS) cone opsins, respectively. SWS cones were concentrated in dorso-temporal retina in the dunnart with a shallow decreasing gradient extending to the periphery (2300–1500/mm2). In the honey possum, SWS cones showed a uniform distribution (2700/mm2), except for a slight increase in a narrow peripheral band (3100/mm2). In both species, M/LWS cones dominated and their distributions were similar to those of retinal ganglion cells: a horizontal streak in the dunnart (31,000–21,000/mm2) and a shallow mid-ventral to peripheral gradient in the honey possum (37,000–26,000/mm2). A low number of cones remained unlabeled when the antisera were combined revealing further minority cone population(s). We discuss cone distributions in relation to visual capabilities and requirements of the species.
45
Woinarski, J. C. Z., P. A. Woolley e S. V. Andyck. "The Distribution of The Dunnart Sminthopsis butleri." Australian Mammalogy 19, n. 1 (1996): 27. http://dx.doi.org/10.1071/am96027.
Testo completoAbstract (sommario):
Three records of the dunnart Sminthopsis butleri from Bathurst and Melville Islands extend the known range of this species from a single location in the Kimberley, Western Australia, to the Northern Territory. The meagre ecological information on this species is documented.
46
Witt, Ryan R., John J. Rodger e John C. Rodger. "Breeding in the fat-tailed dunnart following ovarian suppression with the gonadotrophin-releasing hormone agonist Lucrin® Depot". Reproduction, Fertility and Development 30, n. 3 (2018): 507. http://dx.doi.org/10.1071/rd16518.
Testo completoAbstract (sommario):
Lucrin Depot (AbbVie), a 1-month microsphere gonadotrophin-releasing hormone (GnRH) agonist preparation, was investigated as a potential agent to synchronise cycling in the fat-tailed dunnart (Sminthopsis crassicaudata). Forty-eight randomly selected females were treated with 5 or 10 mg kg−1 Lucrin Depot (n = 24 per dose). Eighteen females per treatment had their reproductive activity scored at 4, 8, 12 and 16 weeks using two ovarian (Graafian follicle and corpus luteum status) and two reproductive tract (uterine and vaginal muscularity and vascularity) parameters that formed a reproductive activity score. Six females per treatment were paired with a male at 4 weeks. Fertility was assessed between 8 and 16 weeks by pouch check, and thereafter by dissection. The effects of the 5 and 10 mg kg−1 doses were statistically equivalent. Females showed suppression at 4–8 weeks, an increase in reproductive activity at 8–12 weeks and all were cycling normally at 16 weeks. Six pouch young were born at 12 weeks to two females treated with the 5 mg kg−1 dose. Nine embryos were recovered at 16 weeks from two females treated with the 10 mg kg−1 dose. In conclusion, Lucrin Depot can suppress breeding, and fertile mating can occur in subsequent cycles in the dunnart. There is potential for Lucrin Depot to be used as an assisted breeding tool, but it may need to be combined with ovarian stimulation treatment to achieve practical levels of synchronisation in the fat-tailed dunnart.
47
Woolley, PA. "New records of the Julia Creek dunnart, Sminthopsis douglasi (Marsupialia : Dasyuridae)". Wildlife Research 19, n. 6 (1992): 779. http://dx.doi.org/10.1071/wr9920779.
Testo completoAbstract (sommario):
The Julia Creek dunnart, Sminthopsis douglasi, previously known from only four specimens, the last of which was collected in 1972, has been found alive. The number of known localities has been increased from three to eleven, and its range in the 'downs country' of north-west Queensland extended.
48
Cooper, S. J. B., M. Adams e A. Labrinidis. "Phylogeography of the Australian dunnart Sminthopsis crassicaudata (Marsupialia : Dasyuridae)". Australian Journal of Zoology 48, n. 5 (2000): 461. http://dx.doi.org/10.1071/zo00014.
Testo completoAbstract (sommario):
Analyses of mitochondrial DNA (mtDNA) and allozymes are used to investigate the population genetic structure, phylogeography and systematics of the fat-tailed dunnart, Sminthopsis crassicaudata. Phylogenetic analyses of control region sequences reveal the presence of two major mtDNA haplotype clades. A survey of the distribution of the two clades using diagnostic restriction endonucleases shows that one clade is restricted to southeast Australia whereas the second clade occupies the remaining central to western range of S. crassicaudata. Allozyme electrophoresis also shows concordant patterns of population structure, with significant differences in allele frequency at three loci between populations in the southeast and northwest. Together, the mtDNA and allozyme data provide evidence that S. crassicaudata consists of two Evolutionarily Significant Units (ESUs). The distribution of each ESU is not concordant with the distribution of the subspecies of S. crassicaudata, and we propose that the current subspecies classification neither reflects the major genetic subdivisions present within S. crassicaudata nor would be appropriate for any future conservation management. The level of divergence between mtDNA clades (3.4%) is indicative of cladogenesis in the Pleistocene and reflects a long-term barrier to maternal gene flow between these two populations. One potential historical barrier was Lake Bungunnia, which persisted in the Murray basin over much of the Pleistocene.
49
Witt, Ryan Robert, Ian Ross Forbes, John McBain e John Cameron Rodger. "Ovarian suppression in a marsupial following single treatment with a gonadotrophin-releasing hormone agonist in microspheres". Reproduction, Fertility and Development 28, n. 12 (2016): 1964. http://dx.doi.org/10.1071/rd14423.
Testo completoAbstract (sommario):
The effect of treatment with Lucrin Depot (1 month), a microsphere gonadotrophin-releasing hormone agonist preparation, was investigated in the fat-tailed dunnart (Sminthopsis crassicaudata) as a potential strategy to synchronise cycling. The status of the ovaries (ovarian size, number and size of Graafian follicles and corpora lutea) and reproductive tract (weight, vascularity and muscularity) in twelve untreated females were assessed to establish the activity parameters for randomly selected cycling animals. Thirty-six females were treated with 1 mg kg–1 (n = 12), 10 mg kg–1 (n = 12) or 20 mg kg–1 (n = 12) Lucrin Depot. At 4, 6 and 8 weeks the reproductive tracts were assessed using the criteria developed in the untreated females. All of the females treated with 10 mg kg–1 showed suppression at 4 weeks and 25% showed return of reproductive activity at 8 weeks. A dose of 1 mg kg–1 did not appear to suppress reproductive activity and 20 mg kg–1 gave equivocal results, with evidence of both suppression and activity. The results indicate that Lucrin Depot appears to be a promising agent to regulate and potentially synchronise breeding activity in the fat-tailed dunnart.
50
Geiser, F., Bronwyn M. McAllan e R. M. Brigham. "Daily torpor in a pregnant dunnart (Sminthopsis macroura Dasyuridae: Marsupialia)". Mammalian Biology 70, n. 2 (marzo 2005): 117–21. http://dx.doi.org/10.1016/j.mambio.2004.06.003.
Testo completo