School of BioSciences - Research Publications
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ItemmRNA vaccine against malaria tailored for liver-resident memory T cells(NATURE PORTFOLIO, 2023-09)Malaria is caused by Plasmodium species transmitted by Anopheles mosquitoes. Following a mosquito bite, Plasmodium sporozoites migrate from skin to liver, where extensive replication occurs, emerging later as merozoites that can infect red blood cells and cause symptoms of disease. As liver tissue-resident memory T cells (Trm cells) have recently been shown to control liver-stage infections, we embarked on a messenger RNA (mRNA)-based vaccine strategy to induce liver Trm cells to prevent malaria. Although a standard mRNA vaccine was unable to generate liver Trm or protect against challenge with Plasmodium berghei sporozoites in mice, addition of an agonist that recruits T cell help from type I natural killer T cells under mRNA-vaccination conditions resulted in significant generation of liver Trm cells and effective protection. Moreover, whereas previous exposure of mice to blood-stage infection impaired traditional vaccines based on attenuated sporozoites, mRNA vaccination was unaffected, underlining the potential for such a rational mRNA-based strategy in malaria-endemic regions.
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ItemNo Preview AvailablePlastid phylogenomics of the Eriostemon group (Rutaceae; Zanthoxyloideae): support for major clades and investigation of a backbone polytomy(CSIRO Publishing, 2023-08-22)Most of Australia’s sclerophyllous Rutaceae belong to a clade informally known as the ‘Eriostemon group’ (including 16 genera, ~209 species). We investigated generic relationships in this group using analyses of complete plastome sequence data for 60 species and analyses of a supermatrix including sequences of four plastome spacer regions for 22 additional species. Maximum likelihood, Bayesian inference, and shortcut coalescent phylogenetic analyses produced congruent phylogenies that were highly supported, except for a series of short unsupported branches in the backbone of the Eriostemon group. We found high support for four major clades branching from this polytomy and discuss evolutionary inferences of generic relationships in each lineage. In an effort to resolve the polytomy, we analysed gene tree topologies in tree space, phylogenetic informativeness with likelihood mapping, and conducted topology tests to assess support for all possible topological resolutions of the polytomy. These approaches did not clarify the polytomy, which may be caused by insufficient data, features of plastome evolution, or rapid radiation. Results from analyses of the combined supermatrix dataset suggest that Philotheca section Philotheca is paraphyletic with regards to Drummondita and Geleznowia. In all phylogenies, Philotheca sections Corynonema and Cyanochlamys were not placed with other members of Philotheca.
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ItemGetting out of a mammalian egg: the egg tooth and caruncle of the echidna(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2023-01-03)In the echidna, after development in utero, the egg is laid in the pouch and incubated for 10 days. During this time, the fetuses develop an egg tooth and caruncle to help them hatch. Using rare and unprecedented access to limited echidna pre- and post-hatching tissues, development of the egg tooth and caruncle were assessed by micro-CT, histology and immunofluorescence. Unlike therian tooth germs that develop by placode invagination, the echidna egg tooth developed by evagination, similar to the first teeth in some reptiles and fish. The egg tooth ankylosed to the premaxilla, rather than forming a tooth root with ligamentous attachment found in other mammals, with loss of the egg tooth associated with high levels of activity odontoclasts and apoptosis. The caruncle formed as a separate mineralisation from the adjacent nasal capsule, and as observed in birds and turtles, the nasal region epithelium on top of the nose expressed markers of cornification. Together, this highlights that the monotreme egg tooth shares many similarities with typical reptilian teeth, suggesting that this tooth has been conserved from a common ancestor of mammals and reptiles.
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ItemGenetic sex test for the short-beaked echidna (Tachyglossus aculeatus)(SPRINGER, 2022-04-30)Monotremes (echidnas and platypus) possess five X and four or five Y sex chromosomes, respectively, that evolved independently from the sex chromosomes found in therian mammals. While the platypus has obvious venomous spurs in the male, the short-beaked echidna (Tachyglossus aculeatus) lacks easily identifiable sexually dimorphic characteristics, making it difficult to sex adults out of the breeding season and almost impossible to sex juveniles or embryonic material. Here, we used restriction-site associated DNA sequencing (RADseq) to identify novel sex-specific markers in the short-beaked echidna. We identified and validated a subset of male-specific markers that can be used as a non-invasive genetic sex test for the short-beaked echidna. We also assessed how laboratory conditions, including DNA extraction protocol and number of PCR cycles, can influence the outcome of genetic sex tests. The combined use of these markers will provide a valuable toolkit for researchers, conservationists, and zoo-keepers to reliably and non-invasively determine sex in the short-beaked echidna.
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ItemAssessment and management of reproduction in Australian monotremes and marsupials(CSIRO Publishing, 2019)
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ItemThe Unique Penile Morphology of the Short-Beaked Echidna, Tachyglossus aculeatus(KARGER, 2021-09)Monotremes diverged from therian mammal ancestors approximately 184 million years ago and have a number of novel reproductive characteristics. One in particular is their penile morphology. There are differences between echidna and platypus phalluses, but both are somewhat similar in structure to the reptilian phallus. The echidna penis consists of 4 rosette glans, each of which contains a termination of the quadrifurcate urethra, but it appears that only 2 of the 4 glans become erect at any one time. Despite this, only a few historical references describe the structure of the echidna penis and none provides an explanation for the mechanisms of unilateral ejaculation. This study confirmed that the echidna penis contains many of the same overall structures and morphology as other mammalian penises and a number of features homologous with reptiles. The corpus cavernosum is well supplied with blood, extends up to the base of the glans penis and is primarily responsible for erection. However, the echidna possesses 2 distinct corpora spongiosa separated by a septum, each of which surround the urethra only distal to the initial urethral bifurcation in the glans penis. Together with the bifurcation of the main penile artery, this provides a mechanism by which blood flow could be directed to only one corpus spongiosum at a time to maintain an open urethra that supplies 2 of the 4 glans to facilitate unilateral ejaculation.
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ItemInvestigating the utility of using fecal hormone metabolites as a reproductive management tool for captive short-beaked echidnas (Tachyglossus aculeatus).(Elsevier, 2023-01-01)This study demonstrates the utility of the analysis of fecal hormone metabolites as a reproductive management tool for captive short-beaked echidnas. Over three breeding seasons daily fecal samples were collected from female echidnas (n = 8) that were monitored continuously by video surveillance to confirm key reproductive events. Fecal progesterone metabolite concentrations were elevated above baseline values (448.0 ± 156.3 ng/g) during pregnancy and the luteal phase. However, compared to plasma progesterone the rise in fecal progesterone metabolite concentrations after copulation was delayed (3.3 ± 0.4 versus 8.3 ± 0.6 days, respectively), such that pregnancy was more reliably detected in its latter half when using fecal samples. Mating and oviposition were observed for 14 of the 19 pregnancies resulting in an estimated gestation of 16.7 ± 0.2 days (range 16.0-18.1 d). The estrogen enzyme-immunoassays tested (n = 3) in this study were not suitable for the fecal samples of the echidna. Fecal progesterone metabolites are an effective tool for confirming the timing and occurrence of estrous cycles in captive echidna colonies and can assist zookeepers in identifying possible causes of sub-optimal reproductive success without the unnecessary stress of repeated capture and anaesthesia for blood collection.
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ItemPlasma progesterone secretion during gestation of the captive short-beaked echidna(BIOSCIENTIFICA LTD, 2021-10-01)This study describes the progesterone profile during pregnancy in sexually mature female captive short-beaked echidnas (Tachyglossus aculeatus aculeatus). Echidnas were monitored daily by video surveillance to confirm key reproductive behaviour. Plasma samples were collected and pouch morphology was assessed three times a week. The pouch of the female echidna only develops during gestation and it was possible to create a four-stage grading system using the most distinguishable characteristics of pouch development. Maximum pouch development was associated with declining progesterone concentrations, with the pouch closing in a drawstring-like manner at oviposition. Control of pouch development in pregnant echidnas is not yet clear but later pouch development is associated with a decrease in progesterone and pouch closure and may be under mechanical influences of the egg or young in the pouch. The length of pregnancy was 16.7 ± 0.2 days with a 15.1 ± 1.0 days luteal phase followed by an incubation period in the pouch. Eggs could be detected in utero at least 4 days before oviposition. Plasma progesterone peaked at 10.5 ± 0.9 ng/mL within 12 days of mating but then declined to basal levels within 1 day of oviposition and remained basal throughout egg incubation, confirming that progesterone is elevated throughout pregnancy and that gestation does not extend beyond the luteal phase. After the loss of an egg or pouch young, most females entered a second oestrous cycle and ovulated, suggesting echidnas are seasonally polyoestrous. The duration of the luteal phase in the echidna corresponds with that observed in other mammals.
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ItemDiet and impacts of non-native fallow deer (Dama dama) on pastoral properties during severe drought(CSIRO Publishing, 2023)There is concern about potential competition between non-native fallow deer (Dama dama) and livestock for food, particularly during times of low rainfall when pasture is scarce. Aims. We aimed to estimate the extent to which a high-density fallow deer population (~37 deer per km2) competed with livestock for food during a severe drought on pastoral properties on the Liverpool Plains, New South Wales, Australia. Methods. We collected rumen contents from 125 fallow deer shot from helicopters during control operations in June and August 2018, and used microhistology to quantify their diets. We then used the diet data to adjust published estimates of stock unit equivalence from farmed fallow deer. Fallow deer sex and age class abundances and stock unit equivalences were multiplied to estimate the grazing pressure of the fallow deer population pre- and post-control relative to recommended sheep and cattle stocking rates. Finally, we estimated density–impact relationships for fallow deer. Key results. Fallow deer diet was dominated by monocots (primarily grasses), but some individuals consumed large amounts of dicots (commonly Eucalyptus). Fallow deer were grazers to intermediate mixed feeders. Fallow deer dry-sheep equivalents (DSEs, based on a 50-kg merino wether) varied from 1.01 (juveniles) to 1.85 (adult females and adult males). Assuming complete diet overlap, the pre-control fallow deer population was equivalent to approximately 60.3 DSEs per km2 and reduced the potential stocking rate of domestic livestock by 50.2%. Discounting the fallow deer DSEs by the amount of browse in the diet resulted in a pre-control population of 45.7 DSEs per km2. The helicopter-based shooting reduced the fallow deer population by 26%, increasing the stocking rate in natural pasture by 22.0% (complete overlap) or 13.8% (discounting for browse). Conclusions. When food is limiting, fallow deer at high density can exert strong competitive pressure on livestock, reducing carrying capacity. Browsing, including on Eucalyptus, likely helped fallow deer to persist at high densities during the severe drought of 2018, when properties had destocked. Implications. Helicopter-based shooting reduced the competitive effects of fallow deer on livestock in our study area to only a small extent, but more intensive shooting would have led to a greaterreduction. The helicopter-based shooting of deer was received positively by landholders at a time of severe stress, suggesting that deer control in agricultural areas can have other important benefits.
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ItemEnvironmental drivers of fish population dynamics in an estuarine ecosystem of south-eastern Australia(WILEY, 2022-05-30)Abstract Estuaries are dynamic environments and often support rich biodiversity and important fisheries. Linking environmental drivers or events to observed biological changes in these systems provides critical information that can facilitate their management. Historical fish and fisheries data for Western Port, a large embayment in south‐east Australia that supports rich biodiversity, were collated, including catch records, recruitment indices and two novel growth time series. Dynamic factor analysis (DFA) identified three common patterns associated with the biological time‐series data, which in turn were related to both local and regional environmental drivers. On a local scale, nitrogen loads and chlorophyll a concentration affected fish metrics, potentially through the food web and via changes to critical seagrass habitat. On a regional scale, offshore sea surface temperature in Bass Strait was important. Step changes (change points) in the three common patterns were predominantly associated with significant El Niño and La Niña events and, to a lesser extent, recruitment pulses and the cessation of commercial netting.