Academic literature on the topic 'Emydura krefftii'

Krefft's tortoise has been maintained at the Royal Melbourne Zoo since 1972. From 1978 to 1983 inclusive, 24 clutches of eggs were laid. For 20 clutches, mean clutch size was 17 eggs, mean egg weight was 7.9 g, mean egg dimensions were 35 x 20 mm, and pipping commenced after 46 days at a constant incubation temperature of 30�C. Internesting periods were 30-51 days, with one female laying four clutches in one season. Hatchling growth was monitored, and young attained a mean weight of 53 g and mean carapace length of 73 mm after 12 months. Development of the embryonic attachment zone was also monitored. The results gained are compared with published data from two populations of wild tortoises.

Fish, amphibians, and reptiles exhibit temperature-dependent ranaviral disease. We performed an experimental infection at four different environmental temperatures (16, 22, 28, and 34 °C) to investigate the effect of temperature on ranaviral infection in Krefft’s turtle ( Emydura macquarii krefftii). Infection rates and viral loads were determined by quantitative polymerase chain reaction to detect ranaviral DNA in liver samples at 21 d postexposure. The rate of infection differed across the temperature treatment groups. Infection rates were 44%, 90%, 60%, and 10% for the 16, 22, 28, and 34 °C temperature groups, respectively. Highest viral load was observed in the 28 °C temperature group, and there was a statistically significant difference in viral load between the 16 and 28 °C temperature groups ( p = 0.027). Based on the results of this study, the temperature of maximal infection rate for ranaviral infection in Krefft’s river turtles is estimated to be 23.2 °C (SD = 4.5). The findings of this study can inform management decisions in terms of disease control and treatment and form a platform for modelling disease outbreaks.

There is increasing recognition that microbiomes are important for host health and ecology, and understanding host microbiomes is important for planning appropriate conservation strategies. However, microbiome data are lacking for many taxa, including turtles. To further our understanding of the interactions between aquatic microbiomes and their hosts, we used next generation sequencing technology to examine the microbiomes of the Krefft’s river turtle (Emydura macquarii krefftii). We examined the microbiomes of the buccal (oral) cavity, skin on the head, parts of the shell with macroalgae and parts of the shell without macroalgae. Bacteria in the phyla Proteobacteria and Bacteroidetes were the most common in most samples (particularly buccal samples), but Cyanobacteria , Deinococcus-thermus and Chloroflexi were also common (particularly in external microbiomes). We found significant differences in community composition among each body area, as well as significant differences among individuals. The buccal cavity had lower bacterial richness and evenness than any of the external microbiomes, and it had many amplicon sequence variants (ASVs) with a low relative abundance compared to other body areas. Nevertheless, the buccal cavity also had the most unique ASVs. Parts of the shell with and without algae also had different microbiomes, with particularly obvious differences in the relative abundances of the families Methylomonaceae, Saprospiraceae and Nostocaceae . This study provides novel, baseline information about the external microbiomes of turtles and is a first step in understanding their ecological roles.

Ranaviral infections cause mass die-offs in wild and captive turtle populations. Two experimental studies were performed to first determine the susceptibility of an Australian turtle species (Emydura macquarii krefftii) to different routes of infection and second examine the effect of viral titre on the morbidity in hatchlings. All inoculation routes (intracoelomic, intramuscular and oral) produced disease, but the clinical signs, histopathology and time to onset of disease varied with the route. The median infectious and lethal doses for intramuscularly inoculated hatchlings were 102 . 52 (1.98–2.93) and 104.43 (3.81–5.19) TCID50 ml−1, respectively. Clinical signs began 14 to 29 days post-inoculation and the median survival time was 22 days (16–25) across all dose groups. For every 10-fold increase in dose, the odds of developing any clinical signs or severe clinical signs increased by 3.39 [P<0.01, 95 % confidence interval (CI): 1.81–6.36] and 3.71 (P<0.01, 95 % CI: 1.76–7.80), respectively. Skin lesions, previously only reported in ranaviral infection in lizards, were observed in the majority of intramuscularly inoculated hatchlings that developed ranaviral disease. The histological changes were consistent with those in previous reports for reptiles and consisted of necrosis at or near the site of injection, in the spleen, liver and oral cavity. Systemic inflammation was also observed, predominantly affecting necrotic organs. The estimates reported here can be used to model ranaviral disease and quantify and manage at-risk populations.

We determined the diet of Emydura krefftii, an abundant and widespread omnivorous freshwater turtle in north-eastern Australia, in an artificial urban impoundment. A potentially significant dietary influence is feeding of bread to the turtles by members of the public. This has led to the formation of a dense aggregation of the species at one end of the impoundment. The most substantial component of the diet by volume was the introduced weed Cabomba. Bread and figs were also important but only in specific locations. Bread was offered to turtles at the feeding aggregation in amounts close to the maximum eaten by captive turtles, and thus probably negatively influences nutrient status. Animal matter (insects, vertebrate carrion) was only a small proportion of the diet. We quantified intake, digestibility and transit time in the laboratory for four commonly occurring dietary items. Fish and bread were the most highly digestible food items and passed quickly through the gut. Despite its contribution to the diet in the wild, captive turtles ate little Cabomba, and it passed slowly through the gut and was poorly digested. Future research on interactive effects between diet items on digestive performance is recommended to understand the performance of turtles on apparently poor-quality diets.

An ecological study was undertaken on four populations of Krefft�s River Turtle Emydura krefftii inhabiting the Townsville Area of Tropical North Queensland. Two sites were located in the Ross River, which runs through the urban areas of Townsville, and two sites were in rural areas at Alligator Creek and Stuart Creek (known as the Townsville Creeks). Earlier studies of the populations in Ross River had determined that the turtles existed at an exceptionally high density, that is, they were superabundant, and so the Townsville Creek sites were chosen as low abundance sites for comparison. The first aim of this study was to determine if there had been any demographic consequences caused by the abundance of turtle populations of the Ross River. Secondly, the project aimed to determine if the impoundments in the Ross River had affected the freshwater turtle fauna. Specifically this study aimed to determine if there were any difference between the growth, size at maturity, sexual dimorphism, size distribution, and diet of Emydura krefftii inhabiting two very different populations. A mark-recapture program estimated the turtle population sizes at between 490 and 5350 turtles per hectare. Most populations exhibited a predominant female sex-bias over the sampling period. Growth rates were rapid in juveniles but slowed once sexual maturity was attained; in males, growth basically stopped at maturity, but in females, growth continued post-maturity, although at a slower rate. Sexual maturity was at 6-7 years of age for males, which corresponded to a carapace length of 150-160 mm, and 8-10 years of age for females, which corresponded to a carapace length of 185-240 mm. The turtles were omnivorous, although in the Ross River they ate more submerged vegetation (by percent amount and occurrence) than those of the Townsville Creeks. Turtles in Townsville Creeks ingested more windfall fruit and terrestrial insects.

Oceanic islands have been used as model systems for studies of evolution and speciation as the range of island sizes coupled with their known geological chronosequence make them ideal systems for the study of spatial and temporal variations in species diversity and distributions. These processes also occur on continental islands and mainland habitats but features of oceanic islands, notably their clearly delimited boundaries, natural isolation and simple geological composition make them more amenable to study. The perched dune lakes of Fraser Island, Australia share many of the properties of oceanic islands. The naturally isolated formation of the perched lakes, clearly delimited boundaries of the freshwater habitat and phase difference compared to the surrounding, terrestrial environment have significant implications for the biota these lakes support. Inhabitants of the perched dune lakes consist of the aquatic and semi-aquatic descendents of colonisers that were able to traverse a land barrier and survive in the oligotrophic, acidic waters over subsequent generations. Barriers to ongoing gene flow among lake populations, are however likely to be different for species with different life history characteristics. I therefore sought to assess the effects of three different life history characteristics on post-colonisation interpopulation gene flow. A representative species was selected to represent one of each of the following life history characteristics: * Aquatic species confined to lake for entire life cycle - freshwater shrimp Caridina indistincta. * Semi-aquatic species capable of terrestrial dispersal - freshwater turtle Emydura krefftii. * Semi-aquatic species capable of aerial dispersal - odonate Orthetrum Boumiera. 137-250 individuals were sampled per species across six lakes separated by 1-6km. Regions of the mitochondrial genome were targeted and molecular screening methods developed and employed to assess the relative levels of post-colonisation gene flow among lake populations. Parsimony analysis of the 25 unique haplotypes identified in the species with no apparent inter-lake dispersal mechanism, the freshwater shrimp Caridina indistincta, demonstrated that there was no sharing of derived haplotypes among lake populations. Star shaped genealogies were identified in four lake populations indicative of a population expansion and mismatch distribution analysis confirmed a recent population expansion estimated to have occurred no more than 200,000 years ago. This demonstrates that each of the perched dune lakes was colonised by C.indistincta soon after their inception but that no ongoing gene flow among lake populations has occurred. The population genetic structure of the species assessed which is capable of terrestrial dispersal suggests that although this species of freshwater turtle, Emydura krefftii, is capable of overland dispersal, gene flow among lake populations is limited. Even at the small spatial scale examined in this study, E.krefftii populations displayed a pattern of isolation by distance (r=0.854, p<0.03). Nested clade analysis also suggested a pattern of restricted gene flow with some long distance dispersal in recent times with long distance dispersal and a possible range expansion occurring historically. The species examined in this study that displayed the most extensive gene flow among lake populations was the dragonfly Orthetrum boumiera. No relationship was found between genetic and geographic distance (r= -0.0852, p>0.05) and nested clade analysis could not identify a geographical association among haplotypes, indicative of panmixia. While larval life stages of this species are fully aquatic, the winged adult stages of this species appear to be connecting seemingly isolated lake populations, at least at the spatial scale examined here. The results of this study have demonstrated that these perched dune lakes provide 'island like' models for recent biogeographic processes. The pattern of colonisation and subsequent diversification identified in these populations takes the form of insitu 'genetic radiations' with those populations that are isolated forming monophyletic clades endemic to a single lake. The genetic diversity and endemism identified in this study has occurred over much smaller temporal (<500,000 years) and spatial (<6.5km) scales than in studies of oceanic island fauna. However, the mode of formation of the perched dune lakes and the implications that their natural isolation and abiotic genesis have for the evolution of colonisers of these unique habitats has resulted in them being analogous to true oceanic islands.

Oceanic islands have been used as model systems for studies of evolution and speciation as the range of island sizes coupled with their known geological chronosequence make them ideal systems for the study of spatial and temporal variations in species diversity and distributions. These processes also occur on continental islands and mainland habitats but features of oceanic islands, notably their clearly delimited boundaries, natural isolation and simple geological composition make them more amenable to study. The perched dune lakes of Fraser Island, Australia share many of the properties of oceanic islands. The naturally isolated formation of the perched lakes, clearly delimited boundaries of the freshwater habitat and phase difference compared to the surrounding, terrestrial environment have significant implications for the biota these lakes support. Inhabitants of the perched dune lakes consist of the aquatic and semi-aquatic descendents of colonisers that were able to traverse a land barrier and survive in the oligotrophic, acidic waters over subsequent generations. Barriers to ongoing gene flow among lake populations, are however likely to be different for species with different life history characteristics. I therefore sought to assess the effects of three different life history characteristics on post-colonisation interpopulation gene flow. A representative species was selected to represent one of each of the following life history characteristics: * Aquatic species confined to lake for entire life cycle - freshwater shrimp Caridina indistincta. * Semi-aquatic species capable of terrestrial dispersal - freshwater turtle Emydura krefftii. * Semi-aquatic species capable of aerial dispersal - odonate Orthetrum Boumiera. 137-250 individuals were sampled per species across six lakes separated by 1-6km. Regions of the mitochondrial genome were targeted and molecular screening methods developed and employed to assess the relative levels of post-colonisation gene flow among lake populations. Parsimony analysis of the 25 unique haplotypes identified in the species with no apparent inter-lake dispersal mechanism, the freshwater shrimp Caridina indistincta, demonstrated that there was no sharing of derived haplotypes among lake populations. Star shaped genealogies were identified in four lake populations indicative of a population expansion and mismatch distribution analysis confirmed a recent population expansion estimated to have occurred no more than 200,000 years ago. This demonstrates that each of the perched dune lakes was colonised by C.indistincta soon after their inception but that no ongoing gene flow among lake populations has occurred. The population genetic structure of the species assessed which is capable of terrestrial dispersal suggests that although this species of freshwater turtle, Emydura krefftii, is capable of overland dispersal, gene flow among lake populations is limited. Even at the small spatial scale examined in this study, E.krefftii populations displayed a pattern of isolation by distance (r=0.854, p<0.03). Nested clade analysis also suggested a pattern of restricted gene flow with some long distance dispersal in recent times with long distance dispersal and a possible range expansion occurring historically. The species examined in this study that displayed the most extensive gene flow among lake populations was the dragonfly Orthetrum boumiera. No relationship was found between genetic and geographic distance (r= -0.0852, p>0.05) and nested clade analysis could not identify a geographical association among haplotypes, indicative of panmixia. While larval life stages of this species are fully aquatic, the winged adult stages of this species appear to be connecting seemingly isolated lake populations, at least at the spatial scale examined here. The results of this study have demonstrated that these perched dune lakes provide 'island like' models for recent biogeographic processes. The pattern of colonisation and subsequent diversification identified in these populations takes the form of insitu 'genetic radiations' with those populations that are isolated forming monophyletic clades endemic to a single lake. The genetic diversity and endemism identified in this study has occurred over much smaller temporal (<500,000 years) and spatial (<6.5km) scales than in studies of oceanic island fauna. However, the mode of formation of the perched dune lakes and the implications that their natural isolation and abiotic genesis have for the evolution of colonisers of these unique habitats has resulted in them being analogous to true oceanic islands.

Australia supports a highly endemic freshwater fauna. The continent's long isolation, Gondwanan heritage, and present aridity make it of particular interest to freshwater biogeographers. Recent molecular genetic studies of freshwater fishes and macroinvertebrates implicate diverse processes of landform evolution, climatic change and sea level fluctuation in shaping current patterns of biodiversity. These studies indicate a biogeographic complexity for Australian freshwaters that is not yet well understood, especially throughout the geographically complex eastern coastal margin. Australian freshwater turtles are one of the continent's few vertebrate freshwater Gondwanan relics that are still taxonomically and ecologically diverse, and geographically widespread. However, in context of their biogeography they remain poorly studied, despite studies on other continents showing turtles to be particularly suited to illuminating complex evolutionary processes. In this thesis is explored the sensitivity of freshwater turtles as models for biogeographic inference in an Australian context, to seek new insights that may clarify and extend our knowledge of Australian freshwater biogeography. Molecular genetic tools are developed and applied to investigate phylogeographies of turtle species from two Australian genera. The evolutionary history of riverine specialist Australian snapping turtles (genus Elseya) is compared to that of the more ecologically generalist and widespread subspecies of Emydura macquarii, and in particular that of Krefft's river turtle, E. m. krefftii. These taxa were chosen as models because both are primarily riverine and broadly sympatric throughout eastern Australia, but differ significantly in niche breadth, range size, and expected dispersal ability. To address the lack of suitable genetic resources available for Australian short-necked turtles, Next-Generation shotgun genome sequencing was evaluated as a cost-effective means of developing novel genetic resources in two species of freshwater turtle. Low-coverage Roche 454-sequencing was used to randomly sample genomic sequence data for microsatellite repeats in the study species Elseya albagula and Emydura macquarii krefftii. Thousands of microsatellite loci suitable for amplification by PCR were found. Of these, 29 loci were developed for high-resolution population genetic analyses in the study species, which also cross-amplified successfully in a range of other Australian short-necked turtle taxa. Further bioinformatic exploration of the genomic sequence datasets enabled reconstruction of nearcomplete mitochondrial genomes, and characterisation of gene content and repetitive elements. A molecular toolkit of nuclear and mitochondrial markers is presented that provides the foundation for research presented in this thesis, and which will also facilitate future genetic research on Australian freshwater turtles generally. Drainages within Australia's mid-eastern coastal region (Fitzroy, Burnett and Mary catchments) face considerable urban pressure and contain high freshwater biodiversity and endemism. Mitochondrial (~1.3 kb control region and ND4) and nuclear microsatellite datasets (12 polymorphic loci) were used to investigate genetic structure in the locally endemic whitethroated snapping turtle, Elseya albagula, to clarify historical biogeography and address pressing conservation issues for this species and this region. Individual drainage basins contained discrete genetic units (average pairwise FST = 0.15 and ФST = 0.75 among drainages), though the degree of divergence among drainages varied. The Fitzroy drainage contained a distinct evolutionary lineage, divergent from a second lineage occurring in both the Burnett and Mary drainages. Genetic data were used to make recommendations regarding recognition of evolutionarily significant units and management units for E. albagula. Geological evidence and genetic data for co-distributed freshwater species were consolidated to propose a shared biogeographic history for a diverse regional biota, reflecting historical isolation of the Fitzroy and recent coalescence of the Burnett-Mary drainages during lowered Pleistocene sea levels. To examine broader-scale evolutionary hypotheses associated with changes to regional riverine connectivity through eustatic sea level change, landform evolution and aridity, a multi-locus molecular approach incorporating mitochondrial (control region, ND4 and 16S) and nuclear (R35 intron) sequences was used to reconstruct phylogenetic relationships and estimate divergence times for all extant Elseya species (including undescribed forms) across Australia and New Guinea. The genus Elseya was shown to contain four divergent, geographically correlated clades, corresponding to all of New Guinea, southern New Guinea plus northern Australia, north-eastern Australia, and south-eastern Australia. These are estimated to have arisen in the Late-Miocene (between ~5.82-9.7 Ma), and diversified further in the early Pleistocene (between ~2.2-2.43 Ma and 1.36-1.66 Ma), coincident with major phases of aridity and climatic upheaval. Overall, snapping turtles were found to have a long vicariant history in Australia and New Guinea, tied to the disconnection of fluvial habitat through landform evolution, sea level change and ongoing aridification. Major implications of these genetic results for understanding freshwater biodiversity evolution in Australia are discussed, including evidence for periodic connectivity with New Guinea, important regional biogeographic barriers (Lake Carpentaria and the Burdekin-Fitzroy drainage divide), and the location of potential freshwater refugia. Krefft's river turtle, Emydura macquarii krefftii, are common throughout eastern coastal Australia and their extensive longitudinal distribution spans landscape and climatic barriers recently proposed as important in structuring regional freshwater biodiversity. Their evolutionary history in response to climatic oscillations and putative biogeographic barriers was examined using range-wide sampling (649 individuals representing 18 locations across 11 drainages) and analysis of mitochondrial sequences (~1.3 kb control region and ND4) and nuclear microsatellite (12 polymorphic loci) data. Competing demographic (local persistence versus range expansion) and biogeographic (arid corridor versus drainage divide) hypotheses were considered. Krefft's turtles exhibit significant genetic structure across their range at mitochondrial and microsatellite markers, consistent with isolation across drainage divides. Deep north-south regional divergence (2.2%, ND4 p-distance) was consistent with long-term isolation across the Burdekin-Fitzroy drainage divide, not the adjacent Burdekin Gap dry corridor. There was also evidence for rare contemporary overland dispersal across the Burdekin- Fitzroy watershed and for hybridisation with Emydura tanybaraga at the northern range limit. Data suggest Krefft's turtles persisted within the arid Burdekin region throughout multiple episodes of Plio-Pleistocene aridity, though very low contemporary genetic diversity indicates this may have been despite potential population bottlenecks. Overall, riverine turtle species examined in this thesis exhibited strong, geographically correlated, phylogeographic structure. A remarkable degree of genealogical concordance was observed in phylogeographical patterns between turtle taxa, and turtles and other freshwater groups. Though differences in range size and niche breadth were expected to produce disparities in dispersal ability and phylogeographic structure between the two turtle taxa, both exhibited a primary pattern of genetic structure reflecting isolation across drainage divides. Riverine turtles are indeed sensitive models for inferring historical processes influencing freshwater biodiversity in an Australian context. Molecular data presented in this thesis collectively demonstrate the importance of comparing phylogeographic patterns among co-distributed taxa with variable ecological tolerances and dispersal abilities. Furthermore, the current work not only highlights the potential value of further phylogeographic research into ecologically diverse freshwater turtles in Australia, but provides a comprehensive molecular toolkit for doing so.

A survey of the community of helminths in Emydura krefftii Gray in central and northern Queensland was undertaken. Then a detailed study of Sychnocotyle kholo Ferguson, Cribb and Smales, 1999, a newly described aspidogastrean parasite of E. krefftii, was conducted. The principal aim of this study was to examine the life history, fine morphology and phylogenetic relationships of this species. Specimens of Emydura krefftii were sampled from six coastal catchments from Cooktown to Bundaberg in northern and central Queensland. Concurrently data were collated on the community structure of helminths of E. krefftii. To examine the life history of S. kholo, molluscs were collected and examined for juvenile aspidogastreans from areas sampled for turtles and S. kholo eggs were collected from the faeces of collected turtles. The study of morphology of this helminth involved staining whole mounts and sections for light microscopy for gross morphology and examination of organ systems. Scanning electron microscopy was used to examine the outer surface of the worm in detail. For fine morphology of organs, transmission electron microscopy and confocal microscopy were applied. Finally characters were identified for a phylogenetic analysis and a data matrix was constructed and executed with Phylogenetic Analysis Using Parsimony (PAUP) software.