Морфогенез органа нюху східної довгошийої черепахи (Chelodina longicollis)

Вивчення розвитку нюхового аналізатора рептилій є дуже важливим в еволюційному та порівняльно-анатомічному аспектах. Нюховий аналізатор різних рептилій має суттєві відмінності в будові. У ящірок та змій нюховий аналізатор анатомічно розділений на основну та додаткову (вомероназальну) системи. Нюховий орган черепах має відмінні риси організації. У більшості черепах в нюховому органі відсутнє морфологічне розмежування основного нюхового та вомероназального органа.У роботі описано ключові стадії розвитку структур нюхового органа східної довгошийої черепахи (Chelodina longicollis). Нюховий орган складається з присінка, власне нюхової порожнини та носоглоткового каналу, який відкривається в ротову порожнину хоанами. Носова порожнина розмежована вузькою ділянкою несенсорного епітелію на дорсальну частину, яка вистелена нюховим епітелієм, та вентральну, яка вистелена вомероназальним епітелієм. Вентральна частина носової порожнини утворює медіальне впячування, що значно збільшує об’єм вомероназального епітелію. Нюховий епітелій має чисельні залози Боумена, які відсутні у вомероназальному епітелії. Протока латеральної нюхової залози впадає на межі переходу присінка в носову порожнину та зволожує основний нюховий епітелій, який найбільше контактує з повітрям. Доказом наявності вомероназальної системи у черепахи слугує наявність вомероназального нерва, окремі волокна якого йдуть від вентральної частини носової порожнини до медіальної поверхні нюхової цибулини.

Quantifying Costs of Urbanisation: Wetland Loss and Impacts in a Rapidly Developing Global City

As cities grow, natural ecosystems decline through conversion to urban environments. Cities are often viewed as biodiversity wastelands, but they can be hotspots of global biodiversity. Urban biodiversity emphasises two fundamentals. First, people living in cities enjoy wildlife and second, there is virtually no planning for species that co-inhabit our cities. If urban biodiversity was a significant part of planning, then we would be far better at integrating green infrastructure into expanding urban environments.Wetlands are among the most important and productive ecosystems in the world. They are the main suppliers of fresh water for human use and provide habitat to critical fauna and flora. In urban areas they are a vital link to nature and social cohesion. Currently, there is an absence of wetland inventory quantifying loss and changes overtime. Hence the broad impacts of urbanisation on wetland loss are difficult to assess.We explored wetland loss and created a wetland inventory for Western Sydney, Australia, one of the world’s fastest growing urban regions. We used satellite imagery to determine wetland number and type, and calculated changes in wetland surface area from 2010-2017. Broad changes to land use were also quantified. We developed species distribution models of a common urban wetland turtle (Chelodina longicollis) that people interact with regularly or have as pets. Chelodina longicollis utilises both aquatic and terrestrial environments, and we determined if changes in distribution were associated with changes in the wetland inventory and urbanisation.Most local government areas (LGA) experienced a decrease in wetland surface area from 2010-2017, ranging from -1% (Cumberland) to -21% (Blacktown). Majority of LGAs experienced a decrease in wetland density, with wetland densities declining by 25% (Blacktown). All LGAs experienced an increase in urban land use, ranging from 3-12%, which was associated with high rates of wetland loss.Changes in turtle distribution over the decade reflects a southern distribution shift away from where wetland losses were concentrated. We estimated that ∼40,000 individual turtles were displaced or killed due to wetland loss and urbanisation.Urbanisation was the leading cause of wetland loss and degradation in Western Sydney between 2010 and 2017. Wetlands provide critical green infrastructure and significant green space for social cohesion in urban areas. Integration of current wetlands, or the creation of functional wetlands, is key for sustainable development of urban landscapes. Urban wetlands (natural and constructed) may provide “biodiversity arks” for endangered species and facilitate community led conservation programs.

Food abundance and diet variation in freshwater turtles from the mid-Murray River, Australia

Consumers usually respond to variations in prey availability by altering their foraging strategies. Generalist consumers forage on a diversity of resources and have greater potential to ‘switch’ their diet in response to fluctuations in prey availability, in comparison to specialist consumers. We aimed to determine how the diets of two specialist species (the eastern long-necked turtle (Chelodina longicollis) and the broad-shelled turtle (Chelodina expansa) and the more generalist Murray River short-necked turtle (Emydura macquarii) respond to variation in habitat and prey availability. We trapped and stomach-flushed turtles, and compared their diets along with environmental variables (turbidity, macrophyte and filamentous green algae cover, and aquatic invertebrate diversity and abundance) at four wetlands in north-central Victoria. Diets of E. macquarii differed from those of both Chelodina species, which overlapped, across all four sites. However, samples sizes for the two Chelodina species were too small to compare among-wetland variation in diet. Dietary composition of E. macquarii was variable but did not differ statistically among sites. Emydura macquarii preferentially selected filamentous green algae at three of the four sites. Where filamentous green algae were rare, total food bolus volume was reduced and E. macquarii only partially replaced it with other food items, including other vegetation, wood, and animal prey. Many turtles at these sites also had empty stomachs. Thus, filamentous green algae may be a limiting food for E. macquarii. Although E. macquarii has previously been described as a generalist, it appears to have limited ability to replace filamentous green algae with other food items when filamentous green algae are rare.

Road mortality of the eastern long-necked turtle (Chelodina longicollis) along the Murray River, Australia: an assessment using citizen science

Turtles face a variety of threats (e.g. habitat destruction, introduced predators) that are pushing many species towards extinction. Vehicle collisions are one of the main causes of mortality of adult freshwater turtles. To conceptualise the level of threat that roads pose to Australians turtles, we analysed data gathered through the citizen science project TurtleSAT along the Murray River. We recorded 124 occurrences of turtle road mortality, which included all three local species (Chelodina expansa, Chelodina longicollis, and Emydura macquarii). Chelodina longicollis was the most commonly reported species killed on roads. We found that rain and time of year affect the likelihood of C. longicollis being killed on roads: increased turtle mortality is associated with rain events and is highest during the month of November, which coincides with their nesting season. Chelodina longicollis was most likely to be killed on the Hume Highway and roads around major urban centres; therefore, we recommend that governing bodies focus management practices and increase awareness at these locations. The degree of road mortality that we detected in this study requires mitigation, as it may contribute to the decline of C. longicollis along the Murray River.

Slow and unsteady: growth of the Australian eastern long-necked turtle near the southern end of its natural range

Knowledge of growth rates and maturation times of freshwater turtles is important in assessing population viability. I analysed growth of Australian eastern long-necked turtles (Chelodina longicollis) from individual capture–recapture records spanning periods of up to 17 years for a population in Gippsland, Victoria, close to the high-latitude end of the species’ natural range. Juvenile growth was rapid and similar among individuals but adult growth was usually slow, highly variable among individuals and erratic within individuals over time. In addition, asymptotic body lengths were disparate among individuals for both males and females. Von Bertalanffy growth models fitted separately to males plus unsexed juveniles and females plus unsexed juveniles performed better than logistic models but tended to underestimate growth rates for very small and very large turtles and overestimate growth for medium-sized individuals. Sexual maturity was estimated to be achieved at 10 years in males and 16 years in females, which is late compared with most estimates for other populations of C. longicollis and for other turtle species in south-eastern Australia. The high variability of individual growth in this population makes age estimation from body size unreliable beyond the first few years of life.

Freshwater turtle hatchlings that stay in the nest: strategists or prisoners?

Hatchlings of several species of freshwater turtles have been reported to remain in subterranean nests for extended periods following hatching from the egg. It has been suggested that this delayed emergence, including overwintering in the nest in populations at temperate latitudes, is an evolved adaptation that enables hatchlings to enter the aquatic environment at the most propitious time for survival and growth. I monitored nests of a temperate-zone population of the freshwater Australian eastern long-necked turtle (Chelodina longicollis) for up to a year after nest construction in fine-grained soils adjacent to oxbow lakes and farm ponds. An estimated 84% of nests were preyed on, probably mainly by non-native red foxes (Vulpes vulpes), whereas hatchlings emerged from autumn to spring from an estimated 5% of nests. The remaining 11% of nests were neither preyed on nor had emergence by a year after nest construction. Live hatchlings were present in some nests with no emergence up to 10 months after nest construction, but substantial numbers of dead hatchlings were present beyond nine months. It therefore seems unlikely that emergence occurs more than a year after nest construction. Delayed emergence of this species in this environment appears less likely to be an adaptive strategy than to be a consequence of imprisonment in the nest by hard soil that is difficult for hatchlings to excavate.

Preliminary evidence suggests freshwater turtles respond positively to an environmental water delivery during drought

Environmental flows (e-flows) are a common management tool to improve the health of flow-regulated river systems and their biota. The effect of e-flows on fish, waterbirds and vegetation has been assessed in Australia, but their influence on turtles remains largely unstudied. We opportunistically examined the effect of e-flows on the eastern long-necked turtle (Chelodina longicollis), a species that occupies ephemeral aquatic habitats, by measuring an index of abundance (catch per unit effort) and body condition before and after an environmental watering event that replenished a severely contracted creek in the mid-Murray region. We found that average body condition increased after watering. Abundance decreased markedly after watering, but the change was not statistically significant. While the causal inference of our study was limited by the opportunistic nature of our before-after experimental design, this study provides preliminary evidence that environmental flows may improve the health of turtles occupying ephemeral floodplain habitats. We encourage further research into the effect of e-flows on turtles to confirm the hypothesis that the increase in average body condition recorded in the current study was a function of e-flows.