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Syngnathid embryos (seahorses, pipefishes and seadragons) develop on or in the male in a specialised brooding structure (brood pouch). Seahorse brood pouches supply nutrients, including lipids, to developing embryos (patrotrophy). We tested the hypothesis that proteins, vital for gene regulation and tissue growth during embryogenesis, are also transported from father to embryos, using the Australian pot-bellied seahorse, Hippocampus abdominalis. We used dry masses and total nitrogen content to estimate the total protein content of newly fertilised egg and neonate H. abdominalis. Neonates contained significantly greater protein mass than newly fertilised eggs. This result indicates that paternal protein transport to developing embryos occurs during H. abdominalis pregnancy. This study is the first to show paternal protein transport during pregnancy in seahorses, and furthers our understanding of paternal influence on embryonic development in male pregnant vertebrates. [ABSTRACT FROM AUTHOR]

Freshwater turtles are important consumers in Australian freshwater ecosystems. They serve as scavengers, nutrient regulators, and as food sources and Totems for Traditional Owners throughout Australia. Despite their importance, most Australian freshwater turtle species are declining. The impact of winter wetland drying on turtle populations remains unknown, and winter exposure of hibernating turtles may be an important additional source of mortality. We aimed to examine turtle responses to seasonal and episodic wetland drying in wetlands using acoustic telemetry and active trapping. Wetlands were chosen that spanned a range of hydrological connectivity to the adjacent Edward/Kolety‐Wakool River. We found that tagged Emydura macquarii typically exit wetlands disconnected from the adjacent permanent river prior to winter, and overwinter in the river. Female E. macquarii rapidly re‐entered 'home' wetlands (wetlands in which they were initially tagged) the following spring, whereas males tended to leave the study area, returning occasionally. Although we were not able to evaluate a winter drying event, one of the wetlands experienced partial summer drying. All three local turtle species (E. macquarii, Chelodina expansa, C. longicollis) exited the wetland long before winter drying would have become a potential threat. Our results suggest that turtles in this system may be protected from winter wetland drying because they move to the adjacent permanent river prior to winter. Spending the winter in the river channel reduces the risks of being trapped in a drying wetland as temperatures drop in winter. [ABSTRACT FROM AUTHOR]

The Australian freshwater turtle fauna is dominated by species in the family Chelidae. The extant fauna comprises a series of distinct lineages, each of considerable antiquity, relicts of a more extensive and perhaps diverse fauna that existed when wetter climes prevailed. Several phylogenetically distinctive species are restricted to single, often small, drainage basins, which presents challenges for their conservation. Specific threats include water resource development, which alters the magnitude, frequency, and timing of flows and converts lentic to lotic habitat via dams and weirs, fragmentation of habitat, sedimentation, nutrification, and a reduction in the frequency and extent of floodplain flooding. Drainage of wetlands and altered land use are of particular concern for some species that are now very restricted in range and critically endangered. The introduced European red fox is a devastatingly efficient predator of turtle nests and can have a major impact on recruitment. In the north, species such as the northern snake‐necked turtle are heavily depredated by feral pigs. Other invasive animals and aquatic weeds dramatically alter freshwater habitats, with consequential impacts on freshwater turtles. Novel pathogens such as viruses have brought at least one species to the brink of extinction. Species that routinely migrate across land are impacted by structural simplification of habitat, reduction in availability of terrestrial refugia, fencing (including conservation fencing), and in some areas, by high levels of road mortality. We report on the listing process and challenges for listing freshwater turtles under the Australian Environment Protection and Biodiversity Conservation Act, summarize the state of knowledge relevant to listing decisions, identify the key threatening processes impacting turtles, and identify key knowledge gaps that impede the setting of priorities. We also focus on how to best incorporate First Nations Knowledge into decisions on listing and discuss opportunities to engage Indigenous communities in on‐ground work to achieve conservation outcomes. [ABSTRACT FROM AUTHOR]

Australia's freshwater turtles have high endemicity and many are threatened by extinction. Following a symposium held at the 2022 conference of the Australian Society of Herpetologists, we summarized the current status of research and conservation for Australian freshwater turtles and identified opportunities for future research. Eight species (32%) of Australia's 25 native freshwater turtles are listed as threatened by Australia's Federal Government. Symposium discussions on the primary gaps in research identified the lack of baseline data to inform population modelling as a key deficiency. Knowledge of the most effective conservation actions, the effectiveness of attempts to aid population recovery, and whether these actions are required at all, remains lacking for many species. A heavy bias exists between some well‐studied species compared with others for which little or no information is published. Community science, engagement with First Nations people, advances in technology, and recognition of the importance of turtles are contributing to better knowledge. [ABSTRACT FROM AUTHOR]

Invasive mammalian predators are efficient at driving native animal declines. The red fox (Vulpes vulpes) kills millions of endemic reptiles in Australia each year. In areas of south‐eastern Australia, the eastern long‐necked turtle (Chelodina longicollis) and Murray River turtle (Emydura macquarii) have declined by more than 50%. High rates of nest predation by foxes limit the recruitment of young turtles in these populations, but previous methods of fox control have been ineffective at protecting turtle nests. Here, we tested the effectiveness of plastic mesh for protecting artificial turtle nests from predation by foxes, in the mid‐Murray catchment, Victoria. We also tested whether protecting a large number of artificial nests in a given area encourages foxes to give up foraging following predictions from giving‐up density theory. We made a series of plots, each containing 32 artificial turtle nests. In each plot, we covered a percentage (0%, 25%, 50%, 81% or 100%) of the nests with either 1 or 2 sheets of plastic mesh. We used remote cameras to photograph and identify any predator that attacked nests in the plots. The cameras also allowed us to estimate the amount of time a fox was visible on each plot, as a metric of how much effort foxes expended on protected nests. Nest survival rate was not increased by either 1 or 2 sheets of mesh, and increasing the number of protected nests on a plot did not reveal a giving‐up density (GUD) value for fox foraging behaviour. Our study demonstrates that plastic mesh is not effective for protecting artificial turtle nests from foxes in this region. [ABSTRACT FROM AUTHOR]

The source of embryonic nutrition for development varies across teleost fishes. A parentotrophy index (ratio of neonate: ovulated egg dry mass) is often used to determine provisioning strategy, but the methodologies used vary across studies. The variation in source and preservation of tissue, staging of embryos, and estimation approach impedes our ability to discern between methodological and biological differences in parentotrophy indices inter- and intra-specifically. The threshold value used to distinguish between lecithotrophy and parentotrophy (0.6–1) differs considerably across studies. The lack of a standardised approach in definition and application of parentotrophy indices has contributed to inconsistent classifications of provisioning strategy. Consistency in both methodology used to obtain a parentotrophy index, and in the classification of provisioning strategy using a threshold value are essential to reliably distinguish between provisioning strategies in teleosts. We discuss alternative methods for determining parentotrophy and suggest consistent standards for obtaining and interpreting parentotrophy indices. [ABSTRACT FROM AUTHOR]

How innovations such as vision, flight and pregnancy evolve is a central question in evolutionary biology. Examination of transitional (intermediate) forms of these traits can help address this question, but these intermediate phenotypes are very rare in extant species. Here we explore the biology and evolution of transitional forms of pregnancy that are midway between the ancestral state of oviparity (egg‐laying) and the derived state, viviparity (live birth). Transitional forms of pregnancy occur in only three vertebrates, all of which are lizard species that also display intraspecific variation in reproductive phenotype. In these lizards (Lerista bougainvillii, Saiphos equalis, and Zootoca vivipara), geographic variation of three reproductive forms occurs within a single species: oviparity, viviparity, and a transitional form of pregnancy. This phenomenon offers the valuable prospect of watching 'evolution in action'. In these species, it is possible to conduct comparative research using different reproductive forms that are not confounded by speciation, and are of relatively recent origin. We identify major proximate and ultimate questions that can be addressed in these species, and the genetic and genomic tools that can help us understand how transitional forms of pregnancy are produced, despite predicted fitness costs. We argue that these taxa represent an excellent prospect for understanding the major evolutionary shift between egg‐laying and live birth, which is a fundamental innovation in the history of animals. [ABSTRACT FROM AUTHOR]

Introduction: Viviparity (live-birth) has evolved from oviparity (egg-laying) multiple times in sharks. While most transitions from oviparity to viviparity have resulted in non-placental forms of viviparity, some sharks develop a yolk sac placenta during pregnancy. The Australian sharpnose shark (Rhizoprionodon taylori) is a placental species that suspends embryonic development in a diapause for most of pregnancy.Methods: To identify structures involved in supporting rapid embryonic growth in late pregnancy, we examined uterine and placental morphology by light and electron microscopy.Results: Paraplacental uterine regions have morphological specialisations consistent with secretion and fluid transport between uterine tissues and the lumen. Uterine secretions in the lumen may be absorbed by the outgrowths on the embryonic umbilical cord ('appendiculae'), which are densely covered by microvilli. The placenta consists of uterine villi that interdigitate with the yolk sac and enhance the surface area available for fetomaternal exchange. The yolk sac does not invade the uterine epithelium, and the egg capsule remains intact at the placental interface, separating maternal and fetal tissues. Some placental uterine epithelial cells are secretory, and endocytic vesicles in the opposing yolk sac ectodermal cells suggest that nutrient transport is by histotrophic uterine secretion followed by fetal absorption. Respiratory gases, water and possibly small nutrients likely diffuse across the placenta, where maternal and fetal blood vessels are ~2 μm apart.Discussion: Placental structure in R. taylori is similar to most other sharks, but there are differences in cellular structures between species that may indicate species-specific placental transport mechanisms. [ABSTRACT FROM AUTHOR]

Citizen science has become a popular way to collect biodiversity data and engage the wider public in scientific research. It has the potential to improve the knowledge and skills of participants, and positively change their behaviour and attitude towards the environment. Citizen science outcomes are particularly valuable for wildlife conservation, as they could help alleviate human impacts on the environment.We used an online questionnaire to investigate the consequences of participating in an Australian turtle mapping app, TurtleSAT, on skills and knowledge gain, and test for any association between these gains and behavioural or attitudinal changes reported by the participants.One hundred and forty‐eight citizen scientists completed our questionnaire, mostly from the states of New South Wales and Victoria. TurtleSAT was the third most common source of correct answers about turtle ecology and conservation, after a talk about turtles and personal observations/research. Citizen scientists who participated more often were more knowledgeable about turtles than infrequent users. Self‐reported gains in knowledge and skills were positively linked to attitudinal and behavioural changes, such as being more aware of turtles on roads. However, behaviour and attitude changes were not related to participation rate. Respondents also reported that after learning about the current decline in turtle populations, they adopted several turtle‐friendly practices, such as habitat restoration or moving turtles out of harm's way, underlining the importance of increasing people's awareness on species declines.The reported changes in attitudes and behaviours are likely to positively impact the conservation of Australian freshwater turtles. Engagement with citizen science projects like TurtleSAT may result in participants being more interested in the natural world, by learning more about it and being more exposed to it, and therefore contributing more actively to its protection. A free Plain Language Summary can be found within the Supporting Information of this article. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address. Australian lizards exhibit a diversity of reproductive traits and provide excellent opportunities to study how those traits function and evolve. We review the contributions that Australian lizard research has made to understanding animal reproductive biology. We then highlight major emergent and outstanding research questions, and urge readers to consider Australian lizards as ideal model organisms for addressing these questions. Photo by C. Friesen. [ABSTRACT FROM AUTHOR]

Our understanding of the evolution of complex biological traits is greatly advanced by examining taxa with intermediate phenotypes. The transition from oviparity (egg‐laying) to viviparity (live‐bearing) has occurred independently in many animal lineages, but there are few phenotypic intermediates. The lizard Saiphos equalis exhibits bimodal reproduction, with some viviparous populations, and other oviparous populations with long egg‐retention, a rare trait where most of embryonic development occurs inside the mother prior to late ovipositioning. We posit that oviparous S. equalis represent an intermediate form between "true" oviparity and viviparity. We used transcriptomics to compare uterine gene expression in these two phenotypes, and provide a molecular model for the genetic control and evolution of reproductive mode. Many genes are differentially expressed throughout the reproductive cycle of both phenotypes, which have clearly different gene expression profiles overall. The differentially expressed genes within oviparous and viviparous individuals have broadly similar biological functions putatively important for sustaining embryos, including uterine remodelling, respiratory gas and water exchange, and immune regulation. These functional similarities indicate either that long egg‐retention is an exaptation for viviparity, or might reflect parallel evolution of similar gravidity‐related changes in gene expression in long egg‐retention oviparity. In contrast, gene expression changes across the reproductive cycle of long egg‐retaining oviparous S. equalis are dramatically different from those of "true" oviparous skinks (such as Lampropholis guichenoti), supporting our assertion that oviparous S. equalis exhibit an intermediate phenotype between "true" oviparity and viviparity. [ABSTRACT FROM AUTHOR]

Citizen science has become popular for data collection in ecology and environmental management. However, most participants in citizen science projects are only involved for a short period of time. Understanding the reasons behind this dropout rate is important for improving long term participation. Here we investigated participation rates in TurtleSAT, an Australian turtle mapping app aimed at collecting data useful for conservation efforts. First, we looked at the TurtleSAT database to examine the number of participants and how many sightings each had uploaded. Then, we distributed an online questionnaire to all TurtleSAT participants and asked what inspired them to participate, if they found the app easy to use, and whether they were still active in the project. Out of 75 respondents, 21 said they were currently not active participants. Their reasons for not participating anymore included lack of time, technical issues, and a perception of high turtle abundance that indicated conservation efforts are unnecessary. The motives that originally inspired their participation were not significantly linked to them leaving the project. We propose possible solutions to some of the issues identified, such as offering online tutorials and a hotline to solve technical issues, a more direct link from the TurtleSAT app to news and academic articles regarding turtles, and establishing an online forum to maintain engagement. [ABSTRACT FROM AUTHOR]

Reproducing sharks must provide their offspring with an adequate supply of nutrients to complete embryonic development. In oviparous (egg-laying) sharks, offspring develop outside the mother, and all the nutrients required for embryonic growth are contained in the egg yolk. Conversely, in viviparous (live-bearing) sharks, embryonic development is completed inside the mother, providing offspring with the opportunity to receive supplementary embryonic nourishment, known as matrotrophy. Viviparous sharks exhibit nearly all forms of matrotrophy known in vertebrates, including a yolk-sac placenta, which involves several significant ontogenetic modifications to fetal and maternal tissues. The selective pressures that have driven the evolution of complex placentas in some shark species, but not in others, are unresolved. Herein we review the mechanisms of reproductive allocation and placental diversity in sharks, and consider the application of both adaptive and conflict hypotheses for the evolution of placental nutrient provisioning. Both have likely played roles in placental evolution in sharks, perhaps at different times in evolutionary history. Finally, we recommend sharks as an outstanding model system to investigate the evolution of placentas and mechanisms for fetal nutrition during pregnancy in vertebrates. Live-bearing reproduction provides developing embryos with the opportunity to receive maternal nutrients during pregnancy, in addition to the yolk. In some sharks, this transfer of nutrients is achieved by a placenta. Herein we consider the adaptive significance and evolution of the placenta in sharks. We recommend sharks as important models to investigate the evolution of vertebrate pregnancy and modes of fetal nutrition. [ABSTRACT FROM AUTHOR]

Abstract: Developmental plasticity in offspring phenotype occurs as a result of the environmental conditions embryos experience during development. The nutritional environment provided to a fetus is an important source of developmental plasticity. Reptiles are a particularly interesting system to study this plasticity because of their varied routes of maternal nutrient allocation to reproduction. Most reptiles provide their offspring with all or most of the nutrients they require in egg yolk (lecithotrophy) while viviparous reptiles also provide their offspring with nutrients via a placenta (placentotrophy). We review the ways in which both lecithotrophy and placentotrophy can lead to differences in the nutrients embryonic reptiles receive, and discuss how these differences lead to developmental plasticity in offspring phenotype. We finish by reviewing the ecological and conservation consequences of nutritional‐driven developmental plasticity in reptiles. If nutritional‐driven developmental plasticity has fitness consequences, then understanding the basis of this plasticity has exciting potential to identify how reptile recruitment is affected by environmental changes in food supply. Such knowledge is critical to our ability to protect taxa threatened by environmental change. [ABSTRACT FROM AUTHOR]

Turtles have persisted for over 220 million years, despite facing threats at every life-history stage. In Australia, nest predation by introduced foxes has driven severe declines in some populations. Our project quantified the nesting habitat of the endangered broad-shelled turtle (Chelodina expansa) to facilitate protection of critical nesting grounds. We determined the nesting preferences of C. expansa at five distinct wetlands on the Murray River from 2011 to 2014. We identified environmental variables associated with nest sites in different habitats and compared those at nests and non-nest sites to determine nesting preferences. Kernel density estimates were used to identify important nesting grounds. Our study has important implications for conservation of C. expansa. Habitat preferences for nest sites of C. expansa are predictable both within and across sites, with females preferring to nest ~50 m from shore (~4 m elevation), in open habitat with little vegetation. Based on these habitat preferences, kernel density estimates showed that C. expansa may select the same nesting beaches in subsequent years. Fox depredation of nests (and nesting adults) drives turtle declines in Australia, so identifying nesting areas for protection is a first step in turtle conservation. Chelodina expansa is an endangered turtle threatened by invasive red fox depredation on nests. Our study identified environmental variables associated with nest site preferences in C. expansa , including elevation above water, ground cover and vegetation. It allows the identification of nesting habitat that can be targeted for conservation management. Photo by Jeremy Pike. [ABSTRACT FROM AUTHOR]

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. We used data collected through the citizen science project TurtleSAT to describe the patterns of road mortality of freshwater turtles along the Murray River. The long-necked turtle (Chelodina longicollis) was the species most commonly reported dead on roads. We discovered a relationship between the likelihood of C. longicollis road mortality, rainfall and time of year. We also observed that dual carriageways such as the Hume Highway were the most likely locations where C. longicollis could be killed. Photo by Claudia Santori. [ABSTRACT FROM AUTHOR]

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. We used environmental sampling and stomach flushing to determine how turtle diets varied with environmental conditions at four wetlands in north-central Victoria. Our results show in particular that Emydura macquarii select filamentous green algae (FGA) as a food source. We suggest that FGA scarcity may be limiting to E. macquarii. Photo by Jules Farquhar. [ABSTRACT FROM AUTHOR]

Large-scale releases of environmental contaminants from industrial facilities can cause considerable damage to surrounding ecosystems and require remediation. The expense and/or undesirable environmental side effects of physical removal may constrain remediation efforts. In 2008, approximately 4.1 million m³ of fly ash were released into the Emory River at a coal-burning power plant in Kingston, Tennessee, USA. Approximately 390?000?m³ of fly ash were not removed (hereafter "residual ash"), to avoid disturbing underlying legacy contamination from unrelated historical industrial activity. In 2011 and 2012, the authors measured trace element concentrations in an assemblage of freshwater turtles in 2 rivers impacted by the spill and in a third river that was unaffected. Concentrations of arsenic, copper, iron, mercury, manganese, selenium, and zinc were higher in turtles from rivers affected by the spill but low relative to concentrations known to be toxic to other vertebrates. Concentrations of some trace elements decreased with distance from the original spill site but were not strongly affected by nearby volumes of residual ash. Among-species differences in trace element bioaccumulation and/or the relatively low spatial resolution of available data on residual ash volumes may have obscured this effect. The results suggest that the spill influenced turtle bioaccumulation of trace elements but that distance from the spill site may be a more important factor than residual ash in influencing postremediation bioaccumulation. [ABSTRACT FROM AUTHOR]

The evolution of viviparity requires the development of mechanisms that facilitate transport of respiratory gases between mother and developing embryo. Of particular importance is maternal excretion of embryonic carbon dioxide (CO2), which increases as the embryo grows in size during development. The carbonic anhydrases are a family of enzymes that convert CO2 to bicarbonate for transport throughout the cardiovascular system and which may also be important for CO2 transport from embryo to mother. We used immunohistochemistry to localize carbonic anhydrase II in the placental tissues of a viviparous and highly placentotrophic lizard, Pseudemoia entrecasteauxii. Carbonic anhydrase II is localized in the uterine component of the paraplacentome, presumably to facilitate transport of embryonic CO2 to the mother. Carbonic anhydrase II is also localized in both the uterine and embryonic components of the placentome, a region heavily involved in placental nutrient transport rather than respiratory gas exchange. In contrast, carbonic anhydrase II is not present in the uterine or embryonic components of the omphaloplacenta, another region responsible for nutrient transport. While carbonic anhydrase II in the paraplacentomal uterus is likely to be responsible for embryo-maternal CO2 transport, the distribution of carbonic anhydrase II throughout the placentome indicates a different function. Instead of transporting embryonic CO2, placentomal carbonic anhydrase II appears to be responsible for transporting CO2 produced by energetically expensive nutrient transport mechanisms in both the uterus and the embryo, which implies that the mechanisms of nutrient transport in the omphaloplacenta may not be as energetically expensive. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 636-646, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Globally, turtles are among the most threatened vertebrate taxa, with over 60% of all species being listed as endangered, threatened, or vulnerable. This special issue of the Journal contains a selection of papers from a conference on freshwater turtle conservation held in Canberra, ACT, in February 2017. [ABSTRACT FROM AUTHOR]

Oviparous vertebrates maternally transfer elements to their offspring during egg production. Maternal transfer occurs because elements mimic, or are incorporated into, nutrients allocated to eggs, but likely differs among species depending on the quantities of specific nutrients allocated to eggs. Developing embryos are often assumed to assimilate all of the elements allocated to eggs, but this assumption has rarely been tested. We tested the hypothesis that maternal transfer and embryonic assimilation of trace elements differed between two species of freshwater turtles exposed to a recently-remediated coal fly-ash spill. Sternotherus odoratus transferred As, Se, and Zn, while Trachemys scripta transferred As, Hg, Se, Sr, and Zn. Logarithmic non-linear relationships between hatchling and egg concentrations indicated that turtles partially assimilated elements present in eggs. In systems contaminated with multiple trace elements, our data show that maternal transfer and embryonic assimilation are element- and species-specific, and may be inconsistent even among closely-related species. [ABSTRACT FROM AUTHOR]

Squamate reptiles (lizards and snakes) are an ideal model system for testing hypotheses regarding the evolution of viviparity (live birth) in amniote vertebrates. Viviparity has evolved over 100 times in squamates, resulting in major changes in reproductive physiology. At a minimum, all viviparous squamates exhibit placentae formed by the appositions of maternal and embryonic tissues, which are homologous in origin with the tissues that form the placenta in therian mammals. These placentae facilitate adhesion of the conceptus to the uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and calcium. However, most viviparous squamates continue to rely on yolk for nearly all of their organic nutrition. In contrast, some species, which rely on the placenta for at least a portion of organic nutrition, exhibit complex placental specializations associated with the transport of amino acids and fatty acids. Some viviparous squamates also exhibit reduced immunocompetence during pregnancy, which could be the result of immunosuppression to protect developing embryos. Recent molecular studies using both candidate-gene and next-generation sequencing approaches have suggested that at least some of the genes and gene families underlying these phenomena play similar roles in the uterus and placenta of viviparous mammals and squamates. Therefore, studies of the evolution of viviparity in squamates should inform hypotheses of the evolution of viviparity in all amniotes, including mammals. [ABSTRACT FROM AUTHOR]

In oviparous vertebrates, trace elements transfer from mother to offspring during egg production. For animals that produce eggs slowly, like turtles, the trace element concentration of each egg reflects an integration of dietary and stored accumulation over the duration of vitellogenesis. Because turtles also produce eggs synchronously, all eggs within a dutch should exhibit uniform trace element concentrations. In contrast, for animals that produce eggs in sequence and primarily from current dietary resources, like many birds, the trace element concentrations of eggs should be less uniform within a clutch, and likely reflect short-term changes in dietary exposure. We tested the hypothesis that stinkpot turtle (Sternotherus odoratus) clutches exhibit lower variability and higher repeatability in barium, selenium, strontium, and thallium concentrations than those of tree swallows (Tachycineta bicolor) from a site impacted by a recent coal ash spill. All four trace elements exhibited significantly lower variability and significantly higher repeatability in stinkpot clutches than in swallow clutches. Mean trace element concentrations of stinkpot eggs were also significantly higher than those of swallow eggs although both species feed primarily on aquatic invertebrates. Variability in swallow egg trace element concentrations was partially due to significant laying order effects. Our results support the hypothesis that interspecific variation in the source of resources and in the synchronicity and rate of egg production can lead to interspecific differences in the variability of egg trace element concentrations. [ABSTRACT FROM AUTHOR]

Selenium (Se) is a bioaccumulative constituent of coal fly-ash that can disrupt reproduction of oviparous wildlife. In food webs, the greatest enrichment of Se occurs at the lowest trophic levels, making it readily bioavailable to higher consumers. However, subsequent enrichment at higher trophic levels is less pronounced, leading to mixed tendencies for Se to biomagnify. We used stable isotopes (1 5N and 13C) in claws to infer relative trophic positions and relative carbon sources, respectively, of seven turtle species near the site of a recently-remediated coal fly-ash spill. We then tested whether Se concentrations differed with relative trophic position or relative carbon source. We did not observe a strong relationship between δ15N and Se concentration. Instead, selenium concentrations decreased with increasing δ13C among species. Therefore, in an assemblage of closely-related aquatic vertebrates, relative carbon source was a better predictor of Se bioaccumulation than was relative trophic position. [Copyright &y& Elsevier]

Reproductive allocation strategies have been historically described as lying on a continuum between capital and income breeding. Capital breeders have been defined as species that allocate stored reserves to reproduction, whereas income breeders have been defined as species that allocate relatively recently-ingested food resources to reproduction. Snakes are considered capital breeders because they efficiently store large amounts of nutrients and energy, potentially enough to support an entire reproductive bout without feeding. We examined the abilities of five viviparous snake species to allocate income to follicles during vitellogenesis. We fed 15N-labelled L-leucine to experimental females of each species during vitellogenesis, whereas control females were fed unlabelled meals. After ovulation, we measured yolk 15N p.p.m. using mass spectrometry. Maternal scale samples taken before labelling were used to estimate endogenous 15N concentrations, which should represent 'capital'. Scale samples taken at ovulation were used to determine whether snakes assimilated 15N-labelled-leucine from labelled diets. Yolks and post-ovulatory scales of labelled females were significantly more enriched in 15N than those of unlabelled females in all species, indicating significant assimilation and allocation of income-derived amino acids to the yolk during vitellogenesis. The lack of among-species differences suggests that all species allocated income amino acids to vitellogenesis. The results obtained in the present study suggest that proportional utilization of income or capital depends on the frequency and timing of foraging success during reproductive events. Therefore, capital and income breeding may be consequences of both life-history and environmental constraints on foraging success, rather than strategies of reproductive allocation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 390-404. [ABSTRACT FROM AUTHOR]

Viviparity and placentation have evolved from oviparity over 100 times in squamate reptiles (lizards and snakes). The independent origins of placentation have resulted in a variety of placental morphologies in different taxa, ranging from simple apposition of fetal and maternal tissues to endotheliochorial implantation that is homoplaslous with mammalian placentation. Because the eggs of oviparous squamates transport gases and water from the environment and calcium from the eggshell, the placentae of viviparous squamates are thought to have Initially evolved to accomplish these functions from within the maternal oviduct. Species with complex placentae have also been shown to rely substantially, or even primarily, on placental transport of organic nutrients for embryonic nutrition. However, it is unclear whether species with only simple placentae are also capable of transporting organic nutrients to offspring. Among viviparous squamates, all of the snakes that have been studied thus far have been shown to have simple placentae. However, most studies of snake placentation are limited to a single lineage, the North American Natricinae. We tested the abilities of four species of viviparous snakes - Agkistrodon contortrix (Viperidae), Boa constrictor (Boldae), Nerodia sipedon (Colubridae: Natricinae) and Thamnophis sirtalls (Colubridae: Natricinae) - to transport diet- derived amino acids to offspring during gestation. We fed [15N]leucine to pregnant snakes, and compared offspring 15N content with that of unlabeled controls. Labeled females allocated significantly more 15N to offspring than did controls, but 15N allocation did not differ among species. Our results indicate that viviparous snakes are capable of transporting diet-derived amino acids to their offspring during gestation, possibly via placentation. [ABSTRACT FROM AUTHOR]

Abstract: Reproductive effort has been defined as the proportion of an organism''s energy budget that is allocated to reproduction over a biologically meaningful time period. Historically, studies of reproductive bioenergetics considered energy content of gametes, but not costs of gamete production. Although metabolic costs of vitellogenesis (MCV) fundamentally reflect the primary bioenergetic cost of reproductive allocation in female reptiles, the few investigations that have considered costs of reproductive allocation have focused on metabolic costs of pregnancy (MCP) in viviparous species. We define MCP as energetic costs incurred by pregnant females, including all costs of maintaining gestation conditions necessary for embryogenesis. MCP by our definition do not include fetal costs of embryogenesis. We measured metabolic rates in five species of viviparous snakes (Agkistrodon contortrix, Boa constrictor, Eryx colubrinus, Nerodia sipedon, and Thamnophis sirtalis) during vitellogenesis and pregnancy in order to estimate MCV and MCP. Across all species, MCV were responsible for 30% increases in maternal metabolism. Phylogenetically-independent contrasts showed that MCV were significantly greater in B. constrictor than in other species, likely because B. constrictor yolk energy content was greater than that of other species. Estimates of MCP were not significantly different from zero in any species. In viviparous snakes, MCV appear to represent significant bioenergetic expenditures, while MCP do not. We suggest that MCV, together with yolk energy content, represent the most significant component of reptilian reproductive effort, and therefore deserve greater attention than MCP in studies of reptilian reproductive bioenergetics. [Copyright &y& Elsevier]

Abstract: We examined functions of residual yolk (RY 1 [1] RY: residual yolk. ) in hatchling Smooth Softshell Turtles (Apalone mutica). Removal of RY did not affect survival, shell growth, or resting metabolic rates of turtles for 40 d after hatching. Our estimates of metabolic rate suggest that RY can fuel maintenance and activity metabolism for approximately 25days. A. mutica absorb more than 1g of water in the first 2 weeks of life, which appears to be the basis of post-hatch shell expansion rather than yolk-provisioned growth. Post-hatch growth may be limited by the magnitude of RY remaining at hatching, but RY protein and lipid proportions do not differ from those of freshly-laid eggs. In addition, A. mutica did not use RY to fuel nest emergence. Our results suggest that RY does not fulfill several hypothetical functions in A. mutica, including postnatal growth, catabolic fuel for nest emergence, and long-term nutritional sustenance for maintenance, activity, or hibernation. Instead, A. mutica appear to absorb most yolk prior to hatching, and are left with a minimum of RY. Variation in RY mass with incubation regime in other species suggests that mothers may overprovision their eggs to ensure successful development across a diversity of possible incubation conditions. [ABSTRACT FROM AUTHOR]

Humans are increasing the frequency of fish kills by degrading freshwater ecosystems. Simultaneously, scavengers like freshwater turtles are declining globally, including in the Australian Murray–Darling Basin. Reduced scavenging may cause water quality problems impacting both ecosystems and humans. We used field and mesocosm experiments to test whether scavenging by turtles regulates water quality during simulated fish kills. In the field, we found that turtles were important scavengers of fish carrion. In mesocosms, turtles rapidly consumed carrion, and water quality in mesocosms with turtles returned to pre-fish kill levels faster than in turtle-free controls. Our experiments have important ecological implications, as they suggest that turtles are critical scavengers that regulate water quality in freshwater ecosystems. Recovery of turtle populations may be necessary to avoid the worsening of ecosystem health, particularly after fish kills, which would have devastating consequences for many freshwater species. [ABSTRACT FROM AUTHOR]

Food availability determines the amount of energy animals can acquire and allocate to reproduction and other necessary functions. Female animals that are food limited thus experience reduced energy available for reproduction. When this occurs, females may reduce frequency of reproductive events or the number or size of offspring per reproductive bout. We assessed how maternal diet affects reproductive output in adult female Murray River short-necked turtles, Emydura macquarii, from four wetlands in Victoria. We previously found that turtle diets differ in the composition of plants and animals between our study wetlands. In this study, we tested whether differences in turtle diet composition (i.e. plants and animals) at these wetlands were associated with differences in clutch mass, individual egg mass, bulk egg composition and hatching success. We found total clutch mass increased with maternal body size at each site. At sites where filamentous green algae were scarce and E. macquarii were carnivorous, females produced smaller clutches relative to body size compared to females from sites where algae were abundant, and turtles were more herbivorous. Individual egg mass, bulk egg composition and hatching success did not differ across wetlands. Isotopic analysis revealed significant positive relationships between the carbon and nitrogen isotopes (δ 13 C, δ 15 N) of the eggs and those of the mothers, indicating that mothers allocated ratios of carbon and nitrogen isotopes to their eggs similar to those present in their tissues. Our study suggests that at sites where females are more carnivorous due to a relative absence of algae, females produce smaller clutches, but other aspects of their reproduction are not significantly impacted. The reduction in clutch size associated with differences in the availability of dietary plants and animals may have long-term consequences for E. macquarii and other freshwater turtle species that are experiencing population declines., Competing Interests: The authors have no conflicts of interest to declare., (© The Author(s) 2024. Published by Oxford University Press and the Society for Experimental Biology.)

The repeated evolution of the same traits in distantly related groups (convergent evolution) raises a key question in evolutionary biology: do the same genes underpin convergent phenotypes? Here, we explore one such trait, viviparity (live birth), which, qualitative studies suggest, may indeed have evolved via genetic convergence. There are >150 independent origins of live birth in vertebrates, providing a uniquely powerful system to test the mechanisms underpinning convergence in morphology, physiology, and/or gene recruitment during pregnancy. We compared transcriptomic data from eight vertebrates (lizards, mammals, sharks) that gestate embryos within the uterus. Since many previous studies detected qualitative similarities in gene use during independent origins of pregnancy, we expected to find significant overlap in gene use in viviparous taxa. However, we found no more overlap in uterine gene expression associated with viviparity than we would expect by chance alone. Each viviparous lineage exhibits the same core set of uterine physiological functions. Yet, contrary to prevailing assumptions about this trait, we find that none of the same genes are differentially expressed in all viviparous lineages, or even in all viviparous amniote lineages. Therefore, across distantly related vertebrates, different genes have been recruited to support the morphological and physiological changes required for successful pregnancy. We conclude that redundancies in gene function have enabled the repeated evolution of viviparity through recruitment of different genes from genomic "toolboxes", which are uniquely constrained by the ancestries of each lineage., (© The Author(s) 2022. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

Turtles and tortoises (chelonians) have been integral components of global ecosystems for about 220 million years and have played important roles in human culture for at least 400,000 years. The chelonian shell is a remarkable evolutionary adaptation, facilitating success in terrestrial, freshwater and marine ecosystems. Today, more than half of the 360 living species and 482 total taxa (species and subspecies combined) are threatened with extinction. This places chelonians among the groups with the highest extinction risk of any sizeable vertebrate group. Turtle populations are declining rapidly due to habitat loss, consumption by humans for food and traditional medicines and collection for the international pet trade. Many taxa could become extinct in this century. Here, we examine survival threats to turtles and tortoises and discuss the interventions that will be needed to prevent widespread extinction in this group in coming decades., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Freshwater turtles may ingest baited fish hooks because many are opportunistic scavengers. Although the ingestion of fish hooks is known to be a source of mortality in multiple vertebrate groups, the prevalence of hook ingestion by freshwater turtles has not been well studied. We trapped turtles from five rivers in the southeastern United States and used radiographs to examine over 600 individuals of four species. Depending on the species, sex, and age class, 0-33% of turtles contained ingested fish hooks. For some species, larger turtles were more likely to contain a fish hook than smaller individuals. Freshwater turtle demography suggests that even small increases in adult mortality may lead to population declines. If our study areas are representative of other aquatic systems that receive fishing pressure, this work likely identifies a potential conflict between a widespread, common recreational activity (i.e., fishing) and an imperiled taxonomic group.

Squamate reptiles (lizards and snakes) are an ideal model system for testing hypotheses regarding the evolution of viviparity (live birth) in amniote vertebrates. Viviparity has evolved over 100 times in squamates, resulting in major changes in reproductive physiology. At a minimum, all viviparous squamates exhibit placentae formed by the appositions of maternal and embryonic tissues, which are homologous in origin with the tissues that form the placenta in therian mammals. These placentae facilitate adhesion of the conceptus to the uterus as well as exchange of oxygen, carbon dioxide, water, sodium, and calcium. However, most viviparous squamates continue to rely on yolk for nearly all of their organic nutrition. In contrast, some species, which rely on the placenta for at least a portion of organic nutrition, exhibit complex placental specializations associated with the transport of amino acids and fatty acids. Some viviparous squamates also exhibit reduced immunocompetence during pregnancy, which could be the result of immunosuppression to protect developing embryos. Recent molecular studies using both candidate-gene and next-generation sequencing approaches have suggested that at least some of the genes and gene families underlying these phenomena play similar roles in the uterus and placenta of viviparous mammals and squamates. Therefore, studies of the evolution of viviparity in squamates should inform hypotheses of the evolution of viviparity in all amniotes, including mammals.