Sex identification in juvenile and adult Indonesian blue-tongued skinks (Tiliqua gigas) through cystoscopy and accuracy of contrast radiography.

OBJECTIVE: To describe a nonsurgical endoscopic technique for sex identification in Indonesian blue-tongued skinks (Tiliqua gigas) and to assess accuracy of contrast radiography of the hemipenile/hemiclitoral pouches. ANIMALS: 42 clinically healthy Indonesian blue-tongued skinks between 6 months and 3 years old and weighing between 22 and 550 g. METHODS: Cystoscopy was performed under general anesthesia. Gonads were visualized through the transparency of the urinary bladder, and their gross morphology was described. Contrast was applied in the tail pouches before obtaining full-body radiographs. Two radiologists, blinded to the sex of the skink, evaluated the radiographs. RESULTS: Cystoscopy was achieved in all 42 skinks. Visualization of the gonads through the urinary bladder was possible in 41 (98%; 95% CI, 87% to 99%) of the skinks, with 18 of them identified as males and 23 identified as females. Median procedure time was 60 seconds (range, 25 to 180 seconds) and was not associated with procedure order (-0.69; 95% CI, -1.83 to 0.45) or with the weight (0.02 g; 95% CI, -0.07 to 1.0) or the identified sex (11.7; 95% CI, -15.07 to 38.45) of the skink. Radiographs had a sensitivity of 69.6% (95% CI, 47.1% to 86.8%) and a specificity of 75.0% (47.6% to 92.7%) to identify female skinks. All the skinks recovered uneventfully. CLINICAL RELEVANCE: Cystoscopic sex identification is feasible in Indonesian blue-tongued skinks of various age and size. Considering the difficulty in identifying their sex otherwise, this technique could provide a significant improvement in the veterinary care of this species. In this population, contrast radiographs showed limited accuracy for sex identification.

The Complete Mitochondrial Genomes of Three Sphenomorphinae Species (Squamata: Scincidae) and the Selective Pressure Analysis on Mitochondrial Genomes of Limbless Isopachys gyldenstolpei.

In order to adapt to diverse habitats, organisms often evolve corresponding adaptive mechanisms to cope with their survival needs. The species-rich family of Scincidae contains both limbed and limbless species, which differ fundamentally in their locomotor demands, such as relying on the movement of limbs or only body swing to move. Locomotion requires energy, and different types of locomotion have their own energy requirements. Mitochondria are the energy factories of living things, which provide a lot of energy for various physiological activities of organisms. Therefore, mitochondrial genomes could be tools to explore whether the limb loss of skinks are selected by adaptive evolution. Isopachys gyldenstolpei is a typical limbless skink. Here, we report the complete mitochondrial genomes of I. gyldenstolpei, Sphenomorphus indicus, and Tropidophorus hainanus. The latter two species were included as limbed comparator species to the limbless I. gyldenstolpei. The results showed that the full lengths of the mitochondrial genomes of I. gyldenstolpei, S. indicus, and T. hainanus were 17,210, 16,944, and 17,001 bp, respectively. Three mitochondrial genomes have typical circular double-stranded structures similar to other reptiles, including 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and the control region. Three mitochondrial genomes obtained in this study were combined with fifteen mitochondrially complete genomes of Scincidae in the NCBI database; the phylogenetic relationship between limbless I. gyldenstolpei and limbed skinks (S. indicus and T. hainanus) is discussed. Through BI and ML trees, Sphenomorphinae and Mabuyinae were monophyletic, while the paraphyly of Scincinae was also recovered. The limbless skink I. gyldenstolpei is closer to the species of Tropidophorus, which has formed a sister group with (T. hainanus + T. hangman). In the mitochondrial genome adaptations between limbless I. gyldenstolpei and limbed skinks, one positively selected site was found in the branch-site model analysis, which was located in ND2 (at position 28, BEB value = 0.907). Through analyzing the protein structure and function of the selected site, we found it was distributed in mitochondrial protein complex I. Positive selection of some mitochondrial genes in limbless skinks may be related to the requirement of energy to fit in their locomotion. Further research is still needed to confirm this conclusion though.

The Curious Case of the "Neurotoxic Skink": Scientific Literature Points to the Absence of Venom in Scincidae.

In contrast to the clearly documented evolution of venom in many animal lineages, the origin of reptilian venom is highly debated. Historically, venom has been theorised to have evolved independently in snakes and lizards. However, some of the recent works have argued for the common origin of venom in "Toxicofera" reptiles, which include the order Serpentes (all snakes), and Anguimorpha and Iguania lizards. Nevertheless, in both these contrasting hypotheses, the lizards of the family Scincidae are considered to be harmless and devoid of toxic venoms. Interestingly, an unusual clinical case claiming neurotoxic envenoming by a scincid lizard was recently reported in Southern India. Considering its potentially significant medicolegal, conservation and evolutionary implications, we have summarised the scientific evidence that questions the validity of this clinical report. We argue that the symptoms documented in the patient are likely to have resulted from krait envenomation, which is far too frequent in these regions.

Morphological study of the integument and corporal skeletal muscles of two psammophilous members of Scincidae (Scincus scincus and Eumeces schneideri).

Sand deserts are common biotopes on the earth's surface. Numerous morphological and physiological adaptations have appeared to cope with the peculiar conditions imposed by sandy substrates, such as abrasion, mechanical resistance and the potential low oxygen levels. The psammophilous scincids (Lepidosauria) Scincus scincus and Eumeces schneideri are among those. S. scincus is a species frequently used to study displacement inside a sandy substrate. E. schneideri is a species phylogenetically closely related to S. scincus with a similar lifestyle. The aims of this study focus on the morphology of the integument and the muscular system. Briefly, we describe interspecific differences at the superficial architecture of the scales pattern and the thickness of the integument. We highlight a high cellular turnover rate at the level of the basal germinal layer of the epidermis, which, we suggest, corresponds to an adaptation to cutaneous wear caused by abrasion. We demonstrate the presence of numerous cutaneous holocrine glands whose secretion probably plays a role in the flow of sand along the integument. Several strata of osteoderms strengthen the skin. We characterize the corporal (M. longissimus dorsi and M. rectus abdominus) and caudal muscular fibers using immunohistochemistry, and quantify them using morphometry. The musculature exhibits a high proportion of glycolytic fast fibers that allow rapid burying and are well adapted to this mechanically resistant and oxygen-poor substrate. Oxidative slow fibers are low in abundance, less than 10% in S. scincus, but a little higher in E. schneideri.

Viviparous Reptile Regarded to Have Temperature-Dependent Sex Determination Has Old XY Chromosomes.

The water skinks Eulamprus tympanum and Eulamprus heatwolei show thermally induced sex determination where elevated temperatures give rise to male offspring. Paradoxically, Eulamprus species reproduce in temperatures of 12-15 °C making them outliers when compared with reptiles that use temperature as a cue for sex determination. Moreover, these two species are among the very few viviparous reptiles reported to have thermally induced sex determination. Thus, we tested whether these skinks possess undetected sex chromosomes with thermal override. We produced transcriptome and genome data for E. heatwolei. We found that E. heatwolei presents XY chromosomes that include 14 gametologs with regulatory functions. The Y chromosomal region is 79-116 Myr old and shared between water and spotted skinks. Our work provides clear evidence that climate could be useful to predict the type of sex determination systems in reptiles and it also indicates that viviparity is strictly associated with sex chromosomes.

Comparative study of the visual system of two psammophilic lizards (Scincus scincus &Eumeces schneideri).

Sand deserts are common biotopes on the earth's surface. Some specialized vertebrate species have colonized these ecological habitats by living buried in the sand. Among these so called psammophilic species are the Scincidae sand dune living species Scincus scincus and Eumeces schneideri. These two skinks share a relatively similar behavioral ecology by living buried in sand, almost all the time for S. scincus and at least for some part of the day for E. schneideri. The visual system of these two lizards was investigated by histological, immunohistochemical, Magnetic Resonance Imaging (MRI) and morphometric techniques. Both skink species exhibit a retina lacking fovea, composed predominantly of cones presenting two types of oil droplets (pale blue-green and colorless). Both species possess a subset of rod like-photoreceptors (about 1 rod for 30 cones) evidenced by anti-rhodopsin immunoreactivity. A ratio 1:1-1:2 between ganglion cells and photoreceptors points to a linear connection (photoreceptors/bipolar neurons/ganglion cells) in the retina and indicates that both skinks more likely possess good visual acuity, even in the peripheral retina. The MRI analysis revealed differences between the species concerning the eye structures, with a more spherical eye shape for S. scincus, as well as a more flattened lens. The relative lens diameter of both species seems to correspond to a rather photopic pattern. Beside the fact that S. scincus and E. schneideri have different lifestyles, their visual capacities seem similar, and, generally speaking, these two psammophilic species theoretically exhibit visual capacities not far away from non-fossorial species.

Hemipenial morphology of nine South American species of Mabuya (Scincidae: Lygosominae) with comments on the morphology of the family.

Species of the genus Mabuya are barely recognizable because of their highly conservative external morphology, resulting in unstable systematic and taxonomic status. Considering that hemipenial morphology has been extensively used as a source of systematic information for several groups of Squamata, we described the hemipenial morphology of nine species of Mabuya, searching for diagnostic features useful to taxonomic and systematic studies. To have comparative parameters within the family, we also presented the description of the hemipenes of two other Scincidae species (i.e., Trachylepis atlantica and Tiliqua rugosa). This information, together with the available literature, was analyzed in a comparative framework, allowing us to define some variation for the genus and family. The hemipenial morphology of the species of Mabuya studied is very conservative; features that show subtle variation were the shape of the protuberances present on the asulcate face of the hemipenial body and the presence and type of a lateral fold, on the body. Also, within the family, some variation was found in the shape and length of lobes, length of branches of the sulcus spermaticus, and in the kind of folds and protuberances in both faces of the lobes and hemipenial body. Although these features were not tested in a systematic context, this information suggested variations in hemipenial morphology that could contribute to taxonomic diagnostics and phylogenetic characters. The importance of obtaining proper preparations for gathering accurate information is emphasized, and the use of fresh-killed specimens that shows fewer difficulties for the procedures of preparation is highly recommended.

The Key to Understanding the European Miocene Chalcides (Squamata, Scincidae) Comes from Asia: The Lizards of the East Siberian Tagay Locality (Baikal Lake) in Russia.

The early middle Miocene (MN 5) lizards from the East Siberian Tagay locality (Baikal Lake, Russia) in Asia are described here. The lizard fauna consists of two clades, Lacertidae and Scincidae. The skink material is allocated to Chalcides. While this taxon was previously reported from Europe, it has rarely been observed in the Neogene record with only jaw fragments and frontal bones described. Its taxonomy was therefore enigmatic. The Tagay material is almost identical to the European fossils of Chalcides from Austria and Hungary, but it also contains the parietal bone. While the material is also similar to the extant Ch. ocellatus, it exhibits several morphological differences. A new species is therefore erected-Chalcides augei sp. nov. These findings further support the connection of the Baikal Lake area with central Europe during the first half of the Miocene. The comparative anatomy of the frontals, parietals and lower jaws was evaluated by micro-CT in selected skink taxa. This comparison highlights several important differences, for example, paired frontals are present in Broadleysaurus (an outgroup taxon), in Acontias and all studied members of Scincidae herein. The character optimization in Mesquite supports fused frontals as being the condition at the basal node of the Ateuchosauridae + Sphenomorphidae + Eugongylidae + Lygosomidae + Egerniidae + Mabuyidae clade. While the parapineal foramen is restricted to the parietal in most taxa studied herein, it is absent (or vestigial) in Acontias and Feylinia. In contrast to all other skinks, this foramen is located on the frontal in Ateuchosaurus chinensis. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1901-1934, 2020. © 2019 American Association for Anatomy.

Two new species of Lerista Bell, 1833 (Reptilia: Scincidae) from north Queensland populations formerly assigned to Lerista storri Greer, McDonald and Lawrie, 1983.

Ongoing surveys for skinks of the genus Lerista in north Queensland have resulted in the collection of voucher specimens from two populations formerly assigned to Lerista storri Greer, McDonald Lawrie, 1983 that are geographically isolated from the type population and show a degree of morphological variation differing from the type population. Analysis of recently collected material has confirmed both populations are specifically distinct to the type population, with one being more closely related to Lerista ameles Greer, 1979, another little known, north Queensland species. Consequently, these populations are described as Lerista alia sp. nov. and Lerista parameles sp. nov. The morphological diversity of L. storri is thereby restricted, necessitating a redescription. The conservation status of all these taxa is discussed.

On the taxonomy of Lygosoma bampfyldei Bartlett, 1895 (Squamata: Scincidae) with descriptions of new species from Borneo and Peninsular Malaysia and the resurrection of Lygosoma schneideri Werner, 1900.

A reassessment of the taxonomy of Lygosoma bampfyldei based on morphology and color pattern indicates that it is a species complex containing L. bampfyldei Bartlett, 1895 from the Rajang River, Sarawak and Croker Range, Sabah in East Malaysia; L. peninsulare sp. nov. from Bukit Larut, Perak and 13.5 km east of Jeli, Kelantan, Peninsular Malaysia; L. kinabatanganensis sp. nov. from the Kinabatangan District, Deramakot camp (=Deramakot Sabah Forestry Department), Sabah, East Malaysia; and L. schneideri Werner, 1900 from Djapura, Indragiri, Sumatra, Indonesia-resurrected herein from the synonymy of L. bampfyldei. The new taxonomy aligns itself well with a growing body of literature demonstrating that semi-fossorial and fossorial Sundaic skinks are more diverse than previously considered.

History cleans up messes: The impact of time in driving divergence and introgression in a tropical suture zone.

Contact zones provide an excellent arena in which to address questions about how genomic divergence evolves during lineage divergence. They allow us to both infer patterns of genomic divergence in allopatric populations isolated from introgression and to characterize patterns of introgression after lineages meet. Thusly motivated, we analyze genome-wide introgression data from four contact zones in three genera of lizards endemic to the Australian Wet Tropics. These contact zones all formed between morphologically cryptic lineage-pairs within morphologically defined species, and the lineage-pairs meeting in the contact zones diverged anywhere from 3.1 to 5.8 million years ago. By characterizing patterns of molecular divergence across an average of 11K genes and fitting geographic clines to an average of 7.5K variants, we characterize how patterns of genomic differentiation and introgression change through time. Across this range of divergences, we find that genome-wide differentiation increases but becomes no less heterogeneous. In contrast, we find that introgression heterogeneity decreases dramatically, suggesting that time helps isolated genomes "congeal." Thus, this work emphasizes the pivotal role that history plays in driving lineage divergence.

Genetic diversity is largely unpredictable but scales with museum occurrences in a species-rich clade of Australian lizards.

Genetic diversity is a fundamental characteristic of species and is affected by many factors, including mutation rate, population size, life history and demography. To better understand the processes that influence levels of genetic diversity across taxa, we collected genome-wide restriction-associated DNA data from more than 500 individuals spanning 76 nominal species of Australian scincid lizards in the genus Ctenotus To avoid potential biases associated with variation in taxonomic practice across the group, we used coalescent-based species delimitation to delineate 83 species-level lineages within the genus for downstream analyses. We then used these genetic data to infer levels of within-population genetic diversity. Using a phylogenetically informed approach, we tested whether variation in genetic diversity could be explained by population size, environmental heterogeneity or historical demography. We find that the strongest predictor of genetic diversity is a novel proxy for census population size: the number of vouchered occurrences in museum databases. However, museum occurrences only explain a limited proportion of the variance in genetic diversity, suggesting that genetic diversity might be difficult to predict at shallower phylogenetic scales.

Tropical specialist vs. climate generalist: Diversification and demographic history of sister species of Carlia skinks from northwestern Australia.

Species endemic to the tropical regions are expected to be vulnerable to future climate change due in part to their relatively narrow climatic niches. In addition, these species are more likely to have responded strongly to past climatic change, and this can be explored through phylogeographic analyses. To test the hypothesis that tropical specialists are more sensitive to climate change than climate generalists, we generated and analyse sequence data from mtDNA and ~2500 exons to compare scales of historical persistence and population fluctuation in two sister species of Australian rainbow skinks: the tropical specialist Carlia johnstonei and the climate generalist C. triacantha. We expect the tropical specialist species to have deeper and finer-scale phylogeographic structure and stronger demographic fluctuations relative to the closely related climate generalist species, which should have had more stable populations through periods of harsh climate in the late Quaternary. Within C. johnstonei, we find that some populations from the northern Kimberley islands are highly divergent from mainland populations. In C. triacantha, one major clade occurs across the deserts and into the mesic Top End, and another occurs primarily in the Kimberley with scattered records eastwards. Where their ranges overlap in the Kimberley, both mitochondrial DNA and nuclear DNA suggest stronger phylogeographic structure and range expansion within the tropical specialist, whereas the climate generalist has minimal structuring and no evidence of recent past range expansion. These results are consistent with the hypothesis that tropical specialists are more sensitive to past climatic change.

Unmasking evolutionary diversity among two closely related South African legless skink species (Acontinae: Acontias) using molecular data.

We examined species boundaries among two phylogenetically closely related and morphologically similar South African fossorial legless skink species, Acontias breviceps and Acontias gracilicauda. Samples of these two species were collected throughout their distribution ranges and sequenced for three DNA loci (two mitochondrial loci, 16S rRNA and cytochrome b (Cyt b), plus the nuclear locus prolactin). Phylogenetic relationships were determined using maximum parsimony, Bayesian inference and maximum likelihood analyses of the combined DNA sequence data set. The total evidence topology retrieved two paraphyletic clades in both Acontias species with strong statistical support. The phylogenetic results revealed that A. breviceps specimens from the Eastern Cape Province were basal (Clade 1), while the Highveld specimens of A. breviceps from the Mpumalanga Province (Clade 2) were retrieved as sister to A. gracilicauda (Clade 1). In addition, the A. gracilicauda specimens from the interior of the Northern Cape Province (Clade 2) were found embedded within the A. occidentalis species complex. These clades were characterised by marked sequence divergence for the Cyt b locus. Furthermore, no maternal or nuclear haplotypes were shared between clades within both A. breviceps and A. gracilicauda, alluding to genetic and reproductive isolation. The results provide overwhelming evidence to assign A. breviceps from the Mpumalanga Highveld to a novel species. Further sampling is required to accurately delineate species boundaries within A. gracilicauda. The conservation implications of our results are briefly discussed.

Extended molecular phylogenetics and revised systematics of Malagasy scincine lizards.

Among the endemic biota of Madagascar, skinks are a diverse radiation of lizards that exhibit a striking ecomorphological variation, and could provide an interesting system to study body-form evolution in squamate reptiles. We provide a new phylogenetic hypothesis for Malagasy skinks of the subfamily Scincinae based on an extended molecular dataset comprising 8060bp from three mitochondrial and nine nuclear loci. Our analysis also increases taxon sampling of the genus Amphiglossus by including 16 out of 25 nominal species. Additionally, we examined whether the molecular phylogenetic patterns coincide with morphological differentiation in the species currently assigned to this genus. Various methods of inference recover a mostly strongly supported phylogeny with three main clades of Amphiglossus. However, relationships among these three clades and the limb-reduced genera Grandidierina, Voeltzkowia and Pygomeles remain uncertain. Supported by a variety of morphological differences (predominantly related to the degree of body elongation), but considering the remaining phylogenetic uncertainty, we propose a redefinition of Amphiglossus into three different genera (Amphiglossus sensu stricto, Flexiseps new genus, and Brachyseps new genus) to remove the non-monophyly of Amphiglossus sensu lato and to facilitate future studies on this fascinating group of lizards.

Basking behavior predicts the evolution of heat tolerance in Australian rainforest lizards.

There is pressing urgency to understand how tropical ectotherms can behaviorally and physiologically respond to climate warming. We examine how basking behavior and thermal environment interact to influence evolutionary variation in thermal physiology of multiple species of lygosomine rainforest skinks from the Wet Tropics of northeastern Queensland, Australia (AWT). These tropical lizards are behaviorally specialized to exploit canopy or sun, and are distributed across marked thermal clines in the AWT. Using phylogenetic analyses, we demonstrate that physiological parameters are either associated with changes in local thermal habitat or to basking behavior, but not both. Cold tolerance, the optimal sprint speed, and performance breadth are primarily influenced by local thermal environment. Specifically, montane lizards are more cool tolerant, have broader performance breadths, and higher optimum sprinting temperatures than their lowland counterparts. Heat tolerance, in contrast, is strongly affected by basking behavior: there are two evolutionary optima, with basking species having considerably higher heat tolerance than shade skinks, with no effect of elevation. These distinct responses among traits indicate the multiple selective pressures and constraints that shape the evolution of thermal performance. We discuss how behavior and physiology interact to shape organisms' vulnerability and potential resilience to climate change.

Hydroregulation in a tropical dry-skinned ectotherm.

While temperature effects on species' vulnerability to climate change are well studied, desiccation effects receive comparatively little attention. In addition, we poorly understand the capacity of ectotherms, and especially reptiles, to control water loss rates behaviourally by selecting suitable microhabitats. This study examined water loss rates and behavioural hydroregulation in the tropical rainforest skink Carlia rubrigularis to assess whether this dry-skinned ectotherm actively avoids desiccation and whether trade-offs occur between desiccation avoidance and selection of optimal temperatures, as previously shown in amphibians. Higher temperatures elicited humid refuge choice despite placing individuals in suboptimal thermal conditions, as indicated by preferred substrate temperatures. This finding emphasizes the importance of water loss even for taxa traditionally assumed to be highly desiccation resistant, and highlights this factor's potential influence on vulnerability to climate change by limiting activity times or by restricting individuals to thermally suboptimal microhabitats.

New provincial records of skinks (Squamata: Scincidae) from northwestern Vietnam.

We report six new records of skinks from northwestern Vietnam: Eutropis macularius, Scincelladevorator , S.monticola, S.ochracea, Sphenomorphuscryptotis and S.indicus. Our new findings increase the species number of skinks (Scincidae) to nine in Dien Bien Province and to 14 in Son La Province. We also provide additional natural history data of aforementioned species.

Spatial variation in the climatic predictors of species compositional turnover and endemism.

Previous research focusing on broad-scale or geographically invariant species-environment dependencies suggest that temperature-related variables explain more of the variation in reptile distributions than precipitation. However, species-environment relationships may exhibit considerable spatial variation contingent upon the geographic nuances that vary between locations. Broad-scale, geographically invariant analyses may mask this local variation and their findings may not generalize to different locations at local scales. We assess how reptile-climatic relationships change with varying spatial scale, location, and direction. Since the spatial distributions of diversity and endemism hotspots differ for other species groups, we also assess whether reptile species turnover and endemism hotspots are influenced differently by climatic predictors. Using New Zealand reptiles as an example, the variation in species turnover, endemism and turnover in climatic variables was measured using directional moving window analyses, rotated through 360°. Correlations between the species turnover, endemism and climatic turnover results generated by each rotation of the moving window were analysed using multivariate generalized linear models applied at national, regional, and local scales. At national-scale, temperature turnover consistently exhibited the greatest influence on species turnover and endemism, but model predictive capacity was low (typically r (2) = 0.05, P < 0.001). At regional scales the relative influence of temperature and precipitation turnover varied between regions, although model predictive capacity was also generally low. Climatic turnover was considerably more predictive of species turnover and endemism at local scales (e.g., r (2) = 0.65, P < 0.001). While temperature turnover had the greatest effect in one locale (the northern North Island), there was substantial variation in the relative influence of temperature and precipitation predictors in the remaining four locales. Species turnover and endemism hotspots often occurred in different locations. Climatic predictors had a smaller influence on endemism. Our results caution against assuming that variability in temperature will always be most predictive of reptile biodiversity across different spatial scales, locations and directions. The influence of climatic turnover on the species turnover and endemism of other taxa may exhibit similar patterns of spatial variation. Such intricate variation might be discerned more readily if studies at broad scales are complemented by geographically variant, local-scale analyses.