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Mimics are under selection from a community of predators possessing different perception abilities and modes of prey capture, yet the efficacy of Batesian/Müllerian mimicry in a mimetic complex has typically been tested using a single predator. The males of Eresus spiders appear to mimic black-and-red colored insects and in particular ladybird beetles. Here, we tested the hypothesis of defensive mimicry in this species using 3 co-occurring visually oriented predators: mantids, lizards, and birds, possessing different visual abilities (di- and tetrachromatic vision). We compared 2 salient traits (movement and coloration) of Eresus males and 3 putative co-mimics (Coccinella septempunctata , Graphosoma italicum , Pyrrhocoris apterus). We found that Eresus spiders are far more mobile than the co-mimics, and this could make them unprofitable due to efficient evasion. According to visual models, all 3 predators should not be able to distinguish the coloration of Eresus from that of 2 co-mimics. The natural diet of the green lizard revealed that lizards captured on average Eresus spiders as frequently as co-mimics. In predation trials, mantises captured Eresus males at greater latency but with similar frequency as co-mimics. In the predation experiment, both hand-reared and wild-caught great tits captured Eresus males far more frequently than Coccinella beetles. Eresus males were palatable to all 3 predators consistent with the Batesian form of mimicry, but when considering evasion abilities, they could be classified as quasi-Batesian mimics. [ABSTRACT FROM AUTHOR]

Colour polymorphic species often exhibit variation in morphology, physiology, and behaviour among morphs. In particular, dominance status may be signalled by the interaction between behaviour and colour morph. Behavioural traits associated with dominance include boldness, exploration, and aggression, which influence access to preferred habitat, territorial defence, and mate acquisition. In ectotherms, the social structure associated with morphs may result in the exploitation of structural niches differing in thermal quality. Hence, social interactions among morphs may generate concordant variation in thermal preference and environmental temperature. However, few studies have assessed thermal preference variation in colour polymorphic species and its covariation with behaviour. Doing so can provide insight into niche specialization and the maintenance of colour polymorphism in populations. Here, we investigated the patterns of covariation in boldness behaviour, exploratory behaviour, and thermal preference in the tree lizard, Urosaurus ornatus. We assessed trait variation between territorial and non‐territorial male morphs and between orange and yellow female morphs. Boldness and exploratory behaviour were repeatable in male U. ornatus and bolder individuals were significantly more likely to incur tail loss, a potential consequence of bold behaviour. Territorial male morphs were significantly bolder and more exploratory and preferred higher body temperatures with a narrower Tset than non‐territorial morphs. Female morphs did not vary in behavioural or thermal traits. This study highlights behavioural mechanisms that underly ecological niche segregation and variable habitat use between morphs in a colour polymorphic species. [ABSTRACT FROM AUTHOR]

Simple Summary: Common blue-tongued skinks (Tiliqua scincoides) are popular pets due to their docile temper. Because of their popularity, they are routinely presented to veterinarians for examinations or procedures; however, to date, there has been limited research evaluating sedation protocols for this species. This study aimed to test different sedation combinations in these skinks: alfaxalone alone, alfaxalone with midazolam, dexmedetomidine with midazolam, and a combination of alfaxalone, dexmedetomidine, and midazolam. All four combinations provided safe sedation, but there were different physiologic responses noted. According to our trials, the combinations of all three drugs or alfaxalone with midazolam are recommended for minor procedures. Common blue-tongued skinks (Tiliqua scincoides) are popular pet reptiles; however, there has been limited research to investigate sedatives for this species. The purpose of this study was to measure the physiologic effects of four combinations of alfaxalone, dexmedetomidine, and midazolam for minor procedures such as intubation and blood collection. Eleven common blue-tongued skinks (Tiliqua scincoides) were used for this prospective, randomized cross-over study. The subcutaneous combinations were used as follows: 20 mg/kg alfaxalone (A); 10 mg/kg alfaxalone and 1 mg/kg midazolam (AM); 0.1 mg/kg dexmedetomidine and 1 mg/kg midazolam (DM); and 5 mg/kg alfaxalone, 0.05 mg/kg dexmedetomidine, and 0.5 mg/kg midazolam (ADM). Heart rate, respiratory rate, palpebral reflex, righting reflex, escape reflex, toe pinch withdrawal reflex, tongue flicking, and the possibility of intubation were recorded at baseline and every 5 min for 60 min. Venous blood gases were measured at baseline, full sedation, and recovery. Heart and respiratory rates decreased significantly in all groups, but the reductions were most prominent in DM and ADM. Analgesic effects, as measured by the toe pinch withdrawal reflex, were only observed in DM and ADM. Intubation was possible in all four protocols; however, it was not possible in two DM skinks. Based on these trials, ADM and AM are recommended for minor procedures in blue-tongue skinks. [ABSTRACT FROM AUTHOR]

Climate change may affect the survival and reproduction of ectotherms. The toad‐headed lizard Phrynocephalus theobaldi, which holds the distinction of occupying the highest elevation among all reptile species on Earth, with an elevational range from 3600 to 5000 m, represents an ideal model for studying the adaptations to climatic changes across elevational gradients. Here, we used mechanistic and hybrid species distribution models (HSDM) together with characteristic measurements of thermal biology (CTmax, CTmin, and Tsel) to simulate and compare the distribution and activity periods of the lizard across elevations in response to climate change. NicheMapR simulations using only climate factors predicted that all populations will be negatively impacted by climate change (+3°C) by suffering a reduced distribution. However, the impact was clearly reduced in simulations that accounted for thermal physiological traits. Longer activity periods were predicted for all populations during climate change. The suitable distribution is predicted to change slightly, with an increase anticipated for both high and low elevation populations. However, the forecast indicates a more pronounced increase in suitable habitats for populations at higher elevations (>4200 m) compared to those at lower elevations (<4200 m). This study underscores the key influence of climate change on population establishment and stresses the importance of physiological traits in distribution simulation for future studies to understand the potential constraints in animal adaptation to extreme high environments. [ABSTRACT FROM AUTHOR]

An organism's gut microbiota can change in response to novel environmental conditions, in particular when colonisation of new habitats is accompanied by shifts in the host species' ecology. Here, we investigated the gut microbiota of three lizard species (A. inornata, H. maculata and S. cowlesi) from their ancestral-like habitat in the Chihuahuan desert and two colonised habitats with contrasting geological and ecological compositions: the White Sands and Carrizozo lava flow. The host species and the lizards' environment both shape gut microbiota composition, but host effects were overall stronger. Further, we found evidence that colonisation of the same environment by independent host species led to parallel changes of the gut microbiota, whereas the colonisation of two distinct environments by the same host species led to gut microbiota divergence. Some of the gut microbiota changes that accompanied the colonisation of the White Sands were associated with shifts in diet (based on diet information from previous studies), which is congruent with the general observation that trophic ecology has a strong effect on gut microbiota composition. Our study provides insights into how shifts in host ecology accompanying colonisation of novel environments can affect gut microbiota composition and diversity.

Acute lethality usually determined as LD50 is defined as median dose predicted to kill 50 percent of a given test population. LD50 is a statistical estimate of the number of milligram of toxicant per kilo gram of body weight administered by any of the methods like oral, dermal, inhalation, or intravenous and is sufficient to kill 50 percent of the large population of test animals usually within certain time. Determination of LD50 has always been a much controversial subject among biologists and animal ethicists due to painful treatments on large number of animals. However, to assess the toxicity of various chemicals on different organisms Median lethal dose is still being used by toxicologists to determine acute lethality to non-target organisms. In the present study we aimed to determine the LD50 of two carbamate insecticides bendiocarb and carbaryl on a non-target species Calotes versicolor a reptilian model. An approximate LD50 was initially determined as a pilot study by a so called ‘staircase method’ using only 2 animals (for each dose) and increasing the doses of the drug. Five doses 10, 15, 20, 25, 30 mg/kg body weight for bendiocarb and 50, 60, 70, 80, 90 mg/kg body weight for carbaryl were chosen for determination of LD50 starting from no death to 100% mortality. Intraperitoneal LD50 value calculated by regression analysis is 15.57 and 64.97 mg/kg body weight for bendiocarb and carbaryl respectively in male Calotes versicolor. The result confirms that bendiocarb is more potent than carbaryl in Calotes suggesting that bendiocarb may cause death even at smaller doses in comparison to carbaryl. Our results will help in adding to the fact sheet related to carbamate toxicity in reptiles.

This study evaluated the sedation and the physiological effects produced by three doses of intranasal midazolam in green iguanas. Eight adult iguanas weighing 850 ± 165 grams, received each of five treatments: intramuscular midazolam 2 mg.kg-1 (IM), intranasally administered midazolam at doses of 2 mg.kg-1 (IN2), 3 mg.kg-1 (IN3) and 5 mg.kg-1 (IN5), and intramuscular saline (CON). The degree of sedation, heart rate, respiratory rate and body temperature were assessed from the baseline to 360 minutes post-administrations. The IM treatment induced mild to deep sedation from 10 (9 [8-12]) to 120 minutes (8 [3-9]). Sedation was not achieved in groups IN2 and IN3. When compared to the baseline, mild sedation was achieved in IN5 at 20 (5 [2-6]), 45 (5 [1-6]) and 90 minutes (5 [1-7]). There was a reduction in heart rate only in the IM group at 360 minutes (40 ± 15.1 bpm). Respiratory rate decreased to the baseline only in IN5, at 30 (12 [8-16] mpm) and 90 minutes (12 [8-24] mpm). No changes in body temperature were observed with any of the treatments during the evaluation period. Intranasally administered midazolam at a dose of 5 mg.kg-1, but not at 2 and 3 mg.kg-1, induced mild sedation in green iguanas. However, the effect exhibited a lower intensity and duration compared to the intramuscular dose of 2 mg.kg-1. Therefore, the administration of intranasal midazolam is not a reasonable option compared to the intramuscular route. [ABSTRACT FROM AUTHOR]

The state of Rio Grande do Sul has a great diversity of reptile species distributed throughout its territory. Due to human actions, such as habitat fragmentation, these animals have been frequently observed in urban and peri-urban environments. This facilitates the spread of pathogens between animals and humans, posing a unique health risk, as many diseases are considered zoonoses. Leptospirosis is among the most common zoonoses in the world and is caused by pathogenic species of bacteria of the genus Leptospira. The role of reptiles in the cycle of this disease is yet unknown. However, serological studies have demonstrated positivity for antibodies against Leptospira spp. in tortoises and snakes, which may indicate that these animals act in maintaining the pathogen in the environment. This observed the presence of antiLeptospira antibodies in rescued reptiles taken to the Center for Rehabilitation of Wild Fauna and Screening Center for Wild Animals at the Universidade Federal de Pelotas (NURFS-CETAS/UFPEL). Samples were collected from 55 animals (39 Trachemys dorbigni; 3 Philodryas patagoniensis; 3 Caiman latirostris; 3 Salvator merianae; 2 Acanthochelys spixii; 2 Phrynops hilarii; 2 Hydromedusa tectifera; 1 Philodryas aestiva) from August 2022 to December 2023 and tested for 12 reference serovars. Two animals demonstrated positivity, one for the pathogenic serovar Pyrogenes and the other for the pathogenic serovar Canicola. This result reflected the importance of different species besides mammals as potential reservoirs and responsible for maintaining leptospirosis in the environment. [ABSTRACT FROM AUTHOR]

Background: This study aims to investigate the urban colonization of the Asian water monitor (Varanus salvator) across its entire range of distribution, addressing the paucity of research on this species in urban ecosystems. The research spans the geographic range of the Asian water monitor, focusing on urbanized areas where the species accumulates more observations (Bangkok, Colombo, Jakarta, Kuala Lumpur and Singapore). Methods: We conducted a systematic review to comprehensively assess the current knowledge of the species' presence in cities. Additionally, citizen science data from repositories like GBIF (Global Biodiversity Information facility) were utilized to analyze the distribution patterns of V. salvator in urban environments. To elucidate urban distribution and correct collection biases, observations were weighted by sampling effort, using as a proxy all squamate occurrences available from 2010–2023, including V. salvator. Results: Despite the widespread presence of the Asian water monitor in numerous cities within its distribution range, the available studies on the topic appear to be scarce. Existing research primarily consists of descriptive reports on diet and behavior. Our findings indicate that V. salvator predominantly colonizes green patches in urban areas, such as parks and small gardens. Larger cities exhibit higher records, potentially due to both permanent populations and increased citizen science reporting. Conclusions: The Asian water monitor, as the largest lizard with established populations in cities, remains scarcely studied on a broader scale. However, the urban design of each city seems relevant to understand the distribution patterns within each context. Our study highlights the need for further research to explore the ecological and human dimensions associated with the species' presence in urban environments. [ABSTRACT FROM AUTHOR]

Despite being a central aspect of a species' ecology and having important conservation implications, the use of fine‐scale habitat features (microhabitats), and how they vary over time, are poorly known for most species. In this study, we leveraged 522 relocations of radio‐tracked mallee tree dragons (Amphibolurus norrisi) and painted dragons (Ctenophorus pictus) to investigate the effect of environmental and individual variables on microhabitat use. Mallee tree dragons were more likely to use trees on hot days and in the middle of the day (the hottest time of day), whereas shrub use was more likely on cool days and in the mornings. Painted dragons were more likely to use shrubs and grass trees on warmer days and during the middle of the day, whereas burrows were used during cooler days and in the mornings and afternoons. We expect these patterns represent animals moving from refuge resources, occupied during unsuitable thermal conditions, to microhabitats offering basking, foraging and social opportunities during periods of thermal optimum. Additionally, we found evidence of an ontogenetic shift, with larger mallee tree dragons favouring tree use and higher perches, suggesting a transition from shrub to tree use with age. Our findings underscore the need for diverse microhabitats to accommodate the thermoregulatory and ontogenetic requirements of lizards. These insights can inform conservation and habitat restoration efforts, ensuring the provision of essential microhabitats to support species persistence. [ABSTRACT FROM AUTHOR]

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Reptile white blood cell (WBC) morphological features are strikingly variable across species. In the Argentine black and white tegu (Salvator merianae), red tegu (Salvator rufescens), and Savannah monitor (Varanus exanthematicus), previous reports described a WBC type with a single distinct, clear, linear- to ovoid- to crescent-shaped inclusion of presumptive monocytic origin. The objective of this study was to further investigate the origin of this unique WBC type with crescent-shaped inclusions. Blood samples from two Argentine black and white tegus, tegu 1, a 4-year-old female, and tegu 2, a 2-year-old presumed male, were submitted for routine hematological evaluation. Additional blood films were prepared and stained with these cytochemical stains: alkaline phosphatase (ALP; naphthol AS-MX phosphate substrate), alpha-naphthyl butyrate esterase, alphachloroacetate esterase, myeloperoxidase, Periodic acid-Schiff, and Sudan black B. Blood films from tegu 1 were also stained with a second ALP stain (5-bromo- 4-chloro-3-indoxyl-phosphate and nitroblue tetrazolium substrate), Luna, luxol fast blue, and toluidine blue. The blood from tegu 1 was cytocentrifuged to isolate and fix the buffy coat in glutaraldehyde 2.5% aqueous solution for transmission electron microscopy. Six morphologically distinct WBC types were identified from tegu 1, including heterophils, basophils, monocytes, azurophils, lymphocytes, and the unique WBC type, which were identified as eosinophils with inclusions. WBC types in tegu 2 were similar; however, eosinophils lacked a discernable inclusion. Proper WBC identification will be useful in obtaining accurate hemogram data for this species. [ABSTRACT FROM AUTHOR]

(1) Background: Although Physaloptera retusa is one of the most widespread species infecting reptiles in the Americas, numerous taxonomic problems and little genetic data are associated with it. To clarify the taxonomy of this species, we used an integrative approach. (2) Methods: Physaloptera retusa-infecting Erythrolamprus typhlus (snake) from the Pantanal wetlands, Brazil, was morphologically and genetically characterised (18S and 28S rDNA; COI mtDNA) and compared with conspecific sequences available in GenBank, from parasites of Tupinambis teguixin (lizard), using species delimitation methods. Type specimens of P. liophis were re-evaluated given its morphological similarities with P. retusa. (3) Results: The morphology of the present specimens was equal to that of P. retusa, in which the only difference from P. liophis was the relative position of the vulva. Species delimitation methods were more accurate for the COI dataset; all of them (except ABGD) indicated interspecificity among P. retusa sequences. However, a lack of morphological data or voucher material, associated with the deposited sequences, prevented more assertive conclusions. (4) Conclusions: The present results highlight the importance of a clear association between genetic data and morphology of the isolation source, or at least its adequate vouchering. Moreover, P. retusa may represent a species complex in cryptic speciation, since it is widespread and has low hosts specificity. [ABSTRACT FROM AUTHOR]

Simple Summary: In order to withstand extreme temperatures, organisms can change their behavior, physiology, and biochemistry prior to or in reaction to environmental variations. This allows them to enhance their chances of survival under challenging conditions. However, lizards are ectothermic, relying on environmental temperature for body heat and making them highly susceptible to climate change. Mitochondria play a crucial role in maintaining body temperature, regulating metabolic rates, and preventing cellular oxidative damage. If mitochondrial respiratory chain complexes become damaged or disrupted, this can be fatal. Mitochondrial DNA also serves as a sentinel for cell stress. Here, we focused on the lizard Sphenomorphus incognitus (Squamata:Scincidae) to explore the expression of the 13 mitochondrial protein-coding genes (PCGs) responding to a wide range of temperatures: 4 °C, 8 °C, 25 °C (control group), 34 °C, and 38 °C for 24 h. The aim was to explore the potential cold resistance and heat tolerance mechanisms of lizards by examining the expression of mitochondrial genes under gradient temperature conditions, as a means to assess the adaptability of lizards in the current context of climate change. In the context of global warming, the frequency of severe weather occurrences, such as unexpected cold spells and heat waves, will grow, as well as the intensity of these natural disasters. Lizards, as a large group of reptiles, are ectothermic. Their body temperatures are predominantly regulated by their environment and temperature variations directly impact their behavior and physiological activities. Frequent cold periods and heat waves can affect their biochemistry and physiology, and often their ability to maintain their body temperature. Mitochondria, as the center of energy metabolism, are crucial for maintaining body temperature, regulating metabolic rate, and preventing cellular oxidative damage. Here, we used RT-qPCR technology to investigate the expression patterns and their differences for the 13 mitochondrial PCGs in Sphenomorphus incognitus (Squamata:Scincidae), also known as the brown forest skink, under extreme temperature stress at 4 °C, 8 °C, 34 °C, and 38 °C for 24 h, compared to the control group at 25 °C. In southern China, for lizards, 4 °C is close to lethal, and 8 °C induces hibernation, while 34/38 °C is considered hot and environmentally realistic. Results showed that at a low temperature of 4 °C for 24 h, transcript levels of ATP8, ND1, ND4, COI, and ND4L significantly decreased, to values of 0.52 ± 0.08, 0.65 ± 0.04, 0.68 ± 0.10, 0.28 ± 0.02, and 0.35 ± 0.02, respectively, compared with controls. By contrast, transcript levels of COIII exhibited a significant increase, with a mean value of 1.86 ± 0.21. However, exposure to 8 °C for 24 h did not lead to an increase in transcript levels. Indeed, transcript levels of ATP6, ATP8, ND1, ND3, and ND4 were significantly downregulated, to 0.48 ± 0.11, 0.68 ± 0.07, 0.41 ± 0.08, 0.54 ± 0.10, and 0.52 ± 0.07, respectively, as compared with controls. Exposure to a hot environment of 34 °C for 24 h led to an increase in transcript levels of COI, COII, COIII, ND3, ND5, CYTB, and ATP6, with values that were 3.3 ± 0.24, 2.0 ± 0.2, 2.70 ± 1.06, 1.57 ± 0,08, 1.47 ± 0.13, 1.39 ± 0.56, and 1.86 ± 0.12, respectively, over controls. By contrast, ND4L exhibited a significant decrease (to 0.31 ± 0.01) compared with controls. When exposed to 38 °C, the transcript levels of the 13 PCGs significantly increased, ranging from a 2.04 ± 0.23 increase in ND1 to a 6.30 ± 0.96 rise in ND6. Under two different levels of cold and heat stress, the expression patterns of mitochondrial genes in S. incognitus vary, possibly associated with different strategies employed by this species in response to low and high temperatures, allowing for rapid compensatory adjustments in mitochondrial electron transport chain proteins in response to temperature changes. Furthermore, this underscores once again the significant role of mitochondrial function in determining thermal plasticity in reptiles. [ABSTRACT FROM AUTHOR]

Despite their evolutionary novelty, lizard venoms are much less studied in comparison to the intense research on snake venoms. While the venoms of helodermatid lizards have long been assumed to be for defensive purposes, there is increasing evidence of toxic activities more useful for predation than defence (such as paralytic neurotoxicity). This study aimed to ascertain the effects of Heloderma, Lanthanotus, and Varanus lizard venoms on the coagulation and cardiovascular systems. Anticoagulant toxicity was demonstrated for the Varanus species studied, with the venoms prolonging clotting times in human and bird plasma due to the destructive cleavage of fibrinogen. In contrast, thromboelastographic analyses on human and bird plasmas in this study demonstrated a procoagulant bioactivity for Heloderma venoms. A previous study on Heloderma venom using factor-depleted plasmas as a proxy model suggested a procoagulant factor was present that activated either Factor XI or Factor XII, but could not ascertain the precise target. Our activation studies using purified zymogens confirmed FXII activation. Comparisons of neonate and adult H. exasperatum, revealed the neonates to be more potent in the ability to activate FXII, being more similar to the venom of the smaller species H. suspectum than the adult H. exasperatum. This suggests potent FXII activation a basal trait in the genus, present in the small bodied last common ancestor. This also indicates an ontogenetic difference in prey preferences in the larger Heloderma species paralleing the change in venom biochemistry. In addition, as birds lack Factor XII, the ability to clot avian plasma suggested an additional procoagulant site of action, which was revealed to be the activation of Factor VII, with H. horridum being the most potent. This study also examined the effects upon the cardiovascular system, including the liberation of kinins from kininogen, which contributes to hypotension induction. This form of toxicity was previously described for Heloderma venoms, and was revealed in this study was to also be a pathophysiological effect of Lanthanotus and Varanus venoms. This suggests that this toxic activity was present in the venom of the last common ancestor of the anguimorph lizards, which is consistent with kallikrein enzymes being a shared toxin trait. This study therefore uncovered novel actions of anguimorph lizard venoms, not only contributing to the evolutionary biology body of knowledge but also revealing novel activities to mine for drug design lead compounds. [ABSTRACT FROM AUTHOR]

ABSTRACT: This study evaluated the sedation and the physiological effects produced by three doses of intranasal midazolam in green iguanas. Eight adult iguanas weighing 850 ± 165 grams, received each of five treatments: intramuscular midazolam 2 mg.kg-1 (IM), intranasally administered midazolam at doses of 2 mg.kg-1 (IN2), 3 mg.kg-1 (IN3) and 5 mg.kg-1 (IN5), and intramuscular saline (CON). The degree of sedation, heart rate, respiratory rate and body temperature were assessed from the baseline to 360 minutes post-administrations. The IM treatment induced mild to deep sedation from 10 (9 [8-12]) to 120 minutes (8 [3-9]). Sedation was not achieved in groups IN2 and IN3. When compared to the baseline, mild sedation was achieved in IN5 at 20 (5 [2-6]), 45 (5 [1-6]) and 90 minutes (5 [1-7]). There was a reduction in heart rate only in the IM group at 360 minutes (40 ± 15.1 bpm). Respiratory rate decreased to the baseline only in IN5, at 30 (12 [8-16] mpm) and 90 minutes (12 [8-24] mpm). No changes in body temperature were observed with any of the treatments during the evaluation period. Intranasally administered midazolam at a dose of 5 mg.kg-1, but not at 2 and 3 mg.kg-1, induced mild sedation in green iguanas. However, the effect exhibited a lower intensity and duration compared to the intramuscular dose of 2 mg.kg-1. Therefore, the administration of intranasal midazolam is not a reasonable option compared to the intramuscular route.

Abstract Colour polymorphic species often exhibit variation in morphology, physiology, and behaviour among morphs. In particular, dominance status may be signalled by the interaction between behaviour and colour morph. Behavioural traits associated with dominance include boldness, exploration, and aggression, which influence access to preferred habitat, territorial defence, and mate acquisition. In ectotherms, the social structure associated with morphs may result in the exploitation of structural niches differing in thermal quality. Hence, social interactions among morphs may generate concordant variation in thermal preference and environmental temperature. However, few studies have assessed thermal preference variation in colour polymorphic species and its covariation with behaviour. Doing so can provide insight into niche specialization and the maintenance of colour polymorphism in populations. Here, we investigated the patterns of covariation in boldness behaviour, exploratory behaviour, and thermal preference in the tree lizard, Urosaurus ornatus. We assessed trait variation between territorial and non‐territorial male morphs and between orange and yellow female morphs. Boldness and exploratory behaviour were repeatable in male U. ornatus and bolder individuals were significantly more likely to incur tail loss, a potential consequence of bold behaviour. Territorial male morphs were significantly bolder and more exploratory and preferred higher body temperatures with a narrower T set than non‐territorial morphs. Female morphs did not vary in behavioural or thermal traits. This study highlights behavioural mechanisms that underly ecological niche segregation and variable habitat use between morphs in a colour polymorphic species.

Explaining biodiversity is a fundamental issue in ecology. A long-standing puzzle lies in the paradox of the plankton: many species of plankton feeding on a limited variety of resources coexist, apparently flouting the competitive exclusion principle (CEP), which holds that the number of predator (consumer) species cannot exceed that of the resources at a steady state. Here, we present a mechanistic model and demonstrate that intraspecific interference among the consumers enables a plethora of consumer species to coexist at constant population densities with only one or a handful of resource species. This facilitated biodiversity is resistant to stochasticity, either with the stochastic simulation algorithm or individual-based modeling. Our model naturally explains the classical experiments that invalidate the CEP, quantitatively illustrates the universal S-shaped pattern of the rank-abundance curves across a wide range of ecological communities, and can be broadly used to resolve the mystery of biodiversity in many natural ecosystems.

As urbanization expands globally, human–wildlife interactions will inevitably increase. Here, we analysed 10 years of wildlife rehabilitation records of squamate (snake and lizard) reptiles (n = 37 075) from the Greater Sydney region, New South Wales, Australia, to explore their value to address management and conservation issues. Rescues were highly non-random regarding taxonomic focus, spatial occurrences and temporal trends due to the combined influence of (i) reptile phenology and behaviour and (ii) human perceptions of reptiles. Seasonal peaks in rescues reflect reptile and, to a lesser extent, human activity. Spatial patterns of rescues were informative about distributions and presence of easily identified taxa but were primarily driven by human presence. Larger squamate species were rescued more frequently, potentially reflecting a perception of greater danger or rescue priority. While uncommon species were often misidentified, accurate reports of these taxa may guide targeted surveys. The value of these data for conservation and management could be enhanced by emphasizing reptile identification training of volunteers and use of applications for informed species identification. Wildlife rehabilitation data offer a cost-effective means of quantifying thousands of human–reptile interactions, identifying foci (in both time and space) of human–wildlife conflict such as snakebite risk and roadkill-related reptile mortality.

Abstract Climate change may affect the survival and reproduction of ectotherms. The toad‐headed lizard Phrynocephalus theobaldi, which holds the distinction of occupying the highest elevation among all reptile species on Earth, with an elevational range from 3600 to 5000 m, represents an ideal model for studying the adaptations to climatic changes across elevational gradients. Here, we used mechanistic and hybrid species distribution models (HSDM) together with characteristic measurements of thermal biology (CTmax, CTmin, and Tsel) to simulate and compare the distribution and activity periods of the lizard across elevations in response to climate change. NicheMapR simulations using only climate factors predicted that all populations will be negatively impacted by climate change (+3°C) by suffering a reduced distribution. However, the impact was clearly reduced in simulations that accounted for thermal physiological traits. Longer activity periods were predicted for all populations during climate change. The suitable distribution is predicted to change slightly, with an increase anticipated for both high and low elevation populations. However, the forecast indicates a more pronounced increase in suitable habitats for populations at higher elevations (>4200 m) compared to those at lower elevations (

Colored oil droplets are a common feature in the cones of almost all diurnal lizards. Using white light microscopy, three chromotypes of droplet can be identified in anoles – yellow, green and colorless. These droplets have been associated with different cone classes using microspectrophotometry. The principal member of double cones contain a yellow droplet while the accessory member contains a diffuse yellow pigment. Both members contain the LWS visual pigment. One class of large single cone contains a yellow droplet and the LWS visual pigment. The two remaining classes of large single cone contain the green droplet and either the LWS or MWS visual pigment. As such, by noting the distribution and numbers of the different droplet chromotypes, information about cone distribution, type, and number can be deduced microscopically. Retinas from three anole species (A. cristatellus, A. sagrei, and A. carolinensis) were isolated, flattened and oriented using the two foveae as landmarks. A 19-gauge needle was used to punch out six full-thickness retinal disks from identical retinal regions from both eyes of the three species. The different oil droplets were microscopically identified by color and counted. In all three species at all six retinal areas, the colorless droplets associated with the UVS and SWS single cones represented approximately 10% of the total droplets counted. However, the proportions of the yellow and green droplets were significantly different between the species. For A. cristatellus, 80% of the droplets were green while 10% were yellow. For A. sagrei approximately 85% of the droplets were yellow while only 5% were green. For A. carolinensis 50% of the droplets were yellow while 40% were green. The possible significance of these variable proportions is discussed in terms of possible effects on color vision and ecotype of the three anoles.

(1) Background: Although Physaloptera retusa is one of the most widespread species infecting reptiles in the Americas, numerous taxonomic problems and little genetic data are associated with it. To clarify the taxonomy of this species, we used an integrative approach. (2) Methods: Physaloptera retusa-infecting Erythrolamprus typhlus (snake) from the Pantanal wetlands, Brazil, was morphologically and genetically characterised (18S and 28S rDNA; COI mtDNA) and compared with conspecific sequences available in GenBank, from parasites of Tupinambis teguixin (lizard), using species delimitation methods. Type specimens of P. liophis were re-evaluated given its morphological similarities with P. retusa. (3) Results: The morphology of the present specimens was equal to that of P. retusa, in which the only difference from P. liophis was the relative position of the vulva. Species delimitation methods were more accurate for the COI dataset; all of them (except ABGD) indicated interspecificity among P. retusa sequences. However, a lack of morphological data or voucher material, associated with the deposited sequences, prevented more assertive conclusions. (4) Conclusions: The present results highlight the importance of a clear association between genetic data and morphology of the isolation source, or at least its adequate vouchering. Moreover, P. retusa may represent a species complex in cryptic speciation, since it is widespread and has low hosts specificity.

Haemogregarine (Apicomplexa: Adeleorina) parasites are considered to be the most common and widespread haemoparasites in reptiles. The genus Hepatozoon (Apicomplexa: Adeleorina: Hepatozoidae) can be found parasitizing a broad range of species and, in reptiles, they infect mainly peripheral blood erythrocytes. The present study detected and characterized a haemogregarine isolated from the lizard species, Ameiva ameiva, collected from the municipality of Capanema, Pará state, north Brazil. Blood smears and imprints from lungs, brain, heart, kidney, liver, bone marrow and spleen were observed using light microscopy and the parasite was genetically identified by molecular analysis. Morphological, morphometric and molecular data were obtained. Parasite gamonts were found in 49.5% (55/111) of the blood smears from A. ameiva, and were characterized as oval, averaging 12.0 ± 0.8 × 5.9 ± 0.6 μm2 in size, which displaced the nuclei of parasitized monocytes laterally. Parasite forms resembling immature gamonts were observed in the spleen and bone marrow of the lizards. Furthermore, phylogenetic analyses of 18S rRNA sequences did not reveal gene similarity with other Hepatozoon spp. sequences from reptiles. Thus, morphological and molecular analyses have identified a new species of Hepatozoon parasite, Hepatozoon lainsoni sp. nov., which infects monocytes of the A. ameiva lizard.

Simple Summary: This study investigates the functional adaptation and underlying molecular mechanisms of hemoglobins (Hbs) in the two species of Eremias lizards dwelling on the Qinghai-Tibet Plateau. By measuring O2 equilibrium curves of purified Hbs at different pH and temperature in the absence and presence of ATP and/or Cl−, the study found that the high-altitude populations of the two species of Eremias lizards exhibit convergent high Hb-O2 affinity compared to the respective lowland counterparts while demonstrating distinct ATP-mediated allosteric regulation. Hbs of the highland E. argus showed high ATP sensitivity and ATP-dependent strong Bohr effect compared to E. multiocellata. The underlying mechanisms of these functional variations may be attributed to the varying β2/β1 globin ratios, combined with substitutions on the β2-type globin, as suggested by Hb isoform identification and structural analysis of tetrameric Hbs. In addition, Hbs of these Eremias lizards have similarly low temperature sensitivities and relatively high Bohr effects at lower temperatures, which could minimize the impact of temperature fluctuations on Hb-O2 affinity and facilitate the release of O2 in the cold extremities at low temperatures. The functional adaptation and underlying molecular mechanisms of hemoglobins (Hbs) have primarily concentrated on mammals and birds, with few reports on reptiles. This study aimed to investigate the convergent and species-specific high-altitude adaptation mechanisms of Hbs in two Eremias lizards from the Qinghai-Tibet Plateau. The Hbs of high-altitude E. argus and E. multiocellata were characterized by significantly high overall and intrinsic Hb-O2 affinity compared to their low-altitude populations. Despite the similarly low Cl− sensitivities, the Hbs of high-altitude E. argus exhibited higher ATP sensitivity and ATP-dependent Bohr effects than that of E. multiocellata, which could facilitate O2 unloading in respiring tissues. Eremias lizards Hbs exhibited similarly low temperature sensitivities and relatively high Bohr effects at lower temperatures, which could help to stably deliver and release O2 to cold extremities at low temperatures. The oxygenation properties of Hbs in high-altitude populations might be attributed to varying ratios of β2/β1 globin and substitutions on the β2-type globin. Notably, the Asn12Ala in lowland E. argus could cause localized destabilization of the E-helix in the tetrameric Hb by elimination of hydrogen bonds, thereby resulting in its lowest O2 affinity. This study provides a valuable reference for the high-altitude adaptation mechanisms of hemoglobins in reptiles. [ABSTRACT FROM AUTHOR]

Simple Summary: Neoplasia is a complex disease that affects many species across the animal kingdom, including lizards. Currently, cancer in lizard species is an understudied part of veterinary medicine. In this study, we focused on identifying factors that could aid in improving patient care and quality of life for lizards with neoplasia. We identified multiple factors including species, type of neoplasia, and type of treatment significantly associated with both positive and negative outcomes for lizards affected by different types of neoplasia. Specifically, we tested for statistical associations between eight clinical factors and patient outcomes. We used reported cases of neoplasia in lizards from published papers, as well as a clinical oncology database for exotic animal species. We also identified a subset of neoplasia types that were not associated with death due to their neoplasia. Our results highlight the importance of determining variables that aid veterinarians in deciding the most appropriate care for their patients. We expect that future research in this area will improve our understanding of neoplasia in lizards and better improve the identification of predictor variables for improving patient outcomes. Neoplasia has been reported in lizards, but more research is needed to accurately document the prevalence and prognosis of the various known neoplasms that affect lizards. This study reviewed medical records from an online database, the Exotic Species Cancer Research Alliance (ESCRA), and reviewed published literature to determine the prevalence of neoplasia, malignancy, metastasis, treatment strategies, and outcomes by species and sex. Records from 55 individual lizards, 20 different species, and 37 different tumors were identified. In the literature, 219 lizards, 59 species, and 86 unique tumors were identified from 72 published case reports. Potential signalment factors such as age, sex, and species were evaluated to see if they affected case outcome. Additional factors including neoplasia type, presence of metastasis, and types of pursued treatments were also evaluated. Statistical analysis was performed to determine whether a factor was significantly associated with animal death due to the identified neoplasia or with animal survival or death due to other causes (non-neoplastic outcomes). Komodo dragons and savannah monitors were more likely to die from neoplasia compared to other lizard species. Cases where the status of metastasis was unknown were significantly associated with death due to neoplasia. Having an unknown status of male versus female was significantly associated with non-neoplastic outcomes of death. Leukemia and islet cell carcinoma were significantly associated with death due to neoplastic causes. Chondrosarcoma, myxosarcoma, osteosarcoma, and squamous cell carcinoma were significantly associated with non-neoplastic outcomes of death. Surgery alone and radiation therapy alone each were significantly associated with non-neoplastic outcomes of death, while lizards not receiving treatment were significantly associated with death due to neoplasia. Benign neoplasia was significantly associated with non-neoplastic outcomes of death. These results will aid in the improved diagnosis and management of neoplasia in lizard species, as well as expanding our understanding of prognostic indicators of neoplasia in lizards. [ABSTRACT FROM AUTHOR]

Simple Summary: Sperm acquire the ability to fertilize the egg during their transit through the female reproductive tract. This process, known as sperm capacitation, is well recognized in mammals and can be accomplished under laboratory conditions using specialized media. However, it remains unknown whether this process occurs in lizards. In this study, we investigated sperm incubation under conditions that promote capacitation to determine if similar changes occurred in their sperm. Our sperm assessment revealed functional changes, such as modifications in movement and staining patterns, commonly observed in mammals. This suggests that sperm capacitation may occur in this group of animals. Understanding sperm physiology is crucial for developing assisted reproduction technologies to aid conservation efforts for threatened species. Sperm capacitation involves biochemical and physiological changes that enable sperm to fertilize the oocyte. It can be induced in vitro under controlled conditions that simulate the environment of the oviduct. While extensively studied in mammals, its approach in lizards remains absent. Understanding the mechanisms that ensure reproduction is essential for advancing the implementation of assisted reproductive technologies in this group. We aimed to perform a sperm analysis to determine if capacitation-related changes were induced after incubation with capacitating media. Fifteen males of Sceloporus torquatus were collected during the early stage of the reproductive season. The sperm were isolated from the seminal plasma and then diluted up to a volume of 150 μL using BWW medium to incubate with 5% CO2 at 30 °C for a maximum duration of 3 h. A fraction was retrieved hourly for ongoing sperm assessment. The sperm analysis included assessments of its motility, viability, the capacitation status using the chlortetracycline (CTC) assay, and the acrosome integrity with the lectin binding assay to detect changes during incubation. We found that total motility was maintained up to 2 h post incubation, after which it decreased. However, sperm viability remained constant. From that moment on, we observed a transition to a deeper and less symmetrical flagellar bending in many spermatozoa. The CTC assay indicated a reduction in the percentage of sperm showing the full (F) pattern and an increase in those exhibiting the capacitated (B) and reactive (RA) patterns, accompanied by an elevation in the percentage of damaged acrosomes as revealed by the lectin binding assay. In mammals, these changes are often associated with sperm capacitation. Our observations support the notion that this process may also occur in saurian. While sperm analysis is a valuable method for assessing certain functional changes, additional approaches are required to validate this process. [ABSTRACT FROM AUTHOR]

Simple Summary: Global climate change is a growing threat to the lives and ranges of reptile species. The present study examines three lizard species (Calotes versicolor, Ateuchosaurus chinensis, and Hemidactylus bowringii) that share a sympatric distribution in the Guangzhou region of Guangdong, China. Mitochondria act as energy-producing centers, and the present study analyses the effects of low temperatures in the context of warm winters on lizards, by examining their responses to low-temperature stress at the level of mitochondrial gene expression. This present study analyses the effects of low temperatures in the context of warm winters on the mitochondrial gene expression of lizards and reveals the implications of the distribution within it. Ecological factors related to climate extremes have a significant influence on the adaptability of organisms, especially for ectotherms such as reptiles that are sensitive to temperature change. Climate extremes can seriously affect the survival and internal physiology of lizards, sometimes even resulting in the loss of local populations or even complete extinction. Indeed, studies have shown that the expression levels of the nuclear genes and mitochondrial genomes of reptiles change under low-temperature stress. At present, the temperature adaptability of reptiles has rarely been studied at the mitochondrial genome level. In the present study, the mitochondrial genomes of three species of lizards, Calotes versicolor, Ateuchosaurus chinensis, and Hemidactylus bowringii, which live in regions of sympatry, were sequenced. We used RT-qPCR to explore the level of mitochondrial gene expression under low-temperature stress, as compared to a control temperature. Among the 13 protein-coding genes (PCGs), the steady-state transcript levels of ND4L, ND1, ATP6, and COII were reduced to levels of 0.61 ± 0.06, 0.50 ± 0.08, 0.44 ± 0.16, and 0.41 ± 0.09 in C. versicolor, respectively, compared with controls. The transcript levels of the ND3 and ND6 genes fell to levels of just 0.72 ± 0.05 and 0.67 ± 0.05 in H. bowringii, compared with controls. However, the transcript levels of ND3, ND5, ND6, ATP6, ATP8, Cytb, and COIII genes increased to 1.97 ± 0.15, 2.94 ± 0.43, 1.66 ± 0.07, 1.59 ± 0.17, 1.46 ± 0.04, 1.70 ± 0.16, and 1.83 ± 0.07 in A. chinensis. Therefore, the differences in mitochondrial gene expression may be internally related to the adaptative strategy of the three species under low-temperature stress, indicating that low-temperature environments have a greater impact on A. chinensis, with a small distribution area. In extreme environments, the regulatory trend of mitochondrial gene expression in reptiles is associated with their ability to adapt to extreme climates, which means differential mitochondrial genome expression can be used to explore the response of different lizards in the same region to low temperatures. Our experiment aims to provide one new research method to evaluate the potential extinction of reptile species in warm winter climates. [ABSTRACT FROM AUTHOR]

Aim: Squamate fitness is affected by body temperature, which in turn is influenced by environmental temperatures and, in many species, by exposure to solar radiation. The biophysical drivers of body temperature have been widely studied, but we lack an integrative synthesis of actual body temperatures experienced in the field, and their relationships to environmental temperatures, across phylogeny, behaviour and climate. Location: Global (25 countries on six continents). Taxa: Squamates (210 species, representing 25 families). Methods: We measured the body temperatures of 20,231 individuals of squamates in the field while they were active. We examined how body temperatures vary with substrate and air temperatures across taxa, climates and behaviours (basking and diel activity). Results: Heliothermic lizards had the highest body temperatures. Their body temperatures were the most weakly correlated with substrate and air temperatures. Body temperatures of non‐heliothermic diurnal lizards were similar to heliotherms in relation to air temperature, but similar to nocturnal species in relation to substrate temperatures. The correlation of body temperature with air and substrate temperatures was stronger in diurnal snakes and non‐heliothermic lizards than in heliotherms. Body‐substrate and body‐air temperature correlations varied with mean annual temperatures in all diurnal squamates, especially in heliotherms. Thermal relations vary with behaviour (heliothermy, nocturnality) in cold climates but converge towards the same relation in warm climates. Non‐heliotherms and nocturnal species body temperatures are better explained by substrate temperature than by air temperature. Body temperature distributions become left‐skewed in warmer‐bodied species, especially in colder climates. Main Conclusions: Squamate body temperatures, their frequency distributions and their relation to environmental temperature, are globally influenced by behavioural and climatic factors. For all temperatures and climates, heliothermic species' body temperatures are consistently higher and more stable than in other species, but in regions with warmer climate these differences become less pronounced. A comparable variation was found in non‐heliotherms, but in not nocturnal species whose body temperatures were similar to air and substrate irrespective of the macroclimatic context. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, a new species of the genus Pseudocalotes is described from Yingjiang County, Dehong Dai, and Jingpo Autonomous Prefecture, Yunnan Province, China, based on four female specimens. Phylogenetic analyses based on NADH dehydrogenase subunit 2 (ND2) and NADH dehydrogenase subunit 4 (ND4) indicated that the new taxon is different from its congeners. Morphologically, the new species can be diagnosed from the other species by a combination of 18 characters. The recognition of this new species brings the number of described Pseudocalotes species to 22. In this study, a new species of the genus Pseudocalotes is described from Yingjiang County, Dehong Dai and Jingpo Autonomous Prefecture, Yunnan Province, China, based on four female specimens. It can be distinguished from its congeners by the following combination of characters: (1) interoculabials 3 or 4; (2) canthals 5–7; (3) cicrcumorbitals 8–11; (4) 1 scale between rostral and nasal; (5) interparietal 1; (6) superciliaries 4–6; (7) supralabials 6–7, the 1st in contact with the nasal; (8) infralabials 6–8; (9) transverse gular fold and antehumeral fold present; (10) 2–3 enlarged scales between eye and ear; (11) nuchal crest single, consists of 3–5 erected spines; (12) dorsal crest row single, discontinuous and low, located between two keeled, parallel and enlarged scale rows; (13) enlarged postrictals absent; (14) scales around midbody 53–62, dorsal body scales heterogenous in size and shape; (15) midventrals smaller than dorsals; (16) subdigital scales on the 4th finger 20–26, and on the 4th toe 24–29; (17) dorsal background coloration light taupe with four irregular brown patches along the middle of dorsal; (18) inner lips wathet, tongue aurantiacus, throat bluish black. The population from Yingjiang County was nested within a highly supported lineage, formed a sister taxon with P. kakhienensis (SH 97/UFB 100) and according to the p-distance, the new species differed from its congeners by 14.5% to 35.2% for NADH dehydrogenase subunit 2 (ND2) and 15.5% to 25.0% for NADH dehydrogenase subunit 4 (ND4). [ABSTRACT FROM AUTHOR]

In the animal kingdom, sexually dimorphic color variation is a widespread phenomenon that significantly influences survival and reproductive success. However, the genetic underpinnings of this variation remain inadequately understood. Our investigation into sexually dimorphic color variation in the desert-dwelling Guinan population of the toad-headed agamid lizard (Phrynocephalus putjatai) utilized a multidisciplinary approach, encompassing phenotypic, ultrastructural, biochemical, genomic analyses, and behavioral experiments. Our findings unveil the association between distinct skin colorations and varying levels of carotenoid and pteridine pigments. The red coloration in males is determined by a genomic region on chromosome 14, housing four pigmentation genes: BCO2 and three 6-pyruvoyltetrahydropterin synthases. A Guinan population-specific nonsynonymous single nucleotide polymorphism in BCO2 is predicted to alter the electrostatic potential within the binding domain of the BCO2-β-carotene complex, influencing their interaction. Additionally, the gene MAP7 on chromosome 2 emerges as a potential contributor to the blue coloration in subadults and adult females. Sex-specific expression patterns point to steroid hormone-associated genes (SULT2B1 and SRD5A2) as potential upstream regulators influencing sexually dimorphic coloration. Visual modeling and field experiments support the potential selective advantages of vibrant coloration in desert environments. This implies that natural selection, potentially coupled with assortative mating, might have played a role in fixing color alleles, contributing to prevalence in the local desert habitat. This study provides novel insights into the genetic basis of carotenoid and pteridine-based color variation, shedding light on the evolution of sexually dimorphic coloration in animals. Moreover, it advances our understanding of the driving forces behind such intricate coloration patterns. [ABSTRACT FROM AUTHOR]

Males and females often differ in use of antipredator behaviors, particularly when antipredator behavior comes at the cost of missed mating opportunities or territory defense. When using thermally suboptimal refugia, ectotherms are especially vulnerable to these costs, as their performance is linked to body temperature. To flee from predators, semi-aquatic Anolis lizards dive underwater for long periods and rebreathe from a bubble of air. We hypothesized that using aquatic refugia would result in body heat loss, that dive duration is influenced by sex, and that oxygen consumption when diving would help explain sex differences. We tested these hypotheses by measuring dive length and body temperatures in A. aquaticus, and by recording oxygen consumption and final oxygen partial pressure during controlled dives in several semi-aquatic Anolis species. Not only was there a significant thermal cost to diving, but A. aquaticus males and females appeared to tolerate different levels of this cost: males re-emerged from water more quickly and at higher body temperatures than did females. Body temperature decreased according to an exponential decay function, dropping up to 6 °C in 5 min. Oxygen consumption rates in semi-aquatic anoles were primarily explained by the expected allometric scaling relationship with mass and, therefore, are unlikely to lead to sex differences in physiological limits to dive times. Instead, shorter male dives may help them maintain physiological performance, mating opportunities or territory defense. Antipredator diving behavior is physiologically costly but undoubtedly beneficial to both sexes, highlighting the need for further study of sex-based antipredator optimization. Significance statement: To avoid predators, semi-aquatic Anolis lizards can dive underwater and remain there for an extended time by rebreathing a bubble of air over their heads. In this study, we reveal that diving to escape predators also comes with a cost: submersion in water reduces lizard body temperatures. Reduced body temperature can impair a lizard’s ability to move quickly and defend mates or territories, suggesting that there may be divergent diving behaviors in males and females. Our findings confirm that males do indeed spend less time underwater than females. We measured oxygen consumption during dives, and our data suggest that sex differences in diving behavior are unrelated to oxygen use. This study sheds light on the sex-specific balance of antipredator behaviors and the maintenance of optimal body temperatures, and more broadly contributes insight into adaptive responses to environmental challenges. [ABSTRACT FROM AUTHOR]

ABSTRACT: The state of Rio Grande do Sul has a great diversity of reptile species distributed throughout its territory. Due to human actions, such as habitat fragmentation, these animals have been frequently observed in urban and peri-urban environments. This facilitates the spread of pathogens between animals and humans, posing a unique health risk, as many diseases are considered zoonoses. Leptospirosis is among the most common zoonoses in the world and is caused by pathogenic species of bacteria of the genus Leptospira. The role of reptiles in the cycle of this disease is yet unknown. However, serological studies have demonstrated positivity for antibodies against Leptospira spp. in tortoises and snakes, which may indicate that these animals act in maintaining the pathogen in the environment. This observed the presence of anti-Leptospira antibodies in rescued reptiles taken to the Center for Rehabilitation of Wild Fauna and Screening Center for Wild Animals at the Universidade Federal de Pelotas (NURFS-CETAS/UFPEL). Samples were collected from 55 animals (39 Trachemys dorbigni; 3 Philodryas patagoniensis; 3 Caiman latirostris; 3 Salvator merianae; 2 Acanthochelys spixii; 2 Phrynops hilarii; 2 Hydromedusa tectifera; 1 Philodryas aestiva) from August 2022 to December 2023 and tested for 12 reference serovars. Two animals demonstrated positivity, one for the pathogenic serovar Pyrogenes and the other for the pathogenic serovar Canicola. This result reflected the importance of different species besides mammals as potential reservoirs and responsible for maintaining leptospirosis in the environment.

Background This study aims to investigate the urban colonization of the Asian water monitor (Varanus salvator) across its entire range of distribution, addressing the paucity of research on this species in urban ecosystems. The research spans the geographic range of the Asian water monitor, focusing on urbanized areas where the species accumulates more observations (Bangkok, Colombo, Jakarta, Kuala Lumpur and Singapore). Methods We conducted a systematic review to comprehensively assess the current knowledge of the species’ presence in cities. Additionally, citizen science data from repositories like GBIF (Global Biodiversity Information facility ) were utilized to analyze the distribution patterns of V. salvator in urban environments. To elucidate urban distribution and correct collection biases, observations were weighted by sampling effort, using as a proxy all squamate occurrences available from 2010–2023, including V. salvator. Results Despite the widespread presence of the Asian water monitor in numerous cities within its distribution range, the available studies on the topic appear to be scarce. Existing research primarily consists of descriptive reports on diet and behavior. Our findings indicate that V. salvator predominantly colonizes green patches in urban areas, such as parks and small gardens. Larger cities exhibit higher records, potentially due to both permanent populations and increased citizen science reporting. Conclusions The Asian water monitor, as the largest lizard with established populations in cities, remains scarcely studied on a broader scale. However, the urban design of each city seems relevant to understand the distribution patterns within each context. Our study highlights the need for further research to explore the ecological and human dimensions associated with the species’ presence in urban environments.

Visual ecology is the study of how visual systems are evolutionarily adapted to the light conditions animals experience and the visual tasks they must perform. The greatest progress in this field has been made in studies of aquatic systems. Our understanding of the influence of how different terrestrial habitats have shaped the evolution of visual physiology and anatomy is more limited. Lizards are an excellent model system for examining terrestrial visual ecology because in most cases, each species experiences a limited range of habitat light conditions and these differ among species. Some aspects of visual physiology and anatomy have evolved in response to habitat conditions, while others are widely shared by a great diversity of species, suggesting that their features are largely inherited and have changed very little through evolutionary time. Understanding which features have evolved as specializations to current conditions and which are inherited and largely unchanged is critical to understanding the role that visual ecology plays in shaping behavior. In this article I review some basic features of the lizard visual system, including the processes by which lizards estimate distance and depth. I then explore the evolutionary response (or lack thereof) to differences in habitat structure, light intensity and spectral quality. I also explore some relationships between lizard color patterns and their color perception. The phylogenetic range of species that have been studied is small, and many key aspects of behavior have received relatively little attention. These are potentially rich areas for future study.

Reptile white blood cell (WBC) morphological features are strikingly variable across species. In the Argentine black and white tegu (Salvator merianae), red tegu (Salvator rufescens), and Savannah monitor (Varanus exanthematicus), previous reports described a WBC type with a single distinct, clear, linear- to ovoid- to crescent-shaped inclusion of presumptive monocytic origin. The objective of this study was to further investigate the origin of this unique WBC type with crescent-shaped inclusions. Blood samples from two Argentine black and white tegus, tegu 1, a 4-year-old female, and tegu 2, a 2-year-old presumed male, were submitted for routine hematological evaluation. Additional blood films were prepared and stained with these cytochemical stains: alkaline phosphatase (ALP; naphthol AS-MX phosphate substrate), alpha-naphthyl butyrate esterase, alpha-chloroacetate esterase, myeloperoxidase, Periodic acid-Schiff, and Sudan black B. Blood films from tegu 1 were also stained with a second ALP stain (5-bromo-4-chloro-3-indoxyl-phosphate and nitroblue tetrazolium substrate), Luna, luxol fast blue, and toluidine blue. The blood from tegu 1 was cytocentrifuged to isolate and fix the buffy coat in glutaraldehyde 2.5% aqueous solution for transmission electron microscopy. Six morphologically distinct WBC types were identified from tegu 1, including heterophils, basophils, monocytes, azurophils, lymphocytes, and the unique WBC type, which were identified as eosinophils with inclusions. WBC types in tegu 2 were similar; however, eosinophils lacked a discernable inclusion. Proper WBC identification will be useful in obtaining accurate hemogram data for this species.

Common blue-tongued skinks (Tiliqua scincoides) are popular pet reptiles; however, there has been limited research to investigate sedatives for this species. The purpose of this study was to measure the physiologic effects of four combinations of alfaxalone, dexmedetomidine, and midazolam for minor procedures such as intubation and blood collection. Eleven common blue-tongued skinks (Tiliqua scincoides) were used for this prospective, randomized cross-over study. The subcutaneous combinations were used as follows: 20 mg/kg alfaxalone (A); 10 mg/kg alfaxalone and 1 mg/kg midazolam (AM); 0.1 mg/kg dexmedetomidine and 1 mg/kg midazolam (DM); and 5 mg/kg alfaxalone, 0.05 mg/kg dexmedetomidine, and 0.5 mg/kg midazolam (ADM). Heart rate, respiratory rate, palpebral reflex, righting reflex, escape reflex, toe pinch withdrawal reflex, tongue flicking, and the possibility of intubation were recorded at baseline and every 5 min for 60 min. Venous blood gases were measured at baseline, full sedation, and recovery. Heart and respiratory rates decreased significantly in all groups, but the reductions were most prominent in DM and ADM. Analgesic effects, as measured by the toe pinch withdrawal reflex, were only observed in DM and ADM. Intubation was possible in all four protocols; however, it was not possible in two DM skinks. Based on these trials, ADM and AM are recommended for minor procedures in blue-tongue skinks.

The variegated toad-headed agama, Phrynocephalus versicolor, lives in the arid landscape of the Chinese Gobi Desert. We analyzed populations from three different locations which vary in substrate color and altitude: Heishankou (HSK), Guazhou County (GZ), and Ejin Banner (EJN). The substrate color is either light-yellow (GZ-y), yellow (EJN-y), or black (HSK-b); the corresponding lizard population colors largely match their substrate in the degree of melanism. We assembled the P. versicolor genome and sequenced over 90 individuals from the three different populations. Genetic divergence between populations corresponds to their geographic distribution. We inferred the genetic relationships among these populations and used selection scans and differential expression to identify genes that show signatures of selection. Slc2a11 and akap12, among other genes, are highly differentiated and may be responsible for pigment adaptation to substrate color in P. versicolor.

The world is facing a biodiversity crisis, and species are in danger of slipping towards extinction before having their conservation status formally determined. Australian squamates (snakes and lizards) form a highly diverse (over 1000 species) fauna, with 12% being either Data Deficient or Not Evaluated. We examined attributes of Australian squamates categorized as Data Deficient or Not Evaluated and compared key traits that are linked with threatened categories via univariate and multivariate models. We further used the machine learning model of Caetano et al. (2022, PloS Biology, 20, e3001544) to predict the putative extinction risk categories for Data Deficient and Not Evaluated Australian squamate species based on an analysis of reptiles globally. We found that Data Deficient Australian squamates are often lacking information on their drivers of threat and distribution, but not intrinsic traits or uncertain taxonomy. Data Deficient, Not Evaluated and threatened species often possess similar traits, including having small range sizes, being insular endemics and recently described, indicating that they may require some similar conservation management. Meanwhile, Not Evaluated species exhibit certain unique traits relative to evaluated species. We predicted 21% of Data Deficient and Not Evaluated species are threatened which is three times greater than currently assessed species (7%). This may indicate that a larger proportion of poorly known squamate species are more likely to be threatened than previously thought. Overall, our findings provide an important resource for the conservation management of Australian squamates by highlighting key traits and missing data, as well as providing a list of Data Deficient and Not Evaluated species that should be prioritized for research. [ABSTRACT FROM AUTHOR]

Introduction: Similar traits appearing in distantly related organisms have intrigued scientists for generations. While anole lizards of the Caribbean are often touted as a classic example of repeated evolution, the adhesive toe pads of gecko lizards are an equally striking yet underappreciated example of relatedly evolved traits. The strikingly diverse toe pads of gecko lizards (Gekkota) have been gained and lost multiple times throughout the clade's evolutionary history. In addition, distantly related genera have repeatedly evolved remarkably similar morphologies. This complicated combination of divergent and repeated evolution represents a useful system for understanding the evolution of complex structures, including repeated adaptation. Methods: Using geometric morphometrics, we evaluated parallel morphological differences across families and expanded existing approaches fitting models of trait evolution to use geometric morphometric data. Adapting the use of phylogenetic independent contrasts for shape data, we conducted a node height test to investigate how toe pad shape has evolved across geckos. Results: We found multiple examples of significant parallel differences in toe pad morphology and support for a model of early burst morphological evolution. Discussion: Our results suggest the diversification of Gekkotan toe pads included repeated parallel changes from padless ancestral morphologies to derived pad bearing morphologies. This morphological diversification occurred rapidly early in the diversification of gecko families and genera and slowed more recently, during diversification within genera. [ABSTRACT FROM AUTHOR]

Simple Summary: Gonads are organs such as testes and ovaries. They are organs with completely different structures which arise in development from common sexually undifferentiated primordia. The development of gonads has been well-studied only in some vertebrates, and lizards remain one of the groups with the least-explored gonadal development. In this study, we analyzed changes in the structure of developing gonads in three species of geckos from the formation of gonadal ridges, the primordia of gonads, through the sexual differentiation of gonads, to the formation of testes and ovaries. We showed that the earliest manifestation of the sexual differentiation of gonads is the differentiation in the thickness of the gonadal cortex and the number of cortical germ cells. The development of gecko gonads was characterized by a different tendency of the ovarian medulla to form cords. The ovarian cortex was thickened at the pole of the gonad and thin near the mesogonium. In differentiating testes, lumens formed very early. This study indicated a number of unique features in the development of geckos, as well as a number of common features in the development of their gonads and other vertebrates. Reptiles constitute a highly diverse group of vertebrates, with their evolutionary lineages having diverged relatively early. The types of sex determination exemplify the diversity of reptiles; however, there are limited data regarding the gonadal development in squamate reptiles. Geckos constitute a group that is increasingly used in research and that serves as a potential reptilian model organism. The aim of this study was to trace the changes in the structure of developing gonads in the embryos of three gecko species: the crested gecko, leopard gecko, and mourning gecko. These species represent different families of the Gekkota infraorder and exhibit different types of sex determination. Gonadal development was examined from the formation of the earliest gonadal ridges through the development of undifferentiated gonadal structures, sex differentiation of gonads, and the formation of testicular and ovarian structures. The study showed that the gonadal primordia of these three gecko species formed on the most dorsally located surface of the dorsal mesentery, and both the coelomic epithelium and the nephric mesenchyme contributed to their development. As in other reptile species, primordial germ cells settled in the gonadal ridges, and the undifferentiated gonad was composed of a cortex and a medulla. Ovarian differentiation started with the thickening of the gonadal cortex and proliferation of germ cells in this region. A characteristic feature of the developing gecko ovaries was the thickened crescent-shaped cortex on the medial and ventral surfaces of the ovaries. The ovarian medulla also grew and exhibited diverse tendencies to form cords. In the leopard gecko, advanced cord-like structures with lumens were observed in the ovaries, which were not seen in the crested gecko. Testicular differentiation was characterized by cortical thinning and the disappearance of germ cells in this region. In the medulla, the development of distinct cords with early lumen formation was noted. A characteristic feature of embryonic gonads was their growth in a horizontal plane. In this study, gonadal development was characterized by several features that are shared by geckos and other reptiles, along with features that are specific only to geckos. [ABSTRACT FROM AUTHOR]

Although growing urbanization has direct negative consequences for local biodiversity, several native species have been observed maintaining populations in urban environments. Understanding which factors influence the ability of native species to persist in urban environments is crucial, both for the study of biological adaptation and of urban planning. The quantification of the proportion of juvenile individuals can be a good proxy for assessing the long-term persistence of urban populations. We present comparative data about spatial and temporal variations in the age-class structure in two suburban and two forest populations of the Cuban endemic lizard Anolis homolechis, obtained during a 20-month survey. We found a four-fold lower proportion of juveniles in the suburban habitat compared to the forest one. There was, however, no evidence for differential female fecundity between the two habitats, as assessed by the proportion of gravid females. Conversely, the rate of tail autotomy (an antipredator behavior) was significantly higher in the suburban juveniles compared to the forest ones, possibly reflecting a higher exposure to predators and, particularly, inter- and intraspecific cannibalism. However, tail loss at initial capture or habitat type had no effect on the probability of recapture of juveniles. We discuss the potential causes and consequences of a modified age-class structure in urbanized environments. [ABSTRACT FROM AUTHOR]

As amniote vertebrates, lizards are the most closely related organisms to humans capable of appendage regeneration. Lizards can autotomize, or release their tails as a means of predator evasion, and subsequently regenerate a functional replacement. Green anoles (Anolis carolinensis) can regenerate their tails through a process that involves differential expression of hundreds of genes, which has previously been analyzed by transcriptomic and microRNA analysis. To investigate protein expression in regenerating tissue, we performed a whole proteomic analysis of regenerating tail tip and base. This is the first proteomic data set available for any anole lizard. We identified a total of 2646 proteins—976 proteins only in the regenerating tail base, 796 only in the tail tip, and 874 in both tip and base. For over 90% of these proteins in these tissues, we were able to assign a clear orthology to gene models in either the Ensembl or NCBI databases. For 13 proteins in the tail base, 9 proteins in the tail tip, and 10 proteins in both regions, the gene model in Ensembl and NCBI matched an uncharacterized protein, confirming that these predictions are present in the proteome. Ontology and pathways analysis of proteins expressed in the regenerating tail base identified categories, including actin filament‐based process, ncRNA metabolism, regulation of phosphatase activity, small GTPase‐mediated signal transduction, and cellular component organization or biogenesis. Analysis of proteins expressed in the tail tip identified categories, including regulation of organelle organization, regulation of protein localization, ubiquitin‐dependent protein catabolism, small GTPase‐mediated signal transduction, morphogenesis of epithelium, and regulation of biological quality. These proteomic findings confirm pathways and gene families activated in tail regeneration in the green anole as well as identify uncharacterized proteins whose role in regrowth remains to be revealed. This study demonstrates the insights that are possible from the integration of proteomic and transcriptomic data in tail regrowth in the green anole, with potentially broader application to studies in other regenerative models. KEY POINTS: This research is highly interdisciplinary, combining our previous analyses with these most recent findings: Appendage regeneration is a conserved trait among vertebrates and has been characterized in animals ranging from teleost fish (zebrafish), urodele amphibians (axolotl), anuran amphibians (Xenopus frog), squamate reptiles (various species of lizards), and even crocodilians (American alligator).Comparative genomic and proteomic analysis of this process allows us to identify the genetic pathways and cellular processes under evolutionary selection for this regrowth capacity. Activating these conserved genetic pathways and cellular processes will be critical to developing regenerative medical therapies in humans.The identification of proteins expressed in regeneration extends analyses based only on predicted proteins from transcriptomic analysis, and permits integration with protein‐expression studies of regrowing nervous and musculoskeletal structures. [ABSTRACT FROM AUTHOR]

Background: Veiled chameleon (Chamaeleo calyptratus) and panther chameleon (Furcifer pardalis) are two of the most popular pet chameleons, and consequently, these species are frequently evaluated in veterinary practices. According to our review of the literature, normal computed tomography (CT) anatomy of these lizards has not been previously described. Aim: The purposes of this prospective study were to describe the normal CT anatomy of the coelomic organs in healthy patients and to provide normal reference values in these species. Methods: Seventeen clinically healthy veiled chameleons and 15 clinically healthy panther chameleons were included. All CT studies were performed with the chameleons under light anesthesia and positioned in sternal recumbency. Studies were performed with a 16-slice helical CT scanner with a slice thickness of 0.625 mm. The authors recorded qualitative and quantitative CT characteristics of the coelomic structures. Macroscopic cross-sectional anatomy was performed for comparison of the CT findings. Results: Heart, lungs, liver, including caudal vena cava, hepatic vessels, gallbladder, esophagus, stomach, intestines, gonads, fat bodies, kidneys, and urinary bladder could be visualized with CT. The spleen, pancreas, and adrenal glands could not be identified. Conclusion: This study provides a guide to the normal cross-sectional and computed tomographic anatomy of the coelomic cavity in veiled and panther chameleons. Our results could be used as a reference for future research studies or comparison of clinically ill patients. [ABSTRACT FROM AUTHOR]

In animals, the success of particular lineages can be measured in terms of their number of species, the extent of their geographic range, the breadth of their habitats and ecological niches, and the diversity of their morphological and life‐history traits. Here, we review the distribution, ecology, morphology and life history of skinks, a diverse lineage of terrestrial vertebrates. We compared key traits between the three subfamilies of skinks, and between skinks and non‐scincid lizards. There are currently 1743 described species of skink, which represent 24% of global lizard diversity. Since 2010, 16% of lizard descriptions have been of skinks. The centres of skink diversity are in Australia, New Guinea, southeast Asia, Oceania, Madagascar and central Africa. Compared with non‐scincid lizards, skinks have larger distributional ranges, but smaller body sizes. Sexual size dimorphism is rare in skinks. Almost a quarter (23%) of skinks exhibit limb reduction or loss, compared with just 3% of non‐scincid lizards. Skinks are more likely to be viviparous (34% of species) compared with non‐scincids (13%), and have higher clutch/litter sizes than non‐scincids. Although skinks mature later than non‐scincids, their longevity is similar to that exhibited by other lizard groups. Most skinks (88%) are active foragers, and they are more likely to be carnivorous than non‐scincids. Skinks are more likely to be diurnal or cathemeral than other lizard groups, but they generally have lower field body temperatures compared with non‐scincids. The success of skinks appears to be both a result of them hitting upon a winning body plan and ecology, and their capacity to regularly deviate from this body plan and adapt their ecology and life history (e.g. repeated limb reduction and loss, transitions to viviparity) to prevailing conditions. [ABSTRACT FROM AUTHOR]

Simple Summary: The recent debate on the theory of evolution focuses on various aspects that arise following the evidence of the advancement of knowledge in genetics and molecular biology. In particular, some researchers are inclined to introduce an extended evolutionary theory involving this hypothesis. Many theoretical hypotheses are based on the ever-increasing knowledge of phenotypic plasticity as well as epigenetic mechanisms. In particular, plasticity increases the complexity of the selection–phenotype–genotype interaction, and the collection of cases deriving from empirical experiments helps understand its role. The case of the blue lizard on islets is particularly intriguing due to the speed of its evolution and the modulation of the genome that make these populations a model of plasticity. We have highlighted the adaptive role of regulation of the genome in tissues such as the brain and testis. This would happen because the phenotype adapted to island life is characterized by inter-individual and sexual interaction behaviors that are controlled by genes differentially expressed in these two districts. The Italian wall lizard (Podarcis siculus) living on islets exhibits a melanic skin coloration and a suite of adaptive traits lacking in nearby mainland populations. On islets, the unpredictable environmental conditions and highly fluctuating population densities are believed to have produced reversed island syndrome (RIS). Several physiological, behavioral, and life-history changes based on the RIS could result from positive selection on increased activity of melanocortins. We hypothesize that phenotypes on islets are the product of a plastic variation depending on the regulation of specific genes. Focusing on control systems that determine the insular-adapted phenotype, we demonstrated that reproductive markers, involved in the hypothalamus–hypophysis–gonadal axis, and metabolism markers, flags for hypophysis-melanocortin receptors, are all up-regulated in island lizards under the RIS. This behavior, combined with the observed limited variation in the mitochondrial genome, agrees with the hypothesis that plasticity enables populations to persist in novel environmental conditions and that over time, natural selection will "fine-tune" the population to the environment by modifying the phenotype under selection. We believe that analysis of the transcriptome and the single gene expression, such that all the variations observed in the island populations, can be useful to shed light on evolutionary plasticity as a process affecting animals' populations in general. [ABSTRACT FROM AUTHOR]

The genus Sarcocystis has approximately 200 species that are able to infect homeothermic and poikilothermic animals. So far, 23 Sarcocystis spp. have snakes as definitive hosts (DHs) and mammals and/or reptiles as intermediate hosts (IHs). Some of these species cause disease or even death in their IH. At least two Sarcocystis spp. from snakes have relevance in public health. Sarcocystis nesbitti causes serious myopathy in humans, and S. singaporensis is lethal for rats and was successfully tested in the biological control of these rodents. Molecular identification was not reported for half of Sarcocystis spp. shed by snakes. For some snake species, their role as DHs for Sarcocystis spp. is totally unknown, including certain snakes which are bred as companion animals. The aim of this review is to discuss the role of snakes as DHs or IHs of Sarcocystis spp. and the future directions for the identification of the parasites and the elucidation of their life cycles. [ABSTRACT FROM AUTHOR]

Background: Veiled chameleon (Chamaeleo calyptratus) and panther chameleon (Furcifer pardalis) are two of the most popular pet chameleons, and consequently, these species are frequently evaluated in veterinary practices. According to our review of the literature normal computed tomography (CT) anatomy of these lizards has not been previously described. Aim: The purposes of this prospective study were to describe the normal CT anatomy of the coelomic organs in healthy patients and to provide normal reference values in these species. Methods: Seventeen clinically healthy veiled chameleons and fifteen clinically healthy panther chameleons were included. All CT studies were performed with the chameleons under light anaesthesia and positioned in sternal recumbency. Studies were performed with a 16-slice helical CT scanner with a slice thickness of 0.625 mm. The authors recorded qualitative and quantitative CT characteristics of the coelomic structures. Macroscopic cross-sectional anatomy was performed for comparison of the CT findings. Results: Lungs, liver -including caudal vena cava, hepatic vessels, and gallbladder-, oesophagus, stomach, intestines, gonads, fat bodies, kidneys, and urinary bladder could be visualized with CT. The spleen, pancreas, and adrenal glands could not be identified. Conclusion: This study provides a guide of the normal cross-sectional and computed tomographic anatomy of the coelomic cavity in veiled and panther chameleons. Our results could be used as a reference for future research studies or for comparison of clinically ill patients. [Open Vet J 2023; 13(9.000): 1071-1081]

An adult, 362 g, male, intact inland bearded dragon (Pogona vitticeps) was admitted to a veterinary clinic due to a temporary cloacal prolapse and a two-week history of reduced overall condition and forage intake. Physical examination revealed an approximately 2 × 1 cm round-shaped, rigid intracoelomic tissue mass. Multiple sand deposits were present on the cloacal mucous membranes, though no signs of cloacal prolapse were present. The lizard was otherwise responsive but showed reduced body tension and movement behavior. Initial fecal examination revealed a high-grade oxyuriasis. A 2 × 1.5 cm sized intracoelomic, well-vascularized, round-shaped mass was subsequently visualized by ultrasonography. After a two-day stabilization therapy, the intracoelomic mass was removed by performing a standard ventral coeliotomy under general anesthesia. Histopathological examination of the excised mass revealed an acinar pancreatic adenocarcinoma with infiltration of the peritumorous connective soft tissue. The lizard remained at the clinic for a further seven days. Its postsurgical condition improved slowly. However, the lizard started regular forage intake 10 days after surgery, and general behavior enhanced constantly within the following three weeks. The animal was presented for a follow-up six weeks after surgery, showing bright and alert behavior with no signs of disease or illness. The lizard was re-examined 20 months after the initial presentation due to a reduced overall condition and reduced food intake. Blood chemistry evaluation revealed markedly decreased protein parameters, and moderate ascites was identified ultrasonographically. A distinct association with the preceding neoplastic disease could not be made, and the lizard returned to its regular condition under supportive therapy within three weeks. To the authors’ knowledge, this is the first report of successful treatment of a pancreatic carcinoma in a bearded dragon.

Despite their evolutionary novelty, lizard venoms are much less studied in comparison to the intense research on snake venoms. While the venoms of helodermatid lizards have long been assumed to be for defensive purposes, there is increasing evidence of toxic activities more useful for predation than defence (such as paralytic neurotoxicity). This study aimed to ascertain the effects of Heloderma, Lanthanotus, and Varanus lizard venoms on the coagulation and cardiovascular systems. Anticoagulant toxicity was demonstrated for the Varanus species studied, with the venoms prolonging clotting times in human and bird plasma due to the destructive cleavage of fibrinogen. In contrast, thromboelastographic analyses on human and bird plasmas in this study demonstrated a procoagulant bioactivity for Heloderma venoms. A previous study on Heloderma venom using factor-depleted plasmas as a proxy model suggested a procoagulant factor was present that activated either Factor XI or Factor XII, but could not ascertain the precise target. Our activation studies using purified zymogens confirmed FXII activation. Comparisons of neonate and adult H. exasperatum, revealed the neonates to be more potent in the ability to activate FXII, being more similar to the venom of the smaller species H. suspectum than the adult H. exasperatum. This suggests potent FXII activation a basal trait in the genus, present in the small bodied last common ancestor. This also indicates an ontogenetic difference in prey preferences in the larger Heloderma species paralleing the change in venom biochemistry. In addition, as birds lack Factor XII, the ability to clot avian plasma suggested an additional procoagulant site of action, which was revealed to be the activation of Factor VII, with H. horridum being the most potent. This study also examined the effects upon the cardiovascular system, including the liberation of kinins from kininogen, which contributes to hypotension induction. This form of toxicity was previously described for Heloderma venoms, and was revealed in this study was to also be a pathophysiological effect of Lanthanotus and Varanus venoms. This suggests that this toxic activity was present in the venom of the last common ancestor of the anguimorph lizards, which is consistent with kallikrein enzymes being a shared toxin trait. This study therefore uncovered novel actions of anguimorph lizard venoms, not only contributing to the evolutionary biology body of knowledge but also revealing novel activities to mine for drug design lead compounds.