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For animals exhibiting range residency, the home range is a useful framework to quantify space use. Some reptiles can live decades in the wild and experience extreme environmental variation that influences patterns of habitat use. Individuals may modify their use of space over time, reducing the utility of single‐year home range estimates. Very high frequency (VHF) telemetry data were collected for Gila monsters (Heloderma suspectum) at three Mojave Desert sites in Clark County, Nevada, and home range utilization distributions were calculated using an autocorrelated kernel density estimator. Home range size was consistent within individuals and populations, and home range size did not vary across years at any site. To measure home range fidelity (year‐to‐year reuse), we calculated Bhattacharyya's coefficient (BC) for each combination of years in which an individual was tracked and averaged estimates across individuals and populations. The average BC score was 0.86 (scale from 0 to 1; 0 = no overlap and 1 = complete overlap) and did not vary among populations. We modeled home range area accumulation to estimate the minimum sample size needed for asymptotic stability and found home range accumulation to be dynamic and variable within and across years and individuals. Analysis of the frequency of movement by individuals, average distance traveled per movement, and cumulative distance traveled per active season revealed that movement patterns vary considerably by year. Heterogeneity of space use among populations and individuals suggests that individual and local environmental variation, rather than annual variation in resource availability, may drive home range size and movement patterns of Gila monsters in southern Nevada. Annual variability in movement patterns did not translate to variability in home range size or location, and the species exhibits extremely high philopatry, using the same areas for periods of at least 3–5 years. [ABSTRACT FROM AUTHOR]

New Mexico is home to many incredible and unique landscapes inhabited by many equally incredible animals. Some of these animals, however, may be an unwelcome sight to many visitors and residents of the Land of Enchantment. Eleven venomous snakes and one venomous lizard call New Mexico home. This document presents information on identification, range, and natural history of the fascinating reptiles.

The Komodo dragon (Varanus komodoensis) is the world's largest living lizard and exists in private captivity worldwide. Bites to humans are rare and have been proposed to be both infectious and venomous. A 43-year-old zookeeper was bitten on the leg by a Komodo dragon and suffered local tissue damage with no excessive bleeding or systemic symptoms to suggest envenomation. No specific therapy was administered other than local wound irrigation. The patient was placed on prophylactic antibiotics and on follow-up, which revealed no local or systemic infections, and no other systemic complaints. Although venomous lizard bites are uncommon, prompt recognition of possible envenomation and management of these bites is important. Komodo dragon bites may produce not only superficial lacerations but also deep tissue injury, but are unlikely to produce serious systemic effects; whereas Gila monster and beaded lizard bites may cause delayed angioedema, hypotension, and other systemic symptoms. Treatment in all cases is supportive. [ABSTRACT FROM AUTHOR]

Many lizard species face extinction due to worldwide climate change. The Guatemalan Beaded Lizard, Heloderma charlesbogerti, is a member of the Family Helodermatidae that may be particularly imperiled; fewer than 600 mature individuals are believed to persist in the wild. In addition, H. charlesbogerti lizards are phenotypically remarkable. They are large in size, charismatically patterned, and possess a venomous bite. Here, we report the draft genome of the Guatemalan Beaded Lizard using DNA from a wild-caught individual. The assembled genome totals 2.31Gb in length, similar in size to the genomes of related species. Single-copy orthologs were used to produce a novel molecular phylogeny, revealing that the Guatemalan Beaded Lizard falls into a clade with the Asian Glass Lizard (Anguidae) and in close association with the Komodo Dragon (Varanidae) and the Chinese Crocodile Lizard (Shinisauridae). In addition, we identified 31,411 protein-coding genes within the genome. Of the genes identified, we found 504 that evolved with a differential constraint on the branch leading to the Guatemalan Beaded Lizard. Lastly, we identified a decline in the effective population size of the Guatemalan Beaded Lizard approximately 400,000 years ago, followed by a stabilization before starting to dwindle again 60,000 years ago. The results presented here provide important information regarding a highly endangered, venomous reptile that can be used in future conservation, functional genetic, and phylogenetic analyses. [ABSTRACT FROM AUTHOR]

We describe the histological appearance of the osteoderms (ODs) of Heloderma suspectum and Varanus komodoensis using multiple staining and microscopy techniques to yield information about their morphology and development. Histological analysis showed that the ODs of H. suspectum are composed of three main tissue types, a superficial layer, herein identified as osteodermine, capping a base composed of Sharpey‐fibre bone and lamellar bone rich in secondary osteons (Haversian bone tissue). In contrast, ODs in V. komodoensis are composed of a core of woven bone surrounded by parallel‐fibred bone without a capping tissue. Thus, in these two species, ODs differ both in terms of their structural composition and in details of their skeletogenesis. The histology of the mineralised tissues observed in these two reptile taxa provides insights into the mechanism of formation of lizard ODs and presents a direct comparison of the histological properties between the ODs of the two species. These data allow greater understanding of the comparative histological appearance of the dermal bones of lizards and highlight their structural diversity. [ABSTRACT FROM AUTHOR]

Type II diabetes mellitus (T2DM) is a chronic non‐communicable disease due to abnormal insulin actions causing uncontrolled hyperglycaemia. The treatment for T2DM, for instance, metformin and incretin mimetic, mainly focuses on the restoration of insulin sensitivity and secretion. Exendin‐4 is a short incretin‐mimetic peptide consisting of 39 amino acids. It is discovered in the venom of Heloderma suspectum as a full agonist for the glucagon‐like peptide 1 (GLP‐1) receptor and produces insulinotropic effects. It is more resistant to enzymatic degradation by dipeptidyl‐peptidase‐4 and has a longer half‐life than the endogenous GLP‐1; thus, it is further developed as an incretin hormone analogue used to treat T2DM. The helical region of the peptide first interacts with the extracellular N‐terminal domain (NTD) of GLP‐1 receptor while the C‐terminal extension containing the tryptophan cage further enhances its binding affinity. After binding to the NTD of the receptor, it may cause the receptor to switch from its auto‐inhibited state of the receptor to its auto‐activated state. Exendin‐4 enhances the physiological functions of β‐cells and the up‐regulation of GLP‐1 receptors, thus reducing the plasma glucose levels. Moreover, exendin‐4 has also been found to ameliorate neuropathy, nephropathy and ventricular remodelling. The therapeutic effects of exendin‐4 have also been extrapolated into several clinical trials. Although exendin‐4 has a reasonable subcutaneous bioavailability, its half‐life is rather short. Therefore, several modifications have been undertaken to improve its pharmacokinetics and insulinotropic potency. This review focuses on the pharmacology of exendin‐4 and the structure‐function relationships of exendin‐4 with GLP‐1 receptor. The review also highlights some challenges and future directions in the improvement of exendin‐4 as an anti‐diabetic drug. [ABSTRACT FROM AUTHOR]

Role of exendin-4 in the Gila monster: Further lessons regarding human oral glucagon-like peptide-1 therapy? Although it is not altogether unusual for regulatory peptides to be found at low concentrations in the saliva of humans, the large amount of exendin-4 in Gila monster saliva is unlikely to have evolved by chance and must have some functional purpose. However, as an alternative and to test bioactivity, we administered exendin-4 orally, together with glucose, to fasted non-diabetic mice and compared the insulin-releasing and glycaemic responses to those induced by glucose given alone or with GLP-1 (Figure 1). [Extracted from the article]

Research into snake venoms has revealed extensive variation at all taxonomic levels. Lizard venoms, however, have received scant research attention in general, and no studies of intraclade variation in lizard venom composition have been attempted to date. Despite their iconic status and proven usefulness in drug design and discovery, highly venomous helodermatid lizards (gila monsters and beaded lizards) have remained neglected by toxinological research. Proteomic comparisons of venoms of three helodermatid lizards in this study has unravelled an unusual similarity in venom-composition, despite the long evolutionary time (~30 million years) separating H. suspectum from the other two species included in this study (H. exasperatum and H. horridum). Moreover, several genes encoding the major helodermatid toxins appeared to be extremely well-conserved under the influence of negative selection (but with these results regarded as preliminary due to the scarcity of available sequences). While the feeding ecologies of all species of helodermatid lizard are broadly similar, there are significant morphological differences between species, which impact upon relative niche occupation.

Population genetic baselines for species perceived to be at-risk are crucial for monitoring population trends and making well-informed management decisions. We characterized the genetic status of a population of Gila monsters (Heloderma suspectum), a large venomous lizard native to deserts of the southwestern United States and northern Mexico, by sampling 100 individuals in Sonoran Desert upland habitat at Saguaro National Park, Arizona, USA. We used 18 microsatellite markers, along with 1195 bp of sequence data from the mitochondrial DNA 12S locus, to examine genetic diversity, estimate effective population size, and assess demographic history. Despite suburban development adjacent to the study area, we observed high genetic diversity with uninhibited gene flow within this protected population. We estimated effective population size (Ne) for the total sample area (80 km2) using the linkage disequilibrium method in NeEstimator to be 94 individuals (95% confidence interval: 80.7-111.2). In 2011, we used capture-recapture methods to estimate that 80 adult Gila monsters (95% CI = 37-225) inhabited the area along the 14-km transect that we surveyed most frequently; probability of detecting resident Gila monsters during surveys was <0.01, highlighting the challenges of studying the species. Despite being considered an elusive and thus potentially rare species, these data reveal that in this protected environment the population appears healthy and robust. The results provide an important genetic baseline for future studies and monitoring, and exemplify the success of protective population measures in National Parks and under Arizona state laws. [ABSTRACT FROM AUTHOR]

Down-regulation of the digestive system between large meals is thought to afford energetic benefits to animals that feed infrequently. However, this idea has not been thoroughly tested. Thus, we assessed the realized benefits of infrequent feeding by examining how the timing of meal consumption influenced digestive efficiency and whole-body growth of juvenile Gila monsters, a binge-feeding lizard. All animals in our study received the same total energy intake for each feeding cycle, but meals were distributed differently over time among groups. One group had a 10-14-day period of down-regulation between meal sets while the other group had a constantly activated digestive system. The groups did not show differences in growth; however, differences in digestive efficiency for a specific meal indicate that feeding regime may have caused digestive adjustments (e.g. more efficient digestion) in one treatment group. Overall, our findings show that the energetic benefits of down-regulation may depend more on species, extent of digestive regulation, or duration of fasting than previously supposed. [ABSTRACT FROM AUTHOR]

The morphological origin of the dark and pink-orange areas in the skin of the venomous lizard Heloderma suspectum is not known. Histology and electron microscopy show that dark-grey areas of the skin derived from dermal chromatophores localized in specific areas present underneath the epidermis. A dynamic chromatophoric unit in the dermis is absent. In the darkest areas of the skin, the accumulation of melanosomes in cells of the beta-layer contributes to increase the black intensity. In the orange-pink areas, the superficial dermis contains xantophores storing numerous carotenoid vesicles, rare or absent lamellated pterinosomes and a variable number of melanosomes. These xanto-melanophores predominate over the remaining chromatophores and form a continuous stratum underneath the epidermis. Beneath this lipoid-rich stratum, iridophores are infrequent and do not form a continuous layer in the dermis. In the paler areas of the skin, melanophores are sparse in both superficial and deeper part of the dermis where irregularly oriented bundles of collagen fibrils are present. The prevalent xanto-melanophores localized in the pink-orange areas of the skin contribute to an effective sunlight protection in desert conditions in addition to the darker regions occupied by melanophores. [ABSTRACT FROM AUTHOR]

The archetypical venomous lizard species are the helodermatids, the gila monsters ( Heloderma suspectum ) and the beaded lizards ( Heloderma horridum ). In the present study, the gila monster venom proteome was characterized using 2D-gel electrophoresis and tandem mass spectrometry-based de novo peptide sequencing followed by protein identification based on sequence homology. A total of 39 different proteins were identified out of the 58 selected spots that represent the major constituents of venom. Of these proteins, 19 have not previously been identified in helodermatid venom. The data showed that helodermatid venom is complex and that this complexity is caused by genetic isoforms and post-translational modifications including proteolytic processing. In addition, the venom proteome analysis revealed that the major constituents of the gila monster venom are kallikrein-like serine proteinases (EC 3.4.21) and phospholipase A 2 (type III) enzymes (EC 3.1.1.4). A neuroendocrine convertase 1 homolog that most likely converts the proforms of the previously identified bioactive exendins into the mature and active forms was identified suggesting that these peptide toxins are secreted as proforms that are activated by proteolytic cleavage following secretion as opposed to being activated intracellularly. The presented global protein identification-analysis provides the first overview of the helodermatid venom composition. Biological significance The helodermatid lizards are the classical venomous lizards, and the pharmacological potential of the venom from these species has been known for years; best illustrated by the identification of exendin-4, which is now used in the treatment of type 2 diabetes. Despite the potential, no global analyses of the protein components in the venom exist. A hindrance is the lack of a genome sequence because it prevents protein identification using a conventional approach where MS data are searched against predicted protein sequences based on the genome sequence. However, in the recent years the development of software tools for de novo sequencing and homology searches have improved significantly facilitating the first global analysis of the major protein components of helodermatid venom presented in this study. We have used a 2D-gel approach and determined the protein components in the 58 major spots resulting in the identification of 39 unique proteins. Of these, 19 have not previously been identified in helodermatid venom. The analysis provides results with impact on our understanding of the function and evolution of venom proteins, and serves as a basis for further unraveling of the pharmaceutical potential of the venom components. [ABSTRACT FROM AUTHOR]

Background. The Gila monster ( Heloderma suspectum) is a venomous lizard native to the deserts of southwestern United States (US) and northern Mexico. The purpose of this study was to describe human exposures to Gila monsters reported to US poison control centers (PCCs) with a focus on Arizona cases. Methods. The American Association of Poison Control Centers' National Poison Data System (NPDS) was used to access and retrospectively review all calls to US PCCs, concerning Gila monsters between January 1, 2000 and October 31, 2011. In addition, detailed records from the two Arizona PCCs were reviewed for the same time period. Results. A total of 319 calls regarding Gila monsters were identified in the NPDS. Of these, 105 (33%) were human exposures; most (79%) occurred in males. A total of 71 (68%) of these 105 cases were referred to a health care facility (HCF); 30 (29%) were managed on-site. Of the 71 HCF referrals, 36 (51%) were discharged home and 17 (24%) were admitted. Most (65%) admissions were to an intensive care unit (ICU). Arizona's PCCs received 70 unique reports of Gila monster bite. Most (77%) of the bites in Arizona involved an upper extremity. Eight (11%) involved patients under the age of 18 years. Eleven (16%) Arizona cases were work-related. Twenty-eight (40%) of the 70 bites in Arizona were evaluated in a HCF, but not admitted. Eleven (16%) were admitted, of which five were to an ICU. Six patients had edema of airway structures; three required emergent airway management, one by cricothyrotomy. There were no deaths. Conclusion. Gila monster bites are uncommon. Many cases did not require hospitalization. Edema of airway structures is an infrequent, but life-threatening complication. [ABSTRACT FROM AUTHOR]

Animals remain an important source of drugs in the search for new medicinal compounds. Drugs from animal sources include insulin, pituitary hormones, vitamins, and antibiotics and biological agents, such as vaccines and immune serums. Insulin, discovered by Frederick Banting, was one of the earliest drugs to derive from animals. Today, a new drug called exenatide from the Gila monster's spit keeps glucose blood levels steady, as well as ensuring weight loss in many patients. Many drugs, adjuvants and cosmetic substances derive from domestic animals, as well as wild ones. Premarin and gelatine, obtained from horses, are vital to our being. Hyaluronic acid, originally found in rooster combs, is a popular skin care ingredient, as well as a medicinal agent for osteoarthritis and eye surgeries. The venom and toxin from animals, like snakes, spiders, scorpions and insects, is extremely potent because it interacts with specific macromolecular targets in the body. Thus, it has been used as the lead compound in the development of novel drugs, such as natural adhesives used in surgeries, and to help to treat strokes, digestive disorders and gastric reflux disease. It may also be useful in treating and preventing cardiovascular disease. Cytarabine, obtained from the Caribbean sponge, is used in the treatment of acute myeloid leukaemia. Many new antibiotics are being developed from alligators and frogs which spend their lives in places that are teeming with infectious microbes. [ABSTRACT FROM AUTHOR]

El escorpión mexicano Heloderma horridum es una de las 2 especies de lagartijas venenosas que se conocen en el mundo; hay 3 subespecies, todas en una distribución muy localizada, a lo largo de la costa del Pacífico. En la parte suroeste de Durango, en el río Presidio, un grupo de técnicos topógrafos observaron un ejemplar de Heloderma horridum y tomaron fotografías, las cuales aportaron al autor de esta nota, quien por medio de claves determinó la especie. Se trata de una especie que se considera amenazada dentro de la NOM-ECOL-059-2001, razón por la cual no se recolectó. Este registro amplía la distribución de la especie hacia el suroeste de la sierra Madre Occidental y confirma su presencia en el estado de Durango, México.The Beaded Mexican Reptile is one of the 2 species recognized as venomous reptiles in the world. There are known 3 subspecies of Heloderma horridum, all show a very localized distribution, along the Pacific Coast. At the Southwestern part of Durango, this species was seen at the river Presidio. One specimen of Heloderma horridum, was observed and photographed, by a group of topography technical, who donated the pictures. By using taxonomic keys, the specimen was determined as Heloderma horridum. This species is registered in NOM-ECOL-059-2001, and is considered Amazing species, so the specimen was not collected. This is new registration, broads the geographical distribution of this taxon towards the southwestern of the Sierra Madre Occidental and its presence in Durango state, Mexico.

Research into snake venoms has revealed extensive variation at all taxonomic levels. Lizard venoms, however, have received scant research attention in general, and no studies of intraclade variation in lizard venom composition have been attempted to date. Despite their iconic status and proven usefulness in drug design and discovery, highly venomous helodermatid lizards (gila monsters and beaded lizards) have remained neglected by toxinological research. Proteomic comparisons of venoms of three helodermatid lizards in this study has unravelled an unusual similarity in venom-composition, despite the long evolutionary time (~30 million years) separating H. suspectum from the other two species included in this study (H. exasperatum and H. horridum). Moreover, several genes encoding the major helodermatid toxins appeared to be extremely well-conserved under the influence of negative selection (but with these results regarded as preliminary due to the scarcity of available sequences). While the feeding ecologies of all species of helodermatid lizard are broadly similar, there are significant morphological differences between species, which impact upon relative niche occupation. [ABSTRACT FROM AUTHOR]

A wide variety of sex determination systems exist among squamate reptiles. They can therefore serve as an important model for studies of evolutionary transitions among particular sex determination systems. However, we still have only a limited knowledge of sex determination in certain important lineages of squamates. In this respect, one of the most understudied groups is the family Helodermatidae (Anguimorpha) encompassing the only two venomous species of lizards which are potentially lethal to human beings. We uncovered homomorphic ZZ/ZW sex chromosomes in the Gila monster (Heloderma suspectum) with a highly heterochromatic W chromosome. The sex chromosomes are morphologically similar to the ZZ/ZW sex chromosomes of monitor lizards (Varanidae). If the sex chromosomes of helodermatids and varanids are homologous, female heterogamety may be ancestral for the whole Anguimorpha group. Moreover, we found that the karyotype of the Gila monster consists of 2n = 36 chromosomes (14 larger metacentric chromosomes and 22 acrocentric microchromosomes). 2n = 36 is the widely distributed chromosomal number among squamates. In his pioneering works representing the only previous cytogenetic examination of the family Helodermatidae, Matthey reported the karyotype as 2n = 38 and suggested a different chromosomal morphology for this species. We believe that this was probably erroneously. We also discovered a strong accumulation of telomeric sequences on several pairs of microchromosomes in the Gila monster, which is a trait documented relatively rarely in vertebrates. These new data fill an important gap in our understanding of the sex determination and karyotype evolution of squamates. [ABSTRACT FROM AUTHOR]

Field metabolic rates (FMR) and water influx rates (WIR) were measured in Gila Monsters ( Heloderma suspectum) in the Mojave Desert of southern Nevada. Gila Monsters had rates of energy use that were less than half of those expected for lizards of their size, including species that live in arid habitats. Free-living Gila Monsters also had comparatively low water flux rates. The annual energy requirements of adult Gila Monsters averaged approximately 3,766 kJ, with two-thirds of the total (2,533 kJ) allocated to activity while above ground, and one-third to resting metabolism (1,233 kJ; mostly while below ground). Unusually low rates of resting metabolism caused relative costs of activity to be high: compared to other lizards, Gila Monsters have among the highest proportional use of energy for activity, relative to total energy use. The average annual water expenditure of adults was approximately 775 mL, and lizards achieved positive mass balance by drinking rain water during the late summer monsoon season. Drinking may be critical in meeting annual water requirements. FMR and WIR differed between seasons but were both highest in early summer (mid-May through June), coinciding with the peak of foraging and breeding activities. Levels of above-ground activity significantly influenced both FMR and WIR, whereas body temperature while burrowed influenced only WIR, and body mass (over the range of 270 to 420 g) did not significantly influence either whole-animal FMR or WIR. [ABSTRACT FROM AUTHOR]

Like most natural product libraries animal venoms have long been recognized as potentially rich source of biologically active molecules with the potential to be mined for the discovery of drugs, drug leads and/or biosimilars. In this work we demonstrate as a proof of concept a novel approach to explore venoms for potential biosimilarity to other drugs based on their ability to alter the transcriptomes of test cell lines followed by informatic searches and Connectivity Mapping to match the action of the venom on the cell gene expression to that of other drugs in the Connectivity Map (C-Map) database. As our test animal venom we chose Heloderma suspectum venom (Gila monster) since exendin-4, a glucagon-like peptide 1 receptor agonist, isolated from the venom is currently on the market to treat type 2 diabetes. The action of Byetta® (exentide, synthetic exendin-4), was also used in transcriptome studies. Analysis of transcriptomes from cells treated with the venom or the drug showed similarities as well as differences. The former case was primarily attributed to the fact that Gila monster venom likely contains a variety of biologically active molecules that could alter the MCF7 cell transcriptome compared to that of the single perturbant Byetta®. Using Ingenuity Pathway Analysis software, insulin-like growth factor 1 signaling was identified in the category of “Top Canonical Pathways” for both the venom and Byetta®. In the category of “Top Molecules” up-regulated, both venom and Byetta® shared IL-8, cyclic AMP-dependent transcription factor 3 (ATF-3), neuron-derived orphan receptor 1 (NR4A3), dexamethasone-induced Ras-related protein 1 (RASD1) and early growth response protein 1, (EGR-1) all with potential relevance in diabetes. Using Connectivity Mapping, Gila monster venom showed positive correlation with 1732 instances and negative correlation with 793 instances in the Connectivity database whereas Byetta® showed positive correlation with 1692 instances and negative correlation with 868 instances. Interestingly, the Gila monster venom and Byetta® both showed positive correlation with the anti-diabetic drugs troglitazone, of the thiazolidinedione class, and metformin, of the biguanide class, although Byetta® as a glucagon-like peptide-1 (GLP-1) agonist functions in a different manner than either of these two classes of anti-diabetic drugs. In summary, despite the fact that Gila monster venom contains a mixture of biologically active molecules, similarities in terms of perturbation of gene expression profiles on MCF7 cells were observed between the venom and the drug Byetta®. Furthermore, using Connectivity Mapping the Gila monster venom was demonstrated to have nodes of positive correlation to several anti-diabetic drugs two of which were the same as observed with Byetta®. Therefore, this study suggests that by using this approach novel drug activities heretofore unconsidered may be discovered in venoms using informatic tools and Connectivity Mapping. [ABSTRACT FROM AUTHOR]

We observed behavior consistent with nest-guarding in Agassiz's desert tortoise (Gopherus agassizii) at two nests in a large wind-energy-generation facility near Palm Springs, California, locally known as the Mesa Wind Farm. As researchers approached the nests, female desert tortoises moved to the entrance of their burrows and positioned themselves sideways, directly over their nests. One female stretched her limbs outward and wedged herself into the burrow (her plastron directly above the nest). Guarding of nests is rarely observed in Agassiz's desert tortoise but can occur as a result of attempted predation on eggs by Gila monsters (Heloderma suspectum) or in direct response to the perceived threat posed by researchers. This is the first report of nest-guarding for G. agassizii in the Sonoran Desert ecosystem of California. [ABSTRACT FROM AUTHOR]

Many xeric organisms maintain water balance by relying on dietary and metabolic water rather than free water, even when free water may be available. For such organisms, hydric state may influence foraging decisions, since meal consumption is meeting both energy and water demands. To understand foraging decisions it is vital to understand the role of dietary water in maintaining water balance. We investigated whether meal consumption was sufficient to maintain water balance in captive Gila monsters (Heloderma suspectum) at varying levels of dehydration. Gila monsters could not maintain water balance over long time scales through meal consumption alone. Animals fed a single meal took no longer to dehydrate than controls when both groups were deprived of free water. Additionally, meal consumption imparts an acute short-term hydric cost regardless of hydration state. Meal consumption typically resulted in a significant elevation in osmolality at 6h post-feeding, and plasma osmolality never fell below pre-feeding levels despite high water content (∼70%) of meals. These results failed to support our hypothesis that dietary water is valuable to Gila monsters during seasonal drought. When considered in conjunction with previous research, these results demonstrate that Gila monsters, unlike many xeric species, are heavily reliant on seasonal rainfall and the resulting free-standing water to maintain water balance. [ABSTRACT FROM AUTHOR]

Abstract: We investigate how a unique dietary specialist, the Gila monster (Heloderma suspectum), uses behavioral thermoregulation to elevate body temperature (T b ) after feeding. Lizards in a laboratory thermal gradient were fed rodent meals of three different sizes (5, 10, or 20% of body mass), or sham fed (meal of 0% body mass), and T b s were recorded for three days before feeding and seven days after feeding. Gila monsters selected a mean T b of 25.2°C while fasting (set-point range 23.6–27.1), and increased T b s after feeding. The magnitude and duration of post-prandial T b increases are positively related to meal size, and Gila monsters selected mean T b s up to 3.0°C higher and maintain elevated T b s for 3–6 days after feeding. Selection of T b does not appear to differ between day and night time periods, and because the lizards are both diurnal and nocturnal (at different times of year), photoperiod may not be an important influence on T b selection. [Copyright &y& Elsevier]

Alibardi, L. and DeNardo, D.F. 2011. Ultrastructural and immunocytochemical features of the epidermis of the lizard Heloderma suspectum indicate richness in lipids and lack of a specialized shedding complex. - Acta Zoologica (Stockholm) 00: 1-9. Abstract The epidermis of the venomous lizard Heloderma suspectum has been studied for detecting generalized and desert adaptations. A thick and non-completely syncytial beta-keratin layer is followed by 60-90 layers of mesos-cells. Non-lamellated or sparse lamellated lipid material is seen among mesos-cells where lipids form the main barrier against water loss. The alpha-layer is made of interlocking cells with irregular perimeter that are connected through desmosomal remnants. Immunocytochemistry shows that beta-keratin is present in beta-cells, disappears in mesos-cells but is diffuse in alpha-cells. Alpha-keratin is seen in mesos-cells but lowers in alpha-cells where alpha-keratin probably mixes with beta-keratin. Although the sequence of layers formed during the renewal stage of the epidermis was not available, a specialized shedding layer with an outer oberhautchen faced to an inner clear layer appears absent in this species. This condition suggests that shedding occurs at the boundary between the outer (old) alpha-layer and the inner (new) beta-layer formed underneath the alpha-layer. The thick mesos layer is likely an efficient adaptation to limit water loss in desert conditions while the poorly specialized shedding complex may suggest a primitive stage in the evolution of the shedding layer in this lizard or a special adaptation to water shortage. [ABSTRACT FROM AUTHOR]