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Dale F Denardo - One of the best experts on this subject based on the ideXlab platform.
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Genome Sequence of a Single-Stranded DNA Virus Identified in Gila Monster Feces
Microbiology resource announcements, 2018Co-Authors: Vasishta Somayaji, Melissa A. Wilson Sayres, Mellecha Blake, Simona Kraberger, Dale F Denardo, Kara Waits, Rinaldo S. Fontenele, Arvind VarsaniAbstract:ABSTRACT The Gila Monster (Heloderma suspectum) is native to the Sonoran Desert. Metagenomic analyses of a Gila Monster fecal sample revealed the presence of a small, circular, single-stranded DNA virus that is most closely related to a gemykrogvirus (family Genomoviridae) genome from caribou feces sharing 88% genome-wide pairwise identity.
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Evidence for atypical nest overwintering by hatchling lizards, Heloderma suspectum
Proceedings of the Royal Society B: Biological Sciences, 2018Co-Authors: Dale F Denardo, Karla T. Moeller, Mark Seward, Roger A. ReppAbstract:The timing of reproductive events (e.g. oviposition and hatching) to coincide with favourable seasonal conditions is critical for successful reproduction. However, developmental time may not match the duration between the optimal time for oviposition and the optimal time for hatchling survival. Thus, strategies that alter the time between oviposition and hatchling emergence can be highly advantageous. Arrested development and the resulting extension of the duration between oviposition and hatching has been widely documented across oviparous amniotes, but nest overwintering by hatchlings has only been documented in aquatic chelonians that live where winters are quite cold. Herein, we present a compilation of evidence regarding reproductive phenology by hatchlings of the Gila Monster ( Heloderma suspectum ), a lizard inhabiting the Sonoran Desert of North America. Our data demonstrate that (i) Gila Monster hatchlings from eggs oviposited in July do not emerge from their nests until late spring or summer of the following year, yet (ii) Gila Monster eggs artificially incubated at field-relevant temperatures hatch in 4–5 months. Furthermore, we describe a fortuitous excavation of a hatching Gila Monster nest in late October, which coincides with the artificial incubation results. Together, these results provide strong support for the existence of overwintering in the nest by a lizard, and suggest that this reproductive strategy should be explored in a broader array of taxa.
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Metabolic and digestive response to food ingestion in a binge-feeding lizard, the Gila Monster (Heloderma suspectum).
Journal of Experimental Biology, 2007Co-Authors: Carolyn M. Christel, Dale F Denardo, Stephen M. SecorAbstract:The gastrointestinal tract possesses the capacity to change in form and function in response to fasting and feeding. Such plasticity can be dramatic for species that naturally experience long episodes of fasting between large meals (e.g. sit-and-wait foraging snakes, estivating anurans). By contrast, for active foraging species that feed more frequently on smaller meals, gastrointestinal responses are more modest in magnitude. The Gila Monster Heloderma suspectum is an active foraging lizard that feeds infrequently on meals weighing up to one-third of its body mass. Additionally, Gila Monsters possess a species-specific salivary peptide, exendin-4, which may be involved in the regulation of metabolic and digestive performance. To investigate the adaptive postprandial response of Gila Monsters and the potential regulatory role of exendin-4, we measured metabolic and intestinal responses to feeding in the presence or absence of circulating exendin-4. Following the consumption of rodent or egg meals equivalent to 10% of lizard body mass, metabolic rates peaked at 4.0- to 4.9-fold of standard metabolic rates and remained elevated for 5-6 days. Specific dynamic action of these meals (43-60 kJ) was 13-18% of total meal energy. Feeding triggered significant increases in mucosal mass, enterocyte width and volume, and the upregulation of D-glucose uptake rates and aminopeptidase-N activity. Total intestinal uptake capacity for L-leucine, L-proline and D-glucose were significantly elevated within 1-3 days after feeding. Whereas the absence of circulating exendin-4 had no impact on postprandial metabolism or the postprandial response of intestinal structure and nutrient uptake, it significantly increased intestinal aminopeptidase-N activity. Within the continuum of physiological responses to feeding and fasting, Gila Monsters occupy an intermediate position in experiencing moderate, though significant, regulation of intestinal performance with feeding.
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The urinary bladder as a physiological reservoir that moderates dehydration in a large desert lizard, the Gila Monster Heloderma suspectum.
Journal of Experimental Biology, 2007Co-Authors: Jon R. Davis, Dale F DenardoAbstract:Animals inhabiting xeric environments use a variety of behavioral and physiological strategies to balance water budgets. We studied the potential contribution of the urinary bladder to osmoregulation in a large desert lizard, the Gila Monster Heloderma suspectum. Here we present results of a series of in vivo laboratory experiments which tested the hypothesis that the Gila Monster urinary bladder serves as a physiological reservoir, as in amphibians and chelonians, providing water that buffers increases in plasma osmolality when food and water are unavailable. Adult Gila Monsters absorbed water from the urinary bladder into circulation and absorption of water from the urinary bladder and drinking water provided similar osmoregulatory benefits within 24 h, although drinking water provided a more immediate osmotic benefit. During food and water deprivation, plasma osmolality increased 2.5 times faster in lizards with an empty urinary bladder compared with those with a full bladder. During rehydration, stereotyped binge drinking behavior increased body mass nearly 22%, which resulted in a 24% reduction in plasma osmolality and a substantial increase in bladder water within 24 h. These results support our hypothesis and demonstrate for the first time in an adult lizard that the urinary bladder can function as a long-term physiological water reservoir. This trait can provide a critical benefit to osmoregulation during the 2- to 3-month summer dry season characteristic of the deserts that Gila Monsters inhabit.
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Release of exendin-4 is controlled by mechanical action in Gila Monsters, Heloderma suspectum.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2006Co-Authors: Carolyn M. Christel, Dale F DenardoAbstract:Exendin-4 is a peptide produced exclusively by the salivary glands of the Gila Monster, Heloderma suspectum. Although exendin-4 is considered a venom component, circulating plasma levels of exendin-4 have been shown to increase in response to feeding. Previous studies using mammals have demonstrated exendin-4 has prolonged plasma glucose-lowering properties. While these findings suggest a possible role of exendin-4 as a metabolic hormone in the Gila Monster, the mechanism controlling its release by the salivary gland has not previously been studied. We investigated possible factors driving exendin-4 release by testing Gila Monsters' response to one of six treatment groups: fed egg, fed juvenile rat, gastric intubation with egg while under anesthesia, olfactory stimulation from egg without ingestion, unfed control, and biting without feeding. These treatments were designed to separately test actions associated with feeding and different food types. We measured plasma exendin-4 levels using an immunoenzymetric assay before and at three time points after each treatment. Exendin-4 levels increased significantly in groups where considerable biting occurred but not in the other treatment groups. These results suggest that exendin-4 is released from the salivary glands in response to mechanical stimulation and not the detection of food either by smell, taste, or distention of the gut. Further study of exendin-4 in its natural organism is needed to elucidate the functional role of exendin-4 as a venom component and/or a metabolic regulator.
Bryan G Fry - One of the best experts on this subject based on the ideXlab platform.
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early evolution of the venom system in lizards and snakes
Nature, 2006Co-Authors: Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Bryan G Fry, Kim Y C Fung, Blair S HedgesAbstract:Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard). Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species). In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system. Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.
Nicolas Vidal - One of the best experts on this subject based on the ideXlab platform.
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Early evolution of the venom system in lizards and snakes
Nature, 2006Co-Authors: Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Kim Fung, S. Blair Hedges, Michael K. Richardson, Wayne. C. HodgsonAbstract:Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard)^ 1 . Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species)^ 2 , 3 , 4 , 5 . In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system^ 1 . Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins. Conventional wisdom has it that among reptiles, venom delivery systems have evolved in only two lineages, advanced snakes and the helodermatid lizards, the latter represented by the Gila Monster and beaded lizard, sole survivors of an ancient group of predators called the Monstersauria. A new study reveals that two additional major lineages of lizards — the varanids and iguanians — also produce venom toxins, and that iguanian lizards even have the signs of venom glands. This suggests that snakes and lizards are much more closely related than was thought, the snakes evolving from relatively advanced lizards, rather than as a separate evolutionary radiation.
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early evolution of the venom system in lizards and snakes
Nature, 2006Co-Authors: Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Bryan G Fry, Kim Y C Fung, Blair S HedgesAbstract:Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard). Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species). In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system. Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.
Michail Rovatsos - One of the best experts on this subject based on the ideXlab platform.
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Sex Chromosomes and Karyotype of the (Nearly) Mythical Creature, the Gila Monster, Heloderma suspectum (Squamata: Helodermatidae)
2016Co-Authors: Martina Johnson Pokorná, Michail RovatsosAbstract: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 ou
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Sex Chromosomes and Karyotype of the (Nearly) Mythical Creature, the Gila Monster, Heloderma suspectum (Squamata: Helodermatidae)
PLoS ONE, 2014Co-Authors: Martina Johnson Pokorná, Michail Rovatsos, Lukáš KratochvílAbstract: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.
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Reprint of the idealized drawings of two examples of male metaphases (a), the schematic depiction of metaphase (b) from Matthey (1931), and the karyotype (c) from Matthey (1933) of the Gila Monster.
2014Co-Authors: Martina Johnson Pokorná, Michail Rovatsos, Lukáš KratochvílAbstract:Reprint of the idealized drawings of two examples of male metaphases (a), the schematic depiction of metaphase (b) from Matthey (1931), and the karyotype (c) from Matthey (1933) of the Gila Monster.
Ty C M Hoffman - One of the best experts on this subject based on the ideXlab platform.
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cloacal evaporative cooling a previously undescribed means of increasing evaporative water loss at higher temperatures in a desert ectotherm the Gila Monster heloderma suspectum
The Journal of Experimental Biology, 2004Co-Authors: Dale F Denardo, Tricia E Zubal, Ty C M HoffmanAbstract:SUMMARY The Gila Monster Heloderma suspectum is an active forager in an environment that, at times, can be extremely hot and arid. Thus, Gila Monsters face extreme thermostatic and hydrostatic demands. For a desert ectotherm routinely risking dehydration, evaporative water loss (EWL) is typically viewed as detrimental. Yet evaporation simultaneously dehydrates and cools an animal. We explored EWL in Gila Monsters by measuring cutaneous, ventilatory and cloacal EWL at five ambient temperatures between 20.5°C and 40°C. Our results show that Gila Monsters have high EWL rates relative to body mass. Cutaneous EWL underwent a consistent, temperature-dependent increase over the entire range of test temperatures (Q 10 =1.61, with EWL ranging from 0.378 to 0.954 mg g –1 h –1 ). Ventilatory EWL did not show a significant temperature-dependent response, but ranged from 0.304 to 0.663 mg g –1 h –1 . Cloacal EWL was extremely low and relatively constant between 20.5°C and 35°C, but rose dramatically above 35°C (Q 10 >8.3×10 7 , from 0.0008 at 35°C to 7.30 mg g –1 h –1 at 40°C). This steep rise in cloacal EWL coincided with an increasing suppression of body temperature relative to ambient temperature. Dehydration to 80% of initial body mass led to a delay in the onset and an attenuation of the dramatic increase in cloacal EWL. These results emphasize the potential value of EWL for thermoregulation in ectotherms and demonstrate for the first time the role of the cloaca in this process.
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Cloacal evaporative cooling: a previously undescribed means of increasing evaporative water loss at higher temperatures in a desert ectotherm, the Gila Monster Heloderma suspectum.
The Journal of experimental biology, 2004Co-Authors: Dale F Denardo, Tricia E Zubal, Ty C M HoffmanAbstract:The Gila Monster Heloderma suspectum is an active forager in an environment that, at times, can be extremely hot and arid. Thus, Gila Monsters face extreme thermostatic and hydrostatic demands. For a desert ectotherm routinely risking dehydration, evaporative water loss (EWL) is typically viewed as detrimental. Yet evaporation simultaneously dehydrates and cools an animal. We explored EWL in Gila Monsters by measuring cutaneous, ventilatory and cloacal EWL at five ambient temperatures between 20.5 degrees C and 40 degrees C. Our results show that Gila Monsters have high EWL rates relative to body mass. Cutaneous EWL underwent a consistent, temperature-dependent increase over the entire range of test temperatures (Q(10)=1.61, with EWL ranging from 0.378 to 0.954 mg g(-1) h(-1)). Ventilatory EWL did not show a significant temperature-dependent response, but ranged from 0.304 to 0.663 mg g(-1) h(-1). Cloacal EWL was extremely low and relatively constant between 20.5 degrees C and 35 degrees C, but rose dramatically above 35 degrees C (Q(10) >8.3 x 10(7), from 0.0008 at 35 degrees C to 7.30 mg g(-1) h(-1) at 40 degrees C). This steep rise in cloacal EWL coincided with an increasing suppression of body temperature relative to ambient temperature. Dehydration to 80% of initial body mass led to a delay in the onset and an attenuation of the dramatic increase in cloacal EWL. These results emphasize the potential value of EWL for thermoregulation in ectotherms and demonstrate for the first time the role of the cloaca in this process.