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Gordon H Rodda - One of the best experts on this subject based on the ideXlab platform.
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movements and activity of juvenile brown treesnakes Boiga irregularis
Copeia, 2014Co-Authors: Bjorn Lardner, Julie A. Savidge, Robert N Reed, Gordon H RoddaAbstract:Understanding the spatial ecology and foraging strategy of invasive animals is essential for success in control or eradication. We studied movements and activity in juvenile Brown Treesnakes on Guam, as this population segment has proven particularly difficult to control. Distance between daytime refugia (from telemetry of 18 juveniles, 423–800 mm snout–vent length) ranged from 0–118 m (n = 86), with a grand mean of 43 m. There were tendencies for shorter snake movements on nights directly following a full moon and on dry nights, but variation among snakes was of a larger magnitude and would greatly reduce chances to detect moon or rain effects unless corrected for. Snake activity was estimated from audio recordings of signals from “tipping” radio transmitters, analyzed for pulse period and amplitude. Activity was highest in the hours immediately after sunset, and gradually declined throughout the night before dropping abruptly in conjunction with sunrise. Snake activity was higher on rainy nights, and ...
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Do predators control prey species abundance? An experimental test with brown treesnakes on Guam
Ecology, 2012Co-Authors: Earl W. Campbell, Thomas H Fritts, Amy A. Yackel Adams, Sarah J. Converse, Gordon H RoddaAbstract:The effect of predators on the abundance of prey species is a topic of ongoing debate in ecology; the effect of snake predators on their prey has been less debated, as there exists a general consensus that snakes do not negatively influence the abundance of their prey. However, this viewpoint has not been adequately tested. We quantified the effect of brown treesnake (Boiga irregularis) predation on the abundance and size of lizards on Guam by contrasting lizards in two 1-ha treatment plots of secondary forest from which snakes had been removed and excluded vs. two 1-ha control plots in which snakes were monitored but not removed or excluded. We removed resident snakes from the treatment plots with snake traps and hand capture, and snake immigration into these plots was precluded by electrified snake barriers. Lizards were sampled in all plots quarterly for a year following snake elimination in the treatment plots. Following the completion of this experiment, we used total removal sampling to census lizar...
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scented guide ropes as a method to enhance brown treesnake Boiga irregularis trap capture success on guam
Journal of Herpetology, 2011Co-Authors: Lisa Mason, Julie A. Savidge, Gordon H Rodda, Amy Yackel A AdamsAbstract:Abstract Current methods for controlling the invasive Brown Treesnake (Boiga irregularis) on Guam include a modified minnow trap with a live mouse lure. We investigated the effects on capture success of augmenting these traps with scented guide ropes leading to trap entrances. Initial screening of scent preferences was based on time spent in scented and unscented arms of a Y-maze. Preferences of large and small snakes were scored for six different prey scents (live and carrion gecko, skink, and mouse). Large snakes spent more time in the maze arm scented with live gecko and carrion gecko, whereas small snakes spent more time in the arm scented with carrion mouse and carrion gecko. After the laboratory study, a pilot trapping session was conducted in the field using three treatments (live mouse-scented ropes, carrion gecko-scented ropes, and carrion mouse-scented ropes) and two controls (traps with unscented guide ropes and those with no ropes attached). Contrary to laboratory results, live mouse-scented r...
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The bioinvasion of Guam: inferring geographic origin, pace, pattern and process of an invasive lizard (Carlia) in the Pacific using multi-locus genomic data
Biological Invasions, 2011Co-Authors: Christopher C. Austin, Gordon H Rodda, Eric N. Rittmeyer, Lauren A. Oliver, John O. Andermann, Nathan D. JacksonAbstract:Invasive species often have dramatic negative effects that lead to the deterioration and loss of biodiversity frequently coupled with the burden of expensive biocontrol programs and subversion of socioeconomic stability. The fauna and flora of oceanic islands are particularly susceptible to invasive species and the increase of global movements of humans and their products since WW II has caused numerous anthropogenic translocations and increased the ills of human-mediated invasions. We use a multi-locus genomic dataset to identify geographic origin, pace, pattern and historical process of an invasive scincid lizard ( Carlia ) that has been inadvertently introduced to Guam, the Northern Marianas, and Palau. This lizard is of major importance as its introduction is thought to have assisted in the establishment of the invasive brown treesnake ( Boiga irregularis ) on Guam by providing a food resource. Our findings demonstrate multiple waves of introductions that appear to be concordant with movements of Allied and Imperial Japanese forces in the Pacific during World War II.
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The results of nocturnal visual surveys are influenced by lamp properties
Applied Herpetology, 2009Co-Authors: Bjorn Lardner, Julie A. Savidge, Gordon H Rodda, Robert N Reed, Amy A. Yackel AdamsAbstract:We conducted standardized visual searches at night for brown treesnakes (Boiga irregularis) and geckos, where we alternated between spotlight and floodlight lamps. Floodlights rendered us 25% more snakes and 71% more geckos than did spotlights. We show data on searcher variability and discuss what might affect the relative benefit of different lamp types.
Stephen P Mackessy - One of the best experts on this subject based on the ideXlab platform.
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transcriptomics guided bottom up and top down venomics of neonate and adult specimens of the arboreal rear fanged brown treesnake Boiga irregularis from guam
Journal of Proteomics, 2018Co-Authors: Daniel Petras, Stephen P Mackessy, Anthony J. Saviola, Cassandra M. Modahl, Libia Sanz, Alicia Pérez, Elena Juárez, Seth Frietze, Pieter C. Dorrestein, Juan J CalveteAbstract:The Brown Treesnake (Boiga irregularis) is an arboreal, nocturnal, rear-fanged venomous snake native to northern and eastern regions of Australia, Papua New Guinea and the Solomon Islands. It was inadvertently introduced onto the island of Guam during the late 1940's to early 1950's, and it has caused massive declines and extirpations of the native bird, lizard, and mammal populations. In the current study, we report the characterization of the venom proteome of an adult and a neonate B. irregularis specimens from Guam by a combination of venom gland transcriptomic and venomic analyses. Venom gland transcriptomic analysis of an adult individual identified toxins belonging to 18 protein families, with three-finger toxin isoforms being the most abundantly expressed transcripts, comprising 94% of all venom protein transcript reads. Transcripts for PIII-metalloproteinases, C-type lectins, cysteine-rich secretory proteins, acetylcholinesterases, natriuretic peptides, ficolins, phospholipase A2 (PLA2) inhibitors, PLA2s, vascular endothelial growth factors, Kunitz-type protease inhibitors, cystatins, phospholipase Bs, cobra venom factors, waprins, SVMP inhibitors, matrix metalloproteinases, and hyaluronidases were also identified, albeit, at very low abundances ranging from 0.05% to 1.7% of the transcriptome. The venom proteomes of neonate and adult B. irregularis were also both overwhelmingly (78 and 84%, respectively) dominated by monomeric and dimeric 3FTxs, followed by moderately abundant (21% (N) and 13% (A)) CRISPs, low abundance (1% (N), 3% (A)) PIII-SVMPs, and very low abundance (<0.01%) PLA2 and SVMP inhibitors. The differences in relative toxin abundances identified between neonate and adult snakes likely correlates to shifts in prey preference between the two age classes, from nearly-exclusively lizards to lizards, birds and small mammals. Immunoaffinity antivenomics with experimentally designed rabbit anti-Brown Treesnake (anti-BTS) venom IgGs against homologous venom from adult snakes demonstrated that CRISPs, PIII-SVMPs, and 60-70% of 3FTxs were effectively immunocaptured. Western blot analysis showed that all venom proteins were recognized by anti-BTS IgGs, and cross-reactivity with other rear-fanged snake venoms was also observed. Incubation of anti-BTS venom IgGs with crude B. irregularis venom resulted in a significant decrease in proteolytic (SVMP) activity against azocasein. These results provide the first comparative venomic and anti-venomic analysis of neonate and adult B. irregularis from Guam, further highlighting evolutionary trends in venom composition among rear-fanged venomous snakes. SIGNIFICANCE PARAGRAPH The Brown Treesnake (Boiga irregularis) has caused extensive ecological and economic damage to the island of Guam where it has become a classic example of the negative impacts of invasive species. In the current study, we report the first combined transcriptomic and proteomic analysis of B. irregularis venom of Guam origin. The transcriptome of an adult snake contained toxin sequences belonging to 18 protein families, with three-finger toxin (3FTx) isoforms being the most abundant and representing 94% of all venom protein transcript reads. Our bottom-up and top-down venomic analyses confirmed that 3FTxs are the major components of B. irregularis venom, and a comparative analysis of neonate and adult venoms demonstrate a clear ontogenetic shift in toxin abundance, likely driven by dietary variation between the two age classes. Second-generation antivenomics and Western blot analysis using purified anti-Brown Treesnake rabbit serum IgGs (anti-BTS IgGs) showed strong immunoreactivity toward B. irregularis venom. Interestingly, our anti-BTS IgGs did not cross-react with 3FTxs found in several other rear-fanged snake venoms, or against 3FTxs in the venom of the elapid Ophiophagus hannah, indicating that epitopes in these 3FTx molecules are quite distinct.
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Transcriptomics-guided bottom-up and top-down venomics of neonate and adult specimens of the arboreal rear-fanged Brown Treesnake, Boiga irregularis, from Guam.
Journal of Proteomics, 2017Co-Authors: Daniel Petras, Anthony J. Saviola, Cassandra M. Modahl, Libia Sanz, Alicia Pérez, Elena Juárez, Seth Frietze, Pieter C. Dorrestein, Stephen P MackessyAbstract:: The Brown Treesnake (Boiga irregularis) is an arboreal, nocturnal, rear-fanged venomous snake native to northern and eastern regions of Australia, Papua New Guinea and the Solomon Islands. It was inadvertently introduced onto the island of Guam during the late 1940's to early 1950's, and it has caused massive declines and extirpations of the native bird, lizard, and mammal populations. In the current study, we report the characterization of the venom proteome of an adult and a neonate B. irregularis specimens from Guam by a combination of venom gland transcriptomic and venomic analyses. Venom gland transcriptomic analysis of an adult individual identified toxins belonging to 18 protein families, with three-finger toxin isoforms being the most abundantly expressed transcripts, comprising 94% of all venom protein transcript reads. Transcripts for PIII-metalloproteinases, C-type lectins, cysteine-rich secretory proteins, acetylcholinesterases, natriuretic peptides, ficolins, phospholipase A2 (PLA2) inhibitors, PLA2s, vascular endothelial growth factors, Kunitz-type protease inhibitors, cystatins, phospholipase Bs, cobra venom factors, waprins, SVMP inhibitors, matrix metalloproteinases, and hyaluronidases were also identified, albeit, at very low abundances ranging from 0.05% to 1.7% of the transcriptome. The venom proteomes of neonate and adult B. irregularis were also both overwhelmingly (78 and 84%, respectively) dominated by monomeric and dimeric 3FTxs, followed by moderately abundant (21% (N) and 13% (A)) CRISPs, low abundance (1% (N), 3% (A)) PIII-SVMPs, and very low abundance (
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Irditoxin, a novel covalently linked heterodimeric three-finger toxin with high taxon-specific neurotoxicity
The FASEB Journal, 2008Co-Authors: Joanna Pawlak, Stephen P Mackessy, Nicole M Sixberry, Enrico A. Stura, Renée Ménez, André Ménez, Selvanayagam Nirthanan, R. Manjunatha KiniAbstract:A novel heterodimeric three-finger neurotoxin, irditoxin, was isolated from venom of the brown treesnake Boiga irregularis (Colubridae). Irditoxin subunit amino acid sequences were determined by Edman degradation and cDNA sequencing. The crystal structure revealed two subunits with a three-finger protein fold, typical for “nonconventional” toxins such as denmotoxin, bucandin, and candoxin. This is the first colubrid three-finger toxin dimer, covalently connected via an interchain disulfide bond. Irditoxin showed taxon-specific lethality toward birds and lizards and was nontoxic toward mice. It produced a potent neuromuscular blockade at the avian neuromuscular junction (IC50=10 nM), comparable to α-bungarotoxin, but was three orders of magnitude less effective at the mammalian neuromuscular junction. Covalently linked heterodimeric three-finger toxins found in colubrid venoms constitute a new class of venom peptides, which may be a useful source of new neurobiology probes and therapeutic leads.—Pawlak, J....
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microhabitat use by brown treesnakes Boiga irregularis effects of moonlight and prey
Journal of Herpetology, 2008Co-Authors: Steven R Campbell, Stephen P Mackessy, Jennifer A ClarkeAbstract:Microhabitat selection by reptiles can be affected by a complex interplay of abiotic and biotic factors. The Brown Treesnake (Boiga irregularis) is an efficient nocturnal predator that hunts in the tropical forest canopy and on the ground, using visual and chemical cues. To identify the factors influencing Brown Treesnake microhabitat use, we experimentally manipulated an abiotic factor, moonlight level, and a biotic factor, prey presence. We hypothesized that (1) moonlight would affect microhabitat use and (2) the presence of prey would alter microhabitat use in various moonlight levels. Trials were conducted in a large laboratory chamber with artificial trees in simulated new, half, and full moonlight. In each trial, the snake's location in canopy, subcanopy, or open ground was recorded at 60-sec intervals for 100 min. Treesnake microhabitat use was determined in three moonlight levels without prey present and in two moonlight levels with a mouse (adult Mus musculus) or a Mangrove Monitor (juvenile Varanus indicus) present. The treesnakes used open ground areas more as moonlight decreased, and they used the canopy more as moonlight increased. No significant differences existed within a moonlight level between trials with or without prey. Thus, moonlight appeared to supercede prey availability in affecting Brown Treesnake microhabitat use. Additionally, the effect of nocturnal illumination on Brown Treesnake habitat use may also have important conservation implications regarding trapping techniques and deterring the snakes from specific areas.
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venom of the brown treesnake Boiga irregularis ontogenetic shifts and taxa specific toxicity
Toxicon, 2006Co-Authors: Stephen P Mackessy, Nicole M Sixberry, William H Heyborne, Thomas FrittsAbstract:The Brown Treesnake (Boiga irregularis), a rear-fanged member of the polyphyletic family Colubridae, is an introduced predator on Guam which has been responsible for numerous human envenomations. Because little is known about this species’ venom, we characterized venom proteins from B. irregularis using enzyme assays, one and 2D electrophoresis, Western blot analysis, mass spectrometry, HPLC and toxicity assays. Venom yields and protein content varied significantly with snake size, and large adult specimens averaged over 500 ml venom (19.2 mg, protein content w90%). Only two enzymes, azocaseinolytic metalloprotease and acetylcholinesterase, were detected in venoms, and both activities increased with snake size/age. Western blot analysis demonstrated a 25 kDa CRiSP homolog in venoms from both neonate and adult snakes. 2D electrophoresis showed variation between venoms from neonate and adult snakes, especially with respect to metalloprotease and acetylcholinesterase. Analysis by MALDI-TOF mass spectrometry revealed the presence of numerous proteins with molecular masses of w8.5‐11 kDa. Adult B. irregularis venom was quite toxic to domestic chickens (Gallus domesticus; 1.75 mg/g) and lizards (Hemidactylus geckos: 2.5 mg/g and Carlia skinks: 4.5 mg/g), and intoxication was characterized by rapid paralysis of all species and neck droop in chickens. Toxicity of venom from neonates toward geckos was 1.1 mg/g, consistent with the presence of a greater diversity of 8‐11 kDa proteins (suspected neurotoxins) in these venoms. All of these values were notably lower than murine LD50 values (neonate: 18 mg/g; adult: 31 mg/g). Like venoms of several front-fanged species, B. irregularis venom showed an ontogenetic shift in enzyme activities and toxicity, and neonate snakes produced more toxic venoms with lower protease and acetylcholinesterase activities. High toxicity toward non-mammalian prey demonstrated the presence of taxaspecific effects (and thus toxins) in B. irregularis venom, likely a characteristic of many colubrid snake venoms. We hypothesize that the lack of significant envenomation effects in humans following most colubrid bites results from this taxaspecific action of colubrid venom components, not from a lack of toxins.
Julie A. Savidge - One of the best experts on this subject based on the ideXlab platform.
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movements and activity of juvenile brown treesnakes Boiga irregularis
Copeia, 2014Co-Authors: Bjorn Lardner, Julie A. Savidge, Robert N Reed, Gordon H RoddaAbstract:Understanding the spatial ecology and foraging strategy of invasive animals is essential for success in control or eradication. We studied movements and activity in juvenile Brown Treesnakes on Guam, as this population segment has proven particularly difficult to control. Distance between daytime refugia (from telemetry of 18 juveniles, 423–800 mm snout–vent length) ranged from 0–118 m (n = 86), with a grand mean of 43 m. There were tendencies for shorter snake movements on nights directly following a full moon and on dry nights, but variation among snakes was of a larger magnitude and would greatly reduce chances to detect moon or rain effects unless corrected for. Snake activity was estimated from audio recordings of signals from “tipping” radio transmitters, analyzed for pulse period and amplitude. Activity was highest in the hours immediately after sunset, and gradually declined throughout the night before dropping abruptly in conjunction with sunrise. Snake activity was higher on rainy nights, and ...
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scented guide ropes as a method to enhance brown treesnake Boiga irregularis trap capture success on guam
Journal of Herpetology, 2011Co-Authors: Lisa Mason, Julie A. Savidge, Gordon H Rodda, Amy Yackel A AdamsAbstract:Abstract Current methods for controlling the invasive Brown Treesnake (Boiga irregularis) on Guam include a modified minnow trap with a live mouse lure. We investigated the effects on capture success of augmenting these traps with scented guide ropes leading to trap entrances. Initial screening of scent preferences was based on time spent in scented and unscented arms of a Y-maze. Preferences of large and small snakes were scored for six different prey scents (live and carrion gecko, skink, and mouse). Large snakes spent more time in the maze arm scented with live gecko and carrion gecko, whereas small snakes spent more time in the arm scented with carrion mouse and carrion gecko. After the laboratory study, a pilot trapping session was conducted in the field using three treatments (live mouse-scented ropes, carrion gecko-scented ropes, and carrion mouse-scented ropes) and two controls (traps with unscented guide ropes and those with no ropes attached). Contrary to laboratory results, live mouse-scented r...
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excluding nontarget species from brown tree snake Boiga irregularis reptilia colubridae bait stations experimental tests of station design and placement
Pacific Science, 2011Co-Authors: Tom Mathies, Russell Scarpino, Brenna A Levine, Craig S Clark, Julie A. SavidgeAbstract:Abstract: Bait stations with toxic baits are an emerging technology for eradication of the invasive brown tree snake (Boiga irregularis) on Guam, yet potential interferences by nontarget species are largely unknown. We tested the efficacies of three bait station designs together with three commonly used station support structures to exclude nonnative rats (roof rat, Rattus rattus; Norway rat, Rattus norvegicus; Polynesian rat, Rattus exulans) and native coconut crabs (Birgus latro). When directly presented, all species readily consumed the dead neonatal mouse baits (nontoxic) including those replicating decomposing baits in the field. When bait stations were made easily accessible by placement near ground level, all rat species were able to enter all station types, but some individual roof rats and Norway rats exhibited apparent neophobia. When stations were placed up on support structures, simulating those in the field (∼1 m above ground level), numbers of station accessions by roof rats and Norway rats ...
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reproductive biology of male brown treesnakes Boiga irregularis on guam
Journal of Herpetology, 2010Co-Authors: John A Cruz, Tom Mathies, Valentine A Lance, Julie A. SavidgeAbstract:Reproductive biology of males in the Guam population of the Brown Treesnake, Boiga irregularis, was investigated through monthly examinations of the urogenital system organs and plasma testosterone levels. All males examined during the 12 consecutive months of the study were spermatogenic and had sperm in the ductus epididymis and ductus deferens. No evidence of testicular recrudescence or regression was observed. Testis mass did not vary among months. Epithelial height of the kidney sexual segment was the only feature examined that varied significantly among months, with lowest heights observed in May through July. Despite this variation, the sexual segment in all males was hypertrophied and contained secretory granules. Plasma testosterone levels did not vary significantly among months, were relatively low compared to those of most other snake species, and were extremely variable among individuals. There were individuals with near-zero levels in most months. Overall, the reproductive biology of males on Guam is aseasonal. In light of this finding, the claim of seasonality in the putative source population is reassessed. Testosterone levels were independent of coelomic fat body mass, which was extremely variable among males and, in many cases, quite low. Observations on morphological features suggest that individual reproductive capacity increases disproportionately with increasing body size. The possibility of facultative aseasonal/seasonal reproduction in the species is discussed. The observed capacity for continuous spermatogenesis and its relative independence from body condition may facilitate the invasive capabilities of this ecologically damaging species.
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reproductive biology of male brown treesnakes Boiga irregularis
2010Co-Authors: Tom Mathies, John A Cruz, Valentine A Lance, Julie A. SavidgeAbstract:Reproductive biology of males in the Guam population of the Brown Treesnake, Boiga irregularis, was investigated through monthly examinations of the urogenital system organs and plasma testosterone levels. All males examined during the 12 consecutive months of the study were spermatogenic and had sperm in the ductus epididymis and ductus deferens. No evidence of testicular recrudescence or regression was observed. Testis mass did not vary among months. Epithelial height of the kidney sexual segment was the only feature examined that varied significantly among months, with lowest heights observed in May through July. Despite this variation, the sexual segment in all males was hypertrophied and contained secretory granules. Plasma testosterone levels did not vary significantly among months, were relatively low compared to those of most other snake species, and were extremely variable among individuals. There were individuals with near-zero levels in most months. Overall, the reproductive biology of males on Guam is aseasonal. In light of this finding, the claim of seasonality in the putative source population is reassessed. Testosterone levels were independent of coelomic fat body mass, which was extremely variable among males and, in many cases, quite low. Observations on morphological features suggest that individual reproductive capacity increases disproportionately with increasing body size. The possibility of facultative aseasonal/seasonal reproduction in the species is discussed. The observed capacity for continuous spermatogenesis and its relative independence from body condition may facilitate the invasive capabilities of this ecologically damaging species.
Kenneth V Kardong - One of the best experts on this subject based on the ideXlab platform.
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mechanics of drinking in the brown tree snake Boiga irregularis
1994Co-Authors: H Berkhoudtl, Kenneth V Kardong, G A ZweersAbstract:Summary The drinking cycle of the brown tree snake was studied with the use of cineradiography, electromyography, high-speed cinematography, and pressure transducers to determine the morphological basis and mechanism of water intake. The drinking cycle is corrlposed of two phases, open and close. During the open phase, the lower jaw is depressed and .the quadrato-mandibular joint moves inward enlarging the oropharyngeal cavity. Through the parted anterior corners of the mouth, water is drawn into the mouth. During the close phase, these displacements are reversed, the edges to the mouth close, volume of the mouth decreases, pressure in the oropharyngeal cavity therefore rises, and water is driven past the esophageal sphincter into the esophagus. Unlike the drinking in primitive snakes, the tongue does not rhythmically protrude from and retract into the mouth during the drinking cycle, but instead the lingual canal is closed by soft tissues (oral mucosa, labial scales) and opened when these part. We propose that drinking is based upon a buccal-pump mechanism that aspirates water into the mouth, then drives it into the esophagus. This permits prolonged drinking bouts without requiring head tipping or the use of gravity for water intake or intraoral transport.
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delivery of duvernoy s secretion into prey by the brown tree snake Boiga irregularis serpentes colubridae
Toxicon, 1993Co-Authors: William K Hayes, Pablo Lavinmurcio, Kenneth V KardongAbstract:Many colubrid snakes, like the more venomous elapid and viperid snakes, can produce and inject an oral secretion that is toxic and may present a human health risk. However, colubrid oral toxins are produced in a Duvernoy's gland and delivered not through a hollow fang, but instead by long, often grooved teeth under low pressure. The possible role of Duvernoy's secretion in functions other than rapid killing of prey make it important to know how and where this secretion is delivered during a feeding strike. We used ELISA analysis to determine the quantity and proportional distribution of Duvernoy's secretion delivered into the integument compared to the viscera during a feeding strike by the colubrid snake Boiga irregularis. We determined that only about 54% (1–5 mg) of the secretion actually reached the viscera and that the rest remained in the integument. The amount reaching the viscera is about three to eight times the i.p. ld50 for mice, but these snakes depend more on constriction than toxins to kill their prey. Consequently, delivery of Duvernoy's secretion by B. irregularis is hypothesized to be part of a digestive function and its toxic properties a by-product of this role.
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histology and histochemistry of the duvernoy s gland of the brown tree snake Boiga irregularis colubridae
Copeia, 1992Co-Authors: Edward J Zalisko, Kenneth V KardongAbstract:The brown tree snake (Boiga irregularis) is an opisthoglyphous colubrid snake indigenous to northern Australia, New Guinea, and the Solomon Islands. Its paired Duvernoy's gland, located lateral to the maxilla and overlapped along its ventral edge by the supralabial gland, is a branched tubular and compound exocrine gland made up of a vertical stack of mostly longitudinal lobules. Ducts within each lobule converge, forming common lobular ducts that empty into a central cistern, a central collecting area of the duct system within the hilus of the gland. From the central cistern, a single main duct carries secretion to enlarged posterior maxillary teeth. Storage area for the secretory product is limited. Histochemical tests of the secretory cells were negative for all lipid and carbohydrate stains (including periodic acid-Schiff) and positive for proteins, suggesting a glandular product that is primarily proteinaceous with few lipid or carbohydrate components. Histochemical tests of the duct epithelium indicate the production of mucins and nonsulfated mucopolysaccharides. The Duvernoy's gland of B. irregularis is histologically and anatomically distinct from a true venom gland.
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the role of sensory receptors in the predatory behavior of the brown tree snake Boiga irregularis squamata colubridae
Journal of Herpetology, 1991Co-Authors: Kenneth V Kardong, Paul R SmithAbstract:The brown tree snake (Boiga irregularis) is indigenous to parts of costal Australia, New Guinea, and the Solomon Islands (McCoy, 1980; Cogger, 1983). It can be found in a variety of habitats (Fritts, 1988), but it is arboreal and most common in primary and secondary growth forests (Savidge, 1986, 1987; Fritts et al., 1987). Its dentition is usually referred to as "rear fanged," in which one or two posterior maxillary teeth are enlarged and bear on their labial faces an open groove associated with a connecting duct from Duvernoy's gland. The snakes appear to feed opportunistically: stomach and intestinal content analyses reveal a diet of birds and their eggs, lizards and their eggs, and small mammals (Savidge, 1988). The diets of males and females are the same, but medium to large snakes (over 120 cm SVL) tend to consume a larger proportion of birds, bird eggs, and mammals (Savidge, 1988). They are considered nocturnal in their natural habitat (Fritts, 1988; Chiszar, 1990), an activity continued in captivity (Chiszar et al., 1985). The eyes of the brown tree snake are large and the pupils are slit-like. A vomeronasal organ is present, but like other colubrid snakes, the brown tree snake lacks anatomically distinct thermosensitive facial pits. Eyes, chemosensory receptors (olfactory epithelium, vomeronasal organ), and thermosensitive pits are known to be important in the predatory behavior of certain venomous snakes (de Cock Buning, 1983). When denied visual information, pit vipers can still uccessfully strike prey, presumably by compensating with thermosensitive receptors (Noble and Schmidt, 1937; Dullemeijer, 1961). However, without such alternative sensory receptors the brown tree snake would seem to require alternative sensory input to compensate for loss of visual information during nocturnal forays for food. To assess feeding performance in the absence of visual information, prey capture success of brown tree snakes with and without blindfolds was compared. The purposes of this experiment were to describe the changes in predatory behavior (normal and blindfolded), and to produce hypotheses about how the sensory versatility of the nervous system might modulate the strike based upon alternative routes of sensory input. All brown tree snakes used were collected on Guam.
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the unique duvernoy s secretion of the brown tree snake Boiga irregularis
Toxicon, 1991Co-Authors: Darwin K Vest, Stephen P Mackessy, Kenneth V KardongAbstract:Abstract D. K. Vest , S. P. Mackessy and K. V. Kardong . The unique Duvernoy's secretion of the brown tree snake (Boiga irregularis). Toxicon29, 532–535, 1991.—Recently, bites by the colubrid Boiga irregularis (brown tree snake) in infants and young children on Guam have produced severe systemic reactions which bear some resemblance to classical manifestations of neurotoxic venom poisoning. This study demonstrates that the Duvernoy's secretion which elicits these reactions is a remarkably simple venom secretion with comparatively low toxicity and generally weak enzymatic activity. The intravenous ld 50 for Swiss-Webster mice was approximately 80 mg/kg; significant neurotoxic manifestations were not observed in mouse trials. Deaths of lethally challenged mice occurred within minutes of injection, and appeared to result from cardiopulmonary crises. Duvernoy's secretion yields, protein content, enzyme activities, electrophoretic data and toxicity characteristics of the secretion are presented.
Hobart M. Smith - One of the best experts on this subject based on the ideXlab platform.
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Experiments on Chemical Control of Behavior in Brown Tree Snakes
2007Co-Authors: David Chiszar, Gordon H Rodda, Hobart M. SmithAbstract:The brown tree snake (Boiga irregularis), accidentally introduced on Guam shortly after World War 11, is the target of extensive efforts aimed at reducing populations and preventing their spread to other Pacific islands. Chemical attractants and repellents have been investigated, and this paper presents an overview of current knowledge. In particular, chemical cues that have strong effects in laboratory tests have had only modest (though significant) effects in field tests on Guam. Reasons for the different outcomes of laboratory and field studies are discussed along with recommendations for the redesign of laboratory experiments.
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a laboratory situation for studying the effects of chemical and visual cues on prey trailing in brown treesnakes Boiga irregularis
Journal of Herpetology, 2002Co-Authors: Patrick C Stark, David Chiszar, Kathryn E Stiles, Hobart M. SmithAbstract:Abstract Because of the deleterious effects of predation by nonnative brown treesnakes (Boiga irregularis) on of native vertebrates on the island of Guam, efforts have been focused on developing effective means of controlling B. irregularis and preventing its spread to neighboring islands. Past laboratory attempts to evaluate potential baits for trapping B. irregularis have often not agreed with field results. Here we present a new laboratory situation for studying effects of various baits on prey finding ability of B. irregularis that uses trailing latencies as a measure of bait efficacy. Our results show that B. irregularis will follow trails made by rodent blood, whole rodent carcasses, and synthetic bait compounds. However, snakes followed trails made by rodent carcasses and blood at a significantly faster rate than those made by synthetic bait compounds. Further, the presence of a visual distracter cue significantly increased trailing latencies. Implications of these results for trapping efforts are ...
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Response of Brown Treesnakes (Boiga irregularis) to Mammalian Blood: Whole Blood, Serum, and Cellular Residue
Journal of Chemical Ecology, 2001Co-Authors: David Chiszar, Thomas M Dunn, Patrick Stark, Hobart M. SmithAbstract:Brown treesnakes (Boiga irregularis) responded with more tongue flicks to blood (from rabbits, rats, and mice) than to water. When rat blood was centrifuged at 3500 rpm for 5 min, separating serum from cellular residue, snakes responded strongly to serum but not to cellular residue.
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Response to Rodent Saliva by Two Species of Rodentiophagous Snakes
Journal of Chemical Ecology, 1997Co-Authors: David Chiszar, William Lukas, Hobart M. SmithAbstract:Brown tree snakes (Boiga irregularis) and prairie rattlesnakes (Crotalus viridis) responded with higher rates of tongue flicking to rodent saliva than to water. Both materials were presented on cotton-tipped applicators touched gently to the snakes' lips. Rattlesnakes also struck more frequently at applicators bearing saliva than at control applicators. Since rodents frequently lick themselves during bouts of grooming behavior, saliva is certainly a component of the chemicals associated with rodent integuments. It is concluded that this association has given rise in rodentiophagous predators to a sensitivity to saliva or to salivary components.
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Response of brown tree snakes (Boiga irregularis) to human blood
Journal of Chemical Ecology, 1993Co-Authors: David Chiszar, Thomas M Dunn, Hobart M. SmithAbstract:Ten specimens of Boiga irregularis were presented with clean or bloody tampons. The latter were used by women during menses. Trial duration was 60 sec, intertrial interval was 24 hr, and the dependent variable was rate of tongue flicking (a measure of chemosensory investigation). Bloody tampons elicited significantly more tongue flicking than did control tampons. An additional snake is shown attacking and ingesting a soiled tampon, confirming that chemosensory interest was associated with predatory behavior.