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Edmund D. Brodie - One of the best experts on this subject based on the ideXlab platform.
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Data from Interacting stressors and the potential for adaptation in a changing world: responses of populations and individuals
2017Co-Authors: Gareth R. Hopkins, Susannah S. French, Edmund D. BrodieAbstract:To accurately predict the impact of environmental change, it is necessary to assay effects of key interacting stressors on vulnerable organisms, and the potential resiliency of their populations. Yet, for the most part, these critical data are missing. We examined the effects of two common abiotic stressors predicted to interact with climate change, salinity and temperature, on the embryonic survival and development of a model freshwater vertebrate, the rough-skinned newt (Taricha granulosa) from different populations. We found that salinity and temperature significantly interacted to affect newt embryonic survival and development, with the negative effects of salinity most pronounced at temperature extremes. We also found significant variation among, and especially within, populations, with different females varying in the performance of their eggs at different salinity–temperature combinations, possibly providing the raw material for future natural selection. Our results highlight the complex nature of predicting responses to climate change in space and time, and provide critical data towards that aim
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Effects of temperature on embryonic and early larval growth and development in the rough-skinned newt (Taricha granulosa).
Journal of thermal biology, 2015Co-Authors: Geoffrey D. Smith, Edmund D. Brodie, Gareth R. Hopkins, Shabnam Mohammadi, Heather M. Skinner, Tyler Hansen, Susannah S. FrenchAbstract:We investigated the effects of temperature on the growth and development of embryonic and early larval stages of a western North American amphibian, the rough-skinned newt (Taricha granulosa). We assigned newt eggs to different temperatures (7, 14, or 21°C); after hatching, we re-assigned the newt larvae into the three different temperatures. Over the course of three to four weeks, we measured total length and developmental stage of the larvae. Our results indicated a strong positive relationship over time between temperature and both length and developmental stage. Importantly, individuals assigned to cooler embryonic temperatures did not achieve the larval sizes of individuals from the warmer embryonic treatments, regardless of larval temperature. Our investigation of growth and development at different temperatures demonstrates carry-over effects and provides a more comprehensive understanding of how organisms respond to temperature changes during early development.
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otter predation on Taricha granulosa and variation in tetrodotoxin levels with elevation
Northwestern Naturalist, 2015Co-Authors: Amber N. Stokes, Brian G Gall, Susannah S. French, Andrew M Ray, Mark W Buktenica, Elva Paulson, Dale Paulson, Edmund D. BrodieAbstract:Abstract Tetrodotoxin (TTX) is a low molecular weight neurotoxin that is found in a wide variety of taxa. Tetrodotoxin blocks voltage-gated sodium channels, preventing the propagation of action potentials and inducing paralysis in susceptible animals. Taricha granulosa have been documented to possess TTX in high quantities and are preyed upon by snakes of the genus Thamnophis. However, recent observations of predation events on T. granulosa by otters were documented in a high-elevation population just outside of Crater Lake National Park, Oregon. We quantified TTX levels in this population as well as 3 populations in Crater Lake National Park using a Competitive Inhibition Enzymatic Immunoassay. We further compared these high elevation populations to a known high-toxicity population from Benton County, Oregon. We found that the populations in Crater Lake have lower levels of TTX relative to populations outside of the lake, and that all high-elevation locations have relatively low levels of TTX. We then an...
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Predator Avoidance in Lab-Reared Juvenile Rough-Skinned Newts, Taricha granulosa
Northwestern Naturalist, 2013Co-Authors: Jory Johnson, Brian G Gall, Edmund D. BrodieAbstract:Predator avoidance strategies are often viewed in the context of innate or learned, yet a true test of this hypothesis requires animals that are completely nao ¨ve to potential predators. We examined the predator avoidance behavior of juvenile Rough-skinned Newts (Taricha granulosa) that had been reared in captivity since being deposited as eggs and had never been exposed to predators or predator stimuli. In contrast to a previous study on adult newts, juveniles avoided a broader range of chemical stimuli from potential predators, including alarm cues from damaged conspecifics and stimuli from 2 Common Gartersnakes (Thamnophis sirtalis) that had recently consumed newts. These results suggest that predator avoidance in Taricha granulosa is innate. Unlike adult newts, the avoidance of a wider range of stimuli by juvenile newts is likely an effective strategy at reducing predation risk given their small size and lower tetrodotoxin concentrations (compared to adults), both of which render them vulnerable to predation by gartersnakes.
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female newts Taricha granulosa produce tetrodotoxin laden eggs after long term captivity
Toxicon, 2012Co-Authors: Brian G Gall, Amber N. Stokes, Susannah S. French, Edmund D. BrodieAbstract:We investigated the presence of tetrodotoxin (TTX) in the eggs of wild-caught newts (Taricha granulosa) at capture and again after one, two, and three years in captivity. Females initially produced eggs that contained quantities of TTX similar to previous descriptions of eggs from wild-caught adults. After the first year in captivity, the egg toxicity from each female declined, ultimately remaining constant during each of the successive years in captivity. Despite declining, all females continued to produce eggs containing substantial quantities of TTX during captivity. The decline in toxicity can not be attributed to declining egg mass but may be the result of the abbreviated reproductive cycle to which the captive newts were subjected in the lab. Finally, an estimate of the amount of TTX provisioned in the entire clutch from each female is similar to the quantity of TTX regenerated in the skin after electrical stimulation. These results, coupled with other long-term studies on the maintenance and regeneration of TTX in the skin, suggests an endogenous origin of TTX in newts.
Frank L Moore - One of the best experts on this subject based on the ideXlab platform.
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identification and characterization of mesotocin and v1a like vasotocin receptors in a urodele amphibian Taricha granulosa
General and Comparative Endocrinology, 2011Co-Authors: Brian T Searcy, Samuel C Bradford, Theresa M Filtz, Richmond R. Thompson, Frank L MooreAbstract:Abstract The cDNA sequences encoding the mesotocin receptor (MTR) and vasotocin 1a receptor (VTR-1a) were identified in a urodele amphibian, the rough-skinned newt, Taricha granulosa . Saturation binding of [ 3 H]oxytocin (OT) to the Taricha MTR (tMTR) was best fit by a two-state model; a high affinity-low abundance site and a lower affinity-high abundance site. Competition-binding studies found the following rank-order affinities for the tMTR: mesotocin (MT) > OT ≈ vasotocin (VT) > vasopressin (VP) > isotocin (IT). Inositol phosphate (IP) accumulation studies demonstrated functional activity of both the tMTR and Taricha VTR-1a (tVTR-1a) in a heterologous cell culture system. The rank-order potencies for the tMTR were MT > OT > VT ≈ VP > IT. The combined binding and IP results indicate that VT may act as a partial agonist of the tMTR. Rank-order potencies for the tVTR-1a were VT > VP > MT ≈ OT > IT. For both receptors, stimulation of IP accumulation was blocked by d(CH 2 ) 5 [Tyr(Me) 2 ]AVP (Manning compound) and d(CH 2 ) 5 [Tyr(Me) 2 ,Thr 4 ,Tyr-NH 2 ]OVT (OTA). OTA was a more potent antagonist for the transiently expressed tMTR while Manning compound was relatively more potent at inhibiting IP accumulation in tVTR-1a expressing cells. In contradiction to earlier assumptions, the absolute IC 50 of Manning compound was lower for the tMTR (27 nM ± 13) than the tVTR-1a (586 nM ± 166) indicating its potential higher affinity for the tMTR, a finding with special relevance to interpretation of comparative studies investigating the behavioral and physiological actions of neurohypophysial peptides in non-mammalian species.
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identification of mesotocin and vasotocin nucleotide sequences in two species of urodele amphibian
General and Comparative Endocrinology, 2009Co-Authors: Brian T Searcy, Eliza A Walthers, Bethany L Heppner, Richmond R. Thompson, Frank L MooreAbstract:We amplified and identified, for the first time in urodele amphibians, cDNA sequences that encode preprovasotocin (preproVT) and prepromesotocin (preproMT) from two distinct urodelian species, Taricha granulosa (the rough-skinned newt) and Plethodon shermanii (the spotted salamander). Each of these cDNA sequences encoded proteins that contained the characteristics of known neurohypophysial peptide precursors; each sequence consisting of (1) a signal peptide, (2) VT- or MT-like peptides, (3) neurophysin, and for the preproVTs, (4) copeptin. In T. granulosa, cDNA sequences encoded for the nine amino acids that define VT or MT. In P. shermani, cDNA sequences encoded for the VT peptide and a previously unidentified isoform of MT, ([Val4]-MT).
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Delta and mu opioid receptors from the brain of a urodele amphibian, the rough-skinned newt Taricha granulosa: cloning, heterologous expression, and pharmacological characterization.
General and comparative endocrinology, 2005Co-Authors: C. Samuel Bradford, Eliza A Walthers, David J. Stanley, Martha M. Baugh, Frank L MooreAbstract:Two full-length cDNAs, encoding delta (delta) and mu (mu) opioid receptors, were cloned from the brain of the rough-skinned newt Taricha granulosa, complementing previous work from our laboratory describing the cloning of newt brain kappa (kappa) and ORL1 opioid receptors. The newt delta receptor shares 82% amino acid sequence identity with a frog delta receptor and lower (68-70%) identity with orthologous receptors cloned from mammals and zebrafish. The newt mu receptor shares 79% sequence identity with a frog mu receptor, 72% identity with mammalian mu receptors, and 66-69% identity with mu receptors cloned from teleost fishes. Membranes isolated from COS-7 cells transiently expressing the newt delta receptor possessed a single, high-affinity (Kd = 2.4 nM) binding site for the nonselective opioid antagonist [3H]naloxone. In competition binding assays, the newt delta receptor displayed highest affinity for Met-enkephalin, relatively low affinity for Leu-enkephalin, beta-endorphin, and [D-penicillamine, D-penicillamine] enkephalin (DPDPE) (a delta-selective agonist in mammals), and very low affinity for mu-, kappa-, or ORL1-selective agonists. COS-7 cells expressing the newt mu receptor also possessed a high-affinity (Kd = 0.44 nM) naloxone-binding site that showed highest affinity for beta-endorphin, moderate-to-low affinity for Met-enkephalin and Leu-enkephalin and DAMGO (a mu-selective agonist in mammals), and very low affinity for DPDPE and kappa- or ORL1-selective agonists. COS-7 cells expressing either receptor type (delta or mu) showed very high affinity (Kd = 0.1-0.3 nM) for the nonselective opioid antagonist diprenorphine. Taricha granulosa expresses the same four subtypes (delta, mu, kappa, and ORL1) of opioid receptors found in other vertebrate classes, but ligand selectivity appears less stringent in the newt than has been documented in mammals.
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behavioral neuroendocrinology of vasotocin and vasopressin and the sensorimotor processing hypothesis
Frontiers in Neuroendocrinology, 2002Co-Authors: James D Rose, Frank L MooreAbstract:Vasotocin (AVT) and vasopressin (AVP) are potent modulators of social behaviors in diverse species of vertebrates. This review addresses questions about how and where AVT and AVP act to modulate social behaviors, focusing on research with an amphibian model (Taricha granulosa). In general, the behaviorally important AVT and AVP neurons occur in the forebrain and project to sites throughout the brain. Social behaviors are modulated by AVT and AVP acting at multiple sites in the brain and at multiple levels in the behavioral sequence. This review proposes that AVT and AVP can act on sensory pathways to modulate the responsiveness of neurons to behaviorally relevant sensory stimuli and also can act on motor pathways in the brainstem and spinal cord to modulate the neuronal output to behaviorspecific pattern generators. This neurobehavioral model, in which AVT and AVP are thought to modulate social behaviors by affecting sensorimotor processing, warrants further research. � 2002 Elsevier Science (USA). All rights reserved.
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Sex steroids and vasotocin interact in a female amphibian (Taricha granulosa) to elicit female-like egg-laying behavior or male-like courtship.
Hormones and behavior, 1992Co-Authors: Frank L Moore, Robin E. Wood, Sunny K. BoydAbstract:Female egg-laying behaviors and male amplectic clasping behaviors in the rough-skinned newt (Taricha granulosa) are similar in that animals clasp an object. In the case of egg-laying, females clasp submerged inanimate objects, whereas in amplexus, males clasp conspecific females. Considering these behavioral similarities and differences, we investigated the possibility that gonadal steroids and vasotocin (AVT) interact to control egg-laying behaviors, as has been shown for the control of amplexus in Taricha males. Intact, gravid T. granulosa females injected ip with AVT, unlike those injected with saline, exhibited egg-laying behaviors and oviposition. In ovariectomy-steroid-implant studies, no saline-injected female exhibited egg-laying behaviors, whereas AVT-injected ovariectomized females exhibited egg-laying behaviors if implanted with estradiol (E2), testosterone, or dihydrotestosterone (DHT), and not if implanted with empty capsules. When given a choice between clasping aquatic vegetation or other females (amplectic clasping), following an AVT injection, unoperated and shamoperated control females and ovariectomized females with E2 implants did not preferentially clasp aquatic vegetation over other females. In contrast, AVT-injected ovariectomized females with DHT implants preferentially clasped other females. Thus, exposure of Taricha females to estrogens or androgens appears to determine whether the AVT-induced clasping is egg-laying or amplectic clasping.
Charles T. Hanifin - One of the best experts on this subject based on the ideXlab platform.
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identification of tricyclic guanidino compounds from the tetrodotoxin bearing newt Taricha granulosa
Organic Letters, 2021Co-Authors: Yuta Kudo, Charles T. Hanifin, Mari YotsuyamashitaAbstract:The biosynthesis of the potent neurotoxin tetrodotoxin (TTX, 1) is still unresolved. We used MS-guided screening and nuclear magnetic resonance analyses including long-range HSQMBC to characterize ...
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Sex-biased Predation on Newts of the Genus Taricha by a Novel Predator and its Relationship with Tetrodotoxin Toxicity
The American Midland Naturalist, 2011Co-Authors: Amber N. Stokes, Charles T. Hanifin, David G. Cook, Edmund D. BrodieAbstract:Abstract Newts of the genus Taricha have long been studied in regards to their skin toxin, tetrodotoxin (TTX). It has been shown that the TTX levels across populations of Taricha are highly variable, and this has been mostly attributed to the interaction between Taricha and their only documented predators, garter snakes of the genus Thamnophis. Here we show that predators other than Thamnophis prey extensively on some newt populations. Ledson Marsh in Annadel State Park in Santa Rosa, CA is a breeding ground for both the California newt (Taricha torosa) and the rough-skinned newt (Taricha granulosa). Predation on these newts was tracked from 1998–2009 and was most often in the form of evisceration and significantly male-biased. As TTX seems to have been developed as an antipredator defense in Taricha, we used Fluorometric High Phase Liquid Chromatography (HPLC) analysis to quantify TTX levels in the skin of ten male and ten female newts of each species to determine the influence that TTX levels may have o...
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secretion and regeneration of tetrodotoxin in the rough skin newt Taricha granulosa
Toxicon, 2004Co-Authors: Brian L Cardall, Edmund D. Brodie, Charles T. HanifinAbstract:Rough-skin newts (Taricha granulosa) released tetrodotoxin (TTX) in their skin secretions in response to mild electric stimulation. This release resulted in a large (21% to almost 90% of the pre-stimulation levels) reduction in the amount of TTX present in the dorsal skin of individual newts. Over the next 9 months newts significantly regenerated the levels of TTX in their skin. These data, in combination with previously published results, are consistent with the hypothesis that these newts produce their own TTX.
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Tetrodotoxin levels in the eggs of the rough-skin newt, Taricha granulosa, are correlated with female toxicity
2003Co-Authors: Charles T. Hanifin, Edmund D. BrodieAbstract:Abstract—We quantified the amount of the neurotoxin tetrodotoxin (TTX) present in females and newly deposited eggs of the rough-skin newt, Taricha granulosa, to examine the relationship between the toxicity of an individual female and the toxicity of her eggs. We found high levels of TTX in individual eggs as well as substantial variation among clutches. Variation in the amount of TTX per egg within individual clutches was extremely low. Female skin toxic-ity was positively correlated with the mean egg toxicity of her clutch. Neither egg volume nor female size was significantly correlated with egg TTX levels. Tetrodotoxin stereoisomer–analog profiles were identical for females and their eggs. The presence of high levels of TTX in individual eggs coupled with the relationship between levels of TTX in female skin and levels of TTX in her eggs suggests that the TTX present in eggs of T. granulosa is maternally derived. The lack of correlation between egg size and TTX levels in individual eggs, as well as the low levels of within clutch variation, may indicate that deposition of TTX in eggs of T. granulosa is not linked to the deposition of other egg resources (e.g., lipids or other yolk components). Key Words—Tetrodotoxin, chemical defense, egg toxicity, Taricha granulosa
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Tetrodotoxin levels of the rough-skin newt, Taricha granulosa, increase in long-term captivity.
Toxicon : official journal of the International Society on Toxinology, 2002Co-Authors: Charles T. Hanifin, Edmund D. BrodieAbstract:We investigated the persistence of the neurotoxin tetrodotoxin (TTX) in individual captive newts (Taricha granulosa) from the Willamette Valley of Oregon using a non-lethal sampling technique. We found that the TTX levels of newts held in the laboratory for 1 yr increased. TTX stereoisomer-analog profiles were not affected by captive husbandry. Levels of TTX were high in newts from our study population and we observed substantial within population variation in quantitative levels of TTX. Females possessed more TTX than males, but the response of TTX levels to captivity did not differ between females and males. The stability of TTX toxicity in newts is consistent with other amphibian species where TTX is present and may indicate that exogenous factors play a less important role in TTX toxicity of newts than previously thought.
Amber N. Stokes - One of the best experts on this subject based on the ideXlab platform.
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of poisons and parasites the defensive role of tetrodotoxin against infections in newts
Journal of Animal Ecology, 2018Co-Authors: Pieter T. J. Johnson, Amber N. Stokes, Dana M Calhoun, Calvin B Susbilla, Travis Mcdevittgalles, Cheryl J Briggs, Jason T Hoverman, Vasyl V Tkach, Jacobus C De RoodeAbstract:Classical research on animal toxicity has focused on the role of toxins in protection against predators, but recent studies suggest these same compounds can offer a powerful defense against parasites and infectious diseases. Newts in the genus Taricha are brightly coloured and contain the potent neurotoxin, tetrodotoxin (TTX), which is hypothesized to have evolved as a defense against vertebrate predators such as garter snakes. However, newt populations often vary dramatically in toxicity, which is only partially explained by predation pressure. The primary aim of this study was to evaluate the relationships between TTX concentration and infection by parasites. By systematically assessing micro- and macroparasite infections among 345 adult newts (sympatric populations of Taricha granulosa and T. torosa), we detected 18 unique taxa of helminths, fungi, viruses and protozoans. For both newt species, per-host concentrations of TTX, which varied from undetectable to >60 μg/cm2 skin, negatively predicted overall parasite richness as well as the likelihood of infection by the chytrid fungus, Batrachochytrium dendrobatidis, and ranavirus. No such effect was found on infection load among infected hosts. Despite commonly occurring at the same wetlands, T. torosa supported higher parasite richness and average infection load than T. granulosa. Host body size and sex (females > males) tended to positively predict infection levels in both species. For hosts in which we quantified leucocyte profiles, total white blood cell count correlated positively with both parasite richness and total infection load. By coupling data on host toxicity and infection by a broad range of micro- and macroparasites, these results suggest that-alongside its effects on predators-tetrodotoxin may help protect newts against parasitic infections, highlighting the importance of integrative research on animal chemistry, immunological defenses and natural enemy ecology.
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otter predation on Taricha granulosa and variation in tetrodotoxin levels with elevation
Northwestern Naturalist, 2015Co-Authors: Amber N. Stokes, Brian G Gall, Susannah S. French, Andrew M Ray, Mark W Buktenica, Elva Paulson, Dale Paulson, Edmund D. BrodieAbstract:Abstract Tetrodotoxin (TTX) is a low molecular weight neurotoxin that is found in a wide variety of taxa. Tetrodotoxin blocks voltage-gated sodium channels, preventing the propagation of action potentials and inducing paralysis in susceptible animals. Taricha granulosa have been documented to possess TTX in high quantities and are preyed upon by snakes of the genus Thamnophis. However, recent observations of predation events on T. granulosa by otters were documented in a high-elevation population just outside of Crater Lake National Park, Oregon. We quantified TTX levels in this population as well as 3 populations in Crater Lake National Park using a Competitive Inhibition Enzymatic Immunoassay. We further compared these high elevation populations to a known high-toxicity population from Benton County, Oregon. We found that the populations in Crater Lake have lower levels of TTX relative to populations outside of the lake, and that all high-elevation locations have relatively low levels of TTX. We then an...
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Predatory Caddisfly Larvae Sequester Tetrodotoxin from Their Prey, Eggs of the Rough-Skinned Newt (Taricha granulosa)
Journal of Chemical Ecology, 2012Co-Authors: Brian G Gall, Amber N. Stokes, Edmund D. Brodie, Susannah S. FrenchAbstract:Caddisfly larvae ( Limnophilus spp.) are important predators of eggs of the rough-skinned newt ( Taricha granulosa ). Newts may possess extremely large quantities of the neurotoxin tetrodotoxin (TTX) in their skin, and females may provision this toxin in their eggs. Using a competitive inhibition enzymatic immunoassay, we examined TTX-resistant caddisflies, sympatric with the known most toxic population of newts, for the presence of TTX. We found that caddisflies sequester TTX after consuming eggs in the laboratory. Caddisfly larvae that were frozen immediately after collecting in the wild possessed TTX. Finally, wild-caught larvae reared on a TTX-free diet in the laboratory retained TTX for up to 134 days, through metamorphosis and into the adult stage.
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female newts Taricha granulosa produce tetrodotoxin laden eggs after long term captivity
Toxicon, 2012Co-Authors: Brian G Gall, Amber N. Stokes, Susannah S. French, Edmund D. BrodieAbstract:We investigated the presence of tetrodotoxin (TTX) in the eggs of wild-caught newts (Taricha granulosa) at capture and again after one, two, and three years in captivity. Females initially produced eggs that contained quantities of TTX similar to previous descriptions of eggs from wild-caught adults. After the first year in captivity, the egg toxicity from each female declined, ultimately remaining constant during each of the successive years in captivity. Despite declining, all females continued to produce eggs containing substantial quantities of TTX during captivity. The decline in toxicity can not be attributed to declining egg mass but may be the result of the abbreviated reproductive cycle to which the captive newts were subjected in the lab. Finally, an estimate of the amount of TTX provisioned in the entire clutch from each female is similar to the quantity of TTX regenerated in the skin after electrical stimulation. These results, coupled with other long-term studies on the maintenance and regeneration of TTX in the skin, suggests an endogenous origin of TTX in newts.
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tetrodotoxin levels in larval and metamorphosed newts Taricha granulosa and palatability to predatory dragonflies
Toxicon, 2011Co-Authors: Brian G Gall, Amber N. Stokes, Susannah S. French, Elizabeth A Schlepphorst, Edmund D. BrodieAbstract:Some populations of the newt Taricha granulosa possess extremely high concentrations of the neurotoxin tetrodotoxin (TTX). Tetrodotoxin is present in adult newts and their eggs, but has been assumed to be absent from the larval stage. We tested larval and metamorphosed juveniles for the presence of TTX and evaluated the palatability of these developmental stages to predatory dragonfly nymphs. All developmental stages retained substantial quantities of TTX and almost all individuals were unpalatable to dragonfly nymphs. Tetrodotoxin quantity varied greatly among individuals. When adjusted for mass, TTX concentrations declined steadily through metamorphosis. Several juveniles were palatable to dragonflies and these individuals had significantly lower TTX levels than unpalatable juveniles. These results suggest that despite previous assumptions, substantial quantities of TTX, originally deposited in the embryo, are retained by the developing larvae and metamorphosed juveniles and this quantity is enough to make them unpalatable to some potential predators.
Brian G Gall - One of the best experts on this subject based on the ideXlab platform.
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only fear the fatal foe predation risk assessment by eastern newts notophthalmus viridescens in response to common snapping turtles and other potential predators
Ethology Ecology & Evolution, 2017Co-Authors: Trevor L Chapman, Kari L Spivey, Jennifer M Lundergan, Alexandra L Schmitz, Derek L Bast, Evie K Sehr, Brian G GallAbstract:Many organisms utilize toxic or noxious compounds as a means of deterring predation. Eastern newts (Notopthalmus viridescens), along with other species in the family Salamandridae, possess a potent neurotoxin called tetrodotoxin (TTX). Although TTX can serve as an effective antipredator mechanism in species of newts with high concentrations (e.g., Taricha), eastern newts have relatively low levels of toxicity in comparison to those species, and it may not serve as an effective antipredator mechanism against all threats. In this case, they may benefit rather by utilizing behavioral changes to avoid initial contact with predators. We tested for predator-avoidance behavior in newts by exposing individuals to kairomones from various predators. We recorded activity patterns of newts when they were exposed to cues from potential predators including bullfrogs (Lithobates catesbeiana), water snakes (Nerodia sipedon) and snapping turtles (Chelydra serpentina), as well as a non-predator (bullfrog tadpoles), and a c...
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otter predation on Taricha granulosa and variation in tetrodotoxin levels with elevation
Northwestern Naturalist, 2015Co-Authors: Amber N. Stokes, Brian G Gall, Susannah S. French, Andrew M Ray, Mark W Buktenica, Elva Paulson, Dale Paulson, Edmund D. BrodieAbstract:Abstract Tetrodotoxin (TTX) is a low molecular weight neurotoxin that is found in a wide variety of taxa. Tetrodotoxin blocks voltage-gated sodium channels, preventing the propagation of action potentials and inducing paralysis in susceptible animals. Taricha granulosa have been documented to possess TTX in high quantities and are preyed upon by snakes of the genus Thamnophis. However, recent observations of predation events on T. granulosa by otters were documented in a high-elevation population just outside of Crater Lake National Park, Oregon. We quantified TTX levels in this population as well as 3 populations in Crater Lake National Park using a Competitive Inhibition Enzymatic Immunoassay. We further compared these high elevation populations to a known high-toxicity population from Benton County, Oregon. We found that the populations in Crater Lake have lower levels of TTX relative to populations outside of the lake, and that all high-elevation locations have relatively low levels of TTX. We then an...
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Predator Avoidance in Lab-Reared Juvenile Rough-Skinned Newts, Taricha granulosa
Northwestern Naturalist, 2013Co-Authors: Jory Johnson, Brian G Gall, Edmund D. BrodieAbstract:Predator avoidance strategies are often viewed in the context of innate or learned, yet a true test of this hypothesis requires animals that are completely nao ¨ve to potential predators. We examined the predator avoidance behavior of juvenile Rough-skinned Newts (Taricha granulosa) that had been reared in captivity since being deposited as eggs and had never been exposed to predators or predator stimuli. In contrast to a previous study on adult newts, juveniles avoided a broader range of chemical stimuli from potential predators, including alarm cues from damaged conspecifics and stimuli from 2 Common Gartersnakes (Thamnophis sirtalis) that had recently consumed newts. These results suggest that predator avoidance in Taricha granulosa is innate. Unlike adult newts, the avoidance of a wider range of stimuli by juvenile newts is likely an effective strategy at reducing predation risk given their small size and lower tetrodotoxin concentrations (compared to adults), both of which render them vulnerable to predation by gartersnakes.
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Predatory Caddisfly Larvae Sequester Tetrodotoxin from Their Prey, Eggs of the Rough-Skinned Newt (Taricha granulosa)
Journal of Chemical Ecology, 2012Co-Authors: Brian G Gall, Amber N. Stokes, Edmund D. Brodie, Susannah S. FrenchAbstract:Caddisfly larvae ( Limnophilus spp.) are important predators of eggs of the rough-skinned newt ( Taricha granulosa ). Newts may possess extremely large quantities of the neurotoxin tetrodotoxin (TTX) in their skin, and females may provision this toxin in their eggs. Using a competitive inhibition enzymatic immunoassay, we examined TTX-resistant caddisflies, sympatric with the known most toxic population of newts, for the presence of TTX. We found that caddisflies sequester TTX after consuming eggs in the laboratory. Caddisfly larvae that were frozen immediately after collecting in the wild possessed TTX. Finally, wild-caught larvae reared on a TTX-free diet in the laboratory retained TTX for up to 134 days, through metamorphosis and into the adult stage.
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female newts Taricha granulosa produce tetrodotoxin laden eggs after long term captivity
Toxicon, 2012Co-Authors: Brian G Gall, Amber N. Stokes, Susannah S. French, Edmund D. BrodieAbstract:We investigated the presence of tetrodotoxin (TTX) in the eggs of wild-caught newts (Taricha granulosa) at capture and again after one, two, and three years in captivity. Females initially produced eggs that contained quantities of TTX similar to previous descriptions of eggs from wild-caught adults. After the first year in captivity, the egg toxicity from each female declined, ultimately remaining constant during each of the successive years in captivity. Despite declining, all females continued to produce eggs containing substantial quantities of TTX during captivity. The decline in toxicity can not be attributed to declining egg mass but may be the result of the abbreviated reproductive cycle to which the captive newts were subjected in the lab. Finally, an estimate of the amount of TTX provisioned in the entire clutch from each female is similar to the quantity of TTX regenerated in the skin after electrical stimulation. These results, coupled with other long-term studies on the maintenance and regeneration of TTX in the skin, suggests an endogenous origin of TTX in newts.
