Search

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 (Tar&ha torosa) and the rough-skinned newt (Tar&ha 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 TFX levels may have on sex-biased predation in this population. We found Taricha females were not significantly more toxic than males. Also, we found that T. torosa were significantly more toxic than T. granulosa, which is in contrast with other newt toxicity studies., INTRODUCTION Unlike many prey species, adult Taricha are highly toxic (Mosher et al., 1964; Wakely et al., 1966; Brodie, 1968; Brodie et al., 1974; Daly et al., 1987; Hanifin et [...]

Author(s): Shana L. Geffeney (corresponding author) [1]; Esther Fujimoto [1, 3]; Edmund D. Brodie, III [2]; Edmund D. Brodie, Jr [1]; Peter C. Ruben [1] Understanding the molecular genetic basis [...]

Populations of the garter snake Thamnophis sirtalis have evolved geographically variable resistance to tetrodotoxin (TTX) in a coevolutionary arms race with their toxic prey, newts of the genus Taricha. Here, [...]

Abstract: Adaptive evolution in response to one selective challenge may disrupt other important aspects of performance. Such evolutionary trade‐offs are predicted to arise in the process of local adaptation, but it is unclear if these phenotypic compromises result from the antagonistic effects of simple amino acid substitutions. We tested for trade‐offs associated with beneficial mutations that confer tetrodotoxin (TTX) resistance in the voltage‐gated sodium channel (NaV1.4) in skeletal muscle of the common garter snake (Thamnophis sirtalis). Separate lineages in California and the Pacific Northwest independently evolved TTX‐resistant changes to the pore of NaV1.4 as a result of arms race coevolution with toxic prey, newts of the genus Taricha. Snakes from the California lineage that were homozygous for an allele known to confer large increases in toxin resistance (NaV1.4LVNV) had significantly reduced crawl speed compared to individuals with the ancestral TTX‐sensitive channel. Heterologous expression of native snake NaV1.4 proteins demonstrated that the same NaV1.4LVNV allele confers a dramatic increase in TTX resistance and a correlated decrease in overall channel excitability. Our results suggest the same mutations that accumulate during arms race coevolution and beneficially interfere with toxin‐binding also cause changes in electrophysiological function of the channel that may affect organismal performance. This trade‐off was only evident in the predator lineage where coevolution has led to the most extreme resistance phenotype, determined by four critical amino acid substitutions. If these biophysical changes also translate to a fitness cost—for example, through the inability of T. sirtalis to quickly escape predators—then pleiotropy at this single locus could contribute to observed variation in levels of TTX resistance across the mosaic landscape of coevolution. [ABSTRACT FROM AUTHOR]

Abstract: Velvet ants are a group of parasitic wasps that are well known for a suite of defensive adaptations including bright coloration and a formidable sting. While these adaptations are presumed to function in antipredator defense, observations between potential predators and this group are lacking. We conducted a series of experiments to determine the risk of velvet ants to a host of potential predators including amphibians, reptiles, birds, and small mammals. Velvet ants from across the United States were tested with predator's representative of the velvet ants native range. All interactions between lizards, free‐ranging birds, and a mole resulted in the velvet ants survival, and ultimate avoidance by the predator. Two shrews did injure a velvet ant, but this occurred only after multiple failed attacks. The only predator to successfully consume a velvet ant was a single American toad (Anaxyrus americanus). These results indicate that the suite of defenses possessed by velvet ants, including aposematic coloration, stridulations, a chemical alarm signal, a hard exoskeleton, and powerful sting are effective defenses against potential predators. Female velvet ants appear to be nearly impervious to predation by many species whose diet is heavily derived of invertebrate prey. [ABSTRACT FROM AUTHOR]

The sequence and intensity of antipredator mechanisms may be displayed according to the risk of predation. We tested this hypothesis using two species of marsupial treefrogs from Brazil's Atlantic Forest. We observed Gastrotheca recava and G. megacephala displaying nine antipredator mechanisms and three types of defensive calls. These behaviours were displayed in an escalated sequence from motionless (passive behaviour) to biting (the most aggressive behaviour). This diversified set of antipredator mechanisms may be related to the interaction between predator and prey at the local scale. The escalated sequence of defensive behaviours should be considered in future studies on anuran-predator interaction. [ABSTRACT FROM AUTHOR]

Many descriptions of evolutionary adaptations are criticized as 'just-so stories' (1) that are based more on intuition than on direct tests of adaptive hypotheses. The elaborate crowns of horns possessed [...]

The potent neurotoxin tetrodotoxin (TTX) is known from a diverse array of taxa, but is unknown in terrestrial invertebrates. Tetrodotoxin is a low molecular weight compound that acts by blocking voltage-gated sodium channels, inducing paralysis. However, the origins and ecological functions of TTX in most taxa remain mysterious. Here, we show that TTX is present in two species of terrestrial flatworm (Bipalium adventitium and Bipalium kewense) using a competitive inhibition enzymatic immunoassay to quantify the toxin and high phase liquid chromatography to confirm the presence. We also investigated the distribution of TTX throughout the bodies of the flatworms and provide evidence suggesting that TTX is used during predation to subdue large prey items. We also show that the egg capsules of B. adventitium have TTX, indicating a further role in defense. These data suggest a potential route for TTX bioaccumulation in terrestrial systems. [ABSTRACT FROM AUTHOR]

The world is increasingly impacted by a variety of stressors that have the potential to differentially influence life history stages of organisms. Organisms have evolved to cope with some stressors, while with others they have little capacity. It is thus important to understand the effects of both developmental and evolutionary history on survival in stressful environments. We present evidence of the effects of both developmental and evolutionary history on survival of a freshwater vertebrate, the rough-skinned newt (Taricha granulosa) in an osmotically stressful environment. We compared the survival of larvae in either NaCl or MgCl2 that were exposed to salinity either as larvae only or as embryos as well. Embryonic exposure to salinity led to greater mortality of newt larvae than larval exposure alone, and this reduced survival probability was strongly linked to the carry-over effect of stunted embryonic growth in salts. Larval survival was also dependent on the type of salt (NaCl or MgCl2) the larvae were exposed to, and was lowest in MgCl2, a widely-used chemical deicer that, unlike NaCl, amphibian larvae do not have an evolutionary history of regulating at high levels. Both developmental and evolutionary history are critical factors in determining survival in this stressful environment, a pattern that may have widespread implications for the survival of animals increasingly impacted by substances with which they have little evolutionary history. [ABSTRACT FROM AUTHOR]

Defense of a limited resource, such as space or food, has recently been discovered in snakes and has been widely documented in lizards. Garter snakes (Thamnophis spp.) are historically considered generalist predators such that food is not a limiting resource. However, in this study we show that the common garter snake (Thamnophis sirtalis) and the aquatic garter snake (Thamnophis atratus) show a strong preference for amphibians as their primary food source at the Santa Lucia Preserve (SLP), Monterey County, California. This food preference forces these snake species at SLP to exploit aquatic habitats. Our principle goal was to investigate the aggressive behavior of T. sirtalis and the potential that this aggression displaces T. atratus from its preferred habitat. We found that when individuals from either species are alone, a 100% preference for aquatic or near aquatic habitat is observed. In contrast, when these species are together, T. sirtalis occupy the aquatic habitat and T. atratus occupy an area far removed from water. Thamnophis sirtalis often physically force T. atratus from the aquatic habitat through repeated biting and other displays of aggression. [ABSTRACT FROM AUTHOR]

Asymmetrical selection on predators and prey may be reduced when prey are dangerous There is an intuitive appeal to viewing natural struggles among species as arms races between enemies. Consider [...]

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 naïve 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 nnate. 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. [ABSTRACT FROM AUTHOR]

Copyright of Western North American Naturalist is the property of Monte L. Bean Life Science Museum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The application of millions of tons of road deicing salts every winter in North America presents significant survival challenges to amphibians inhabiting roadside habitats. While much is known of the effects of NaCl on anuran tadpoles, less is known of effects on amphibian eggs, or any caudate life stage. In addition, little is known of the effects of MgCl2, which is now the 2nd most commonly used road deicer. Most studies have considered amphibians to be helpless victims of deicing salts, and ignore the possibility of the evolution of local adaptation to this stressor. We attempt to address these knowledge gaps and explore this evolutionary potential by examining the effects of NaCl and MgCl2 on the survival and development of eggs from different female rough-skinned newts (Taricha granulosa) from the same population. We demonstrate that both salts, at environmentally relevant concentrations, severely affect the embryonic survival and development of this amphibian, but that the effects of the salt are dependent on the identity of the mother. This female × treatment interaction results in substantial variation in tolerance to road deicing salts among newt families, providing the raw material necessary for natural selection and the evolution of local adaptation in this amphibian. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study that investigated the level of protection offered by caddisfly portable cases constructed with rock, stick or leaf material against predatory dragonfly nymps, Anax junius. A supposition is given that the cases made of stronger material are more effective at deterring predators. However, the study showed that there was no difference in survival between the case types.

New salamanders of the genus Oedipina are described from the xeric Motagua Valley in eastern Guatemala, the El Trifinio highlands near the Honduras/El Salvador borders, and the Pacific versant of south-central Guatemala. These new species have been previously associated with known species, but possess distinctive foot morphology, different numbers of teeth, and body morphology and inhabit distinctive environments. [ABSTRACT FROM AUTHOR]

Natural selection often produces convergent changes in unrelated lineages, but the degree to which such adaptations occur via predictable genetic paths is unknown. If only a limited subset of possible mutations is fixed in independent lineages, then it is clear that constraint in the production or function of molecular variants is an important determinant of adaptation. We demonstrate remarkably constrained convergence during the evolution of resistance to the lethal poison. tetrodotoxin. in six snake species representing three distinct lineages from around the globe. Resistance-conferring amino acid substitutions in a voltage-gated sodium channel, Na~1.4. are clustered inonly two regions of the protein, and a majority of the replacements are confined to the same three positions. The observed changes represent only a small fraction of the experimentally validated mutations known to increase Na~1 .4 resistance to tetrodotoxin. These results suggest that constraints resulting from functional tradeoffs between ion channel function and toxin resistance led to predictable patterns of evolutionary convergence at the molecular level. Our data are consistent with theoretical predictions and recent microcosm work that suggest a predictable path isfollowed during an adaptive walk along a mutational landscape, and that natural selection may be frequently constrained to produce similar genetic outcomes even when operating on independent lineages. [ABSTRACT FROM AUTHOR]

Detailing the genetic basis of adaptive variation in natural populations is a first step towards understanding the process of adaptive evolution, yet few ecologically relevant traits have been characterized at the genetic level in wild populations. Traits that mediate coevolutionary interactions between species are ideal for studying adaptation because of the intensity of selection and the well-characterized ecological context. We have previously described the ecological context, evolutionary history and partial genetic basis of tetrodotoxin (TTX) resistance in garter snakes (Thamnophis). Derived mutations in a voltage-gated sodium channel gene (Nav1.4) in three garter snake species are associated with resistance to TTX, the lethal neurotoxin found in their newt prey (Taricha). Here we evaluate the contribution of Nav1.4 alleles to TTX resistance in two of those species from central coastal California. We measured the phenotypes (TTX resistance) and genotypes (Nav1.4 and microsatellites) in a local sample of Thamnophis atratus and Thamnophis sirtalis. Allelic variation in Nav1.4 explains 23 per cent of the variation in TTX resistance in T. atratus while variation in a haphazard sample of the genome (neutral microsatellite markers) shows no association with the phenotype. Similarly, allelic variation in Nav1.4 correlates almost perfectly with TTX resistance in T. sirtalis, but neutral variation does not. These strong correlations suggest that Nav1.4 is a major effect locus. The simple genetic architecture of TTX resistance in garter snakes may significantly impact the dynamics of phenotypic coevolution. Fixation of a few alleles of major effect in some garter snake populations may have led to the evolution of extreme phenotypes and an 'escape' from the arms race with newts. [ABSTRACT FROM AUTHOR]

Where do the genetic variants underlying adaptive change come from? Are currently adaptive alleles recruited by selection from standing genetic variation within populations, moved through introgression from other populations, or do they arise as novel mutations? Here, we examine the molecular basis of repeated adaptation to the toxin of deadly prey in 3 species of garter snakes (Thamnophis) to determine whether adaptation has evolved through novel mutations, sieving of existing variation, or transmission of beneficial alleles across species. Functional amino acid substitutions in the skeletal muscle sodium channel (Nav1.4) are largely responsible for the physiological resistance of garter snakes to tetrodotoxin found in their newt (Taricha) prey. Phylogenetic analyses reject the hypotheses that the unique resistance alleles observed in multiple Thamnophis species were present before the split of these lineages, or that alleles were shared among species through occasional hybridization events. Our results demonstrate that adaptive evolution has occurred independently multiple times in garter snakes via the de novo acquisition of beneficial mutations. [ABSTRACT FROM AUTHOR]

A biography of naturalist Robert Macleod Storm, Dean of Pacific Northwest Herpetology, is presented. He was born on July 9, 1918 in Calgary, Alberta and studied at the Oregon State Agricultural College. Storm has three children from his first marriage to Carol Offner, and three more children from his second marriage to Marvene Christensen. He was closely associated with the Friends of Three Sisters Wilderness and has co-authored and contributed extensively to field guides to amphibians and reptiles of the Northwest.

Who wins in the arms race between predators and prey? In the interaction between snakes and toxic newts, predators sometimes escape the arms race through the evolution of extreme resistance, but prey never come out ahead. [ABSTRACT FROM AUTHOR]

Two species of horned lizards are sympatric along the periphery of the Salton Trough. Phrynosoma mcallii, endemic to the trough, is of conservation concern because its limited habitat has been fragmented by human activities. A more common and widespread species, Phrynosoma platyrhinos, occurs around the periphery of the trough and much further to the North. The two species are syntopic at a few localities, where morphological intermediates have also been found. Here, we used nested clade phylogeographical analysis (NCPA) and analysis of molecular variance (amova), to examine 781 bp of mitochondrial DNA ( nad4 and two tRNAs) from 82 individuals of P. mcallii. We tested whether populations of this species were recently connected, or if they were historically isolated prior to human modification of the region. Our NCPA results indicated significant population structure associated with the Colorado River, suggesting limited gene flow and potential isolation across this barrier. Populations west of the Colorado River, currently isolated from one another by human development, show less genetic differentiation. We also collected homologous sequence data from 34 individuals of P. platyrhinos and seven specimens morphologically intermediate between P. mcallii and P. platyrhinos, as a preliminary investigation of hybridization between these two species. From phylogenetic results of these data, we identified a species ( Phrynosoma goodei) previously recognized as a subspecies of P. platyrhinos. Six of the morphologically intermediate specimens shared mtDNA haplotypes with P. goodei, while one was nested among P. mcallii haplotypes. [ABSTRACT FROM AUTHOR]

Tetrodotoxin (TTX) is a potent neurotoxin which is known to occur in numerous taxa, including newts. The origin of TTX is unknown, but production by symbiotic bacteria is suspected for some groups. Using PCR primers that specifically amplify 16S rRNA genes of bacteria, we examined tissues from rough-skin newts, Taricha granulosa, for the presence of bacteria which may produce TTX. No amplification of bacterial DNA was seen in samples taken from skin, liver, gonads or oviposited eggs-tissues known to contain TTX. Amplification of bacterial DNA was seen only in samples taken from newt intestines, a tissue with low concentrations of TTX. These results indicate that symbiotic bacteria are unlikely to be the source of TTX in newts. [Copyright &y& Elsevier]

Deals with a study which determined how abundance of stream-breeding Cascade torrent salamanders changes in response to forest harvest and subsequent regeneration in southern Washington during the summers of 1998 and 1999. Background to the study; Study area and methods; Results and discussion; Implications for wildlife management.

Examines the geographic pattern of genetically determined resistance in the garter snake Thamnopis sirtalis over much of its ecological interaction with toxic newts of genus Taricha. Importance of geographic structure to coevolutionary interactions between predators and prey; Predictions of the geographic mosaic process; Evidence which suggests that selection is essential in determining population variation in resistance.

Caecilians (order Gymnophiona) are apodan, snake-like amphibians, usually with fossorial habits, constituting one of the most unknown groups of terrestrial vertebrates. As in orders Anura (frogs, tree frogs and toads) and Caudata (salamanders and newts), the caecilian skin is rich in mucous glands, responsible for body lubrication, and poison glands, producing varied toxins used in defence against predators and microorganisms. Whereas in anurans and caudatans skin gland morphology has been well studied, caecilian poison glands remain poorly elucidated. Here we characterised the skin gland morphology of the caecilian Siphonops annulatus, emphasising the poison glands in comparison to those of anurans and salamanders. We showed that S. annulatus glands are similar to those of salamanders, consisting of several syncytial compartments full of granules composed of protein material but showing some differentiated apical compartments containing mucus. An unusual structure resembling a mucous gland is frequently observed in lateral/apical position, apparently connected to the main duct. We conclude that the morphology of skin poison glands in caecilians is more similar to salamander glands when compared to anuran glands that show a much-simplified structure. [ABSTRACT FROM AUTHOR]

Presents a study which investigated whether resistance to the neurotoxin of a prey and locomotor performance were negatively associated in a species of garter snakes. Genetic basis of the trade-off; Methodology of the study; Results and discussions.

Examines the anti-predator responses of the mountain dusky salamander Desmognathus ochrophaeus to the larger predatory salamanders G. porphyriticus and D. quadramaculatus. Types of experiments conducted; Predator avoidance; Efficacy of anti-predator mechanisms.

The article offers information on the behavioral mimicry in the defensive displays of the urodele amphibians Notophthalmus viridescens and Pseudotriton ruber. It is cited that there is a relationship between the distribution of granural or poison glands, and the nature of the defensive behavior in amphibians, in which glands posture to exhibit pigmented portions of the body. This is said to deter predation by warning predators of the noxious taste associated with a proliferation of granural glands. It is mentioned that the defensive displays were elicited from salamanders by pinching their toes and touching their snouts and backs with a dull probe.