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body size impacts critical thermal maximum measurements in lizards.understanding the mechanisms behind critical thermal maxima (ctmax; the high body temperature at which neuromuscular coordination is lost) of organisms is central to understanding ectotherm thermal tolerance. body size is an often overlooked variable that may affect interpretation of ctmax, and consequently, how ctmax is used to evaluate mechanistic hypotheses of thermal tolerance. we tested the hypothesis that body size affects ctmax and its interpretation in two experimental contexts. first, i ...202032851814
downsizing for downtown: limb lengths, toe lengths, and scale counts decrease with urbanization in western fence lizards (sceloporus occidentalis).urbanization induced habitat loss and alteration causes significant challenges for the survival of many species. identifying how species respond to urbanization can yield insights for the conservation of wildlife, but research on reptiles has been narrowly-focused. we compared morphology among four populations of western fence lizards (sceloporus occidentalis) to determine whether a common native species affected by urbanization exhibits morphological differences consistent with habitat use. we ...201932774080
the lizard gut microbiome changes with temperature and is associated with heat tolerance.vertebrates harbor trillions of microorganisms in the gut, collectively termed the gut microbiota, which affect a wide range of host functions. recent experiments in lab-reared vertebrates have shown that changes in environmental temperature can induce shifts in the gut microbiota, and in some cases these shifts have been shown to affect host thermal physiology. however, there is a lack of information about the effects of temperature on the gut microbiota of wild-caught vertebrates. moreover, in ...202032591376
establishment of brown anoles (anolis sagrei) across a southern california county and potential interactions with a native lizard species.the brown anole, anolis sagrei, is a native species to the caribbean; however, a. sagrei has invaded multiple parts of the usa, including florida, louisiana, hawai'i and more recently california. the biological impacts of a. sagrei invading california are currently unknown. evidence from the invasion in taiwan shows that they spread quickly and when immediate action is not taken eradication stops being a viable option. in orange county, california, five urban sites, each less than 100 ha, were s ...202032296613
melanization, α-melanocyte stimulating hormone and steroid hormones in male western fence lizards from nine populations.hormones can mediate suites of correlated traits. melanocortins regulate melanin synthesis and elements of the melanocortin system can directly, and indirectly, affect a number of other traits, such as stress reactivity. trait correlations within the melanocortin system have been studied mainly in birds and mammals but less so in reptiles. we examined adult male western fence lizards (sceloporus occidentalis) and if melanization was correlated with plasma levels of three hormones, including pept ...202031563645
to cool or not to cool? intestinal coccidians disrupt the behavioral hypothermia of lizards in response to tick infestation.it is generally accepted that parasites exert negative effects on their hosts and that natural selection favors specific host responses that mitigate this impact. it is also known that some components of the host immune system often co-evolve with parasite antigens resulting in a host-parasite arms race. in addition to immunological components of the anti-parasitic response, host behavioral responses are also important in this arms race and natural selection may favor avoidance strategies that p ...202031540802
multiple color patches and parasites in sceloporus occidentalis: differential relationships by sex and infection.parasites generally have a negative influence on the color expression of their hosts. sexual selection theory predicts resistant high-quality individuals should show intense coloration, whereas susceptible low-quality individuals would show poor coloration. however, intensely colored males of different species of old and new world lizards were more often infected by hemoparasites. these results suggest that high-quality males, with intense coloration, would suffer higher susceptibility to hemopa ...201830538729
multiple environmental stressors induce complex transcriptomic responses indicative of phenotypic outcomes in western fence lizard.the health and resilience of species in natural environments is increasingly challenged by complex anthropogenic stressor combinations including climate change, habitat encroachment, and chemical contamination. to better understand impacts of these stressors we examined the individual- and combined-stressor impacts of malaria infection, food limitation, and 2,4,6-trinitrotoluene (tnt) exposures on gene expression in livers of western fence lizards (wfl, sceloporus occidentalis) using custom wfl ...201830518325
scanning electron microscopy of scales from different body regions of three lizard species.the oberhautchen of scales from the dorsal, parietal, and ventral regions of sceloporus occidentalis (iguanidae), gerrhonotus multicarinatus (anguinidae), and anniella pulchra (anniellidae) were examined with a scanning electron microscope. at low magnification, all scales of s. occidentalis exhibit well-defined outlines of cells belonging to the oberhautchen layer and the previously overlying clear layer. the dorsal and parietal cells of this species exhibit a minutely dentate oberhautchen that ...197330336655
parallel behavioral and morphological divergence in fence lizards on two college campuses.the spread of urban development has dramatically altered natural habitats, modifying community relationships, abiotic factors, and structural features. animal populations living in these areas must perish, emigrate, or find ways to adjust to a suite of new selective pressures. those that successfully inhabit the urban environment may make behavioral, physiological, and/or morphological adjustments that represent either evolutionary change and/or phenotypic plasticity. we tested for effects of ur ...201829444102
correlates of melanization in multiple high- and low-elevation populations of the lizard, sceloporus occidentalis: behavior, hormones, and parasites.hormones mediate the expression of suites of correlated traits and hence may act either to facilitate or constrain adaptive evolution. selection on one trait within a hormone-mediated suite of traits may lead to a change in the strength of the hormone signal, causing changes in correlated traits. growing evidence suggests that melanization, which is in part regulated by hormonal signals, is tightly linked to other traits, such as aggression and stress physiology. here, we examine six populations ...201729356435
environmental temperature and thyroid activity in the lizard, sceloporus occidentalis.the relationship between temperature and the hypophyseal-thyroidal axis in sceloporus occidentalis has been investigated by a study of radioiodine incorporation by the thyroid in intact animals, and animals with the pars distalis removed, kept at temperatures of 15°, 21°, 30° and 38° c. over the range of 21 to 38° c there was no evidence of any significant temperature-related change in the normal and experimental animals, although the thyroid activity was reduced after the operation. at 15° c th ...197029332483
lead bioaccumulation in texas harvester ants (pogonomyrmex barbatus) and toxicological implications for texas horned lizard (phrynosoma cornutum) populations of bexar county, texas.uptake of lead from soil was examined in order to establish a site-specific ecological protective concentration level for the texas horned lizard (phrynosoma cornutum) at the former humble refinery in san antonio, texas. soils, harvester ants, and rinse water from the ants were analyzed at 11 texas harvester ant (pogonomyrmex barbatus) mounds. soil concentrations at the harvester ant mounds ranged from 13 to 7474 mg/kg of lead dry weight. ant tissue sample concentrations ranged from < 0.82 to 21 ...201829305803
phylogenetic analyses reveal that schellackia parasites (apicomplexa) detected in american lizards are closely related to the genus lankesterella: is the range of schellackia restricted to the old world?species of schellackia reichenow, 1919 have been described from the blood of reptiles distributed worldwide. recently, schellackia spp. detected in european and asian lizards have been molecularly characterised. however, parasites detected in american lizard hosts remain uncharacterised. thus, phylogenetic affinities between the old and new world parasite species are unknown.201729017602
fear no colors? observer clothing color influences lizard escape behavior.animals often view humans as predators, leading to alterations in their behavior. even nuanced aspects of human activity like clothing color affect animal behavior, but we lack an understanding of when and where such effects will occur. the species confidence hypothesis posits that birds are attracted to colors found on their bodies and repelled by non-body colors. here, we extend this hypothesis taxonomically and conceptually to test whether this pattern is applicable in a non-avian reptile and ...201728792983
absence of measurable malaria-induced mortality in western fence lizards (sceloporus occidentalis) in nature: a 4-year study of annual and over-winter mortality.theoretical models of parasite virulence often quantify virulence by mortality. however, there is a lack of empirical studies of parasite-induced host mortality because it is often difficult to quantify in natural populations. i have estimated annual and over-winter mortality in a population of fence lizards (sceloporus occidentalis) infected with a malaria parasite, plasmodium mexicanum, in northern california. the duration of time a lizard was observed (an estimate of life-span) throughout the ...200128547496
lowering metabolic rate mitigates muscle atrophy in western fence lizards.extended periods of skeletal muscle disuse can cause a significant loss of contractile proteins, which compromises the ability to generate force, mechanical work or power, thus compromising locomotor performance. several hibernating organisms can resist muscle atrophy despite months of inactivity. this resistance has been attributed to a reduction in body temperature and metabolic rate and activation of physiological pathways that counteract pathways of protein degradation. however, in these sys ...201728507191
thermal sensitivity of growth rate in hatchling sceloporus lizards: environmental, behavioral and genetic aspects.to investigate the physiological, behavioral, and genetic contributions to growth rate, we studied the thermal sensitivity of growth rate in hatchlings of the iguanid lizards sceloporus occidentalis and s. graciosus in the laboratory. we used a cycling thermal regime patterned after thermal environments found in nature. growth rates increased with duration of access to radiant heat. thus, variation in the thermal environment can cause phenotypic variation in growth rate and hence body size. the ...198928312590
parasites and showy males: malarial infection and color variation in fence lizards.hamilton and zuk (1982) proposed that the quality of male showy traits reflects genetically-based resistance to parasites and can be used by females to select mates that are less prone to parasitic attack. the hypothesis requires that a particular state of a variable showy trait should be associated with parasite infection. we tested this idea with a population of western fence lizards, sceloporus occidentalis, infected with the malarial parasite, plasmodium mexicanum. ventral color pattern is s ...198928312354
malarial parasitism and male competition for mates in the western fence lizard, sceloporus occidentalis.the effect of malarial parasitism on the ability of male western fence lizards, sceloporus occidentalis, to compete for access to females was assessed experimentally. pairs of male lizards, one infected with the malarial parasite, plasmodium mexicanum, and the other not infected, were matched by size and color and placed in large seminatural outdoor enclosures along with an adult female lizard. infected males displayed to females and to other males less often than did noninfected male lizards. n ...198728311520
tick microbiome and pathogen acquisition altered by host blood meal.lyme disease, a zoonotic disease, is the most prevalent vector-borne disease in the northern hemisphere. diversity of the vector (tick) microbiome can impact pathogen transmission, yet the biotic and abiotic factors that drive microbiome diversity are largely unresolved, especially under natural, field conditions. we describe the microbiome of ixodes pacificus ticks, the vector for lyme disease in the western united states, and show a strong impact of host blood meal identity on tick microbiome ...201727858931
populations of the lizard, sceloporus occidentalis, that differ in melanization have different rates of wound healing.mechanisms underlying production of animal coloration can affect key traits besides coloration. melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits, such as immune function. we asked whether melanization and a whole-organism measure of immune function are associated with wound healing. working with two populations of adult male western fence lizards, sceloporus occidentalis, we compared one high-elevation and one low-elevation population in calif ...201627597293
oxygen concentration affects upper thermal tolerance in a terrestrial vertebrate.we tested the oxygen limitation hypothesis, which states that animals decline in performance and reach the upper limits of their thermal tolerance when the metabolic demand for oxygen at high temperatures exceeds the circulatory system's ability to supply adequate oxygen, in air-breathing lizards exposed to air with different oxygen concentrations. lizards exposed to hypoxic air (6% o2) gaped, panted, and lost their righting response at significantly lower temperatures than lizards exposed to no ...201627264957
phenotypic correlates of melanization in two sceloporus occidentalis (phrynosomatidae) populations: behavior, androgens, stress reactivity, and ectoparasites.mechanisms underlying production of animal coloration can affect key traits besides coloration. melanin, and molecules regulating melanin, can directly and indirectly affect other phenotypic traits including aggression, stress-reactivity, and immune function. we studied correlation of melanization with these other traits, comparing within- and between-population differences of adult male western fence lizards, sceloporus occidentalis. we compared one high- and one low-elevation population in cal ...201627137079
direct and indirect effects of petroleum production activities on the western fence lizard (sceloporus occidentalis) as a surrogate for the dunes sagebrush lizard (sceloporus arenicolus).the dunes sagebrush lizard (sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of new mexico and texas (usa). because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. the congeneric western fence lizard (sceloporus occidentalis) was used as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas d ...201626456391
effects of temperature on feeding duration, success, and efficiency of larval western black-legged ticks (acari: ixodidae) on western fence lizards.the western black-legged tick (ixodes pacificus) is a common tick species throughout the western usa and is the major vector for borrelia burgdorferi, the lyme disease causing bacterium. western fence lizards (sceloporus occidentalis) are a major host for juvenile i. pacificus, but are incompetent hosts for b. burgdorferi, which makes this host-parasite relationship of particular interest. in order to shed further light on this complex host-parasite relationship, we investigated the effects of t ...201526188858
improving reptile ecological risk assessment: oral and dermal toxicity of pesticides to a common lizard species (sceloporus occidentalis).reptiles have been understudied in ecotoxicology, which limits consideration in ecological risk assessments. the goals of the present study were 3-fold: to improve oral and dermal dosing methodologies for reptiles, to generate reptile toxicity data for pesticides, and to correlate reptile and avian toxicity. the authors first assessed the toxicity of different dosing vehicles: 100 μl of water, propylene glycol, and acetone were not toxic. the authors then assessed the oral and dermal toxicity of ...201525760295
leukocyte profiles for western fence lizards, sceloporus occidentalis, naturally infected by the malaria parasite plasmodium mexicanum.plasmodium mexicanum is a malaria parasite that naturally infects the western fence lizard, sceloporus occidentalis , in northern california. we set out to determine whether lizards naturally infected with this malaria parasite have different leukocyte profiles, indicating an immune response to infection. we used 29 naturally infected western fence lizards paired with uninfected lizards based on sex, snout-to-vent length, tail status, and the presence-absence of ectoparasites such as ticks and m ...201424945903
unraveling the relative importance of oral and dermal contaminant exposure in reptiles: insights from studies using the western fence lizard (sceloporus occidentalis).despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. to conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. we exposed western fence lizards, sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral s ...201424941063
permeability of roads to movement of scrubland lizards and small mammals.a primary objective of road ecology is to understand and predict how roads affect connectivity of wildlife populations. road avoidance behavior can fragment populations, whereas lack of road avoidance can result in high mortality due to wildlife-vehicle collisions. many small animal species focus their activities to particular microhabitats within their larger habitat. we sought to assess how different types of roads affect the movement of small vertebrates and to explore whether responses to ro ...201323772966
effect of host lizard anemia on host choice and feeding rate of larval western black-legged ticks (ixodes pacificus).although ticks are known to exhibit preferences among host species, there is little evidence that ticks select hosts within a species based on physiological condition. it may be beneficial for ticks to choose hosts that are easier to feed upon if the ticks can perceive indicative chemical or other signals from the host. for example, if ticks can detect host hematocrit they may choose hosts with high hematocrit, facilitating a faster blood meal. it may similarly be adaptive for ticks to avoid ane ...201323760685
eco-epidemiological factors contributing to the low risk of human exposure to ixodid tick-borne borreliae in southern california, usa.little is known about the eco-epidemiology of lyme disease in southern california, a region where the incidence is much lower than it is in northern california. here, we sought to discover the previously unknown microhabitats of nymphs of the primary vector, the western black-legged tick (ixodes pacificus), in 3 moderately to heavily-utilized state parks in the santa monica mountains in los angeles county; to elucidate the seasonal distribution and abundance of adults of i. pacificus and another ...201323643357
multiple environmental stressors elicit complex interactive effects in the western fence lizard (sceloporus occidentalis).evaluation of multiple-stressor effects stemming from habitat degradation, climate change, and exposure to chemical contaminants is crucial for addressing challenges to ecological and environmental health. to assess the effects of multiple stressors in an understudied taxon, the western fence lizard (sceloporus occidentalis) was used to characterize the individual and combined effects of food limitation, exposure to the munitions constituent 2,4,6-trinitrotoluene (tnt), and plasmodium mexicanum ...201222975894
the effect of exogenous testosterone on ectoparasite loads in free-ranging western fence lizards.numerous factors impact the dynamics of host-parasite relationships, such as host sex, hormonal state, reproductive condition, host health, and behavior. in particular, males from a variety of taxa frequently carry heavier parasite burdens than females, particularly during breeding season when testosterone concentrations are elevated. using western fence lizards (sceloporus occidentalis), we tested the hypothesis that high circulating testosterone concentrations in male lizards induce high tick ...201222689269
impacts of an introduced forest pathogen on the risk of lyme disease in california.global changes such as deforestation, climate change, and invasive species have the potential to greatly alter zoonotic disease systems through impacts on biodiversity. this study examined the impact of the invasive pathogen that causes sudden oak death (sod) on the ecology of lyme disease in california. the lyme disease bacterium, borrelia burgdorferi, is maintained in the far western united states by a suite of animal reservoirs including the dusky-footed woodrat (neotoma fuscipes) and deer mo ...201222607076
how do host sex and reproductive state affect host preference and feeding duration of ticks?parasitism is one of the most notable forms of symbiosis in the biological world, with nearly all organisms hosting parasites. in many vertebrates, males have higher ectoparasite burdens than females, especially when testosterone concentrations are elevated. furthermore, reproductive females may have higher ectoparasite burdens than non-reproductive females. it is possible that testosterone-stimulated behaviors in males and offspring investment by females incur energetic costs that inhibit immun ...201222526292
evolution of thermal physiology and growth rate between populations of the western fence lizard (sceloporus occidentalis).hatchling sceloporus occidentalis from northern populations (central oregon) grow more slowly than hatchlings from southern populations (southern california) in nature. in this study, i determine whether this difference in growth rate results from differences in thermal environment and/or in thermoregulatory behavior. to determine the degree to which the thermal environment affects growth rate among populations, i reared hatchings from the northern and southern populations in a cycling thermal r ...199022160116
geographic variation in the effects of heat exposure on maximum sprint speed and hsp70 expression in the western fence lizard sceloporus occidentalis.we examined whether western fence lizards sceloporus occidentalis occurring in thermally divergent environments display differential responses to high temperature in locomotor performance and heat-shock protein (hsp) expression. we measured maximum sprint speed in s. occidentalis from four populations at paired latitudes and elevations before and after exposure to an experimental heat treatment and then quantified hind-limb muscle hsp70 expression. lizards collected from northern or high-elevati ...201122030850
relative clonal proportions over time in mixed-genotype infections of the lizard malaria parasite plasmodium mexicanum.vertebrate hosts of malaria parasites (plasmodium) often harbour two or more genetically distinct clones of a single species, and interaction among these co-existing clones can play an important role in plasmodium biology. however, how relative clonal proportions vary over time in a host is still poorly known. experimental mixed-clone infections of the lizard malaria parasite, plasmodium mexicanum, were followed in its natural host, the western fence lizard using microsatellite markers to determ ...201121396372
impact of the experimental removal of lizards on lyme disease risk.the distribution of vector meals in the host community is an important element of understanding and predicting vector-borne disease risk. lizards (such as the western fence lizard; sceloporus occidentalis) play a unique role in lyme disease ecology in the far-western united states. lizards rather than mammals serve as the blood meal hosts for a large fraction of larval and nymphal western black-legged ticks (ixodes pacificus-the vector for lyme disease in that region) but are not competent reser ...201121325326
toxic effects of oral 2-amino-4,6-dinitrotoluene in the western fence lizard (sceloporus occidentalis).the compound 2-amino-4,6-dinitrotoluene (2a-dnt) was evaluated under laboratory conditions in the western fence lizard (sceloporus occidentalis) to assess the potential for reptile toxicity. oral ld(50) values were 1406 and 1867 mg/kg for male and female lizards, respectively. based on responses from a 14-day subacute study, a 60-day subchronic experiment followed where lizards were orally dosed at 0, 5, 15, 20, 25, 30 mg/kg-d. at day 60, number of days and survivors, food consumption, and chang ...201121067851
effects of an invasive forest pathogen on abundance of ticks and their vertebrate hosts in a california lyme disease focus.invasive species, including pathogens, can have important effects on local ecosystems, including indirect consequences on native species. this study focuses on the effects of an invasive plant pathogen on a vertebrate community and ixodes pacificus, the vector of the lyme disease pathogen (borrelia burgdorferi) in california. phytophthora ramorum, the causative agent of sudden oak death, is a non-native pathogen killing trees in california and oregon. we conducted a multi-year study using a grad ...201020941513
toxicity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (hmx) in three vertebrate species.the explosive, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine or high-melting explosive (hmx), has been found in soils in areas used for testing and training by the military. many of these areas contain habitat for valued wildlife species. in an effort to better understand the environmental consequences from exposure, a reptilian (western fence lizard [sceloporus occidentalis]), an amphibian (red-backed salamander [plethodon cinereus]), and a mammalian species (rabbit [oryctolagus cuniculus]) ...201020012743
geographic genetic differentiation of a malaria parasite, plasmodium mexicanum, and its lizard host, sceloporus occidentalis.gene flow, and resulting degree of genetic differentiation among populations, will shape geographic genetic patterns and possibly local adaptation of parasites and their hosts. some studies of plasmodium falciparum in humans show substantial differentiation of the parasite in locations separated by only a few kilometers, a paradoxical finding for a parasite in a large, mobile host. we examined genetic differentiation of the malaria parasite plasmodium mexicanum, and its lizard host, sceloporus o ...201019916631
effects of inorganic lead on western fence lizards (sceloporus occidentalis).although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. we evaluated the toxicity of pb as lead acetate to the western fence lizard (sceloporus occidentalis). the acute lethal dose and sub-acute (14-day) toxicity studies were used to narrow exposure concentrations for a sub-chronic (60-day) study. in the sub-chronic study, adult and juvenile male lizards were dosed via gavage with 0, 1, 10 and 20 mg pb/kg-bw/day. mortality was limi ...200919631431
clonal diversity of a malaria parasite, plasmodium mexicanum, and its transmission success from its vertebrate-to-insect host.infections of the lizard malaria parasite plasmodium mexicanum are often genetically complex within their fence lizard host (sceloporus occidentalis) harbouring two or more clones of parasite. the role of clonal diversity in transmission success was studied for p. mexicanum by feeding its sandfly vectors (lutzomyia vexator and lutzomyia stewarti) on experimentally infected lizards. experimental infections consisted of one, two, three or more clones, assessed using three microsatellite markers. a ...200919523471
the effects of prey species on food conversion efficiency and growth of an insectivorous lizard.little is known about the effects of different prey species on lizard growth. we conducted a 6-week study to determine the relative effects of prey species on growth parameters of hatchling western fence lizards, sceloporus occidentalis. lizards were fed house cricket nymphs, acheta domesticus, or mealworm larvae, tenebrio molitor. the effects of prey species on growth were determined by measuring prey consumption, gross conversion efficiency of food [gain in mass (g)/food consumed (g)], gain in ...200819360616
reproductive and thyroid hormone profiles in captive western fence lizards (sceloporus occidentalis) after a period of brumation.seasonal fluctuation in serum concentrations of sex steroid (testosterone [t] and 17beta-estradiol [e(2)]) and thyroid (triiodothyronine [t(3)] and thyroxine [t(4)]) hormones was determined in captive western fence lizards (sceloporus occidentalis). samples were collected from male and female breeding pairs weekly for a 4-month period after their emergence from artificial brumation. circulating levels of e(2) corresponded with the expected vitellogenic and ovulatory cycles in females, and surpri ...200819360602
reptile infection with anaplasma phagocytophilum, the causative agent of granulocytic anaplasmosis.granulocytic anaplasmosis (ga) is a potentially fatal tick-borne rickettsial disease that occurs sporadically in the far western united states. we evaluated the prevalence of anaplasma phagocytophilum in multiple species of lizards and snakes from enzootic sites in northern california, described the infestation prevalence of its tick vector ixodes pacificus on reptiles, and conducted an experimental challenge of western fence lizards (sceloporus occidentalis) and pacific gopher snakes (pituophis ...200919281295
use of tricaine methanesulfonate (ms222) for euthanasia of reptiles.tricaine methanesulfonate (ms222) injected into the intracoelomic cavity of reptiles was evaluated as a chemical euthanasia method. three western fence lizards, 2 desert iguanas, 4 garter snakes, and 6 geckos were euthanized by intracoelomic injection of 250 to 500 mg/kg of 0.7% to 1% sodium-bicarbonate-buffered ms222 solution followed by intracoelomic injection of 0.1 to 1.0 ml unbuffered 50% (v/v) ms222 solution. a simple 2-stage protocol for euthanasia of reptiles by using ms222 is outlined. ...200919245747
feeding preferences of the immature stages of three western north american ixodid ticks (acari) for avian, reptilian, or rodent hosts.larval and nymphal ixodes pacificus cooley and kohls, i. (ixodes) jellisoni cooley and kohls, and dermacentor occidentalis marx were tested for host preference when simultaneously presented with a deer mouse (peromyscus maniculatus wagner), california kangaroo rat (dipodomys californicus merriam), western fence lizard (sceloporus occidentalis baird and girard), and california towhee (pipilo crissalis vigors) in an experimental apparatus. differences were observed in the preferences among the thr ...200919198525
toxic effects of oral hexahydro-1,3,5-trinitro-1,3,5-triazine in the western fence lizard (sceloporus occidentalis).hexahydro-1,3,5-trinitro-1,3,5-triazine (rdx) has been widely used as an explosive in munition formulations, resulting in contamination of wildlife habitat on military installations. to estimate health effects for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted using the western fence lizard (sceloporus occidentalis). estimated oral median lethal doses were 72 (95% confidence interval [ci], 49-106) mg/kg body weight (slope, 3.754) for males and 88 (95% ci, ...200919102580
clonal diversity within infections and the virulence of a malaria parasite, plasmodium mexicanum.both verbal and mathematical models of parasite virulence predict that genetic diversity of microparasite infections will influence the level of costs suffered by the host. we tested this idea by manipulating the number of co-existing clones of plasmodium mexicanum in its natural vertebrate host, the fence lizard sceloporus occidentalis. we established replicate infections of p. mexicanum made up of 1, 2, 3, or >3 clones (scored using 3 microsatellite loci) to observe the influence of clone numb ...200818937882
toxicity of oral exposure to 2,4,6-trinitrotoluene in the western fence lizard (sceloporus occidentalis).contamination of the soil with the explosive 2,4,6-trinitrotoluene (tnt) has been found at military sites, many of which are habitats used by reptiles. to provide data useful in assessing ecological risk for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted with the western fence lizard (sceloporus occidentalis). oral median lethal dose (ld50) values for tnt in corn oil were 1,038 and 1,579 mg/kg of body weight for male and female lizards, respectively. over ...200818419183
estimating maximum performance: effects of intraindividual variation.researchers often estimate the performance capabilities of animals using a small number of trials per individual. this procedure inevitably underestimates maximum performance, but few studies have examined the magnitude of this effect. in this study we explored the effects of intraindividual variation and individual sample size on the estimation of locomotor performance parameters. we measured sprint speed of the lizard sceloporus occidentalis at two temperatures (20 degrees c and 35 degrees c), ...200818375858
dose-related effects following oral exposure of 2,4-dinitrotoluene on the western fence lizard, sceloporus occidentalis.2,4-dintitrotoluene (2,4-dnt) is an explosive frequently found in the soil of military installations. because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-dnt could be improved with toxicity data specific to reptiles. western fence lizards, sceloporus occidentalis, were used to develop a laboratory toxicity model for reptiles. a hierarchical approach was used; acute to subchronic studies were conducted to provide toxicity data relevant to short- an ...200818348623
effect of exogenous corticosterone on respiration in a reptile.release of glucocorticoids (gcs) enables organisms to meet energy requirements during stressful situations by regulating intermediary metabolism. in the absence of compensatory mechanisms, increased metabolic activity (e.g., protein catabolism, lipolysis, and gluconeogenesis) should translate to increases in whole animal metabolism, and therefore energy expenditures, by organisms. however, to our knowledge, no study has estimated the total energy cost of elevated plasma gcs in any organism. here ...200818249406
effect of acclimation on the preferred body temperature of the lizard, sceloporus occidentalis.the preferred body temperature was determined for several groups of sceloporus occidentalis previously acclimated to several constant temperature levels. acclimation to a high temperature (35 degrees c) resulted in the selection of a lowered mean preferred body temperature, whereas acclimation to lower temperatures (12 degrees c and 25 degrees c) produced no change in the preferred body temperature.196017775548
sceloporus occidentalis: preferred body temperature of the western fence lizard.given equal thermal opportunities during four seasonal test periods, western fence lizards active above ground preferred constant body temperature throughout the year. lizards recovered from subsurface retreats in the fall exhibited a mean body temperature significantly lower than that for sequestered lizards recorded during winter, spring, and summer.196617754818
allometric engineering: an experimental test of the causes of interpopulational differences in performance.hatchling lizards (sceloporus occidentalis) from a southern population are large and have high locomotor performance (speed and stamina) relative to hatchlings from northern populations. in order to determine whether differences in performance are an allometric consequence of interpopulation differences in size, yolk was removed from southern eggs, thereby producing miniaturized hatchlings equivalent in size to northern hatchlings. miniaturized southern hatchlings no longer had higher speed than ...199017733374
effects of repeated exposure to malathion on growth, food consumption, and locomotor performance of the western fence lizard (sceloporus occidentalis).effects of repeated pollutant exposure on growth, locomotor performance, and behavior have rarely been evaluated in reptiles. we administered three doses of malathion (2.0, 20, or 100mg/kg body weight) to western fence lizards (sceloporus occidentalis) over an 81day period. eight and 23% mortality occurred at 20 and 100mg/kg (p=0.079) and 85% of lizards in the 100mg/kg group exhibited clinical symptoms of poisoning. growth, food consumption, body condition index, and terrestrial locomotor perfor ...200817611009
clonal diversity of a lizard malaria parasite, plasmodium mexicanum, in its vertebrate host, the western fence lizard: role of variation in transmission intensity over time and space.within the vertebrate host, infections of a malaria parasite (plasmodium) could include a single genotype of cells (single-clone infections) or two to several genotypes (multiclone infections). clonal diversity of infection plays an important role in the biology of the parasite, including its life history, virulence, and transmission. we determined the clonal diversity of plasmodium mexicanum, a lizard malaria parasite at a study region in northern california, using variable microsatellite marke ...200717594442
selenomethionine biotransformation and incorporation into proteins along a simulated terrestrial food chain.selenium is an essential trace element in vertebrates, but there is a narrow concentration range between dietary requirement and toxicity threshold. although a great deal is known about the biochemistry of se from a nutritional perspective, considerably less attention has been focused on the specific biochemistry of se as an environmental toxicant. recent advances in hyphenated analytical techniques have provided the capability of quantifying specific chemical forms of se in biological tissues a ...200717547184
experimental test for premunition in a lizard malaria parasite (plasmodium mexicanum).premunition in plasmodium spp. is the prevention of superinfection by novel genotypes entering an already established infection in a vertebrate host. evidence for premunition was sought for the lizard malaria parasite, p. mexicanum, in its natural host, the fence lizard, sceloporus occidentalis. clonal diversity (= alleles for the haploid parasite) was determined with the use of 3 microsatellite markers. both naturally infected lizards (n = 25) and previously noninfected lizards (n = 78) were in ...200717539410
assessment of lead uptake in reptilian prey species.as part of an investigation determining the trophically available fraction of metals in a model terrestrial food web, i.e., invertebrate prey to western fence lizards (sceloporus occidentalis), we evaluated the ability of several invertebrate prey to bioaccumulate lead and to form metals-rich granules, which are hypothesized to be non-available to predators. crickets (acheta domestica), tenebroid beetle larvae (tenebrio molitor), and isopods (porcellio scaber) were selected as model prey organis ...200717490716
ability of transstadially infected ixodes pacificus (acari: ixodidae) to transmit west nile virus to song sparrows or western fence lizards.the hypothesis that ixodes pacificus cooley & kohls (acari: ixodidae) may serve as a reservoir and vector of west nile virus (family flaviviridae, genus flavivirus, wnv) in california was tested by determining the ability of this tick species to become infected with the ny99 strain of wnv while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit wnv to recipient naive song sparrows and western fence lizards during the nymphal stage. the percentage of ...200717427704
energy acquisition and allocation in an ectothermic predator exposed to a common environmental stressor.stressors are commonly encountered by organisms and often prove to be energetically costly. certain stressors can simultaneously affect multiple components of an animal's energy budget and can either exacerbate energetic costs to the individual or offset one another. here we used a commonly encountered stressor, the pesticide carbaryl, to examine the complex effects that acute environmental disturbances can have on energy expenditure, allocation, and acquisition, important processes that influen ...200717374566
impaired terrestrial and arboreal locomotor performance in the western fence lizard (sceloporus occidentalis) after exposure to an ache-inhibiting pesticide.we examined the effects of a commonly used ache-inhibiting pesticide on terrestrial and arboreal sprint performance, important traits for predator avoidance and prey capture, in the western fence lizard (sceloporus occidentalis). lizards were exposed to carbaryl (2.5, 25, and 250 microg/g) and were raced before and 4, 24, and 96 h after dosing. in the terrestrial setting, exposure to low concentrations of carbaryl had stimulatory effects on performance, but exposure to the highest concentration ...200717360091
refractoriness of the western fence lizard (sceloporus occidentalis) to the lyme disease group spirochete borrelia bissettii.the western fence lizard, sceloporus occidentalis, is refractory to experimental infection with borrelia burgdorferi sensu stricto, one of several lyme disease spirochetes pathogenic for humans. another member of the lyme disease spirochete complex, borrelia bissettii, is distributed widely throughout north america and a similar, if not identical, spirochete has been implicated as a human pathogen in southern europe. to determine the susceptibility of s. occidentalis to b. bissettii, 6 naïve liz ...200616995383
isolation and partial characterization of proteins involved in maternal transfer of selenium in the western fence lizard (sceloporus occidentalis).selenium from dietary exposure is efficiently transferred from mother to offspring in oviparous vertebrates, where it can cause severe teratogenic effects. we isolated and partially characterized proteins involved in maternal transfer of selenium in the oviparous lizard sceloporus occidentalis using size-exclusion chromatography, inductively coupled plasma-mass spectrometry, and polyacrylamide gel electrophoresis. selenium from dietary selenomethionine exposure was incorporated into at least thr ...200616833149
effect of acute exposure to malathion and lead on sprint performance of the western fence lizard (sceloporus occidentalis).there are few ecotoxicological studies involving reptiles, despite the fact that anthropogenic pollutants have been identified as a major threat to reptile populations worldwide. particularly lacking are effects-based studies in reptiles exposed to known concentrations of contaminants. we hypothesized that acute exposure to neurotoxic metals and pesticides could influence locomotor performance of reptiles. to test this hypothesis, we exposed western fence lizards (sceloporus occidentalis) to two ...200616465557
the roles of birds, lizards, and rodents as hosts for the western black-legged tick ixodes pacificus.we compared the infestation by ixodid ticks of lizards, rodents, and birds collected simultaneously within areas representing common habitat types in mendocino county, ca. lizards were infested only by ixodes pacificus cooley and kohls, birds by i. pacificus and haemaphysalis leporispalustris (packard), and rodents by i. pacificus, i. spinipalpis hadwen and nuttall, i. woodi bishopp, dermacentor occidentalis marx, and d. variabilis (say). infestation by i. pacificus larvae and nymphs of lizards ...200415709249
transfer of selenium from prey to predators in a simulated terrestrial food chain.little is known about the accumulation and effects of selenium in reptiles. we developed a simplified laboratory food chain where we fed commercial feed laden with seleno-d,l-methionine (30 microg/g dry mass) to crickets (acheta domestica) for 5-7 d. se-enriched crickets (approximately 15 microg/g se [dry mass]) were fed to juvenile male and female lizards (sceloporus occidentalis) for 98 d while conspecifics were fed uncontaminated crickets. lizards fed contaminated prey accumulated se concentr ...200515620590
respiratory and behavioral effects of ozone on a lizard and a frog.ozone at concentrations found in urban air pollution is known to have significant physiological effects on humans and other mammals. exposure of the lizard, sceloporus occidentalis, to 0.6 ppm ozone for 4 h at 25 degrees c induced 1.6 degrees c of behavioral hypothermia immediately following exposure, but selected body temperature recovered to control 35.3 degrees c the next day. lizards exposed at 35 degrees c to 0.6 ppm ozone for 4 h selected body temperatures 1.9 degrees c below controls afte ...200415556394
mitochondrial dna sequences of five squamates: phylogenetic affiliation of snakes.complete or nearly complete mitochondrial dna sequences were determined from four lizards (western fence lizard, warren's spinytail lizard, terrestrial arboreal alligator lizard, and chinese crocodile lizard) and a snake (texas blind snake). these genomes had a typical gene organization found in those of most mammals and fishes, except for a translocation of the glutamine trna gene in the blind snake and a tandem duplication of the threonine and proline trna genes in the spinytail lizard. althou ...200415449546
habitat-related variation in infestation of lizards and rodents with ixodes ticks in dense woodlands in mendocino county, california.during the spring and early summer of 2002, we examined the relative importance of borrelia-refractory lizards (sceloporus occidentalis, elgaria spp.) versus potential borrelia burgdorferi sensu lato (s.l.)-reservoirs (rodents) as hosts for ixodes pacificus immatures in 14 woodland areas (six oak, five mixed oak/douglas fir, and three redwood/tanoak areas) distributed throughout mendocino county, california. lizards were estimated to serve as hosts for 93-98% of all larvae and > or =99.6% of all ...200415347025
life-history studies on two molecular strains of mesocestoides (cestoda: mesocestoididae): identification of sylvatic hosts and infectivity of immature life stages.life-cycle studies were conducted on 2 molecular strains of mesocestoides tapeworms that represent different evolutionary lineages (clades a and b). wild carnivores, reptiles, and rodents were examined for tapeworm infections at 2 enzootic sites: (1) san miguel island (smi), a small island off the coast of southern california and (2) hopland research and extension center (hrec), a field station in northern california. results indicate that deer mice (peromyscus maniculatus) and coyotes (canis la ...200415040675
gametocyte sex ratio of a malaria parasite: response to experimental manipulation of parasite clonal diversity.sex ratio theory posits that the adaptive proportion of male to female gametocytes of a malaria parasite within the vertebrate host depends on the degree of inbreeding within the vector. gametocyte sex ratio could be phenotypically flexible, being altered based on the infection's clonal diversity, and thus likely inbreeding. this idea was tested by manipulating the clonal diversity of infections of plasmodium mexicanum in its lizard host, sceloporus occidentalis. naive lizards were inoculated wi ...200415002900
bacteriolytic activity of selected vertebrate sera for borrelia burgdorferi sensu stricto and borrelia bissettii.an in vitro assay to evaluate the bacteriolytic activity of the complement pathway was applied to 2 strains of borrelia bissettii, co501 and dn127, and compared with that of b. burgdorferi sensu stricto b31. sera from mule deer (odocoileus hemionus) and the western fence lizard (sceloporus occidentalis) were completely borreliacidal for b. burgdorferi and for both strains of b. bissettii. serum from bobwhite quail (colinus virginianus) was nonlytic for b. burgdorferi and partially lytic for b. b ...200314740924
the western black-legged tick, ixodes pacificus, in the sutter buttes.the western black-legged tick, ixodes pacificus, was collected from huff canyon in the sutter buttes in north central california, sutter county. the sutter buttes are within the sacramento valley and outside the normal distribution of i. pacificus in california. adult i. pacificus were collected via flagging as they quested along deer trails; subadult life stages were collected from three species of lizard, elgaria multicarinata, sceloporus occidentalis, and s. graciosus. adult ticks were tested ...200314714665
parietal eye nerve in the fence lizard.a nerve from the parietal eye of the western fence lizard, sceloporus occidentalis, is described as leaving inconspicuously from the third-eye and extending caudally under the dura mater and then ventrally along the left anterolateral surface of the epiphysis to the habenular commissure of the brain. the existence of a parietal nerve must be considered in interpreting the effects of parietalectomy.195913819089
further observations on the fine structure of the parietal eye of lizards.an electron microscopical study of the third eye of the western fence lizard, sceloporus occidentalis, fixed with 1 per cent osmium tetroxide, ph 7.4-7.6, for 16 to 20 hours at 0 degrees c., revealed the following new facts. the fibrillar system of the retinal photoreceptor consists of nine double fibrils enclosed in a sheath. pigment cells and lens cells possess similar systems. two short cylindrical centrioles are associated with the fibrillar apparatus: one, from which striated rootlets exten ...196013725484
effects of parietalectomy and sustained temperature on thyroid of lizard, sceloporus occidentalis. 195913658226
the gross and microscopic anatomy of the liver and gall bladder of the lizard, sceloporus occidentalis biseriatus (hallowell). 195413189140
effects of 17alpha-ethinylestradiol on immune parameters in the lizard sceloporus occidentalis.we examined the effect of 17alpha-ethinylestradiol on immunity of the western fence lizard, sceloporus occidentalis. injection of 17alpha-ethinylestradiol resulted in dose-dependent suppression of peripheral blood leukocyte levels as determined by cell counts, whereas total spleen cell levels were decreased only at higher doses of 17alpha-ethinylestradiol. in contrast, spleen cell proliferation was enhanced by 17alpha-ethinylestradiol as measured by reduction of mtt to formazan following a two-w ...200312900939
hot rocks or no hot rocks: overnight retreat availability and selection by a diurnal lizard.i used radio telemetry to determine the effects of substrate size and composition on overnight retreat site selection by western fence lizards (sceloporus occidentalis). in watersheds of northern california (usa), these lizards occupy two habitat types differing in substrate characteristics: rocky cobble bars found in the dry, active channels of rivers and grassy upland meadows. rocky substrates, found almost exclusively on cobble bars, provided warmer potential retreat sites than all available ...200312802672
manipulation of the vertebrate host's testosterone does not affect gametocyte sex ratio of a malaria parasite.gametocyte sex ratio of the malaria parasite plasmodium mexicanum is variable in its host, the western fence lizard (sceloporus occidentalis), both among infections and within infections over time. we sought to determine the effect of host physiological quality on the gametocyte sex ratio in experimentally induced infections of p. mexicanum. adult male lizards were assigned to 4 treatment groups: castrated, castrated + testosterone implant, sham implant, and unmanipulated control. no significant ...200312659329
relative importance of lizards and mammals as hosts for ixodid ticks in northern california.abstract lizards and mammals were trapped and examined for ticks from august 1992 to june 1993 in two habitat types, chaparral and woodland-grass, in northern california. five tick species were collected from mammals (dermacentor occidentalis, haemaphysalis leporispalustris, ixodes pacificus, i. spinipalpis, i. woodi), but only i. pacificus was found on lizards. dermacentor occidentalis, i. pacificus, and i. woodi occurred in both habitats, whereas h. leporispalustris and i. spinipalpis were fou ...200212475082
dose-response and time course relationships for vitellogenin induction in male western fence lizards (sceloporus occidentalis) exposed to ethinylestradiol.the long-term goal of this research is to develop and validate an in vivo reptile model for endocrine-mediated toxicity using fence lizards (sceloporus spp.). one of the best defined estrogenic responses in oviparous vertebrates is induction of the yolk precursor protein, vitellogenin (vtg). in this study, dose-response and time course relationships for vtg induction were determined in male western fence lizards (sceloporus occidentalis) given intraperitoneal injections of 17alpha-ethinylestradi ...200212109741
gametocyte sex ratio of a malaria parasite: experimental test of heritability.the gametocyte sex ratio of plasmodium mexicanum, a malaria parasite of western fence lizards, was studied in a modified garden experiment. each of 6 naturally infected lizards was used to initiate 20 replicate-infections in naive western fence lizards. a significant donor effect was observed for the sex ratios of recipient infections at their maximal parasitemia, and this effect was associated with the sex ratio of the donor infection. in 20 infections in which sex ratio was followed during the ...200212099417
evaluation of western fence lizards (sceloporus occidentalis) and eastern fence lizards (sceloporus undulatus) as laboratory reptile models for toxicological investigations.a need is recognized for one or more laboratory reptile models for use in ecotoxicological studies and risk assessments. maintenance of breeding populations of most reptile species under laboratory conditions is not practical because of their size and slow maturation rate. however, a number of species of spiny lizards (sceloporus sp.) are small, mature quickly, and reproduce under laboratory conditions. we evaluated three populations of western fence lizards (s. occidentalis) and four population ...200212013135
nymphs of the western black-legged tick (ixodes pacificus) collected from tree trunks in woodland-grass habitat.nymphs of the western black-legged tick, ixodes pacificus, were found on the trunks of trees during spring and summer in northwestern california. in a woodland-grass habitat, large- and medium-sized (> 130 cm and 80-130 cm in circumference, respectively), moss-covered oak (quercus spp.) trees supported ticks significantly more often than trees without these characteristics. additionally, trees with basal leaf-litter and lacking shade (at time of sampling) were significantly associated with the p ...200111813653
prevalence and abundance of ixodes pacificus immatures (acari: ixodidae) infesting western fence lizards (sceloporus occidentalis) in northern california: temporal trends and environmental correlates.the prevalence and abundance of immature ixodes pacificus ticks on western fence lizards (sceloporus occidentalis) were examined in relation to time of year, host attributes (i.e., age, gender, and presence or absence of blood parasites), and 5 environmental characteristics, including topographic exposure and ground cover substrate, over a 2-year period in northern california. lizards were infested with subadult ticks from early march until late july or early august, with peak median numbers of ...200111780813
birds and their ticks in northwestern california: minimal contribution to borrelia burgdorferi enzootiology.birds and their attendant ticks were surveyed for infection with the lyme disease spirochete borrelia burgdorferi, in chaparral and woodland-grass habitats in northwestern california from march to july, 1998 to 1999. in total, 234 birds were captured and recaptured (15%); nearly 2.5 times more birds were captured in chaparral than in woodland-grass. overall, 34 species representing 15 families were collected during this study; of these, 24 species were caught in chaparral, 19 in woodland-grass, ...200111534638
landscape features associated with infection by a malaria parasite (plasmodium mexicanum) and the importance of multiple scale studies.in a 3-year study, we examined landscape features (aspect, slope, sun exposure, canopy cover, type of ground cover, and nearest water source) that were potentially related to prevalence of infection with plasmodium mexicanum in fence lizards (sceloporus occidentalis) within a 4.5 ha study area in northern california, usa. logistic regression analysis showed that ground cover type was the primary mediator of the probability of p. mexicanum infection. infected lizards were captured more often in r ...200111393823
a comparative study of mammalian and reptilian alternative pathway of complement-mediated killing of the lyme disease spirochete (borrelia burgdorferi).the potential bactericidal activity of the alternative complement pathway of mammalian and reptilian sera to borrelia burgdorferi sensu stricto (s.s.) was evaluated in vitro. complement-mediated killing was observed when cultured spirochetes were inoculated into sera from the western fence lizard (sceloporus occidentalis) and from the southern alligator lizard (elgaria multicarinata), but not when they were inoculated into serum from either the deer mouse (peromyscus maniculatus) or from humans. ...200011191895
life history of a malaria parasite (plasmodium mexicanum) in its host, the western fence lizard (sceloporus occidentalis): host testosterone as a source of seasonal and among-host variation?the course of infection of a malaria parasite (plasmodium mexicanum) is highly variable in its host, the fence lizard (sceloporus occidentalis). however, a seasonal trend is superimposed on this variation such that gametocyte production is intensified during mid- to late summer. host testosterone levels follow a similar seasonal fluctuation and are variable among individual lizards. we sought to determine if testosterone levels affect seasonal and among-host variation in 11 p. mexicanum life his ...200011128477
oxygen consumption by mitochondria from an endotherm and an ectotherm.comparisons of metabolic properties of mitochondria from an endothermic and an ectothermic vertebrate were performed. oxygen (o2) consumption rates of liver mitochondria from laboratory mice and western fence lizard (sceloporus occidentalis) were determined over a range of temperatures (10, 20, 30 and 37 degrees c) and in the presence of a variety of substrates. at 37 degrees c the o2 consumption rate of mouse mitochondria was 4-11 times higher than lizard mitochondria in the presence of five of ...199910582317
abundance of ticks (acari: ixodidae) infesting the western fence lizard, sceloporus occidentalis, in relation to environmental factors.we examined the impact of environmental characteristics, such as habitat type, topographic exposure and presence of leaf litter, on the abundance of ixodes pacificus ticks infesting the western fence lizard (sceloporus occidentalis) at the university of california hopland research and extension center (hrec), mendocino county, california. a total of 383 adult lizards were slip-noosed and examined for tick infestation in april and may 1998. at least 94% of the lizards were infested by ticks and a ...199910581712
borreliacidal factor in the blood of the western fence lizard (sceloporus occidentalis).in some populations of the western black-legged tick, ixodes pacificus, the prevalence of infection with lyme disease spirochetes (borrelia burgdorferi) in nymphal ticks exceeds those in adult ticks by 3-4-fold. experiments were conducted to determine if the reduced spirochetal prevalence in adult ticks is due to the presence of anti-borrelial antibodies or to another borreliacidal factor in the blood of the western fence lizard, sceloporus occidentalis, a primary host of subadult i. pacificus, ...19989488334
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