Sceloporus Undulatus Research Articles

Microbial genetic variation impacts host eco-immunological strategies and microparasite fitness in Lyme borreliae-reptile system

Tolerance and resistance are two host eco-immunological strategies in response to microparasite invasion. In the strategy of "resistance", host responses are induced to decrease microparasite replication while the "tolerance" strategy allows hosts coexistence with microparasites by minimizing responses to avoid immune-mediated damage. The causative agent of Lyme disease is a group of genotypically diverse bacterial species, Borrelia burgdorferi sensu lato (Bb), which is transmitted by Ixodes ticks and persists in different reservoir animals. In North America, eastern fence lizards (Sceloporus undulatus) can be fed on by Ixodes ticks but are incompetent to one genotype of Bb (i.e., ospC type A). However, field-collected lizards showed evidence of previous infection by Bb strains with undefined genotypes. Supporting this evidence, we introduced three genotypically different Bb strains individually to eastern fence lizards and found a Bb genotype-dependent manner of infectivity. We compared liver transcriptomics and observed elevated immune responses triggered by a lizard-incompetent Bb strain (strain B31). We showed two lizard-competent strains with one having no immunomodulation (strain B379) but the other developing upregulated immune responses (strain 297). These results suggest that genetic variation in microparasites both induces different host strategies for dealing with infection and determines microparasite fitness in the hosts. These findings demonstrate that Bb and eastern fence lizards can serve as a model to investigate the mechanisms underlying eco-immunological strategies of tolerance vs. resistance during host-microparasite interaction.

Tick-tock, racing the clock: parasitism is associated with decreased sprint performance in the Eastern fence lizard

Abstract Host–parasite relationships are important components of ecological systems that influence the evolution of both hosts and parasites. High levels of ectoparasitic infections can disrupt host homeostasis, causing adverse effects on health and performance. However, the effects of natural ectoparasite levels on host physiology are less understood, with most research designs implementing experimental or hormonal manipulations of hosts. In this study, we examined the interplay between tick parasitism and host characteristics on body condition and locomotor performance in Eastern fence lizards in natural settings. We found a higher frequency of tick infections in male lizards relative to females, with larger males being more likely to experience tick infection. Infected lizards had reduced locomotor performance, max sprint speed and 2-m run speed. Together this suggests an energetic trade-off between increased immune function and reduced locomotor performance, which is consistent with the immunocompetence–handicap hypothesis. Higher numbers of ticks on adult male lizards may be explained by age as well as the immunosuppressive effects of testosterone. Tick infection did not appear to reduce overall body condition of lizard hosts. Our findings shed light on the interplay between ectoparasitic infection, host characteristics, and locomotor performance under natural conditions. Such insights are crucial for understanding host–parasite dynamics and determining the trade-offs for hosts within ecological contexts.

The effects of early-life and intergenerational stress on the brain.

Stress experienced during ontogeny can have profound effects on the adult phenotype. However, stress can also be experienced intergenerationally, where an offspring's phenotype can be moulded by stress experienced by the parents. Although early-life and intergenerational stress can alter anatomy, physiology, and behaviour, nothing is known about how these stress contexts interact to affect the neural phenotype. Here, we examined how early-life and intergenerational stress affect the brain in eastern fence lizards (Sceloporus undulatus). Some lizard populations co-occur with predatory fire ants, and stress from fire ant attacks exerts intergenerational physiological and behavioural changes in lizards. However, it is unclear if intergenerational stress, or the interaction between intergenerational and early-life stress, modulates the brain. To test this, we captured gravid females from fire ant invaded and uninvaded populations, and subjected offspring to three early-life stress treatments: (1) fire ant attack, (2) corticosterone, or (3) a control. Corticosterone and fire ant attack decreased some aspects of the neural phenotype while population of origin and the interaction of early-life stress and population had no effects on the brain. These results suggest that early-life stressors may better predict adult brain variation than intergenerational stress in this species.

Effects of testosterone on urogenital tract morphology and androgen receptor expression in immature Eastern Fence lizards (Sceloporus undulatus)

In non-avian reptiles, the onset of sexual dimorphism of the major structures of the urogenital tract varies temporally relative to gonadal differentiation, more so than in other amniote lineages. In the current study, we used tonic-release implants to investigate the effects of exogenous testosterone (T) on postnatal development of the urogenital tract in juvenile Eastern Fence Lizards (Sceloporus undulatus) to better understand the mechanisms underlying the ontogeny of sexual differentiation in reptiles. We examined gonads, mesonephric kidneys and ducts (male reproductive tract primordia), paramesonephric ducts (oviduct primordia), sexual segments of the kidneys (SSKs), and hemiphalluses to determine which structures were sexually dimorphic independent of T treatment and which structures exhibited sexually dimorphic responses to T. To better understand tissue-level responsiveness to T treatment, we also characterized androgen receptor (AR) expression by immunohistochemistry. At approximately 4 months after hatching in control animals, gonads were well differentiated but quiescent; paramesonephric ducts had fully degenerated in males; mesonephric kidneys, mesonephric ducts, and SSKs remained sexually undifferentiated; and hemiphalluses could not be everted in either sex. Exogenous T caused enlargement, regionalization, and secretory activity of the mesonephric ducts and SSKs in both sexes; enlargement and regionalization of the oviducts in females; and enlargement of male hemipenes. The most responsive tissues exhibited moderate but diffuse staining for AR in control lizards and intense nuclear staining in T-treated lizards, suggestive of autoregulation of AR. The similarity between sexes in the responsiveness of the mesonephric ducts and SSK to T indicates an absence of sexually dimorphic organizational effects in these structures prior to treatment, which was initiated approximately 2 months after hatching. In contrast, the sex-specific responses in oviducts and hemipenes indicate that significant organization and/or differentiation had taken place prior to treatment.

Chigger mite (Eutrombicula alfreddugesi) ectoparasitism does not contribute to sex differences in growth rate in eastern fence lizards (Sceloporus undulatus).

Parasitism is nearly ubiquitous in animals and is frequently associated with fitness costs in host organisms, including reduced growth, foraging, and reproduction. In many species, males tend to be more heavily parasitized than females and thus may bear greater costs of parasitism. Sceloporus undulatus is a female-larger, sexually size dimorphic lizard species that is heavily parasitized by chigger mites (Eutrombicula alfreddugesi). In particular, the intensity of mite parasitism is higher in male than in female juveniles during the period of time when sex differences in growth rate lead to the development of sexual size dimorphism (SSD). Sex-biased differences in fitness costs of parasitism have been documented in other species. We investigated whether there are growth costs of mite ectoparasitism, at a time coinciding with sex differences in growth rate and the onset of SSD. If there are sex-biased growth costs of parasitism, then this could suggest a contribution to the development of SSD in S. undulatus. We measured growth and mite loads in two cohorts of unmanipulated, field-active yearlings by conducting descriptive mark-recapture studies during the activity seasons of 2016 and 2019. Yearling males had consistently higher mid-summer mite loads and consistently lower growth rates than females. However, we found that growth rate and body condition were independent of mite load in both sexes. Furthermore, growth rates and mite loads were higher in 2019 than in 2016. Our findings suggest that juveniles of S. undulatus are highly tolerant of chigger mites and that any costs imposed by mites may be at the expense of functions other than growth. We conclude that sex-biased mite ectoparasitism does not contribute to sex differences in growth rate and, therefore, does not contribute to the development of SSD.

Trace Amounts of Ranavirus Detected in Common Musk Turtles (Sternotherus odoratus) at a Site Where the Pathogen Was Previously Common.

Ranaviruses are global multi-host pathogens that infect ectothermic vertebrates and cause mass mortality events in some species. In 2021-2022, we surveyed two species of aquatic turtles in a Virginia site where previous research found ranavirus in lizards (Sceloporus undulatus) and turtles (Chrysemys picta picta and Terrapene carolina carolina). We sampled tissues from 206 turtles and tested 249 samples (including recaptures) for ranavirus using qPCR. We detected trace amounts of ranavirus DNA in 2.8% of Common Musk Turtles (Sternotherus odoratus). We did not detect the virus in Eastern Painted Turtles (C. p. picta). The Ct values from animals carrying ranavirus corresponded to positive controls with a concentration of one copy of ranavirus DNA per microliter and likely reflect DNA in the environment rather than ranavirus infection in turtles. Turtles carrying ranavirus DNA came from only one pond in one year. The amount of ranavirus in our study site, as indicated by tissue samples from turtles, appears to have dropped dramatically since previous research conducted over a decade ago. This study represents the first report of ranavirus detected in S. odoratus and contributes to the scarce literature on longitudinal surveys of ranavirus in wild chelonians. We emphasize the need for large sample sizes and multi-year sampling to detect this pathogen in wild populations.

Locomotor performance differs between foraging and predator escape but is not related to survival in hatchling lizards

Abstract Behaviour is influenced by many factors, including morphology, performance capabilities and the surrounding environment. Behavioural adjustments in response to these factors have important fitness consequences, and therefore behaviour should be considered when evaluating relationships among morphology, performance and fitness. We used hatchling fence lizards (Sceloporus undulatus) to test if sprinting speed and movement behaviours (e.g. latency to approach prey, number of pauses when fleeing or foraging) differ between foraging and anti-predator contexts and if these behaviours are associated with body size, locomotor performance capacity and survival. We quantified maximal sprint performance of individuals and evaluated their running speed in laboratory trials of foraging (moving towards crickets) and predator escape (response to a swooping avian predator). We show that hatchlings run at ~17–36% of total capacity when foraging. Although the most common anti-predator behaviour was to remain still, those that fled from the predator ran at full burst speed. However, foraging and escape speed/behaviours were not associated with body size or locomotor capacity. Hatchlings were subsequently released at our field site for a recapture study to assess phenotypic relationships with survival. We found no evidence that survival was influenced by performance or behaviour, but body size was positively related to survival in the field. These results highlight how seemingly important fitness-relevant behavioural and performance traits may not mediate the relationship between body size and survival.

Divergent effects of climate change on the egg-laying opportunity of species in cold and warm regions.

Climate warming can substantially impact embryonic development and juvenile growth in oviparous species. Estimating the overall impacts of climate warming on oviparous reproduction is difficult because egg-laying events happen throughout the reproductive season. Successful egg laying requires the completion of embryonic development as well as hatching timing conducive to offspring survival and energy accumulation. We propose a new metric-egg-laying opportunity (EO)-to estimate the annual hours during which a clutch of freshly laid eggs yields surviving offspring that store sufficient energy for overwintering. We estimated the EO within the distribution of a model species, Sceloporus undulatus, under recent climate condition and a climate-warming scenario by combining microclimate data, developmental functions, and biophysical models. We predicted that EO will decline as the climate warms at 74.8% of 11,407 sites. Decreasing hatching success and offspring energy accounted for more lost EO hours (72.6% and 72.9%) than the occurrence of offspring heat stress (59.9%). Nesting deeper (at a depth of 12cm) may be a more effective behavioral adjustment for retaining EO than using shadier (50% shade) nests because the former fully mitigated the decline of EO under the considered warming scenario at more sites (66.1%) than the latter (28.3%). We advocate for the use of EO in predicting the impacts of climate warming on oviparous animals because it encapsulates the integrative impacts of climate warming on all stages of reproductive life history.

Outer surface protein E (OspE) mediates Borrelia burgdorferi sensu stricto strain-specific complement evasion in the eastern fence lizard, Sceloporus undulatus

In North America, Lyme disease is primarily caused by the spirochetal bacterium Borrelia burgdorferi sensu stricto (Bb), which is transmitted between multiple vertebrate hosts and ixodid ticks, and is a model commonly used to study host-pathogen interactions. While Bb is consistently observed in its mammalian and avian reservoirs, the bacterium is rarely isolated from North American reptiles. Two closely related lizard species, the eastern fence lizard (Sceloporus undulatus) and the western fence lizard (Sceloporus occidentalis), are examples of reptiles parasitized by Ixodes ticks. Vertebrates are known to generate complement as an innate defense mechanism, which can be activated before Bb disseminate to distal tissues. Complement from western fence lizards has proven lethal against one Bb strain, implying the role of complement in making those lizards unable to serve as hosts to Bb. However, Bb DNA is occasionally identified in distal tissues of field-collected eastern fence lizards, suggesting some Bb strains may overcome complement-mediated clearance in these lizards. These findings raise questions regarding the role of complement and its impact on Bb interactions with North American lizards. In this study, we found Bb seropositivity in a small population of wild-caught eastern fence lizards and observed Bb strain-specific survivability in lizard sera. We also found that a Bb outer surface protein, OspE, from Bb strains viable in sera, promotes lizard serum survivability and binds to a complement inhibitor, factor H, from eastern fence lizards. Our data thus identify bacterial and host determinants of eastern fence lizard complement evasion, providing insights into the role of complement influencing Bb interactions with North American lizards.

Habitat Use for Two Heliothermic Lizards in Longleaf Pine Savannas

Heliothermic lizards, like Aspidoscelis sexlineata (Six-lined Racerunner) and Sceloporus undulatus (Eastern Fence Lizard), use direct solar radiation to maintain high body temperatures needed to fulfill their basic life functions. These lizards are often found in frequently burned Pinus palustris (Longleaf Pine) savannas that provide open, high-quality thermal habitat and foraging opportunities. We examined microhabitat features surrounding 42 locations where we captured lizards using drift-fences within Longleaf Pine savannas from March to May 2017 to better understand the fine-scale habitat components important for these 2 species. We used negative binomial regression, model selection (AICc), and model averaging to identify important variables associated with lizard habitat use. We found both Six-lined Racerunners (n = 52) and Eastern Fence Lizards (n = 38) used microhabitats that were characteristic of open-canopied sites (i.e., more bare ground and grass, and less litter, midstory, and canopy cover). However, their use of sites differed in the forest structure selected. The surface-dwelling Six-lined Racerunner selected sites with more stumps and the arboreal Eastern Fence Lizard selected sites with greater Quercus (oak) basal area. Management for these lizards should include activities that promote their habitat, foraging, and thermoregulatory requirements, such as frequent prescribed fire to maintain savanna-like conditions and the retention of forest structures for basking and refuge.

Shared and unique responses in the microbiome of allopatric lizards reared in a standardized environment.

The gut microbiome can influence host fitness and, consequently, the ecology and evolution of natural populations. Microbiome composition can be driven by environmental exposure but also by the host's genetic background and phenotype. To contrast environmental and genetic effects on the microbiome we leverage preserved specimens of eastern fence lizards from allopatric lineages east and west of the Mississippi River but reared in standardized conditions. Bacterial composition was indistinguishable between lineages but responded significantly to host age-a proxy for environmental exposure. This was accompanied by a continuous decrease in bacterial diversity in both lineages, partially driven by decreasing evenness seen only in western lizards. These findings indicate that longer exposure to a homogeneous habitat may have a depreciating effect on microbiome diversity in eastern fence lizards, a response shared by both lineages. We highlight the importance of such effects when extrapolating patterns from laboratory experiments to the natural world.

Masculinized Sexual Ornaments in Female Lizards Correlate with Ornament-Enhancing Thermoregulatory Behavior.

SynopsisThe adaptive significance of colorful or exaggerated traits (i.e., ornaments) expressed in females is often unclear. Competing hypotheses suggest that expression of female ornaments arises from maladaptive (or neutral) genetic inheritance from males along with incomplete epigenetic regulation, or from positive selection for ornaments in females under social competition. Whether costly or advantageous, the visibility of such traits can sometimes be behaviorally modulated in order to maximize fitness. Female eastern fence lizards express blue badges that are variable in size and color saturation. These are rudimentary compared to those seen in males and carry important costs such as reduced mating opportunities. Body temperature is a well-established enhancer of badge color, and thus thermoregulation may be one way these animals modulate badge visibility. We quantified realized body temperatures of female lizards paired in laboratory trials and observed that females with larger badges attained higher body temperatures when freely allowed to thermoregulate, sometimes beyond physiological optima. In this association between phenotype and behavior, females with larger badges exhibited thermoregulatory patterns that increase their badges’ visibility. This signal-enhancing behavior is difficult to reconcile with the widely held view that female ornaments are maladaptive, suggesting they may carry context-dependent social benefits.

Avoidance of invasive prey reduces subsequent consumption of similar native prey

Learned avoidance of invasive species could carry over to ecologically similar non-threatening native taxa, altering predator-prey interactions and food webs. The red imported fire ant, Solenopsis invicta, is an invasive prey of the eastern fence lizard, Sceloporus undulatus. Despite potentially lethal outcomes, juvenile fence lizards innately consume fire ants; however, they rapidly learn to avoid eating them with early-life exposure. Ants comprise a large portion of fence lizards' diets and a generalized avoidance of ants could thus reduce their prey pool. We tested whether learned avoidance following exposure to invasive fire ants would reduce the subsequent consumption of a palatable native ant. Lizards that consumed invasive fire ants for five days were less likely to subsequently consume native common pyramid ants, Dorymrymex bureni, than were lizards that initially consumed these non-threatening native ants. Our results suggest that learned avoidance of invasive prey can carry-over to avoidance of palatable native prey. The broad avoidance of native ants, due to the presence of invasive fire ants, could potentially increase native ant populations affecting their predators and competitors.

Active regulation of ultraviolet light exposure overrides thermal preference behaviour in eastern fence lizards

Abstract Over a century of ecophysiological studies on lizards have perpetuated the assumption that basking and shuttling movements between sun and shade function solely for temperature regulation. However, these behaviours also modulate exposure to ultraviolet (UV) wavelengths that are essential for maintaining physiological homoeostasis as well as ensuring proper growth and development and enhancing long‐term fitness. An alternative hypothesis is that lizards also actively regulate their UV exposure. In this scenario, UV needs may even override temperature needs (or vice versa), generating asymmetries in the ability of a lizard to regulate both conditions equally. We test this hypothesis using field and laboratory data collected on adult Sceloporus undulatus. We found that S. undulatus actively regulate UV exposure and prioritize UV over temperature, favouring body temperatures much higher than preferred values to sustain preferred UV exposure. In stark contrast, temperature had no reciprocal impact on UV regulation behaviour. Our field data support these patterns, suggesting that lizards may even seek out hotter environments despite thermal costs to enhance UV exposure. We conclude that S. undulatus actively regulate for UV as well as temperature. Unfortunately, outside of zoos and private hobbyists, appreciation of the importance of UV for ectotherm survival and reproductive success has been minimal. Addressing this deficit will therefore be vital to improve our understanding of the factors shaping the evolution of ectotherm photoregulation behaviour in nature. Read the free Plain Language Summary for this article on the Journal blog.

Fitness Costs of Maternal Ornaments and Prenatal Corticosterone Manifest as Reduced Offspring Survival and Sexual Ornament Expression.

Colorful traits (i.e., ornaments) that signal quality have well-established relationships with individual condition and physiology. Furthermore, ornaments expressed in females may have indirect fitness effects in offspring via the prenatal physiology associated with, and social consequences of, these signaling traits. Here we examine the influence of prenatal maternal physiology and phenotype on condition-dependent signals of their offspring in adulthood. Specifically, we explore how prenatal maternal testosterone, corticosterone, and ornament color and size correlate with female and male offspring survival to adulthood and ornament quality in the lizard Sceloporus undulatus. Offspring of females with more saturated badges and high prenatal corticosterone were less likely to survive to maturity. Badge saturation and area were negatively correlated between mothers and their male offspring, and uncorrelated to those in female offspring. Maternal prenatal corticosterone was correlated negatively with badge saturation of male offspring in adulthood. Our results indicate that maternal ornamentation and prenatal concentrations of a stress-relevant hormone can lead to compounding fitness costs by reducing offspring survival to maturity and impairing expression of a signal of quality in surviving males. This mechanism may occur in concert with social costs of ornamentation in mothers. Intergenerational effects of female ornamentation and prenatal stress may be interdependent drivers of balancing selection and intralocus sexual conflict over signaling traits.

Compensating for a stressful pregnancy? Glucocorticoid treatment during gravidity reduces metabolic rate in female fence lizards post-parturition

Reproduction is a critical part of an animal's life history, but one which incurs significant costs to survival and future reproductive potential. These physiological consequences are likely to be influenced by context – for example, if an individual is subject to environmental stressors, physiological and behavioral changes associated with reproduction may be altered. Glucocorticoids, hormones produced as part of the physiological response to stressors, may alter how reproduction affects female physiology and behavior, and therefore the outcomes of reproductive trade-offs. Glucocorticoids prioritize immediate survival over reproduction, for example through changes in immune function, metabolic rate, and foraging, which may reduce energy expenditure or increase energy gain. However, we previously found that female eastern fence lizards (Sceloporus undulatus) experiencing elevated glucocorticoid levels during gestation were nevertheless able to maintain reproductive output and body condition. Here we investigate compensatory mechanisms by which eastern fence lizard females may maintain reproduction under experimental increases in a glucocorticoid, corticosterone (CORT). We found that, although CORT-treated females had similar immune function and behavior, they had reduced metabolic rates 3-5 days post-parturition compared to control females. Given that CORT-treated females spent a similar time basking and had equal food intake compared to control females, we suggest that the reduced metabolic rate is a mechanism by which CORT-treated females maintain their energy balance and reduce the energetic costs of gestation during periods of stress. This study suggests that physiological responses to reproduction may be context-dependent and could act to minimize costs of reproduction in situations where CORT is elevated (such as during periods of environmental stress).

A chromosome-level genome assembly for the eastern fence lizard (Sceloporus undulatus), a reptile model for physiological and evolutionary ecology.

BackgroundHigh-quality genomic resources facilitate investigations into behavioral ecology, morphological and physiological adaptations, and the evolution of genomic architecture. Lizards in the genus Sceloporus have a long history as important ecological, evolutionary, and physiological models, making them a valuable target for the development of genomic resources.FindingsWe present a high-quality chromosome-level reference genome assembly, SceUnd1.0 (using 10X Genomics Chromium, HiC, and Pacific Biosciences data), and tissue/developmental stage transcriptomes for the eastern fence lizard, Sceloporus undulatus. We performed synteny analysis with other snake and lizard assemblies to identify broad patterns of chromosome evolution including the fusion of micro- and macrochromosomes. We also used this new assembly to provide improved reference-based genome assemblies for 34 additional Sceloporus species. Finally, we used RNAseq and whole-genome resequencing data to compare 3 assemblies, each representing an increased level of cost and effort: Supernova Assembly with data from 10X Genomics Chromium, HiRise Assembly that added data from HiC, and PBJelly Assembly that added data from Pacific Biosciences sequencing. We found that the Supernova Assembly contained the full genome and was a suitable reference for RNAseq and single-nucleotide polymorphism calling, but the chromosome-level scaffolds provided by the addition of HiC data allowed synteny and whole-genome association mapping analyses. The subsequent addition of PacBio data doubled the contig N50 but provided negligible gains in scaffold length.ConclusionsThese new genomic resources provide valuable tools for advanced molecular analysis of an organism that has become a model in physiology and evolutionary ecology.

The influence of maternal glucocorticoids on offspring phenotype in high- and low-risk environments.

Elevated maternal glucocorticoid levels during gestation can lead to phenotypic changes in offspring via maternal effects. Although such effects have traditionally been considered maladaptive, maternally derived glucocorticoids may adaptively prepare offspring for their future environment depending upon the correlation between maternal and offspring environments. Nevertheless, relatively few studies test the effects of prenatal glucocorticoid exposure across multiple environments. We tested the potential for ecologically relevant increases in maternal glucocorticoids in the eastern fence lizard (Sceloporus undulatus) to induce adaptive phenotypic changes in offspring exposed to high or low densities of an invasive fire ant predator. Maternal treatment had limited effects on offspring morphology and behavior at hatching, but by 10 days of age, we found maternal treatment interacted with offspring environment to alter anti-predator behaviors. We did not detect differences in early-life survival based on maternal treatment or offspring environment. Opposing selection on anti-predator behaviors from historic and novel invasive predators may confound the potential of maternal glucocorticoids to adaptively influence offspring behavior. Our test of the phenotypic outcomes of transgenerational glucocorticoid effects across risk environments provides important insight into the context-specific nature of this phenomenon and the importance of understanding both current and historic evolutionary pressures.

Functional remodeling of adrenal steroidogenic tissue by food deprivation in the lizard, Sceloporus undulatus

The present study examined how food availability interacts with age to modulate lizard adrenal steroidogenic function at the cellular level. Adult male and juvenile male and female Eastern Fence Lizards (Sceloporus undulatus) underwent a period of food deprivation with or without a shorter re-feeding period. Lizards maintained on a full feeding regimen served as the controls. Across the feeding regimens, plasma corticosterone of adult lizards was unchanged whereas that of food-deprived juvenile lizards was increased nearly 7 times and this increase was normalized by a short re-feeding period. Freshly dispersed adrenocortical cells derived from these lizards were incubated with ACTH and the production of selected steroids was measured by highly specific radioimmunoassay. Net maximal steroid rates of juvenile cells were 161% greater than those of adult cells. Adult and juvenile progesterone rates were consistently suppressed by food deprivation (by nearly 48%) and were normalized by a re-feeding period, whereas divergent effects were seen with corticosterone and aldosterone rates. Food deprivation suppressed corticosterone rates of adult cells by 43% but not those of juvenile cells. In a reciprocal manner, food deprivation had no significant effect on aldosterone rates of adult cells, but it suppressed those of juvenile cells by 52%. A short re-feeding period normalized most rates in both adult and juvenile cells and further augmented the adult aldosterone rate by 54%. The effect of the feeding regimens on ACTH sensitivity varied with life stage and with steroid. The overall sensitivity of adult cells to ACTH was nearly three times that of juvenile cells. Collectively, the data presented here and data from previous work indicate that food restriction/deprivation in Sceloporus lizard species causes a functional remodeling of the adrenocortical tissue. Furthermore, life stage adds more complexity to this remodeling.

Brain transcriptomic responses of Yarrow's spiny lizard, Sceloporus jarrovii, to conspecific visual or chemical signals.

Species with multimodal communication integrate information from social cues in different modalities into behavioral responses that are mediated by changes in gene expression in the brain. Differences in patterns of gene expression between signal modalities may shed light on the neuromolecular mechanisms underlying multisensory processing. Here, we use RNA-Seq to analyze brain transcriptome responses to either chemical or visual social signals in a territorial lizard with multimodal communication. Using an intruder challenge paradigm, we exposed 18 wild-caught, adult, male Sceloporus jarrovii to either male conspecific scents (femoral gland secretions placed on a small pebble), the species-specific push-up display (a programmed robotic model), or a control (an unscented pebble). We conducted differential expression analysis with both a de novo S. jarrovii transcriptome assembly and the reference genome of a closely related species, Sceloporus undulatus. Despite some inter-individual variation, we found significant differences in gene expression in the brain across signal modalities and the control in both analyses. The most notable differences occurred between chemical and visual stimulus treatments, closely followed by visual stimulus versus the control. Altered expression profiles could explain documented aggression differences in the immediate behavioral response to conspecific signals from different sensory modalities. Shared differentially expressed genes between visually- or chemically-stimulated males are involved in neural activity and neurodevelopment and several other differentially expressed genes in stimulus-challenged males are involved in conserved signal-transduction pathways associated with the social stress response, aggression and the response to territory intruders across vertebrates.