Pesticides compromise health: a comparison between lizards collected within and outside an agricultural area.

Reptiles are the least studied vertebrates regarding the impact of pesticides on their health, despite being good models for ecotoxicological studies given their abundance and easy handling. Salvator merianae is widely distributed in South America and often found in agricultural cultivation areas. Here, we compared the morphological, biochemical, and physiological parameters of S. merianae from an exposed area (EA) to pesticides and a reference area (RA) or control. These parameters were measured in plasma (albumin, alanine transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase, glucose, total proteins, uric acid, triglycerides, VLDL, and corticosterone) and in erythrocytes (TBARS, glutathione S-transferase, superoxide dismutase, and catalase activity). Blood samples were collected from 28 lizards (EA: three juveniles, three adult females, and three adult males; RA: nine juveniles, four females, and five males) in southern Brazil during the reproductive period. We observed a decrease in body mass, the ratio between body mass and total length and snout-vent length in juvenile lizards collected at EA. The levels of TBARS, glutathione S-transferase, triglycerides, VLDL, and uric acid were altered for juveniles in EA. When comparing the two areas, females differed in superoxide dismutase activity and total proteins, while males differed in superoxide dismutase, catalase, and glutathione S-transferase activity. This set of results shows that S. merianae, especially juveniles, suffers a negative impact when inserted in an agricultural area. The analyzed biomarkers proved suitable for monitoring these lizards and the quality of this environment.

Sex and early-life conditions shape telomere dynamics in an ectotherm.

Telomeres, the repetitive DNA regions that protect the ends of chromosomes, and their shortening have been linked to key life history trade-offs among growth, reproduction and lifespan. In contrast to most endotherms, many ectotherms can compensate for telomere shortening throughout life by upregulation of telomerase in somatic tissues. However, during development, marked by rapid growth and an increased sensitivity to extrinsic factors, the upregulation of telomerase may be overwhelmed, resulting in long-term impacts on telomere dynamics. In ectotherms, one extrinsic factor that may play a particularly important role in development is temperature. Here, we investigated the influence of developmental temperature and sex on early-life telomere dynamics in an oviparous ectotherm, Lacerta agilis. While there was no effect of developmental temperature on telomere length at hatching, there were subsequent effects on telomere maintenance capacity, with individuals incubated at warm temperatures exhibiting less telomere maintenance compared with cool-incubated individuals. Telomere dynamics were also sexually dimorphic, with females having longer telomeres and greater telomere maintenance compared with males. We suggest that selection drives this sexual dimorphism in telomere maintenance, in which females maximise their lifetime reproductive success by investing in traits promoting longevity such as maintenance, while males invest in short-term reproductive gains through a polygynous mating behaviour. These early-life effects, therefore, have the potential to mediate life-long changes to life histories.

Genetic basis and expression of ventral colour in polymorphic common lizards.

Colour is an important visual cue that can correlate with sex, behaviour, life history or ecological strategies, and has evolved divergently and convergently across animal lineages. Its genetic basis in non-model organisms is rarely known, but such information is vital for determining the drivers and mechanisms of colour evolution. Leveraging genetic admixture in a rare contact zone between oviparous and viviparous common lizards (Zootoca vivipara), we show that females (N = 558) of the two otherwise morphologically indistinguishable reproductive modes differ in their ventral colouration (from pale to vibrant yellow) and intensity of melanic patterning. We find no association between female colouration and reproductive investment, and no evidence for selection on colour. Using a combination of genetic mapping and transcriptomic evidence, we identified two candidate genes associated with ventral colour differentiation, DGAT2 and PMEL. These are genes known to be involved in carotenoid metabolism and melanin synthesis respectively. Ventral melanic spots were associated with two genomic regions, including a SNP close to protein tyrosine phosphatase (PTP) genes. Using genome re-sequencing data, our results show that fixed coding mutations in the candidate genes cannot account for differences in colouration. Taken together, our findings show that the evolution of ventral colouration and its associations across common lizard lineages is variable. A potential genetic mechanism explaining the flexibility of ventral colouration may be that colouration in common lizards, but also across squamates, is predominantly driven by regulatory genetic variation.

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.

Expression analysis of alpha keratins and corneous beta-protein genes during embryonic development of Gekko japonicus.

Epidermal appendages of birds and reptiles, including claws, feathers, scales, and setae, are primarily composed of alpha keratins (KRTs) and corneous beta-proteins (CBPs). A comprehensive and systematic knowledge of KRTs and CBPs in Schlegel's Japanese gecko (Gekko japonicus) is still lacking. In this study, 22 candidate Gecko japonicus keratin (GjKRT) family genes (12 type I genes, 10 type II genes) were identified in the G. japonicus genome. The majority of GjKRT genes across various subgroups had undergone a prolonged and highly conservative evolutionary process. Through a combination of morphological observation, RNA-seq analysis, and qRT-PCR assay, it was possible to discern the dynamic alterations in the expression of GjKRTs and Gecko japonicus corneous beta-proteins genes (GjCBPs). These findings strongly indicate that GjKRTs gradually accumulate to constitute an α-layer, which is subsequently succeeded by the formation of the corneous beta layer containing GjCBPs at late stages (40-42) of embryonic development. The epidermal appendages in G. japonicus may result from the joint accumulation of KRTs and CBPs, with stages 40-42 being critical for their development. These findings provide novel insights into KRTs and CBPs of G. japonicus and offer a foundation for investigating the functions of GjKRT and GjCBP gene families. Furthermore, this knowledge contributes to unraveling the molecular mechanisms underlying the formation of epidermal appendages in G. japonicus.

Genome-wide analysis of RNA-chromatin interactions in lizards as a mean for functional lncRNA identification.

BACKGROUND: Long non-coding RNAs (lncRNAs) are defined as transcribed molecules longer than 200 nucleotides with little to no protein-coding potential. LncRNAs can regulate gene expression of nearby genes (cis-acting) or genes located on other chromosomes (trans-acting). Several methodologies have been developed to capture lncRNAs associated with chromatin at a genome-wide level. Analysis of RNA-DNA contacts can be combined with epigenetic and RNA-seq data to define potential lncRNAs involved in the regulation of gene expression. RESULTS: We performed Chromatin Associated RNA sequencing (ChAR-seq) in Anolis carolinensis to obtain the genome-wide map of the associations that RNA molecules have with chromatin. We analyzed the frequency of DNA contacts for different classes of RNAs and were able to define cis- and trans-acting lncRNAs. We integrated the ChAR-seq map of RNA-DNA contacts with epigenetic data for the acetylation of lysine 16 on histone H4 (H4K16ac), a mark connected to actively transcribed chromatin in lizards. We successfully identified three trans-acting lncRNAs significantly associated with the H4K16ac signal, which are likely involved in the regulation of gene expression in A. carolinensis. CONCLUSIONS: We show that the ChAR-seq method is a powerful tool to explore the RNA-DNA map of interactions. Moreover, in combination with epigenetic data, ChAR-seq can be applied in non-model species to establish potential roles for predicted lncRNAs that lack functional annotations.

Temperature-Dependent Bioaccumulation, Metabolism, and Hepatotoxicity of Flufiprole in Lizards (Eremias argus).

As a phenylpyrazole insecticide, flufiprole is an important substitute for fipronil in the agricultural field of China. However, its bioaccumulation and metabolism in terrestrial organisms especially in the lizards living in the agricultural area have rarely been investigated. As an ectothermic animal, lizards are also sensitive to temperature changes. Considering global warming, this study measured bioaccumulation, metabolism, and hepatotoxicity of flufiprole in the Chinese native lizard (Eremias argus) under different temperature stresses. Lizards exposed to flufiprole-contaminated soil adsorbed flufiprole through the skin and flufiprole was preferred to accumulate in lizard liver and brain. The oxidation product fipronil sulfone was the main metabolite of flufiprole in both lizard liver and human liver microsomes, which were mainly metabolized by lizard CYP3A19 or human CYP3A4. The fipronil sulfone concentration increased with increased temperature in lizard tissues. In addition, more serious oxidative damage was shown under higher temperature as the glutathione (GSH), malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in lizards increased with increased temperature after flufiprole exposure. Flufiprole exposure also induced lizard liver lesions, and these lesions became more serious in the higher-temperature groups. This study provided new insights into the risk assessment of flufiprole in lizards under global warming.

Sexually dimorphic expression of AMH facilitates testis differentiation pathway in the tropical lizard, Calotes versicolor (Daud.).

The Anti-mullerian hormone (AMH), also known as Mullerian inhibiting substance (MIS), is a glycoprotein that belongs to transforming growth factor ß superfamily. The significance of AMH during gonadal differentiation is not clearly deciphered in reptiles. Hence, current study aims to know the onset of AMH secretion and its functional role in Mullerian duct regression gonadal differentiation in tropical lizard, Calotes versicolor which exhibits a novel Female-Male-Female-Male (FMFM) pattern of temperature-dependent sex determination (TSD). The Immunohistochemistry and qRT-PCR techniques were employed to analyze the gonadal expression profile of AMH during different stages of embryonic development. The eggs of the lizard were incubated at both male-producing temperature (MPT: 25.5 ± 0.5 °C) and female-producing temperatures (FPT: 31.5 ± 0.5 °C). The results reveal that the onset of AMH gene expression was observed as early as oviposition prior to the immunolocalization of AMH protein at early-TSP (Temperature-sensitive period). The substantial rise in the intensity of the immunoreaction of AMH protein in the cytoplasm confining to Sertoli cells of seminiferous cords at MPT with low level of expression at FPT during gonadal sex differentiation, specify sexually dimorphic expression of AMH protein. Further, with the onset of sexual differentiation, the developing testis immensely expresses AMH gene which is 7-fold greater than that of transcripts levels in female embryos; signifies its conserved role in Mullerian duct regression thereby promoting testis differentiation. The robust immunnoexpression of AMH protein during post-gonadal differentiation coincides with the onset of the regression of Mullerian duct point out a positive correlation between testis differentiation and Mullerian duct regression, thus facilitating testis differentiation pathway. Based on the immunoexpression pattern of AMH protein and transcript levels of AMH gene, it is inferred that AMH plays a significant role in Mullerian duct regression, favoring testis differentiation.

Nesfatin-1 in a reptile: its role and hormonal regulation in wall lizard testis.

Nesfatin-1 is a pleiotropic hormone implicated in various physiological functions including reproduction. Studies though limited, have established an important role of the peptide in regulation of testicular functions in mammals and fishes. However, role of nesfatin-1 in regulation of spermatogenesis and testicular steroidogenesis remains completely unexplored in reptiles. Therefore, present study aimed to develop an insight into reproductive phase-dependent testicular expression, function and regulation of nucb2/nesfatin-1 in a reptile, Hemidactylus flaviviridis. Expression of nucb2/nesfatin-1 in testis of wall lizard varied significantly depending upon reproductive phase, being highest in the active phase while lowest during regressed phase. Further, in vitro treatment of wall lizard testis with nesfatin-1 showed a concentration- and time-dependent stimulatory effect of the peptide on expression of cell proliferation and differentiation markers like scf, c-kit and pcna suggesting a spermatogenic role of nesfatin-1 in wall lizard. Also, nesfatin-1 stimulated the anti-apoptotic marker, bcl-2 while inhibited the apoptotic marker, caspase-3, suggesting its role as an inhibitor of apoptosis of testicular cells. Further, treatment with nesfatin-1 resulted in significantly higher expression of star along with a concomitant increase in testosterone production by the lizard testis. The present study also demonstrates hormonal regulation of testicular nucb2/nesfatin-1 wherein follicle-stimulating hormone (FSH) inhibited while sex steroids like dihydrotestosterone (DHT) and 17ß-estradiol-3-benzoate (E2) stimulated the mRNA expression of nesfatin-1. Observations from the current study for the first time provide comprehensive evidence of spermatogenic and steroidogenic role of nesfatin-1 as well as its hormonal regulation in the testis of a reptile, H. flaviviridis.

Super-high procoagulant activity of gecko thrombin: A gift from sky dragon.

AIMS: Gecko, the "sky dragon" named by Traditional Chinese Medicine, undergoes rapid coagulation and scarless regeneration following tail amputation in the natural ecology, providing a perfect opportunity to develop the efficient and safe drug for blood clotting. Here, gecko thrombin (gthrombin) was recombinantly prepared and comparatively studied on its procoagulant activity. METHODS: The 3D structure of gthrombin was constructed using the homology modeling method of I-TASSER. The active gthrombin was prepared by the expression of gecko prethrombin-2 in 293 T cells, followed by purification with Ni2+ -chelating column chromatography prior to activation by snake venom-derived Ecarin. The enzymatic activities of gthrombin were assayed by hydrolysis of synthetic substrate S-2238 and the fibrinogen clotting. The vulnerable nerve cells were used to evaluate the toxicity of gthrombin at molecular and cellular levels. RESULTS: The active recombinant gthrombin showed super-high catalytic and fibrinogenolytic efficiency than those of human under different temperatures and pH conditions. In addition, gthrombin made nontoxic effects on the central nerve cells including neurons, contrary to those of mammalian counterparts, which contribute to neuronal damage, astrogliosis, and demyelination. CONCLUSIONS: A super-high activity but safe procoagulant candidate drug was identified from reptiles, which provided a promising perspective for clinical application in rapid blood clotting.

Venom phenotype conservation suggests integrated specialization in a lizard-eating snake.

Biological specialization reduces the size of niche space while increasing efficiency in the use of available resources. Specialization often leads to phenotypic changes via natural selection aligning with niche space constraints. Commonly observed changes are in size, shape, behavior, and traits associated with feeding. One often selected trait for dietary specialization is venom, which, in snakes, often shows variation dependent on diet across and within species. The Neotropical Blunt-headed Treesnake (Imantodes cenchoa) is a highly specialized, rear-fanged, arboreal, lizard hunter that displays a long thin body, enlarged eyes, and a large Duvernoy's gland. However, toxin characterization of I. cenchoa has never been completed. Here, we use RNA-seq and mass spectrometry to assemble, annotate, and analyze the venom gland transcriptomes of four I. cenchoa from across their range. We find a lack of significant venom variation at the sequence and expression levels, suggesting venom conservation across the species. We propose this conservation provides evidence of a specialized venom repertoire, adapted to maximize efficiency of capturing and processing lizards. Importantly, this study provides the most complete venom gland transcriptomes of I. cenchoa and evidence of venom specialization in a rear-fanged snake, giving insight into selective pressures of venom across all snake species.

Cell-permeable chameleonic peptides: Exploiting conformational dynamics in de novo cyclic peptide design.

Membrane-traversing peptides offer opportunities for targeting intracellular proteins and oral delivery. Despite progress in understanding the mechanisms underlying membrane traversal in natural cell-permeable peptides, there are still several challenges to designing membrane-traversing peptides with diverse shapes and sizes. Conformational flexibility appears to be a key determinant of membrane permeability of large macrocycles. We review recent developments in the design and validation of chameleonic cyclic peptides, which can switch between alternative conformations to enable improved permeability through cell membranes, while still maintaining reasonable solubility and exposed polar functional groups for target protein binding. Finally, we discuss the principles, strategies, and practical considerations for rational design, discovery, and validation of permeable chameleonic peptides.

Sex steroid receptors in the ovarian follicles of the lizard Sceloporus torquatus.

Estradiol and progesterone have been recognized as important mediators of reproductive events in the female mainly via binding to their receptors. This study aimed to characterize the immunolocalization of the estrogen receptor alfa (ERα), estrogen receptor beta (ERß) and progesterone receptor (PR) in the ovarian follicles of the lizard Sceloporus torquatus. The localization of steroid receptors has a spatio-temporal pattern that depends on the stage of follicular development. The immunostaining intensity of the three receptors was high in the pyriform cells and the cortex of the oocyte of previtellogenic follicles. During the vitellogenic phase, the granulosa and theca immunostaining was intense even with the modification of the follicular layer. In the preovulatory follicles, the receptors were found in yolk and additionally, ERα was also located in the theca. These observations suggest a role for sex steroids in regulating follicular development in lizards, like other vertebrates.

Individual variation within wild populations of an arid-zone lizard dictates oxidative stress levels despite exposure to sublethal pesticides.

The relationship between sublethal pesticide exposure and oxidative stress in an ecologically relevant field setting is relatively unknown for reptiles. Oxidative stress is a multi-faceted concept that dictates key survival and fitness parameters in any organism. Fipronil and fenitrothion are two pesticides widely used globally for agricultural pest management. Using a field-based, BACI designed experiment we investigated the impact of sublethal pesticide exposure on oxidative stress biomarkers protein carbonyl and DNA damage (8-OHdG), in an arid-zone lizard species, Pogona vitticeps. A single ecologically relevant dose of pesticide was applied via oral gavage to treatment animals. Lizard condition, activity measures, and blood biomarkers were measured at relevant sampling intervals. Cholinesterase (ChE) and acetylcholinesterase (AChE) enzymatic biomarkers were measured in response to fenitrothion, and fipronil blood residues were measured for fipronil-treated lizards. Results suggested no significant treatment effect of either pesticide on parameters measured, however, 8-OHdG levels decreased by ≥ 45% for both pesticide treatment groups and not controls. Protein carbonyl levels showed a high degree of individual variation that proved more influential than pesticide exposure. Building our understanding of the macromolecular impacts of sublethal pesticide exposure on wild lizard populations is an integral step in addressing the current gap in literature and management practices. Our study has also highlighted the complex nature of studying oxidative stress in the field and the sheer necessity of future study.

Macrophage Migration Inhibitory Factor Promotes Expression of Matrix Metalloproteinases 1 and 3 in Spinal Cord Astrocytes following Gecko Tail Amputation.

BACKGROUND: The matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that play a variety of physiological and pathological roles in development, remodeling of tissues and diseases, mainly through degradation of various components of the extracellular matrix (ECM). Particularly, the MMPs have increasingly been found to mediate neuropathology following spinal cord injury (SCI). Proinflammatory mediators are potent activators of the MMPs. However, how the spinal cord regenerative vertebrates circumvent MMPs-mediated neuropathogenesis following SCI remains unclear. METHODS: Following the establishment of gecko tail amputation model, the correlation of MMP-1 (gMMP-1) and MMP-3 (gMMP-3) expression with that of macrophage migration inhibitory factor in gecko (gMIF) was assayed by RT-PCR, Western blot and immunohistochemistry. Transcriptome sequencing of primary astrocytes was performed to analyze the intracellular signal transduction of macrophage migration inhibitory factor (MIF). The effects of MMP-1 and MMP-3 induced by MIF on astrocyte migration were assessed by transwell migration assay. RESULTS: The expression of gMIF significantly increased at lesion site of the injured cord, in parallel with those of gMMP-1 and gMMP-3 in the gecko astrocytes (gAS). Transcriptome sequencing and in vitro cell model revealed that gMIF efficiently promoted the expression of gMMP-1 and gMMP-3 in gAS, which in turn contributed to the migration of gAS. Inhibition of gMIF activity following gecko SCI remarkably attenuated astrocytic expression of the two MMPs, and further influenced gecko tail regeneration. CONCLUSIONS: Gecko SCI following tail amputation promoted production of gMIF, which induced the expression of gMMP-1 and gMMP-3 in gAS. The gMIF-mediated gMMP-1 and gMMP-3 expression was involved in gAS migration and successful tail regeneration.

Egg viability and egg mass underlie immune tradeoffs and differences between urban and rural lizard egg yolk physiology.

Urbanization can cause innumerable abiotic and biotic changes that have the potential to influence the ecology, behavior, and physiology of native resident organisms. Relative to their rural conspecifics, urban Side-blotched Lizard (Uta stansburiana) populations in southern Utah have lower survival prospects and maximize reproductive investment via producing larger eggs and larger clutch sizes. While egg size is an important predictor of offspring quality, physiological factors within the egg yolk are reflective of the maternal environment and can alter offspring traits, especially during energetically costly processes, such as reproduction or immunity. Therefore, maternal effects may represent an adaptive mechanism by which urban-dwelling species can persist within a variable landscape. In this study, we assess urban and rural differences in egg yolk bacterial killing ability (BKA), corticosterone (CORT), oxidative status (d-ROMs), and energy metabolites (free glycerol and triglycerides), and their association with female immune status and egg quality. Within a laboratory setting, we immune challenged urban lizards via lipopolysaccharide injection (LPS) to test whether physiological changes associated with immune system activity impacted egg yolk investment. We found urban females had higher mite loads than rural females, however mite burden was related to yolk BKA in rural eggs, but not urban eggs. While yolk BKA differed between urban and rural sites, egg mass and egg viability (fertilized vs. unfertilized) were strong predictors of yolk physiology and may imply tradeoffs exist between maintenance and reproduction. LPS treatment caused a decrease in egg yolk d-ROMs relative to the control treatments, supporting results from previous research. Finally, urban lizards laid a higher proportion of unfertilized eggs, which differed in egg yolk BKA, CORT, and triglycerides in comparison to fertilized eggs. Because rural lizards laid only viable eggs during this study, these results suggest that reduced egg viability is a potential cost of living in an urban environment. Furthermore, these results help us better understand potential downstream impacts of urbanization on offspring survival, fitness, and overall population health.

Proteomic analysis of the mandibular glands from the Chinese crocodile lizard, Shinisaurus crocodilurus - Another venomous lizard?

Based on its phylogenetic relationship to monitor lizards (Varanidae), Gila monsters (Heloderma spp.), and the earless monitor Lanthanotus borneesis, the Chinese crocodile lizard, Shinisaurus crocodilurus, has been assigned to the Toxicofera clade, which comprises venomous reptiles. However, no data about composition and biological activities of its oral secretion have been reported. In the present study, a proteomic analysis of the mandibular gland of S. crocodilurus and, for comparison, of the herbivorous Solomon Island skink Corucia zebrata, was performed. Scanning electron microscopy (SEM) of the teeth from S. crocodilurus revealed a sharp ridge on the anterior surface, but no grooves, whereas those of C. zebrata possess a flattened crown with a pointed cusp. Proteomic analysis of their gland extracts provided no evidence of venom-derived peptides or proteins, strongly supporting the non-venomous character of these lizards. Data are available via ProteomeXchange with identifier PXD039424.

Association of plasma metabolites and diagnostic imaging findings with hepatic lipidosis in bearded dragons (Pogona vitticeps) and effects of gemfibrozil therapy.

OBJECTIVES: To evaluate the association between plasma metabolites, biochemical analytes, diagnostic imaging findings, and the histologic diagnosis of hepatic lipidosis in bearded dragons. To assess the effects of gemfibrozil therapy on hepatic lipid accumulation and associated diagnostic tests. ANIMALS: Fourteen bearded dragons (Pogona vitticeps) with varying severity of hepatic lipid accumulation (with and without hepatic lipidosis) were included. PROCEDURES: Animals underwent coelomic ultrasound, computed tomography (CT) scans, and coelioscopic hepatic biopsies. Clinical pathology tests included lipidologic tests, hepatic biomarkers, and mass spectrometry-based metabolomics. Animals were medicated with gemfibrozil 6mg/kg orally once a day for 2 months in a randomized blinded clinical trial prior to repeating previous diagnostic testing. RESULTS: Hounsfield units on CT were negatively associated with increased hepatic vacuolation, while ultrasound and gross evaluation of the liver were not reliable. Beta-hydroxybutyric-acid (BHBA) concentrations were significantly associated with hepatic lipidosis. Metabolomics and lipidomics data found BHBA and succinic acid to be potential biomarkers for diagnosing hepatic lipidosis in bearded dragons. Succinic acid concentrations were significantly lower in the gemfibrozil treatment group. There was a tendency for improvement in the biomarkers and reduced hepatic fat in bearded dragons with hepatic lipidosis when treated with gemfibrozil, though the improvement was not statistically significant. CONCLUSIONS: These findings provide information on the antemortem assessment of hepatic lipidosis in bearded dragons and paves the way for further research in diagnosis and treatment of this disease.

Consolidation of temperature-dependent toxicity and thermoregulatory behavior into risk assessments of insecticides under thermal scenarios: A prospective study on Eremias argus.

In this study, the temperature-dependent chemical toxicity of three insecticides and the resulting thermoregulatory (TR) behavior of the lizard Eremias argus have been consolidated into the current risk assessment framework. According to acute dermal toxicity assays, an increase of ambient temperature from 15 °C to 35 °C decreased the acute dermal toxicity of beta-cyfluthrin (BC) but increased the toxicity of chlorpyrifos (CPF). The toxicity of avermectin (AVM) did not show significant temperature-dependent responses. Based on thermal preference trials, lizards changed their body temperature via TR behavior to adaptively reduce toxicity under sub-lethal doses, which can be understood as a "self-rescue" behavior attenuating lethal effects. However, the risk quotient indicated that the effectiveness of this "self-rescue" behavior is limited. Metabolomics analysis showed that six different metabolites (i.e., creatine, glutamate, succinate, N-acetylaspartate, acetylcholine, and lactate) contributed to TR behavior changes. Biochemical assays and insecticide residue results demonstrated that the temperature-dependent toxicity of BC, CPF, and AVM affected lizards in the three aspects of biotransformation, oxidative stress, and neurometabolic interference. This work clarifies the ecotoxicological impacts of representative insecticides on reptiles from toxicological understanding to risk relevance. This knowledge may improve ecological predictions of agrochemical applications in the context of global climate change.

Seabirds subsidize terrestrial food webs and coral reefs in a tropical rat-invaded archipelago.

Allochthonous resource fluxes mediated by organisms crossing ecosystem boundaries may be essential for supporting the structure and function of resource-limited environments, such as tropical islands and surrounding coral reefs. However, invasive species, such as black rats, thrive on tropical islands and disrupt the natural pathways of nutrient subsidies by reducing seabird colonies. Here, we used stable isotopes of nitrogen and carbon to examine the role of seabirds in subsidizing the terrestrial food webs and adjacent coral reefs in the Abrolhos Archipelago, Southwest Atlantic Ocean. By sampling invasive rats and multiple ecosystem compartments (soil, plants, grasshoppers, tarantulas, and lizards) within and outside seabird colonies, we showed that seabird subsidies led to an overall enrichment in 15 N across the food web on islands. However, contrary to other studies, δ15 N values were consistently lower within the seabird colonies, suggesting that a higher seabird presence might produce a localized depletion in 15 N in small islands influenced by seabirds. In contrast, the nitrogen content (%N) in plants and soils was higher inside the colonies, corresponding to a higher effect of seabirds at the base of the trophic web. Among consumers, lizards and invasive rats seemed to obtain allochthonous resources from subsidized terrestrial organisms outside the colony. Inside the colony, however, they showed a more direct consumption of marine matter, suggesting that subsidies benefit these native and invasive animals both directly and indirectly. Nonetheless, in coral reefs, scleractinian corals assimilated seabird-derived nitrogen only around the two smaller and lower-elevation islands, as demonstrated by the substantially higher δ15 N values in relation to the reference areas. This provides evidence that island morphology may influence the incorporation of seabird nutrients in coral reefs around rat-invaded islands, likely because guano lixiviation toward seawater is facilitated in small and low-elevation terrains. Overall, these results showed that seabirds affected small islands across all trophic levels within and outside colonies and that these effects spread outward to coral reefs, evidencing resiliency of seabird subsidies even within a rat-invaded archipelago. Because rats are consumers of seabird chicks and eggs, however, rat eradication could potentially benefit the terrestrial and nearshore ecosystems through increased subsides carried by seabirds.