Search

Abstract Background Understanding the natural microbiome and resistome of wildlife from remote places is necessary to monitor the human footprint on the environment including antimicrobial use (AU). Marine iguanas are endemic species from the Galapagos Islands where they are highly affected by anthropogenic factors that can alter their microbiota as well as their abundance and diversity of antimicrobial-resistant genes (ARGs). Thus, this study aims to apply culture-independent approaches to characterize the marine iguana’s gut metagenomic composition of samples collected from the uninhabited islands Rabida (n = 8) and Fernandina (Cabo Douglas, n = 30; Punta Espinoza, n = 30). Fresh feces from marine iguanas were analyzed through SmartChip RT-PCR, 16S rRNA, and metagenomic next-generation sequencing (mNGS) to identify their microbiome, microbial-metabolic pathways, resistome, mobilome, and virulome. Results The marine iguana’s gut microbiome composition was highly conserved despite differences in ecological niches, where 86% of taxa were shared in the three locations. However, site-specific differences were mainly identified in resistome, mobilome, virulorome, and metabolic pathway composition, highlighting the existence of factors that induce microbial adaptations in each location. Functional gut microbiome analyses revealed its role in the biosynthesis and degradation of vitamins, cofactors, proteinogenic amino acids, carbohydrates, nucleosides and nucleotides, fatty acids, lipids, and other compounds necessary for the marine iguanas. The overall bacterial ARG abundance was relatively low (0.006%); nevertheless, the presence of genes encoding resistance to 22 drug classes was identified in the iguana’s gut metagenome. ARG-carrying contig and co-occurrence network analyses revealed that commensal bacteria are the main hosts of ARGs. Taxa of public health interest such as Salmonella, Vibrio, and Klebsiella also carried multidrug-resistance genes associated with MGEs which can influence the dissemination of ARGs through horizontal gene transfer. Conclusion Marine iguanas depend on the gut microbiome for the biosynthesis and degradation of several compounds through a symbiotic relationship. Niche-specific adaptations were evidenced in the pool of microbial accessory genes (i.e., ARGs, MGEs, and virulence) and metabolic pathways, but not in the microbiome composition. Culture-independent approaches outlined the presence of a diverse resistome composition in the Galapagos marine iguanas from remote islands. The presence of AR pathogens in marine iguanas raises concerns about the dispersion of microbial-resistant threats in pristine areas, highlighting wildlife as sentinel species to identify the impact of AU.

Background: Understanding the natural microbiome and resistome of wildlife from remote places is necessary to monitor the human footprint on the environment including antimicrobial use (AU). Marine iguanas are endemic species from the Galapagos Islands where they are highly affected by anthropogenic factors that can alter their microbiota as well as their abundance and diversity of antimicrobial-resistant genes (ARGs). Thus, this study aims to apply culture-independent approaches to characterize the marine iguana's gut metagenomic composition of samples collected from the uninhabited islands Rabida (n = 8) and Fernandina (Cabo Douglas, n = 30; Punta Espinoza, n = 30). Fresh feces from marine iguanas were analyzed through SmartChip RT-PCR, 16S rRNA, and metagenomic next-generation sequencing (mNGS) to identify their microbiome, microbial-metabolic pathways, resistome, mobilome, and virulome. Results: The marine iguana's gut microbiome composition was highly conserved despite differences in ecological niches, where 86% of taxa were shared in the three locations. However, site-specific differences were mainly identified in resistome, mobilome, virulorome, and metabolic pathway composition, highlighting the existence of factors that induce microbial adaptations in each location. Functional gut microbiome analyses revealed its role in the biosynthesis and degradation of vitamins, cofactors, proteinogenic amino acids, carbohydrates, nucleosides and nucleotides, fatty acids, lipids, and other compounds necessary for the marine iguanas. The overall bacterial ARG abundance was relatively low (0.006%); nevertheless, the presence of genes encoding resistance to 22 drug classes was identified in the iguana's gut metagenome. ARG-carrying contig and co-occurrence network analyses revealed that commensal bacteria are the main hosts of ARGs. Taxa of public health interest such as Salmonella, Vibrio, and Klebsiella also carried multidrug-resistance genes associated with MGEs which can influence the dissemination of ARGs through horizontal gene transfer. Conclusion: Marine iguanas depend on the gut microbiome for the biosynthesis and degradation of several compounds through a symbiotic relationship. Niche-specific adaptations were evidenced in the pool of microbial accessory genes (i.e., ARGs, MGEs, and virulence) and metabolic pathways, but not in the microbiome composition. Culture-independent approaches outlined the presence of a diverse resistome composition in the Galapagos marine iguanas from remote islands. The presence of AR pathogens in marine iguanas raises concerns about the dispersion of microbial-resistant threats in pristine areas, highlighting wildlife as sentinel species to identify the impact of AU. [ABSTRACT FROM AUTHOR]

Marine iguanas (Amblyrhynchus cristaus) are indigenous to the Galápagos Islands, a group of islands in the Pacific Ocean formed by volcanoes. Materials you will need: A computer or device with internet access Students will be involved in cutting-edge research on marine iguanas and their habitat while engaged in Iguanas from Above. Is a citizen science project designed to answer questions about marine iguanas, their population, and their habitat. [Extracted from the article]

The Galápagos marine iguana (Amblyrhynchus cristatus), the world's only extant marine lizard, may have had one of the most unique and challenging transitions to aquatic life. Curiously, previous studies have identified relatively few physiological adaptations in the marine iguana; however, little is known about the extent of morphological specialization and performance trade-offs associated with the marine environment. By examining the morphology and locomotory performance of the marine iguana in comparison to their closely related mainland ancestors, the black spiny-tailed iguana (Ctenosaura similis) and green iguana (Iguana iguana), we found variation reflected specialization to ecological niches. However, variation was more pronounced among subspecies of marine iguana, suggesting that little morphological or performance modification is required for iguanids to successfully invade aquatic environments, thus raising the question why there are so few extant aquatic reptilian lineages. Our findings indicate that specialization for the marine environment likely resulted in a trade-off in sprint speed in a terrestrial environment, which may explain why other lizards have not undergone transitions to the marine environment. Additionally, we found that the magnitude of morphological and performance variation was more pronounced between subspecies of marine iguana than between iguanid species. This illustrates that the form-function relationship is more complex than previously thought and sheds light on the ecomorphological mysteries of the marine iguana. [ABSTRACT FROM AUTHOR]

Three new species of chigger mites are described from two species of iguana endemic to the Galápagos Islands. Odontacarus cruzisp. nov. and Schoengastia galapasp. nov. are found on the marine iguana, Amblyrhynchus cristatus Bell, and Eutrombicula pachytrichiasp. nov. is found on the Santa Fe land iguana, Conolophus pallidus Heller. All these mite species were collected, identified, and named by P.H. Vercammen-Grandjean, but remained undescribed until the present. [ABSTRACT FROM AUTHOR]

The article focuses on Short-eared Owl (Asio flammeus) is a globally occurring species and one of the most widely distributed owl species in the world and the dietary preferences for this species are well known, with small mammals making up a vast majority of prey items throughout its range. Topics include the Short-eared Owls take whatever small mammals are most locally available, and the little difference in prey items taken seasonally or by sex or age of individuals.

Effective conservation of marine megafauna requires a thorough understanding of the ecology, physiology, population dynamics, and health of vulnerable species. Assessing the health of large, mobile marine animals poses particular challenges, in part because the subjects are difficult to capture and restrain, and in part because standard laboratory and diagnostic tools are difficult to apply in a field setting. Radiography is a critically important diagnostic tool used routinely by veterinarians, but it has seldom been possible to image live marine vertebrates in the field. As a first step toward assessing the feasibility of incorporating radiography into studies of vulnerable species in remote locations, we used portable radiographic equipment to acquire the first digital internal images of living marine iguanas, Amblyrhynchus cristatus, an iconic lizard endemic only to the Galápagos Islands of Ecuador. The radiographic machinery was powered by batteries and performed well on a rocky beach environment of an uninhabited island, despite high heat and humidity. The accuracy of radiographic measurements was validated by computing a snout-vent length (SVL) using bone dimensions and comparing this to standard measurements of SVL made externally with a tape measure. These results demonstrate the feasibility of using radiography to study animals in remote sites, a technique that may prove useful for a variety of physiological, ecological, and biomechanical studies in which reliable measurements of skeletal and soft-tissue dimensions must be acquired under challenging field conditions. Refinements are discussed that will help the technology reach its full potential in field studies.

Marine iguanas are among the most highly emblematic taxa of the Galápagos archipelago but have paradoxically received little attention from taxonomists. Amblyrhynchus is currently considered as a monotypic genus with a total of seven subspecies, A. cristatus cristatus, A. c. nanus, A. c. venustissimus, A. c. albemarlensis, A. c. hassi, A. c. mertensi and A. c. sielmanni. Although consensually followed for more than half a century, this classification does not properly reflect the main natural subdivisions inferred by more recent molecular evolutionary studies. We integrate population genetics, phylogenomics and comparative morphology to propose an updated taxonomy reflecting the evolutionary history of this group. We recognize a single species with 11 divergent population clusters at the level of subspecies: A. c. albermarlensis is recognized as a junior synonym of A. c. cristatus, and five new subspecies are described: A. c. godzilla subsp. nov. (San Cristóbal-Punta Pitt), A. c. jeffreysi subsp. nov. (Wolf and Darwin), A. c. hayampi subsp. nov. (Marchena), A. c. trillmichi subsp. nov. (Santa Fé) and A. c. wikelskii subsp. nov. (Santiago). Recognizing the genetically divergent population clusters as subspecies also highlights several of them as management units in need of conservation efforts, such as the two subspecies endemic to San Cristóbal. [ABSTRACT FROM AUTHOR]

Human population and thus anthropogenic disturbance of natural systems are increasing at staggering rates. However, the impact of disturbance on natural systems likely varies with the extent of disturbance. While a considerable amount of research has been conducted on high-impact disturbances (e.g., environmental contamination, urban development), much less is known about the effects of less obtrusive activities such as ecotourism and outdoor recreation. Past research has documented behavioral and hormonal changes to non-consumptive wildlife activities; however, these studies rarely provide direct health and survival consequences, or examine impacts over a gradient of disturbances. In the current study, we quantified endocrine and immune responses and reproductive investment in six Galápagos marine iguana ( Amblyrhynchus cristatus ) populations located across a gradient of human disturbance stemming from the ecotourism industry, including urban development, boat traffic, and ecotourist activities. We regressed fitness-related physiological metrics to the intensity of human disturbance across these populations. As predicted, immunological capabilities decreased and oxidative stress increased with increasing intensity of human disturbance and development. Sexes also differed in their endocrine responses to disturbance intensity, with only males showing elevated baseline corticosterone at sites impacted by tourism. Testosterone and estradiol were both positively related to disturbance intensity. There was also a significant overall negative effect of the presence of human disturbance, but not its intensity, on reproductive investment. These results are the first to demonstrate that measures of physiological performance are sensitive to the intensity, and not merely the presence/absence of human disturbance, and that immunological measures in addition to more traditional methods can serve as important indicators of stress and potentially compromised fitness in natural populations. [ABSTRACT FROM AUTHOR]

Remote island archipelagos offer superb opportunities to study the evolution of community assembly because of their relatively young and simple communities where speciation contributes to the origin and evolution of community structure. There is great potential for common phylogeographic patterns among remote archipelagos that originate through hotspot volcanism, particularly when the islands formed are spatially isolated and linearly arranged. The progression rule is characterized by a phylogeographic concordance between island age and lineage age in a species radiation. Progression is most likely to arise when a species radiation begins on an older island before the emergence of younger islands of a hotspot archipelago. In the simplest form of progression, colonization of younger islands as they emerge and offer appropriate habitat, is coincident with cladogenesis. In this paper, we review recent discoveries of the progression rule on seven hotspot archipelagos. We then discuss advantages that progression offers to the study of community assembly, and insights that community dynamics may offer toward understanding the evolution of progression. We describe results from two compelling cases of progression where the mosaic genome may offer insights into contrasting demographic histories that shed light on mechanisms of speciation and progression on remote archipelagos. [ABSTRACT FROM AUTHOR]

Oceanic islands are often inhabited by endemic species that have undergone substantial morphological evolutionary change due to processes of multiple colonizations from various source populations, dispersal, and local adaptation. Galápagos marine iguanas are an example of an island endemic exhibiting high morphological diversity, including substantial body size variation among populations and sexes, but the causes and magnitude of this variation are not well understood. We obtained morphological measurements from marine iguanas throughout their distribution range. These data were combined with genetic and local environmental data from each population to investigate the effects of evolutionary history and environmental conditions on body size and shape variation and sexual dimorphism. Our results indicate that body size and shape are highly variable among populations. Sea surface temperature and island perimeter, but not evolutionary history as depicted by phylogeographic patterns in this species, explain variation in body size among populations. Conversely, evolutionary history, but not environmental parameters or island size, was found to influence variation in body shape among populations. Finally, in all populations except one, we found strong sexual dimorphism in body size and shape in which males are larger, with higher heads than females, while females have longer heads than males. Differences among populations suggest that plasticity and/or genetic adaptation may shape body size and shape variation in marine iguanas. This study will help target future investigations to address the contribution of plasticity versus genetic adaptation on size and shape variation in marine iguanas. [ABSTRACT FROM AUTHOR]

The authors discuss the critically small population size of the threatened marine iguana species Amblyrhynchus cristatus on San Cristóbal Island in the Galápagos archipelago. Topics covered include the species' genetic effective sizes, indications that the population is undergoing a speciation process, and heterozygosity values. Also mentioned are monitoring and conservation practices and population size estimation methods used.

Traditionally, conservation management focuses efforts on taxonomic units. However, when the taxa used do not reflect biologically meaningful units, such methods should be reconsidered to avoid the loss of irreplaceable biodiversity. The Galápagos marine iguana (Amblyrhynchus cristatus) is listed as Vulnerable on the IUCN Red List of Threatened Species and is facing growing anthropogenic threats. Currently, management is based on a taxonomy which is questionable in the light of recent molecular data. As such, there is a danger that evolutionarily significant populations may be left vulnerable to extirpation. Herein, we apply molecular data to elucidate the population structure of this species across the Galápagos archipelago, and thus advise conservation management in the absence of a revised taxonomy. Applying a wealth of molecular data including 12 microsatellite loci and 1181 bp of the mitochondrial control region in over 1200 individuals, we delineate distinct populations and prioritize their management. Bayesian population structure analysis revealed 10 distinct population clusters, which we propose as management units (MUs). All MUs are significantly differentiated, with one unit on San Cristóbal Island being particularly distinct in terms of both microsatellite loci and mitochondrial data. Based on estimates of the genetic effective population size (Ne), we find the MUs comprised of populations occurring on Floreana, Española, Marchena, and San Cristóbal to be alarmingly small. In consideration of both Ne and anthropogenic threats, we recommend that conservation practitioners focus efforts on Floreana and San Cristóbal islands, and argue that better census size estimates of populations are urgently needed. [ABSTRACT FROM AUTHOR]

In this study, a metagenome-based analysis of the fecal samples from the macrophytic algae-consuming marine iguana (MI; Amblyrhynchus cristatus) and terrestrial biomass-consuming land iguanas (LI; Conolophus spp.) was conducted. Phylogenetic affiliations of the fecal microbiome were more similar between both iguanas than to other mammalian herbivorous hosts. However, functional gene diversities in both MI and LI iguana hosts differed in relation to the diet, where the MI fecal microbiota had a functional diversity that clustered apart from the other terrestrial-biomass consuming reptilian and mammalian hosts. A further examination of the carbohydrate-degrading genes revealed that several of the prevalent glycosyl hydrolases (GH), glycosyl transferases (GT), carbohydrate binding modules (CBM), and carbohydrate esterases (CE) gene classes were conserved among all examined herbivorous hosts, reiterating the important roles these genes play in the breakdown and metabolism of herbivorous diets. Genes encoding some classes of carbohydrate-degrading families, including GH2, GH13, GT2, GT4, CBM50, CBM48, CE4, and CE11, as well as genes associated with sulfur metabolism and dehalogenation, were highly enriched or unique to the MI. In contrast, gene sequences that relate to archaeal methanogenesis were detected only in LI fecal microbiome, and genes coding for GH13, GH66, GT2, GT4, CBM50, CBM13, CE4, and CE8 carbohydrate active enzymes were highly abundant in the LI. Bacterial populations were enriched on various carbohydrates substrates (e.g., glucose, arabinose, xylose). The majority of the enriched bacterial populations belong to genera Clostridium spp. and Enterococcus spp. that likely accounted for the high prevalence of GH13 and GH2, as well as the GT families (e.g., GT2, GT4, GT28, GT35, and GT51) that were ubiquitously present in the fecal microbiota of all herbivorous hosts. [ABSTRACT FROM AUTHOR]

The oldest known specimen of Galapagos marine iguana ( Amblyrhynchus cristatus), now in the University Museum, Oxford, was originally thought to have come from Mexico. A plausible history of its origin with sealers in the Galapagos Islands about 1824 and transportation to and across Mexico is advanced. The naturalists David Douglas and John Scouler, on James (Santiago) Island in January 1825, encountered and attempted unsuccessfully to preserve specimens of the land iguana ( Conolophus subcristatus) but only a Scouler specimen of marine iguana made it back to England, and it has since disappeared. Published and previously unpublished journal entries from the voyage of HMS Blonde, which had shore parties at Albemarle (Isabela) and Narborough (Fernandina) islands in March 1825, establish that the specimens on which the original description of Amblyrhynchus (later Conolophus) subcristatus J. E. Gray, 1831, was based originated in the voyage of the Blonde. Banks Bay, Albemarle Island, is here designated as the type locality for Conolophus subcristatus. Specimens of the marine iguana were also brought back by the Blonde. The published accounts of Scouler and the voyage of the Blonde established the Galapagos as the true home of the marine iguana well before the return of Charles Darwin and HMS Beagle in 1836. [ABSTRACT FROM AUTHOR]

Amblyrhynchus cristatus, the marine iguana, is unique among the ~7,000 species of living limbed lizards as it has successfully evolved adaptations that allow it to live in both terrestrial and marine environments. This species is endemic to the Galápagos Archipelago and has evolved a specialized feeding behavior, consuming primarily the algae that grow on the rocky seafloor. The intriguing questions arising around the evolution of the marine iguana concerns the use of exaptations of terrestrial features for aquatic and specifically marine adaptations. However, the lack of fundamental information about its anatomy currently prevents us from understanding how it became adapted to such a peculiar lifestyle in comparison to all other iguanids. The goal of this study is to provide the first ever description of the skull, mandible, and hyoid of Amblyrhynchus. We examined several specimens of marine iguana, including skeletal, wet, and ct-scanned material, and individuals at different ontogenetic stages. We also analyzed specimens of all other modern iguanid genera (Conolophus, Iguana, Ctenosaura, Cyclura, Dipsosaurus, Brachylophus, Sauromalus) in order to make comparisons between Amblyrhynchus and its closest relatives. We were able to identify several autapomorphic features that distinguish the marine iguana from all other iguanids. These unique morphologies are mostly associated with the modified configuration of the snout (nasal chamber), increased muscle attachments in the temporal-postorbital region of the skull, and dentition. Since Amblyrhynchus is the only nonophidian squamate currently able to exploit the ocean at least for some vital functions (i.e., feeding), we used comparisons to fossil marine lizards (e.g., mosasaurids) to discuss some of these unique traits. The new cranial features described for Amblyrhynchus may represent a source of novel morphological characters for use in future phylogenetic analyses of iguanian (or squamate) relationships, which will then serve as the foundation for the exploration of evolutionary patterns and processes that led to the development of such unique adaptations., (© 2021 American Association for Anatomy.)

We describe the development and characterisation of six new dinucleotide motif microsatellite loci for populations of marine iguanas (Amblyrhynchus cristatus), endemic to the Galápagos archipelago. Primers were based on microsatellite-bearing sequences and initially developed using universally labelled primers. When analysed across 5 populations (repre-senting 150 individuals), new loci displayed, on average, high levels of genetic diversity (range: 2-13 alleles, mean: 5.73) and values of heterozygosity (range: 0.0-0.906, mean: 0.605). No consistent deviations from Hardy-Weinberg equilibrium or significant linkage disequilibrium were observed, and all loci were shown to be free of common microsatellite errors. Utilising the 13 previously available microsatellite loci for this species, we describe here four multiplex combinations for the successful amplification of 19 microsatellite loci for marine iguanas. This powerful set of highly polymorphic markers will allow researchers to explore future questions regarding the ecology, evolution, and conservation of this unique species [ABSTRACT FROM AUTHOR]

The skeletal adaptations of Amblyrhynchus cristatus (Marine Iguanas) are of particular interest based on their amphibious lifestyle, which is unique among living lacertilian squamates. The well-known ecological data are applied to new bone histological findings, which revealed expected and unexpected congruencies. The cortical bone matrix consists of avascular lamellar-zonal bone tissue type. The geometrical disposition of the growth marks (i.e., their spacing) shows an unusual pattern for lizards: the growth cycles maintain a constant thickness until the growth is terminated, which is marked by the development of the external fundamental system (efs). Minor resorption processes within the inner periosteal cortical region and the occurrence of these thick growth cycles in A. cristatus result in high mean bone compactness values. The reported life-history data from ecological studies and the hypothesized annuality of the growth cycles indicate that this first decline in annual bone deposition rate is not congruent with the attainment of sexual maturity. In contrast, this event might be indicated by other histological changes in the growth record of A. cristatus, which they share exclusively with their sister group, Conolophus subcristatus (Land Iguana). The bone matrix of the growth zones and annuli differ in their thickness, their color in polarized light, and vary slightly in the amount and shape of osteocyte lacunae in both A. cristatus and C. subcristatus. These well-recognizable growth zones and annuli of the growth cycles change their thickness abruptly within the reported time frame of the attainment of sexual maturity in A. cristatus. [ABSTRACT FROM AUTHOR]

It is thought that dispersal limitation primarily structures host-associated bacterial populations because host distributions inherently limit transmission opportunities. However, enteric bacteria may disperse great distances during food-borne outbreaks. It is unclear if such rapid long-distance dispersal events happen regularly in natural systems or if these events represent an anthropogenic exception. We characterized Salmonella enterica isolates from the feces of free-living Galápagos land and marine iguanas from five sites on four islands using serotyping and genomic fingerprinting. Each site hosted unique and nearly exclusive serovar assemblages. Genomic fingerprint analysis offered a more complex model of S. enterica biogeography, with evidence of both unique strain pools and of spatial population structuring along a geographic gradient. These findings suggest that even relatively generalist enteric bacteria may be strongly dispersal limited in a natural system with strong barriers, such as oceanic divides. Yet, these differing results seen on two typing methods also suggests that genomic variation is less dispersal limited, allowing for different ecological processes to shape biogeographical patterns of the core and flexible portions of this bacterial species' genome. [ABSTRACT FROM AUTHOR]

The article offers information on marine reptiles. It states that reptiles are the most diverse terrestrial vertebrates with about 12,000 described forms, including about 9,350 currently recognized species and about 3,000 subspecies. It mentions that Among them are seven species of sea turtles and about 80 species and subspecies of sea snakes, as well as a few other species that are occasionally or regularly found in brackish waters, including various other snakes, the saltwater crocodile, and the marine iguana of the Galapagos Islands. The largest group of marine reptiles, the sea snakes, occur in the tropical and subtropical waters of the Indian and Pacific Oceans from the east coast of Africa to the Gulf of Panama.

Herbivorous reptiles depend on complex gut microbial communities to effectively degrade dietary polysaccharides. The composition of these fermentative communities may vary based on dietary differences. To explore the role of diet in shaping gut microbial communities, we evaluated the fecal samples from two related host species-the algae-consuming marine iguana (Amblyrhynchus cristatus) and land iguanas (LI) (genus Conolophus) that consume terrestrial vegetation. Marine and LI fecal samples were collected from different islands in the Galápagos archipelago. High-throughput 16S rRNA-based pyrosequencing was used to provide a comparative analysis of fecal microbial diversity. At the phylum level, the fecal microbial community in iguanas was predominated by Firmicutes (69.5±7.9%) and Bacteroidetes (6.2±2.8%), as well as unclassified Bacteria (20.6±8.6%), suggesting that a large portion of iguana fecal microbiota is novel and could be involved in currently unknown functions. Host species differed in the abundance of specific bacterial groups. Bacteroides spp., Lachnospiraceae and Clostridiaceae were significantly more abundant in the marine iguanas (MI) (P-value>1E−9). In contrast, Ruminococcaceae were present at >5-fold higher abundance in the LI than MI (P-value>6E−14). Archaea were only detected in the LI. The number of operational taxonomic units (OTUs) in the LI (356-896 OTUs) was >2-fold higher than in the MI (112-567 OTUs), and this increase in OTU diversity could be related to the complexity of the resident bacterial population and their gene repertoire required to breakdown the recalcitrant polysaccharides prevalent in terrestrial plants. Our findings suggest that dietary differences contribute to gut microbial community differentiation in herbivorous lizards. Most importantly, this study provides a better understanding of the microbial diversity in the iguana gut; therefore facilitating future efforts to discover novel bacterial-associated enzymes that can effectively breakdown a wide variety of complex polysaccharides. [ABSTRACT FROM AUTHOR]

Abstract: Anthropogenic disturbance is a relevant and widespread facilitator of environmental change and there is clear evidence that it impacts natural populations. While population-level responses to major anthropogenic changes have been well studied, individual physiological responses to mild disturbance can be equally critical to the long-term survival of a species, yet they remain largely unexamined. The current study investigated the impact of seemingly low-level anthropogenic disturbance (ecotourism) on stress responsiveness and specific fitness-related immune measures in different breeding stages of the marine iguana (Amblyrhynchus cristatus). Specifically, we found stress-induced elevations in plasma corticosterone among tourist-exposed populations relative to undisturbed populations. We also found changes in multiple immunological responses associated with stress-related effects of human disturbance, including bacterial killing ability, cutaneous wound healing, and hemolytic complement activity, and the responses varied according to reproductive state. By identifying health-related consequences of human disturbance, this study provides critical insight into the conservation of a well-known species that has a very distinct ecology. The study also broadens the foundation of knowledge needed to understand the global significance of various levels of human disturbance. [Copyright &y& Elsevier]

Abstract: Island tameness is a widely documented phenomenon in which island species, particularly those that have evolved with no or few natural predators, show a greatly reduced behavioral response when faced with unfamiliar predators. This insufficient anti-predator response has led to widespread population declines among many island species exposed to novel predators, and has become a serious conservation problem. Despite its prevalence, the underlying physiology of island tameness is not known. Here we report that although Galápagos marine iguanas (Amblyrhynchus cristatus) initiated flight from an evolutionarily recent and unfamiliar potential predator (humans), they failed to show the cardiovascular stress response that facilitates successful escape, even after a prior capture experience. In contrast, when approached by a native predator (the Galápagos hawk; Buteo galapagoensis), marine iguanas show markedly increased heart rate independent of initiating escape movement. The secretion of catecholamines appears to be central to the initiation of escape behavior: naïve animals remotely injected with epinephrine immediately increased flight initiation distance, whereas those injected with corticosterone did not. Our results provide the first evidence that muted escape behavior in predator-naïve species is indicative of both a cognitive deficit in recognizing potential predators and a catecholamine deficit in response. Understanding how the response to predators differs in predator-naïve species could enable the design of maximally effective techniques for inducing an anti-predator response in these vulnerable species. [Copyright &y& Elsevier]

Summary The presence of Vibrio isolates was investigated in cloacal swabs from the Galápagos marine iguana ( Amblyrhyncus cristatus). Such unique iguana is endemic to the Galápagos Archipelago, it is listed as vulnerable in the IUCN Red List (2009), and is strictly protected by CITES and Ecuador laws. Our results revealed an uneven isolation frequency of vibrios from animals living in different settings: maximal among the Santa Fe population, scarce at Bahía Tortuga but practically absent in the samples from Puerto Ayora and Plaza Sur. A 16S sequencing confirmed that the isolates belonged to the genus Vibrio, placing them within the V. alginolyticus group; the biochemical identification was, indeed, consistent with V. alginolyticus features. The reason of the observed discrepancy is not clear, but could be either linked to a higher pollution in the inhabited or more touristic places or to differential influence of chemical and physical parameters at a local scale. As V. alginolyticus is an opportunistic pathogen for man and it is known to cause disease in sea-living animals, the ability of these vibrios to enter and persist to a certain extent in the marine iguana gut should be regarded as a risk for health of both the animals and the human personnel involved in monitoring activities. [ABSTRACT FROM AUTHOR]

Abstract: It is unusual for seasonal breeders to frequently skip opportunities for reproduction. We investigated the relationship between physiological state and reproductive decision-making in Galápagos marine iguanas (Amblyrhynchus cristatus), a species in which females typically reproduce biennially, although the proportion of breeding individuals varies significantly across years. Nearly all adult-sized females initiated follicular development prior to the lekking period, but 38% of females resorbed all developing follicles 5–15 days before the start of copulations. Receptive and non-receptive females differed in reproductive hormones during the mate choice period. Testosterone peaked in receptive females immediately prior to copulation, indicating that testosterone or its derivative estradiol likely mediates female receptivity in Galápagos marine iguanas. Non-receptive females showed significant peaks in both testosterone and progesterone during follicular atresia, suggesting that these hormones may be involved in inhibiting vitellogenesis. Two to three weeks prior to the period of reproductive decision-making (and the onset of follicular atresia in non-receptive females) receptive females were in higher body condition, were developing larger follicles, and had lower levels of both baseline and stress-induced corticosterone. Reproduction is extremely costly in this long-lived species, and increases the likelihood of mortality in the year following breeding; females could therefore gain significant benefits from being attuned to indicators of reproductive success. We suggest that corticosterone may modulate reproductive decisions by altering individual sensitivity to both internal and external cues of the likelihood of successful reproduction. [Copyright &y& Elsevier]

Changes in mate selectivity can significantly alter the direction and strength of sexual selection. When the direct cost of mate search increases selectivity often declines; however, little is known about how the relative cost of mate search affects investment in mate choice. Here, I investigate whether male and female Galápagos marine iguanas ( Amblyrhynchus cristatus) alter their investment in mate choice behaviors when resources are limited and the relative cost of mate search is increased. Moderate resource limitation had little effect on male reproductive behavior: in both years, a similar number of males were territorial, and the mean display rate and copulation success of territorial males did not differ. In contrast, female mate search appeared to be affected by the prevailing environmental conditions. During the reproductive season following a moderate El Niño event, when food availability declined, females were in poorer body condition, assessed fewer territorial males, and mated with a male with lower relative reproductive success. Circulating hormone levels also differed between years: when resource availability was limited, receptive females had higher levels of testosterone and stress-induced corticosterone. The frequency and magnitude of climatic fluctuations are expected to increase in the future across many regions of the globe. Determining how sexual selection is shaped by changes in resource availability is vital for predicting the impact of climate change. [ABSTRACT FROM AUTHOR]

Squamates are a diverse order of vertebrates, representing more than 7,000 species. Yet, descriptions of full-length major histocompatibility complex (MHC) genes in this group are nearly absent from the literature, while the number of MHC studies continues to rise in other vertebrate taxa. The lack of basic information about MHC organization in squamates inhibits investigation into the relationship between MHC polymorphism and disease, and leaves a large taxonomic gap in our understanding of amniote MHC evolution. Here, we use both cDNA and genomic sequence data to characterize a class I MHC gene (Amcr-UA) from the Galápagos marine iguana, a member of the squamate subfamily Iguaninae. Amcr-UA appears to be functional since it is expressed in the blood and contains many of the conserved peptide-binding residues that are found in classical class I genes of other vertebrates. In addition, comparison of Amcr-UA to homologous sequences from other iguanine species shows that the antigen-binding portion of this gene is under purifying selection, rather than balancing selection, and therefore may have a conserved function. A striking feature of Amcr-UA is that both the cDNA and genomic sequences lack the transmembrane and cytoplasmic domains that are necessary to anchor the class I receptor molecule into the cell membrane, suggesting that the product of this gene is secreted and consequently not involved in classical class I antigen-presentation. The truncated and conserved character of Amcr-UA lead us to define it as a nonclassical gene that is related to the few available squamate class I sequences. However, phylogenetic analysis placed Amcr-UA in a basal position relative to other published classical MHC genes from squamates, suggesting that this gene diverged near the beginning of squamate diversification. [ABSTRACT FROM AUTHOR]

Abstract: Polygynous lek-mating systems are characterized by high reproductive skew, with a small number of males gaining a disproportionate share of copulations. In lekking species, where female choice drives male mating success and patterns of reproductive skew, female preferences for ‘good genes’ should lead to preferred males having high reproductive success in all years. Here we investigate whether these ‘hotshot’ males have steroid hormone patterns that are consistent over time (between two mating seasons), and whether hormone levels consistently predict display behavior. We test these questions in the Galápagos marine iguana (Amblyrhynchus cristatus), a lekking vertebrate with high male reproductive skew. We found that male mating success and testosterone levels were not consistent across years. The most successful males showed an inverse relationship in copulation success between years. Similarly, territorial males that had high testosterone in one year had low levels in the next. Across years, testosterone was strongly associated with head-bob display, suggesting that this steroid plays a key role in mate attraction. These results suggest that female marine iguanas are not choosing the same ‘hotshot’ males in every year, but instead base their reproductive decisions on male behavioral traits that are hormonally mediated and variable across years. By using testosterone to regulate their costly display behaviors male marine iguanas appear to have a mechanism that allows them to adjust their reproductive effort depending on extrinsic and/or intrinsic factors. [Copyright &y& Elsevier]

Abstract: The Galápagos marine iguana, Amblyrhynchus cristatus, is unique among lizards in foraging subtidally, leading to activity across a broad range of ambient temperatures (∼14–40 °C). To determine whether the marine iguana shows any biochemical changes consistent with maintaining enzyme function at both warm and cold body temperatures, we examined the function of the aerobic enzyme citrate synthase (CS) and the muscle isoform of the anaerobic enzyme lactate dehydrogenase (A4-LDH) in A. cristatus and a confamilial species, Iguana iguana, from 14 to 46 °C. We also deduced amino acid sequences from cDNA of each enzyme. In CS, despite two amino acid substitutions, we found no difference in the apparent Michaelis–Menten constant K m of oxaloacetate at any temperature, indicating that the substrate affinity of CS in A. cristatus has not adapted to changes in thermal environment. In A4-LDH, we used site-directed mutagenesis to show that the substitutions T9A and I283V (A. cristatus → I. iguana) individually have no effect on kinetics, but together significantly decrease the K m of pyruvate and catalytic rate constant (k cat) of the A. cristatus ortholog. Thus, our data show that A. cristatus A4-LDH has not become cold adapted in response to this species'' aquatic foraging behavior, and instead may be consistent with moderate warm adaptation with respect to the I. iguana ortholog. [Copyright &y& Elsevier]