78 research outputs found
Ophthalmic segment of internal carotid artery aneurysm mimicking normal tension glaucoma.
No full textA 41-year-old caucasian male was referred to the Glaucoma clinic at our tertiary referral centre with a diagnosis of normal tension glaucoma after the finding of increased bilateral asymmetrical cup/disc ratios, with normal intraocular pressures. On examination, the authors confirmed the presence of bilateral reduced optic disc rims alongside a left pale residual rim, and a further discovered a positive dyschromatopsia with a bilateral visual field alteration. The left visual field showed a relative scotoma confined to the vertical midline. After initiating investigation for suspected glaucoma, the authors ordered a magnetic resonance imaging that evidenced an internal carotid aneurysm along the ophthalmic segment, stretching across the optic chiasm with a major involvement of the left optic nerve and partial involvement of the right optic nerve. Aneurysm embolisation was performed with complete resolution of signs and symptoms achieved 5 months post-operatively. Despite glaucoma being the most frequent condition causing optic disc atrophy and visual field loss, it is not the only cause. Any atypical visual field defect not in keeping with a glaucomatous field loss should be further investigated. The ophthalmologist should thoroughly assess all signs that could lead to different diagnosis
Turks and Caicos rock iguana (Cyclura carinata) : conservation and management plan 2020–2024
No full textThe Endangered Turks and Caicos rock iguana, Cyclura carinata, is found only on the islands and cays of Turks and Caicos Islands (TCI), and on Booby Cay in The Bahamas, northwest of Providenciales. These iguanas now occupy less than 10 percent of their historic range largely due to the impact of invasive mammalian predators. Although conservation efforts have led to stabilisation of the population resulting in the 2020 down-listing of this species from Critically Endangered to Endangered on the IUCN Red List of Threatened Species, threats persist and management efforts are needed. This document presents a comprehensive four-year plan for the conservation and management actions considered essential to ensuring the long-term survival of Cyclura carinata in the wild. This document combines knowledge and expertise from local government, local and international NGOs, the tourism industry, educators, homeowners, private island managers, civil society, and members of the IUCN SSC Iguana Specialist Group working in the TCI
Genetic diversity and structure in the Endangered Allen Cays Rock Iguana, Cyclura cychlura inornata
No full textThe Endangered Allen Cays Rock Iguana (Cyclura cychlura inornata) is endemic to the Allen Cays, a tiny cluster of islands in the Bahamas. Naturally occurring populations exist on only two cays (<4 ha each). However, populations of unknown origin were recently discovered on four additional cays. To investigate patterns of genetic variation among these populations, we analyzed nuclear and mitochondrial markers for 268 individuals. Analysis of three mitochondrial gene regions (2,328 bp) and data for eight nuclear microsatellite loci indicated low genetic diversity overall. Estimates of effective population sizes based on multilocus genotypes were also extremely low. Despite low diversity, significant population structuring and variation in genetic diversity measures were detected among cays. Genetic data confirm the source population for an experimentally translocated population while raising concerns regarding other, unauthorized, translocations. Reduced heterozygosity is consistent with a documented historical population decline due to overharvest. This study provides the first range-wide genetic analysis of this subspecies. We suggest strategies to maximize genetic diversity during ongoing recovery including additional translocations to establish assurance populations and additional protective measures for the two remaining natural populations
Sponges as natural environmental DNA samplers
No full textAt a time of unprecedented impacts on marine biodiversity, scientists are rapidly becoming persuaded by the potential of screening large swathes of the oceans through the retrieval, amplification and sequencing of trace DNA fragments left behind by marine organisms; an approach known as ‘environmental DNA’ (eDNA) [1]. In trying to circumvent the many challenges associated with water filtration and DNA isolation from environmental samples, significant investment is being made in high-tech solutions, such as automated underwater vehicles and robots [2]. Here, instead, we explored a simpler, alternative option, based on the recovery of eDNA from sponges (phylum Porifera), the planet’s most effective water-filterers. We obtained sponge samples from Mediterranean and Antarctic surveys, extracted total DNA from their tissues, and obtained tens of thousands of fish DNA reads via metabarcoding, which were able to clearly distinguish samples from the two regions. One Antarctic sample yielded hundreds of reads from chinstrap penguin (Pygoscelis antarcticus) and Weddell seal (Leptonychotes weddellii). We argue that this ‘natural sampler DNA’ (nsDNA) approach is poised to become a powerful, affordable, universal tool for aquatic biodiversity monitoring globally
Inferred vs realized patterns of gene flow: an analysis of population structure in the Andros Island Rock Iguana.
No full textEcological data, the primary source of information on patterns and rates of migration, can be integrated with genetic data to more accurately describe the realized connectivity between geographically isolated demes. In this paper we implement this approach and discuss its implications for managing populations of the endangered Andros Island Rock Iguana, Cyclura cychlura cychlura. This iguana is endemic to Andros, a highly fragmented landmass of large islands and smaller cays. Field observations suggest that geographically isolated demes were panmictic due to high, inferred rates of gene flow. We expand on these observations using 16 polymorphic microsatellites to investigate the genetic structure and rates of gene flow from 188 Andros Iguanas collected across 23 island sites. Bayesian clustering of specimens assigned individuals to three distinct genotypic clusters. An analysis of molecular variance (AMOVA) indicates that allele frequency differences are responsible for a significant portion of the genetic variance across the three defined clusters (Fst = 0.117, p<<0.01). These clusters are associated with larger islands and satellite cays isolated by broad water channels with strong currents. These findings imply that broad water channels present greater obstacles to gene flow than was inferred from field observation alone. Additionally, rates of gene flow were indirectly estimated using BAYESASS 3.0. The proportion of individuals originating from within each identified cluster varied from 94.5 to 98.7%, providing further support for local isolation. Our assessment reveals a major disparity between inferred and realized gene flow. We discuss our results in a conservation perspective for species inhabiting highly fragmented landscapes
Natural population dynamics of rock iguanas in the Bahama Archipelago
No full textUnderstanding whether groups of individuals represent a single panmictic gene pool, or multiple genetically structured populations across a species range should aid in predicting whether specific conservation strategies would be more or less effective for species preservation. Further, contrasting the population structures of multiple coexisting taxa could foster an even deeper understanding of evolutionary divergence among demes and potentially even suggest local adaptation in the form of tight coevolutionary relationships. Finally, the analysis of population dynamics within small and isolated populations could improve our understanding of the relative importance that different evolutionary mechanisms have in predicting population persistence in the wild. Using microsatellite markers I characterized the population genetic structure in the critically endangered Cyclura cychlura cychlura iguanas on Andros Island. I found significant differences between inferred and realized rates of gene flow. This finding demonstrates that evolutionarily independent populations can occur even with high rates of dispersal. In the second and third study I contrasted patterns of genetic variability in Cyclura cychlura cychlura iguanas, ticks in the genus Amblyomma parasitizing these iguanas, and Rickettsia spp., potential pathogens transmitted by these ticks. I determined that genetic differences among Rickettsia samples and Amblyomma samples are highly concordant with genetic divergence among iguana populations. This finding suggests largely vertical dispersal of ticks and their super-parasite, a high specificity of this reptile-tick interaction, and historically low rates of dispersal in iguanas. This finding also indicates that island populations of iguanas may be locally adapted due to tight coevolutionary relationships. Finally, I investigated the mechanisms that eliminate harmful mutations in small isolated and natural populations of the critically endangered Cyclura cychlura cychlura iguanas. Using molecular tools I found indirect evidence suggesting that small natural populations can maintain significant levels of genetic variation in spite of strong selection acting against harmful mutations. Under regimes of random mating, the buildup of harmful mutations in small populations may result in a large number of inviable young. However, harmful mutations may also be eliminated when exposed to natural selection through increased competition, as population density increases. However, quantification of the relative role of competition was not feasible in this study
Microsatellites data set: Correlated population genetic structure in a three-tiered host-parasite system: the potential for coevolution and adaptive divergence
No full textThree subspecies of Northern Bahamian Rock Iguanas, Cyclura cychlura, are currently recognized: C. c. cychlura,restricted to Andros Island, and C. c. figginsi and C. c. inornata, native to the Exuma Island chain. Populations on Andros are genetically distinct from Exuma Island populations, yet genetic divergence among populations in the Exumas is inconsistent with the two currently recognized subspecies from those islands. The potential consequences of this discrepancy might include the recognition of a single subspecies throughout the Exumas rather than two. That inference also ignores evidence that populations of C. cychlura are potentially adaptively divergent. We compared patterns of population relatedness in a three-tiered host-parasite system: C. cychlura iguanas, their ticks (genus Amblyomma, preferentially parasitizing these reptiles), and Rickettsia spp. endosymbionts (within tick ectoparasites). Our results indicate that while C. c. cychlura on Andros is consistently supported as a separate clade, patterns of relatedness among populations of C. c. figginsi and C. c. inornata within the Exuma Island chain are more complex. The distribution of the hosts, different tick species, and Rickettsia spp., supports the evolutionary independence of C. c. inornata. Further, these patterns are also consistent with two independent evolutionarily significant units within C. c. figginsi. Our findings suggest coevolutionary relationships between the reptile hosts, their ectoparasites, and rickettsial organisms, suggesting local adaptation. This work also speaks to the limitations of using neutral molecular markers from a single focal taxon as the sole currency for recognizing evolutionary novelty in populations of endangered species.Data in this set have been produced thorugh sanger sequencing and fragment analysis.
411 Cyclura cychlura iguana individuals have been scored for variability at 21 microsatellites. Since the dataset has been compiled from a variety of sources no all individuals are scored for the same loci. Individuals come from 31 different sites.
The data is organized in a spreasheet formatted for GenAlEx
Hand grab or noose pole? Evaluating the least stressful practice for capture of endangered Turks and Caicos Rock Iguanas Cyclura carinata
No full textAs the analysis of blood metabolites has become more readily accessible thanks to the use of point-of-care analyzers, it is now possible to evaluate stress level of wild animals directly in the field. Lactate is receiving much attention as a good stress level proxy in individuals subjected to capture, manual restraint, and data sampling in the wild, and appropriate protocols to maintain lactate values low should be preferred. In this study we compare how two different capture methodologies, hand grab vs. noose pole, affect the variation of blood lactate values in Cyclura carinata iguanas when captured for sampling. We used blood lactate concentration, measured immediately upon- and 15 min after-capture, as a proxy for stress level. While the primary goal of this work is to determine the least stressful capture methodology to be favored when sampling this and other wild iguanas, we also evaluated additional baseline physiological parameters relevant to the health and disease monitoring for this species. Our results show that while initial lactate values level-out in sampled individuals after 15 min in captivity, regardless of the capture methodology, rock iguanas captured by noose pole showed significantly higher lactate concentration and increased heartbeat rate immediately after capture. While the overall health evaluation determined that all analyzed individuals were in good health, based on our results we recommend that, when possible, hand capture should be preferred over noose pole when sampling wild individuals
Genetic structure of Rhinoceros Rock Iguanas, Cyclura cornuta, in the Dominican Republic, with insights into the impact of captive facilities and the taxonomic status of Cyclura on Mona Island
No full textHispaniola is the second largest island in the Caribbean and harbors an extensive amount of biodiversity. The geologic history and resulting complex topography of the island has led to significant differentiation across various taxonomic groups. Hispaniola is the only Caribbean Island with two species of Rock Iguanas, genusCyclura. Rhinoceros Rock Iguanas (C. cornuta) are wide-ranging across Hispaniola, occurring in isolated pockets, primarily in low elevation xeric areas. To better understand the population structure of this species, we used a combination of mtDNA and nuclear markers to elucidate the genetic variation of wild populations across 13 sampling regions in the Dominican Republic (DR), as well as neighboring Mona Island, home to aCyclurapopulation of uncertain taxonomic status. Further, we evaluate the origin of iguanas in captive facilities throughout the DR. Our data reveal a high degree of genetic diversity across wild populations within the DR and shed light on the taxonomic status of the Mona island population. Further, novel genetic diversity is found in captive facilities, most likely resulting from interbreeding between individuals from genetically distinct populations within the captive facilities. Our results suggest that the captive facilities may pose a threat to wild populations and increased regulation of these facilities is needed
Health assessment of the pink land iguana, Conolophus marthae
No full textThe pink land iguana, Conolophus marthae, is one of four species of iguanas (three terrestrial and one marine) in the Galápagos Islands, and the only one listed as critically endangered by the IUCN. The species can only be found on the north-west slopes of the highest volcano on the island of Isabela and was first described to science in 2009. As part of a population telemetry study, a health assessment was authorized by the Galápagos National Park. Wild adult iguanas were captured on Wolf Volcano in September 2019 and April 2021 to record morphological and physiological parameters including body temperature, heart rate, body measurements, intraocular pressures, tear formation, and infrared iris images. Blood samples were also collected and analyzed. An i-STAT portable blood analyzer was used to obtain values for base excess in the extracellular fluid compartment (BEECF), glucose, hematocrit, hemoglobin, ionized calcium (iCa), partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2), percent oxygen saturation (sO2%), pH, potassium (K), and sodium (Na). Standard laboratory hematology techniques were employed for packed-cell-volume (PCV) determination. When possible, data were compared to previously published and available data for the other Galápagos iguanas. The results reported here provide baseline values that may be useful in detecting changes in health status among pink land iguanas affected by climate change, invasive species, anthropogenic threats, or natural disturbances
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