North-central Venezuela Research Articles

Atlantic ITCZ variability during the Holocene based on high-resolution speleothem isotope records from northern Venezuela

Few high-resolution paleoclimate proxy records exist in the region located under the direct influence of the Intertropical Convergence Zone (ITCZ) in South America and most of them were retrieved from the Cariaco Basin off the coast of Venezuela. Here we present new ẟ18O and ẟ13C records of Venezuelan speleothems collected in caves adjacent to Cariaco, covering the mid- and late-Holocene. We document previously undetected secular-to multidecadal-scale climate variability in the core region of the ITCZ, which is compared to other high-resolution records from the North Atlantic, Caribbean and tropical South America. Over the mid-Holocene our record exhibits broad swings between periods of reduced (8.3–8.0, 6.5–5.0, 4.1–3.6 ka BP) and increased (8.5, 8.0–6.5, 4.9–4.2 ka BP) rainfall. In particular, between 5.5 and 5.0 ka BP, increases in polar and subpolar North Atlantic ice rafted debris and a reduction in North Atlantic Deep Water (NADW) formation might have contributed to the southward displacement of the North Atlantic Subtropical High (NASH) and the ITCZ, which led to severe dry conditions in north central Venezuela and an enhancement of the South American Monsoon System (SAMS). During the late-Holocene, contrary to data from Cariaco reported in previous studies, our results point to drier conditions during the Medieval Climate Anomaly (MCA, 900–1100 CE), which were further amplified during positive Atlantic Multidecadal Oscillation (AMO) phases. Wet conditions, however, prevailed during the first part of the Little Ice Age (LIA, 1400–1500 CE). No speleothem deposition occurred during the main LIA period, which might be related to drier conditions in response to a southward displacement of the ITCZ that led to major moisture convergence over the SASM domain. Our new records from Venezuela provide a reliable proxy for ITCZ behavior over the Atlantic – South America domain and document past dynamics in relation to other climate systems (NASH and SAMS), while providing new evidence of ITCZ – North Atlantic teleconnections during the Holocene.

Insights into equine piroplasmosis in Venezuelan sport horses: Molecular diagnosis, clinical, and cardiovascular findings.

Equine piroplasmosis (EP) is a tick-borne infectious disease highly prevalent in tropical and subtropical regions, such as Venezuela. EP affects wild and domestic equids leading to several clinical presentations, from asymptomatic to severely affected animals. In this study, thirty-three (33) sport horses under regular training activities and from endemic regions of north-central Venezuela were submitted to an observational survey, case-control, to describe the presence of clinical signs and natural EP infections. A conventional PCR assay targeting the SSU rRNA gene revealed EP etiologic agents in 13 out of 33 sampled horses (~ 39.4% infections). Nine (9) of these EP-positive samples were confirmed as infected with Babesia caballi (6/9=66.7%) or Theileria equi (3/9=33.3%) by DNA sequencing and BLASTN analyses. A phylogeny of SSU rRNA gene sequences revealed that these new B. caballi and T. equi sequences clustered within the worldwide distributed phylogenetic genotype A, respectively. No acute EP cases were observed in this study; however, six (6) PCR-positive animals displayed mild clinical signs compatible with EP, including a mild leukocytosis (P<0.05). The heart rate variability frequency domain analysis in four (4) of these EP-positive infected animals revealed a significant (P<0.05) higher low-frequency/high-frequency ratio suggesting a sympathovagal imbalance in these chronically infected animals. Other clinical and cardiovascular parameters were similar between the different groups. Sport horses are routinely submitted to intense training programs and sport-related activities that could lead to loss of the host-parasite equilibrium that characterizes enzootic regions, increasing the likelihood of infection reactivation and the risk of transmission. Heart rate variability analysis contributes to evaluate the sympathovagal balance and detecting homeostasis disturbances in sport horses. Molecular diagnostic tests for EP based on the detection of parasite DNA in equine blood samples should be included in the health programs of sport horses in endemic areas.

Biomass and instar estimation of larvae of Phylloicus cressae Prather, 2003 (Trichoptera, Calamoceratidae) in a montane forest stream, northcentral Venezuela

Biological and ecological aspects of organisms are important to understand the role of species in aquatic ecosystems. Measuring growth rate is useful to analyse these aspects through the estimation of instar and biomass in aquatic insects like shredder trichopterans. We aimed to produce allometric relationships based on larval body parts and case dimensions to estimate larval instars and biomass for Phylloicus cressae Prather, 2003. Here, we showed that classification tree analysis and power and exponential models proved that dorsal and ventral length of cases were good predictors of larval instars and biomass for P. cressae. We also found that allometric relationships involving the length of the prothoracic mid-dorsal ecdysial suture were suited for assessing larval instars but performing these measurements on cased trichopterans is difficult without damaging them. So, allometric models like ours, based on case dimensions, are invaluable when dealing with live individuals.

Petrogenesis of the chromitite body from the Cerro Colorado ophiolite, Paraguaná Peninsula, Venezuela

Ultramafic-mafic rocks of ophiolitic affinity crop out along the Venezuelan Caribbean region. They have been interpreted as remnants of the oceanic lithosphere of the Caribbean volcanic arc (135-70 Ma) as well as relicts of proto-Caribbean oceanic lithosphere (Upper Jurassic-Lower Cretaceous) related to Pangea’s break-up. The Cerro Colorado ophiolite, located in the Paraguaná Peninsula, together with the case of the Cordillera de la Costa in north-central Venezuela, are a unique case of these Venezuelan ophiolites containing chromitite bodies. However, the petrogenesis of such a mafic-ultramafic complex and associated chromite ore remains are unknown to date. To advance our understanding of chromite ores in the Caribbean region, the genesis of the Cerro Colorado chromitite body is challenged. The Cerro Colorado chromitite body is characterized by a low-Cr content [Cr# =Cr/ Cr+Al= 0.44-0.60] and a distribution of trace elements in chromite as is typical of high-Al chromitites found in the shallower portions of the petrological Moho Transition Zone of Mesozoic ophiolites. The calculated melts in equilibrium with chromite forming this high-Al chromitite body are back-arc basin basalts. These melts were extracted after ~20 % partial melting of moderately depleted peridotites, which resulted in the precipitation of high-Al chromitite relatively impoverished in PGE (≤ 100 ppb total PGE). A comparison of the geochemical signatures of minor and trace elements in chromite and bulk-PGE contents of the Cerro Colorado chromitite with those of other known chromitites in the peri-Caribbean ophiolites show certain similitude with those high-Al described in the Moa-Baracoa ophiolite in eastern Cuba. The obtained results allow us to suggest that the ultramafic rocks of the Cerro Colorado and the chromitite body associated with it are closely related to the formation of a back-arc basin developed between ca. 125-120 Ma in the rear of the Great Antilles Arc.

History of the indigenous peoples of the sixteenth-century province of Caracas, Venezuela

Indigenous peoples forged their lives in present-day north-central Venezuela across millennia until confronted by Spanish conquerors in the early sixteenth century. Some historical trajectories wer...

Deep Neural Networks for Earthquake Detection and Source Region Estimation in North-Central Venezuela

ABSTRACTReliable earthquake detection algorithms are necessary to properly analyze and catalog the continuously growing seismic records. We report the results of applying a deep convolutional neural network, called UPC-UCV (Universitat Politecnica de Catalunya - Universidad Central de Venezuela), over single-station three-channel signal windows for P-wave earthquake detection and source region estimation in north-central Venezuela. The analysis is performed on a new dataset of handpicked arrivals of P waves from local events, named CARABOBO, built and made public for reproducibility and benchmarking purposes. The CARABOBO dataset consists of three-channel continuous data recorded by the broadband stations of the Venezuelan Foundation for Seismological Research in the region of 9.5°–11.5°N and 67.0°–69.0°W during the time period from April 2018 to April 2019. During this period, 949 earthquakes were recorded in that area, corresponding to earthquakes with magnitudes in the range from Mw 1.1 to 5.2. To estimate the epicentral source region of a detected event, the proposed network employs geographical distribution of the CARABOBO dataset into K clusters as a basis. This geographical partitioning is automatically performed by the k-means algorithm, and the optimality of the K-values for our dataset has been assessed using the elbow (K=5) and silhouette (K=3) methods. For target seismicity, the proposed network achieves 95.27% detection accuracy and 93.36% source region estimation accuracy, when using K=5 geographic clusters. The location accuracy slightly increases to 95.68% in the case of K=3 geographic partitions. The detection capability of this network has also been tested on the OKLAHOMA dataset, which compiles more than 2000 local earthquakes that occurred in this U.S. state. Without any modification, the proposed network yields excellent detection results when trained and evaluated on that dataset (98.21% accuracy; ConvNetQuake, fine-tuned for this dataset, achieves a 97.32% accuracy), corresponding to a totally different geographical region.

Description of larva and pupa of Phylloicus cressae Prather 2003 (Trichoptera: Calamoceratidae) from a montane forest stream in the peri-urban area of Caracas, Venezuela.

Phylloicus is the most species-rich genus of the Neotropical Calamoceratidae. In Venezuela, twelve species are known from the adult stage and, from those, only one has its larval and pupal stages described. Here, we describe and illustrate the larva, pupa, and case of Phylloicus cressae, from a first order stream of the heavily disturbed Tuy River watershed in the peri-urban area of Caracas, northcentral Venezuela.

Vibrant pasts in museum drawers: Advances in the study of late precolonial (AD 800–1500) materials collected from north-central Venezuela

ABSTRACTStarting in the second half of the nineteenth century, museums and private collectors across the Americas and Europe began amassing objects produced by the indigenous peoples of north-central Venezuela before the European conquest. The rich imagery displayed on decorated pottery and figurines, as well as on skilfully made body ornaments, strongly appealed to the aesthetic tastes of the museum curators and visitors of that time. With some laudable exceptions, most of the excavations that expanded these collections did not follow the archaeological practice standards of our time and did not leave behind any written reports. In consequence, these objects and associated data have remained disconnected from subsequent advances in regional archaeology. In this paper, we provide a general overview of the diverse archaeological collections from the region under study and insert them, critically, into the current understanding of north-central Venezuelan archaeology. We go on to focus on body adornments in order to show how microwear analysis of their production, along with the use wear traces they exhibit, combined with data concerning raw material procurement and depositional contexts, can shed light on the intricacies of the social life of these objects. We argue that up-to-date knowledge of regional archaeology interwoven with new interdisciplinary approaches on museum collections enables researchers to resuscitate the vibrant indigenous pasts lying in museum drawers.

Re-thinking the Migration of Cariban-Speakers from the Middle Orinoco River to North-Central Venezuela (AD 800)

Moving back in time from the early colonial to the late pre-colonial period we evaluate the hypothesis asserting the migratory movement of Cariban-speaking groups from the Middle Orinoco River area towards north-central Venezuela. The explanation in vogue maintains that the migration followed fluvial routes and occurred between 1350 and 1150 BP (AD 600–800). We examine archaeological, linguistic, ethnohistorical, genetic, and ecological data seeking similarities between the Orinoco emigrants and their north-central Venezuelan descendants. As a result, we propose an alternative terrestrial/fluvial route and suggest these events occurred between 1150 and 1050 BP (AD 800–900). The route first proceeded upstream along rivers of the central llanos and later followed a natural terrestrial geomorphological corridor into the Lake Valencia Basin. We argue that, while future interdisciplinary (especially archaeo-linguistic and bioarchaeological) research is needed to further assess the results of these analyses, the Orinocan descendants in north-central Venezuela emerge as one of the most dynamic sociopolitical Cariban-speaking entities in all northeastern South America and the insular Caribbean on the eve of the European Conquest.

Challenges for microwear analysis of figurative shell ornaments from pre-Colonial Venezuela

Figurative ornaments displaying biomorphic and geometric designs have often been recovered from pre-Colonial sites in the Caribbean and northern South America. Such artefacts are held in museum and private collections, but often have not been the focus of systematic research. On the other hand, recent research into ornaments worldwide has focused on simple beads and automorphic shell ornaments. In this article, microwear analysis is used to assess technologies of production and use-wear of figurative shell ornaments from north-central Venezuela. It is our goal to reflect on the challenges posed by such collections, in terms of reproducibility of traces through experiments, post-depositional and curatorial modifications, and the complexity of past attachment configurations. The underlying question is how to deal with the limitations posed by the very nature of the studied collection in terms of preservation and of the high skill required in the reproduction of figurative artefacts.

Digital modelling of landscape and soil in a mountainous region: A neuro-fuzzy approach

Research on genetic relationships between soil and landforms has largely improved soil mapping. Recent technological advances have created innovative methods for modelling the spatial soil variation from digital elevation models (DEMs) and remote sensors. This generates new opportunities for the application of geomorphology to soil mapping. This study applied a method based on artificial neural networks and fuzzy clustering to recognize digital classes of land surfaces in a mountainous area in north-central Venezuela. The spatial variation of the fuzzy memberships exposed the areas where each class predominates, while the class centres helped to recognize the topographic attributes and vegetation cover of each class. The obtained classes of terrain revealed the structure of the land surface, which showed regional differences in climate, vegetation, and topography and landscape stability. The land-surface classes were subdivided on the basis of the geological substratum to produce landscape classes that additionally considered the influence of soil parent material. These classes were used as a framework for soil sampling. A redundancy analysis confirmed that changes of landscape classes explained the variation in soil properties (p=0.01), and a Kruskal–Wallis test showed significant differences (p=0.01) in clay, hydraulic conductivity, soil organic carbon, base saturation, and exchangeable Ca and Mg between classes. Thus, the produced landscape classes correspond to three-dimensional bodies that differ in soil conditions. Some changes of land-surface classes coincide with abrupt boundaries in the landscape, such as ridges and thalwegs. However, as the model is continuous, it disclosed the remaining variation between those boundaries.

The 1900 Mw 7.6 earthquake offshore north–central Venezuela: Is La Tortuga or San Sebastián the source fault?

A new high resolution shallow marine seismic survey provides further insights on the fault source of the October 29th, 1900 earthquake, which affected a large region of North–central Venezuela, both offshore islands and mainland. This Mw 7.6 to 7.7 seismic event has been indistinctly ascribed to either the La Tortuga or San Sebastián fault, which has installed a live debate among different authors. These two faults allegedly run roughly east–west offshore, along the Coastal range. The San Sebastián fault (SSF) bounds this range to the north, being responsible for its linearity and the steep slope of its northern flank, whereas the La Tortuga fault (LTF) would do about the same, but some 20–30 km farther north, based on acoustic surveys carried out in the late 70's and early 80's. We herein bring strong evidence to support that the SSF is the source fault of this major offshore earthquake, mainly based on the freshness of its submarine scarp and recent fault throw, preserved at the Chuspa bay (close to Cabo Codera, eastern end of the Coastal range in central Venezuela), as depicted by one of the profiles. In addition, it is shown that most of the previous extent ascribed to LTF is not so. The LTF, besides exhibiting mainly normal slip, is much shorter than originally proposed. This precludes that LTF may have the seismic potential for an earthquake as big as the 1900 event. Finally, available reflection seismic data reveal the existence of a major fault system bounding the La Guaira shelf on the north, which exhibits tectonic inversion of pre existing extensional faults, shortening and strong syn-tectonic deformation during the Plio-Quaternary deposition. Sedimentation in the Bonaire basin during the Plio-Quaternary time is strongly controlled by this system activity.

Household social determinants of ascariasis and trichuriasis in North Central Venezuela

Ascariasis and trichuriasis are highly prevalent parasitoses in tropical countries caused by Ascaris lumbricoides and Trichuris trichiura, respectively. Their prevalence is associated with poor sanitation and hygiene, among other biological and social factors. In this study, the associations of household social determinants with these soil-transmitted helminthiases in North Central Venezuela was assessed in the context of a National Study on Human Growth and Development (SENACREDH). This was a probabilistic, stratified, cross-sectional survey with a sample of 3388 individuals that weighted represents 4 675 433 inhabitants from the region. The prevalence of ascariasis and trichuriasis was 3.73% and 1.13%, respectively. In the univariate and multivariate analyses, these prevalences were significantly higher in those living in vulnerable houses [adjusted OR (AOR) = 1.479, 95% CI 1.428-1.532; and AOR = 10.519, 95% CI 9.971-11.097, respectively], houses located in rural areas (AOR = 2.067, 95% CI 2.035-2.101; and AOR = 1.918, 95% CI 1.868-1.970, respectively) and houses with a soil floor (AOR = 5.027, 95% CI 4.895-5.162; and AOR = 5.190, 95% CI 4.944-5.448, respectively), among other factors. People living in rural households with inappropriate building materials, insufficient basic public services such as water and waste disposal, and surrounding disease-prone environments are at higher risk of acquiring A. lumbricoides and T. trichiura infections.

Prevalence of Dientamoeba fragilis among asymptomatic individuals from North Central Venezuela

Prevalence of Dientamoeba fragilis among asymptomatic individuals from North Central Venezuela

Relative abundance and temporal variation of macroinvertebrates in a Venezuelan cloud forest habitat

Tree-hole phytotelmata encompass the internodal water pools that form in many species of bamboo (Gramineae). Using bamboo traps, we sampled macroinverte-brate communities in a habitat within the subtropical cloud forest of Henri Pittier National Park, Rancho Grande, north-central Venezuela, and quantified the temporal differences in their abundance and composition. In total, 1024 invertebrates were collected during the 7 months between February and August 2008. The insect orders Diptera and Coleoptera were abundant, particularly Culex (Anoedioporpa) conservator Dyar & Knab, Culex (Culex) mollis (Dyar & Knab), Wyeomyia (Wyeomyia) arthrostigma (Lutz) and Toxorhynchites (Lynchiella) theobaldi (Dyar & Knab). The traps also contained predators, detritivores and collectors (filtering and gathering). Macroinvertebrate abundance in the traps was higher during the rainy season. This observation was attributed to a greater abundance of Ephydridae, Blattaria and Culicidae during wetter months, and an increased availability of potential new breeding sites in the environment, which resulted in increased adult eclosion, and higher rates of oviposition in the bamboo traps. Temporal differences in pH and dissolved oxygen levels of trap water were observed.

Cutaneous leishmaniasis imported from Colombia to Northcentral Venezuela: Implications for travel advice

Imported leishmaniasis could be defined as any case acquired outside of a defined area in which the diagnosis of leishmaniasis is made. This definition has been used for the diagnosis of disease in a patient who arrives from an endemic area and displays symptoms or seeks medical attention in a nonendemic zone. However, this phenomenon can also occur between two endemic zones. We evaluated the epidemiologic features of imported cases of cutaneous leishmaniasis imported from Colombia into Northcentral Venezuela from 2001 to 2006. A total of 29 patients with the clinical diagnosis of cutaneous leishmaniasis arriving from Colombia were evaluated at our referral center. Different diagnostic methods were used to confirm the diagnosis (the Montenegro skin test; an indirect immunofluorescence test and smear of cutaneous lesion). Clinical and epidemiological features of cutaneous leishmaniasis among these patients were evaluated. We identified that most identified patients were male with a mean age of 35 years (age range was 7-64); all cases were from northern departments of Colombia. These patients presented a mean clinical evolution of 3 months. Most patients presented with one cutaneous lesion (17%), which were located mostly in extremities (20%). Of the 29 patients, in 16 (55%) cutaneous leishmaniasis was confirmed by different diagnostic techniques. In 2 patients the diagnosis was made by smear. In the rest, 14 (100%) patients were positive by the Montenegro skin test and 11 (79%) were positive by the indirect immunofluorescence test (79% were positive simultaneously by both tests). The identification of imported cutaneous leishmaniasis in our setting becomes important, given the differences in the epidemiology of the disease and the clinical severity of leishmaniasis between both zones (ecological characteristics, circulating Leishmania spp., and population characteristics) and the risk of the mucocutaneous forms of the disease.

Integrated seismic, flexural and gravimetric modelling of the Coastal Cordillera Thrust Belt and the Guárico Basin, North-Central Region, Venezuela

We constructed two integrated geodynamic transects for the eastern and western areas of the Coastal Cordillera Thrust Belt and the Guárico Basin (North-Central region of Venezuela), based on information from depth-converted reflection seismic cross-sections, surface geology, Bouguer anomaly and deep refraction seismic profiling. These geodynamic transects were modelled in order to: (1) understand the geodynamic processes responsible for the formation of the Guárico Basin, (2) quantitatively determine the contribution of the Coastal Cordillera thrust sheet loading in the generation of the basin fill (i.e. the effective elastic thickness of the northern part of the South American lithosphere, the total shortening of the thrust belt and the maximum subsidence of the basin) and (3) characterize the crustal structure and Moho depth in North-Central Venezuela. We used flexural modelling to obtain important quantitative information related to the total Middle Eocene to Recent shortening of the Coastal Cordillera, the total subsidence observed in the Guárico Basin and the effective elastic thickness of the South American lithosphere in northern Venezuela. We conclude that the load of the Coastal Cordillera on the South American lithosphere is sufficient to generate the subsidence observed in the Guárico Basin. The total shortening and subsidence obtained in the western transect are 44 km and 5 km, whereas they are 10 km and 7 km, in the eastern transect, respectively. The effective elastic thickness of the South American lithosphere obtained from the modelling is 25 km. The seismically-constrained deep structure of North-Central Venezuela indicates that Moho reaches a maximum depth of 45 km under the Guayana Shield and shallows to the north, to 35 km beneath the Guárico Basin. According to the gravity models, Moho is deeper under the Coastal Cordillera Thrust Belt than expected from flexural modelling, pointing to the existence of a crustal root more than 35 km deep. The Moho gets shallower (30 km) towards the Caribbean Sea.

Characterization of Tityus scorpion venoms using synaptosome binding assays and reactivity towards Venezuelan and Brazilian Antivenoms

Venoms from Tityus species inhabiting five endemic regions of scorpionism in Venezuela (Andean, Perijá range, north-central, northeastern, and Guayana) and also southeast Brazil ( T. serrulatus and T. bahiensis) were characterized immunologically in ELISA experiments using mouse- and rabbit-derived antibodies to evaluate their cross-reactivity and also functionally, utilizing synaptosome binding assays. While Brazilian and Venezuelan antivenoms cross-reacted poorly, T. discrepans (north-central Venezuela) and T. zulianus (Andean) venoms shared a greater immunological relatedness than with T. perijanensis (Perijá range). Anti- T. breweri (Guayana) antibodies fully cross-reacted with T. discrepans. Native PAGE indicated species-specific fingerprints for all venoms and revealed differences between two populations (Anzoátegui and Monagas States) of T. nororientalis (northeastern Venezuela). Components antigenically related to T. serrulatus β-toxin TsVII were also detected in T. breweri, T. nororientalis (Anzoátegui) and T. funestus (Andean). Antibodies against T. serrulatus anatoxin TsNTxP did not cross-react significantly with any Venezuelan venoms indicating lack of TsNTxP homologues. The results suggest that the extent of antigenic reactivity depends on the studied species rather than the geographical distance between their habitats. All venoms, with T. discrepans to a lesser extent, were able to significantly displace [ 125I]-TsVII from its binding site in rat brain synaptosomes. Our data indicate that β-toxins functionally related to TsVII but differing significantly in their antigenic regions exist in Venezuelan venoms from different endemic regions. Identification of shared epitopes with TsVII, at least for some species, may lead to the design of antibodies based on common epitopes for treating scorpion envenoming in Venezuela and Brazil.

Tityus perijanensis González-Sponga (Scorpiones, Buthidae): Molecular assessment of its geographical distribution and venom lethality of Venezuelan populations

An extensive field survey allowed us to expand the geographical distribution of the scorpion Tityus perijanensis in the Perijá range, western Zulia State, Venezuela, including areas where adult cases of severe scorpionism have been reported. 16S ribosomal RNA (rRNA) gene sequencing, DL 50 determination, and native PAGE suggest low genetic and venom proteomic divergence across the distribution range. The results also indicate phylogenetic divergence between T. perijanensis and T. discrepans, the species prevalent in northcentral Venezuela. T. perijanensis venom lethality (0.91–0.94 mg/kg) is comparable to that of the Brazilian T. serrulatus and ranks highest among toxic Venezuelan Tityus studied so far. The data indicate that the Perijá range should be included amongst the endemic areas of scorpionism of Venezuela and Colombia.

Neutron Activation Analysis of Pre-Columbian Pottery in Venezuela

Pre-Hispanic pottery figurines from north-central Venezuela islands and mainland were analysed by neutron activation analysis (INAA and PGAA) at the Budapest Research to establish their provenience. In order to classify the samples of figurines, characteristic molecular and atomic components were determined. Several mass ratios were calculated for significant classification of the object of two origins. Results shed light on the origin of island figurines and suggest specific areas of their production on the mainland, contributing to better understanding of late pre-Hispanic migration patterns in the southeastern Caribbean region.