Southern Venezuela Research Articles

Biogeographic area relationships in Venezuela: A Parsimony analysis of Culicidae—Phytotelmata distribution in National Parks

This study represents the first attempt to understand the current distribution and evolutionary history of Culicidae in Venezuela and adjacent areas using cladistic methods. We studied the association between immature mosquitoes and their aquatic habitats in plants (phytotelmata) in 16 protected natural areas of Venezuela. A total of 68 mosquito species was collected from 47 host-plant species. Parsimony Analysis of Endemicity using localities and mosquito species was used to find the most parsimonious cladograms depicting the biogeographic relationships. Varying degrees of mosquito-plant associations were observed, with the greatest specificity existing at the genus and subgenus levels. Implicit enumeration algorithms obtained one parsimonious tree (L=101 steps) with four well-supported groups named "Amazonas" (southern Venezuela), “Bolivar” (southeastern Venezuela), "Los Andes Cordillera” and "Coastal Cordillera" (northern Caribbean mountain range). These results support the hypothesis that the Guayana Shield was an ancestral center of speciation, followed by the Andean Region, whereas the mosquito fauna from the Central Cordillera was derived from the latter.

Indigenous Shifting Cultivation and the New Amazonia: A Piaroa Example of Economic Articulation

This article argues against the idea that indigenous cultural change and knowledge loss are inevitably bonded to one another, with particular reference to agro-productive transformations. This view has not only ignored the potential of these productive systems—well documented in recent decades—but has often threatened them by promoting development policies based on mistaken premises. It is suggested here that some indigenous peoples’ productive responses to market integration may in fact offer alternatives to the paradoxes of development in seemingly fragile tropical environments. This article reports, in particular, on the strategies developed by the Piaroa, from southern Venezuela. Contemporary large and permanent Piaroa communities, which resulted from their involvement in aspects of national society, have been able to sustain the forests on which they depend while satisfying their food and market necessities. This has been possible due to a series of market strategies based on their agroforestal tradition, which have emphasised the commercialization of secondary forest products. The article proposes that these strategies have been underestimated due to the market conditions in which Piaroa farmers are immersed, and from which they have learnt the very principles of “capitalism.” Oil dependent and saturated with corruption, the Venezuelan market hampers their full economic integration, contributing to the idea that their agroforestry system can only produce at subsistence levels.

Vector bionomics and malaria transmission in the Upper Orinoco River, Southern Venezuela

A longitudinal epidemiological and entomological study was carried out in Ocamo, Upper Orinoco River, between January 1994 and February 1995 to understand the dynamics of malaria transmission in this area. Malaria transmission occurs throughout the year with a peak in June at the beginning of the rainy season. The Annual Parasite Index was 1,279 per 1,000 populations at risk. Plasmodium falciparum infections accounted for 64% of all infections, P. vivax for 28%, and P. malariae for 4%. Mixed P. falciparum/P. vivax infections were diagnosed in 15 people representing 4% of total cases. Children under 10 years accounted for 58% of the cases; the risk for malaria in this age group was 77% higher than for those in the greater than 50 years age group. Anopheles darlingi was the predominant anopheline species landing on humans indoors with a biting peak between midnight and dawn. A significant positive correlation was found between malaria monthly incidence and mean number of An. darlingi caught. There was not a significant relationship between mean number of An. darlingi and rainfall or between incidence and rainfall. A total of 7295 anophelines were assayed by ELISA for detection of Plasmodium circumsporozoite (CS) protein. Only An. darlingi (55) was positive for CS proteins of P. falciparum (0.42%), P. malariae (0.25%), and P. vivax-247 (0.1%). The overall estimated entomological inoculation rate was 129 positive bites/person/year. The present study was the first longitudinal entomological and epidemiological study conducted in this area and set up the basic ground for subsequent intervention with insecticide-treated nets.

Four New Hypancistrus (Siluriformes: Loricariidae) from Amazonas, Venezuela

Hypancistrus contradens, H. debilittera, H. furunculus, and H. lunaorum are described based on specimens from the upper Río Orinoco of southern Venezuela. Hypancistrus furunculus differs from other Hypancistrus based on color pattern: distinct dark oblique stripes ending at posterior insertion of dorsal fin and vertical bands in caudal fin (vs. oblique stripes ending at end of caudal fin in H. zebra and thin, indistinct, light-colored bands and vermiculations on a dark background in H. debilittera) and color pattern dark with white spots in H. contradens, H. inspector, and H. lunaorum. Hypancistrus contradens and H. lunaorum differ from H. inspector by having the dorsal fin reaching the adipose fin when adpressed (vs. not reaching), having spots on the head the same size as the body or spots absent (vs. spots smaller on head) and by usually having 22–23 mid-ventral plates (vs. 24); and from H. debilittera, H. furunculus, and H. zebra by lacking bars, saddles, or stripes on the body and bands in the fins. Hypancistrus lunaorum differs from H. contradens by having white spots on the body smaller than nasal aperture diameter (vs. white spots larger than the nasal aperture diameter).Se describen como especies nuevas a Hypancistrus contradens, H. debilittera, H. furunculus, e H. lunaorum sobre la base de especímenes provenientes de la cuenca alta del río Orinoco en el sur de Venezuela. Hypancistrus furunculus difiere de todas las demás especies de Hypancistrus por su patrón de coloración: barras oscuras oblicuas en el cuerpo que terminan al nivel del punto posterior de la base de la aleta dorsal y bandas verticales en la aleta caudal (vs. barras oblicuas oscuras terminando en el borde posterior de la aleta caudal en H. zebra y barras delgadas, indistintas y de color claro con manchas iregulares vermiformes sobre un color base oscuro en H. debilittera) y patrón de coloración con puntos blancos en H. contradens, H. inspector, e H. lunaorum. Hypancistrus contradens e H. lunaorum difieren de H. inspector en que la aleta dorsal alcanza la aleta adiposa cuando esta plegada contra el cuerpo (vs. aleta dorsal que no alcanza la adiposa), los puntos de la cabeza son del mismo tamaño de los puntos del cuerpo, o carece de puntos (vs. puntos de la cabeza mas pequeños que los puntos del cuerpo) y en tener usualmente 22–23 placas medioventrales (vs. 24); estas especies difieren de H. debilittera, H. furunculus, e H. zebra en que tienen barras, manchas en forma de silla de montar o franjas en el cuerpo y bandas en las aletas. Hypancistrus lunaorum difiere de H. contradens en que los puntos blancos del cuerpo son más pequeños que el diámetro de la apertura nasal (vs. puntos blancos más grandes que el diámetro de la apertura nasal).

Litter decomposition in primary forest and adjacent fire-disturbed forests in the Gran Sabana, southern Venezuela

Litter decomposition and nutrient dynamic were studied in tall primary forest (TF) and in adjacent slightly fire-affected (MF) and strongly fire-affected (LF) forests of the Gran Sabana, southern Venezuela. The aim of the study was to compare the mass and nutrient loss of litter in undisturbed forest and adjacent fire-disturbed forests growing under the same soil conditions. The results showed no significant differences in the dry-mass reduction among TF, MF, and LF after 1-year of decomposition. At the end of the decomposition period, the mass loss was 31% in TF, 24% in MF, and 25% in LF. With few exceptions, the initial nutrient content of the litter did not show significant differences among the studied forests. The initial litter was poor in nutrients, especially in P, with C/N ratio extremely high, particularly in LF. Both residual P content and C/N ratio were the most effective predictors of dry-mass loss. The general trend in the three studied forests was net N and to less extend P immobilization and release of K, Mg, and Ca. We concluded that during a 1-year period, the decomposition process was similar in undisturbed and adjacent fire-disturbed forests in the Gran Sabana and that the low litter decomposition seems to be mainly controlled by the low chemical quality of the decomposing litter.

Community‐randomized trial of lambdacyhalothrin‐treated hammock nets for malaria control in Yanomami communities in the Amazon region of Venezuela

We conducted a community-randomized controlled trial in an area of moderate malaria transmission in the Amazon region, southern Venezuela, home of the Yanomami indigenous ethnic group. The aim was to compare the malaria incidence rate in villages with lambdacyhalothrin-treated hammock nets (ITHN) or with placebo-treated hammock nets (PTHN). In both arms of the study, intensive surveillance for early case detection was maintained and prompt malaria treatment was administered. Baseline data were collected before the intervention and a population of around 924 Yanomami was followed for 2 years. Despite the recent introduction of nets in the Yanomami villages and the adverse natural conditions in the area, the nets were accepted enthusiastically by the study population, used conscientiously and looked after carefully. The malaria incidence rate per thousand person-years at risk was 114.6 in the IHTN group and 186.8 in the PTHN group. The adjusted rate ratios indicated that ITHN prevent 56% [IRR: 0.44, 95% confidence interval (CI): 52-59%] of new malaria cases. ITHN reduced the prevalence of parasitaemia by 83% [relative risks (RR): 0.17, 95% CI: 47-100%], according to a cross-sectional survey carried out during the high transmission season. The prevalence of splenomegaly and anaemia was too low to detect any possible reduction as a result of ITHN. The main conclusion of the present study is that ITHN can reduce malaria incidence in the area and it is the most feasible method for malaria control in a forested area where indigenous villages are scattered over a large territory. This is the first community-level epidemiological trial to show that ITHN are highly effective against malaria transmitted by Anopheles darlingi.

Characteristics of the water and energy balance in an Amazonian lowland rainforest in Venezuela and the impact of the ENSO-cycle

Summary From 1996 to 2000 microclimatic conditions (profiles of wind-speed, temperature, humidity and radiation) have been investigated to determine the energy balance within a primary Amazonian rainforest in southern Venezuela (Surumoni crane project), located on the banks of the upper Rio Orinoco. Since 1997 main components of the water balance were examined additionally: gross and net precipitation, stemflow, sapflow and soilwater were measured. The main goal was to determine the water and energy balance for the study site as a contribution to an interdisciplinary ecological research project and to assess consequences of possible land use change. In this study the most important link between energy balance and hydrological cycle, the evapotranspiration, was determined independently by two different approaches. The results indicate a high interannual variability, which probably was influenced by the strong La Nina-epsiode in 1996 and the very strong El-Nino-event in 97/98. The impact of the ENSO-cycle is well documented for coastal and marine environments in South America; detailed observations in the Amazon basin however, are very scarce. Beyond the scope of supplying detailed information for a typical pristine tropical lowland forest, this study may also help to improve the understanding of ecosystem impact of ENSO in the Amazon region.

Introduction: focusing on breeding for durable disease resistance of the Andean highland food crops

The Andes forms a long chain of mountains of over 7,000 km long that range form Southern Venezuela to the South of Chile. The crops discussed in this issue are grown at altitudes ranging from 1,500 m to over 4,000 m in a very heterogeneous environment, characterised by large differences in rainfall, humidity and temperature. Also the latitude and direction of the slopes have significant effects on the amount and distribution of rainfall. Farmers have great experiences and skills in adapting their farming systems to these specific conditions. In the Andean region the majority of the farmers can be classified as low input small-holders, typical for marginal areas.

Degradation of extracellular matrix proteins (fibronectin, vitronectin and laminin) by serine-proteinases isolated from Lonomia achelous caterpillar hemolymph

Lonomia achelous is a caterpillar distributed in southern Venezuela and in northern Brazil that causes an acute hemorrhagic syndrome in people who have contact with its bristles. The effect of the crude hemolymph and its chromatographic fractions (FDII, Lonomin V and Lonomin V-2) on extracellular matrix proteins was studied. The chromatographic fractions show activities similar to plasmin and urokinase. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, both lonomins appear as a protein band of 25 kDa under reduced conditions. By exclusion chromatography, the molecular weights of Lonomin V and Lonomin V-2 were 26.5 and 24.5 kDa, respectively. Fibronectin, laminin and vitronectin were degraded by all venom components. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under reduced conditions, shows that lonomins degrade fibronectin in four main fragments of 116, 60, 50 and 30 kDa. Molecular exclusion chromatography in native conditions shows that the molecular masses of these fragments are > or = 300, 62 and 27 kDa. The proteolytic effect of lonomins was abolished by benzamidine/HCl, iodoacetic acid and aprotinin. The extracellular matrix protein degradation together with the fibrino(geno)lytic activity of hemolymph and its fractions could explain, in part, the hemorrhagic syndrome, and the wound dehiscence in persons who have had contact with the L. achelous caterpillar.

A new Eleutherodactylus (Anura, Brachycephalidae) from the Venezuelan Guayana, and redescription of Eleutherodactylus vilarsi (Melin)

Eleutherodactylus aracamuni sp. nov. is described from the summit of Cerro Aracamuni, a granitic mountain in southern Amazonas state, Venezuelan Guiana. The new species is easily distinguished from other Guianan Eleutherodactylus by the absence of vomerine teeth, notched finger and toe discs, and its yellowish green coloration in life. It appears to be closely related to E. cavernibardus. Eleutherodactylus vilarsi, a common lowland species, is redescribed on the basis of additional specimens from southern Venezuela.

Nutrient fluxes in incident rainfall, throughfall, and stemflow in adjacent primary and secondary forests of the Gran Sabana, southern Venezuela

Rainfall partitioning into throughfall and stemflow was studied during a year in a primary forest (tall forest) and in two adjacent secondary forests with contrasting structure (medium and low forests) in the Gran Sabana. Mean annual concentrations of nutrients in throughfall and stemflow were significantly higher ( P < 0.05) than those in incident rainfall, particularly for K. Concentrations of N were very low not only in rainfall but also in throughfall and stemflow, indicating absence of N leaching in these forests. Concentration of P in rainfall was under the detection limit, and in throughfall and stemflow was very low. With very few exceptions, the mean annual concentrations of nutrients in throughfall and stemflow did not differ significantly ( P > 0.05) between the forests, which seem to indicate that differences in structure and floristic composition do not play an important role in the nutrient dynamic at the canopy level. Throughfall and stemflow amounts represented 71–77% and 2–8% of the annual incident rainfall, respectively. Annual volumes of throughfall were quite similar in tall, medium and low forests, while the annual volume of stemflow decreased from tall to medium and low forests. With some exceptions, the annual inputs of nutrients in throughfall tended to be quite similar between the studied forests. Stemflow input tended to decrease with decreasing tree density from tall to medium and low forests, which is more related to the decrease in the volume of this flow from tall to medium and low forests than with changes in the element concentration of the stemflow among the forests. We concluded that incident rainfall is an important means of nutrient transfer from the forest canopy to the soils, and that a decrease in the tree density affected negatively the inputs of nutrients in stemflow but not in throughfall.

Migração transfronteiriça na Venezuela

AS ZONAS fronteiriças são zonas de empréstimos e apropriações culturais e, por isso, um lugar privilegiado para a compreensão do fenômeno migratório internacional. O objetivo deste trabalho é apresentar alguns aspectos do processo de deslocamentos transfronteiriços no norte do Brasil, no município de Pacaraima (Estado de Roraima) e na fronteira sul da Venezuela, no município de Gran Sabana (Estado Bolívar), e, ao mesmo tempo, apontar as tendências e reflexos nas configurações socioculturais nessas zonas de contato. Nessa fronteira Brasil-Venezuela, podemos afirmar que o trânsito maior é de brasileiros para a Venezuela e para a Guiana, em decorrência das possibilidades de atuarem nas atividades de mineração, no comércio local e no setor de transportes, além das atividades ilegais, como tráfico de mulheres, contrabando de combustível e câmbio ilegal de moeda. Apresenta-se, no entanto, uma nova tendência que é a imigração de estrangeiros de outros países do continente, tais como peruanos e colombianos. Esses migrantes transfronteiriços percorrem os países fronteiriços em itinerários cuja porta de entrada é a Venezuela e a Guiana, mas também o Estado do Amazonas.

The Catfish Genus Tetranematichthys (auchenipteridae)

The neotropical auchenipterid catfish genus Tetranematichthys is reviewed. Tetranematichthys was previously thought to be monotypic with its single species, T. quadrifilis, reported to have a broad range encompassing major portions of the Amazon basin and southern tributaries of the Río Orinoco. Tetranematichthys quadrifilis was rather found to be endemic to the Rio Guaporé in the southwestern portions of the Amazon basin and a new species of the genus is described from material originating in the upper Rio Negro system in Brazil and Venezuela and the upper Río Orinoco basin in southern Venezuela. The new species is also apparently widespread within the Amazon basin and the southern and north-central portions of the Río Orinoco system. The species of Tetranematichthys have distinctive modifications of the mandibular barbel and associated systems, which are proposed as synapomorphic for the species of the genus and that potentially function as a fishing lure.

National Politics, Indigenous Constituencies, and Cultural Change in Southern Venezuela Commentary on "State-led Democratic Politics . . ."

National Politics, Indigenous Constituencies, and Cultural Change in Southern Venezuela Commentary on "State-led Democratic Politics . . ."

Piaroa Sorcery and the Navigation of Negative Affect: To Be Aware, To Turn Away

An overemphasis on the interpretation of language has impeded understanding of the cultural and cognitive logic of sorcery's focal acts: divination and sorcery battle. Among the Piaroa of southern Venezuela, divination and sorcery battle are conducted during hallucinogen‐induced visions, and are predicated on an epistemology that privileges forms of knowing that are neither linguistic nor language‐like. I suggest that Piaroa sorcerers use hallucinogen‐induced visions to map the social ecology of emotions in ways partially explainable by cognitive science, and that mature contemplation may provide the anthropologist with a means of understanding relationships between nonlinguistic thought and culture. I interweave an account of my participation in a sorcery battle with neuropsychological interpretations of cognition and emotion to present a navigation of a negative affect theory of sorcery. The navigation of negative affect theory complements sociological and psychoanalytic approaches while emphasizing the cognitive skills and visionary experiences that underpin the practice of sorcery by shamans.

A new dendrobatid frog (Anura: Dendrobatidae: Colostethus) from Aprada tepui, southern Venezuela

A new species of Colostethus is described from Venezuelan Guayana. It inhabits the slopes of Aprada tepui, a sandstone table mountain in southern Venezuela. The new species is distinguished from close relatives by its particular pattern, absence of fringes on fingers, presence of a lingual process, and yellow and orange ventral coloration. It is the 18 th described species of Colostethus from Venezuelan Guayana.

Floristic diversity of African and South American inselbergs: a comparative analysis

Inselbergs are isolated rock outcrops that rise abruptly above the surrounding plains. Granitic and gneissic inselbergs are geologically and geo-morphologically old and are geographically widespread. Inselbergs form micro-climatically and edaphically dry growth sites that bear a highly specialized vegetation. Based on physiognomic criteria a number of habitat types can be distinguished (e.g. ephemeral flush vegetation, monocotyledonous mats, rock pools) that are widespread on inselbergs. In Africa, the eastern and southeastern part of the continent support the species-richest inselbergs. In particular in the savanna biomes the ephemeral flush vegetation forms the species-richest habitat. In South America, southern Venezuela and the Brazilian Mata Atlantica region are important centers of diversity for inselberg plant communities.

Baryancistrus demantoides and Hemiancistrus subviridis, two new uniquely colored species of catfishes from Venezuela (Siluriformes: Loricariidae)

Baryancistrus demantoides and Hemiancistrus subviridis are two new species of loricariids from southern Venezuela with an olive ground coloration and white to cream-colored or golden-yellow spots. Baryancistrus demantoides is known only from the upper río Orinoco drainage while H. subviridis is also known from the río Casiquiare drainage. In addition to its coloration, B. demantoides can be distinguished from all other ancistrins by having the dorsal and adipose fins connected by an expanded posterior section of the dorsal-fin membrane, golden-yellow spots confined to the anterior portion of the body, and greater than 30 teeth per jaw ramus. Hemiancistrus subviridis can be separated from all other ancistrins by coloration, lacking a connection between the dorsal and adipose fins and having less than 30 teeth per jaw ramus.

Modeling humic acids transport in a bauxite profile: Los Pijiguaos, Venezuela

Los Pijiguaos bauxite deposit is located in Southern Venezuela, in a tropical rain forest environment. Among the various impurities during the bauxite processing (Bayer process), organic matter compounds present in Bayer liquor can slow the rate of alumina precipitation, and reduce product yield and quality. Soil samples were taken from a 37-m-deep core and the distribution of organic carbon (OC) was investigated as well as its relationship with major oxides Al 2O 3, Fe 2O 3, SiO 2 and with the mineral phases gibbsite, hematite, kaolinite and quartz. Each sample was subjected to an adsorption process of humic acids by interaction with solutions of known concentrations. Maximum adsorption capacity was also studied in each mineral separately, which allowed calculation of the theoretical adsorption capacity of each soil sample. Even if concentrations of OC were higher in the first 5 m of the profile (0.2–0.5%), samples exhibited a low adsorption capacity (0.02%), while at depth between 10 and 37 m, samples showed lower OC concentrations (0.03–0.05%), and a larger OC adsorption capacity (0.08%). The model for the adsorption capacity only works between 10 and 30 m of depth, since in the first 10 m the bauxitic profile seems to be saturated in OC, because the concentration of OC is higher than the maximum predicted by adsorption experiments.

Human infection patterns and heterogeneous exposure in river blindness.

Here we analyze patterns of human infection with Onchocerca volvulus (the cause of river blindness) in different continents and ecologies. In contrast with some geohelminths and schistosome parasites whose worm burdens typically exhibit a humped pattern with host age, patterns of O. volvulus infection vary markedly with locality. To test the hypothesis that such differences are partly due to heterogeneity in exposure to vector bites, we develop an age- and sex-structured model for intensity of infection, with parasite regulation within humans and vectors. The model is fitted to microfilarial data from savannah villages of northern Cameroon, coffee fincas of central Guatemala, and forest-dwelling communities of southern Venezuela that were recorded before introducing ivermectin treatment. Estimates of transmission and infection loads are compared with entomological and epidemiological field data. Host age- and sex-heterogeneous exposure largely explains locale-specific infection patterns in onchocerciasis (whereas acquired protective immunity has been invoked for other helminth infections). The basic reproductive number, R0, ranges from 5 to 8, which is slightly above estimates for other helminth parasites but well below previously presented values.