Results 1 - 10 of 268
Results 1 - 10 of 268. Search took: 0.023 seconds
|Sort by: date | relevance|
[en] In order to evaluate the role of heterotrophic bacteria on carbon flow in food chains of an Amazonian floodplain lake, monthly collections of these organisms were made during the hydrological year from December 2007 to November 2008. Littoral, pelagic, and aquatic macrophyte regions of the Catalao Lake in central Amazonia were sampled and bacteria were multiplied in vitro, using dissolved organic carbon (COD) of each one of the regions studied as a substrate. The bacterial biomass obtained was used for stable isotope analyses of carbon and nitrogen. These data were confronted with COD values of the four hydrological periods of the lake (dry, rising, flood and fall). In general, it was found that the main source of carbon for heterotrophic bacteria was that of C4 origin, which presented a minimum contribution of 75% of bacterial biomass, to the extent that the bacteria D13C average value -17.72 Per Mille ± 2.25 was comparing this value with the D13C of zooplankton in the same period (-33.04 Per Mille ± 3.81) permit concludes that the contribution of heterotrophic bacteria in the carbon flow to higher trophic levels in the Catalao lake is minimal.
[en] The distribution and abundance of organisms within a pond or lake can reflect the result of a variety of factors. We examined the abundance of the endemic fish, Poblana alchichica, in Lago de Alchichica, Puebla, Mexico, as well as how the abundance varied among months. Dissolved oxygen, temperature, and salinity varied among months. The abundance of Poblana alchichica peaked in December and February. For the months when fish were observed, their abundances were positively related to dissolve oxygen concentration and were generally not related to temperature. Our results provide evidence that there is substantial seasonal variation in the abundances of Poblana alchichica and that within months; their distributions are likely driven by dissolved oxygen than either temperature or salinity.
[en] The transgenic crops were the result of the application of recombinant DNA technology in agriculture. These crops were developed by transfer of foreign genes (transgenes) from any biological origin (animal, plant, microbial, viral) to the genome of cultivated species of plants. The crops genetically modified (GM) have been used in the world since 1996; up to December 2010 they counted to a billion hectares planted throughout the period. In just the past year 2010 148 million hectares were planted, grown by 15.4 million farmers in 29 countries. GM crops that are used in global agriculture are mainly soybean, cotton, corn and canola, which express transgenes derived from bacteria, and confer resistance to lepidopteron insects (ILR) or herbicide tolerance (HT; glyphosate and glufosinate ammonium). the first transgenic varieties containing only a single transgene, or simple event, while the current varieties express several transgenes, or stacked, conferring resistance to different species of Lepidoptera and coleopteran insects and tolerance to two different herbicides. In 2010 were planted in Colombia, 18.874 hectares of GM cotton, 16.793 hectares of GM corn, and 4 hectares of GM carnations and GM roses. GM corn and GM cotton were planted in Sucre, Cesar, Cordoba, Huila and Tolima. GM corn was planted in Antioquia, Valle del Cauca, Meta, Cundinamarca and Santander. Carnations and roses were planted in Cundinamarca. GM maize and GM cotton expressing ILR and HT features, as simple events or stacked. In the case of GM carnation and GM roses, these genotypes that express the color blue. Academia has tried to organize the debate on the adoption of GM crops around the analysis of biological risks and environmental vs environmental and economic benefits. Biological hazards are defined by the possible negative effects on human consumers or negative effects on the environment. The environmental benefits are related to reduce use of agrochemicals (insecticides and herbicides), and the economic benefits from the reduction in losses due to insect and weed competition to reduction of production costs.
[en] The predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus are used in programs of mass rearing for the control of phytofagous mites. the effect on survival, longevity, predator capacity and fecundity of this predators was studied after storage them to a temperature of 8 Celsius degrade and relative humidity of 85+/-5 % during different periods of time (0, 7, 14, 21, 28 y 35 days). During the time of evaluation the predators were individualized and kept at 25 Celsius degrade of temperature and relative humidity of 85+/-5 %. the survival, longevity predator capacity and fecundity presented during all the time of evaluation of P. persimilis displayed a decrease after being stored during 21 or more days, the same happened to the survival and consumption of N. californicus sp. however, the longevity and oviposition during all time of evaluation for N. californicus was reduced after storing them for 28 or more days. Daily consumption and daily fecundity of both predators had no effect, except on daily consumption of eggs for P. persimilis and daily consumption of nymphs for N. californicus after storing them for 35 days.
[en] Lutzomyia (Helcocyrtomyia) hartmanni is a sand fly that has been implicated in the transmission of Leishmania (Viannia) colombiensis, an etiologic agent of cutaneous Leishmaniasis in Colombia. The objective of this work was to explore the potential usefulness of the mitochondrial serine transfer RNA (UCN) (tRNASer) in the taxonomic determination of L. hartmanni. Mitochondrial DNA was extracted, amplified and sequenced from entomological material collected in Envigado, Antioquia, Colombia. The tRNASer gene length was 68 nucleotide pairs, with an average adenine-thymine content of 80.9%. The studied tRNASer differs from other sand fly tRNASer known to date, on the basis of its primary and secondary structure. The observed number of intrachain base pairing was 7 in the acceptor arm, 3 in the dihydrouridine (DHU) arm, 5 in the anticodon arm, and 5 in the ribothymidine-pseudouridine-cytosine (TC) arm. The size of the DHU, anticodon, variable and TC loops was estimated to be 5, 7, 4, and 8 nucleotides, respectively. The notorious absence of non-Watson-Crick base pairs in the four arms of the tRNASer distinguishes that of L. hartmanni from others Lutzomyia spp.
[en] To estimate the diversity, structure and genetic flow in three Colombian southwest afrodescendent populations (Buenaventura, Mulalo y Tumaco), the alleles revealed by 8 autosomal STR's were analyzed in 78 no-related individuals, by the use of PCR and comparison with specific allelic ladders for every system resolved by polyacrylamide gel (8%). the results were compared with 2 Amerindian populations (Awa-Kuaikier and Coyaima) and 2 mixed Colombian populations (Valle del Cauca and Cauca). For the afrodescendent and Amerindian populations was found moderate diversity (h between 0.768±0.414 and 0.796±0.424), in contrast, the mixed population showed higher rates (>0.803), which is probably caused by mixing with Amerindians, that also can explain the high endogamy seen in mixed populations. The AMOVA exhibited moderate genetic structure between the afrodescendent populations (FST= 0.098; p<0.05), but higher between the three ethnical groups compared (FST=0.26723; p<0.05). The closer genetics distances are in favor of Tumaco and Buenaventura, supported for the migration rate found (34.298), which was the same inside of Amerindian and mixed populations. Maybe, because Mulalo is a closed isolated population, its differences in front others afrodescendent populations are explained. The neighbor-joining tree showed nearest relations among Amerindian and mixed populations, furthermore, the ancestral character for the afrodescendents. That sustains the idea of genetic flow maintained between the 3 ethnical groups, principally between Amerindian and mixed populations, supported because the genetic differences, migration rates and Amerindian matrilineality reported in the literature
[en] The effect of climatic seasons (rainy and dry) and the stratum sample (rhizospheric soil, roots and leaves) the population of the genera Azotobacter, Beijerinckia, Derxia, Azospirillum, Herbaspirillum, Gluconacetobacter and Burkholderia in soil rhizosphere, roots and leaves of eucalyptus (eucalyptus sp.). It also assesses their ability to produce indoles compounds as plant growth promoters and their acetylene reduction activity as an indicator of biological fixation of nitrogen. The results showed no statistically significant differences in the Duncan test (p ≤ 0.05) in the population with respect to the climate epoch, suggesting that these bacteria are able to tolerate stress conditions by different physiological mechanisms. With respect to the stratum sample isolates attempts of Herbaspirillum sp. and Azospirillum sp. significant differences in rhizospheric soil and roots. we obtained 44 isolates of which were grouped by phenotypic characterization as 14 suspected of Beijerinckia sp., 12 Azotobacter sp., 8 Derxia sp., 4 Herbaspirillum sp., 5 Azospirillum sp., 1 Gluconacetobacter sp. and 1 Burkholderia sp. due to their high potential were selected isolates C27, C26 and C25. These four strains present the best values of efficiency in vitro, exceeding production values of the reference strains used (A. chroococcum (AC1) and a. brasilense (SP7)).
[en] Box-jellyfishes of the Colombian Caribbean are still poorly known, it is for this reason that exploratory sampling was done in the region of Santa Marta, Colombia, during the period between February and October 2009, to determine which species are in this region. were collected and identified a total of five samples of box-jellyfishes to the cubozoa class, three samples of chiropsalmus genera (chirodropida family) and two samples of alatina (alatinidae family), both specimens are the first record of Boxjellyfishes from the Colombian Caribbean.
[en] In this work, endophytic fungi from leaves and pods of bean presenting anthracnose symptoms were isolated from plants collected at different municipalities in the province of Antioquia (Colombia). Isolates were identified by sequencing the RDNA its regions together with the examination of reproductive structures during sporulation in culture media. Colletotrichum lindemuthianum, the causal agent of anthracnose was isolated in all samples showing symptoms of this disease. These results were confirmed by duplex PCR using the specific primers CD1/CD2 and CY1/CY2. Additionally, 17 endophytic fungi were obtained. Fourteen isolates did not sporulate in culture media (Mycelia sterilia) but were identified by phylogenetic analysis of the regions as the Ascomycetes: Leptosphaerulina (3), Diaporthe (3), Gibberella (1), Plectosphaerella (1) and Biscogniauxia (1) and the Mitosporic genera phoma (2), Alternaria (2) and Stemphylium (1) Three isolates were identified combining morphological and molecular analysis as Fusarium (2) and Curvularia lunata (1). This work increases our knowledge of the mycobiota of legume plants and will serve as support of future studies aimed at determining the effect of these fungi on the development of anthracnose as well as other problems affecting the bean crop.
[en] The first record of the West Indian drywood termite Cryptotermes brevis (Walker, 1853) in the city of Corrientes (Argentina) is reported. Several C. brevis colonies were detected inside a local deposit, from wooden crates used for carrying fresh fruits. The observed damage consisted of small rounded holes, partially hollowed wood pieces and presence of debris. The importance of weather factors and the type of material of vegetable and fruit containers in the colonization and dispersion of C. brevis in this region of Argentina are discussed. Illustrations of soldiers and reproductive C. brevis, and an updated map of the distribution of this termite in Argentina are given.