Geographic differences in the allele frequencies of the human Y-linked tetranucleotide polymorphism DYS19

We have studied the allele frequency distribution of the microsatellite locus DYS 19 in several populations with different geographical origins worldwide. Three new alleles were found. In addition, remarkable geographic and ethnic differences were observed in the allele frequency profiles and DNA marker (gene) diversity among populations and major ethnic groups. Amerindians showed an overwhelming predominance of the A allele, while in Caucasians the B allele was modal, and in Greater Asians and Africans allele C became predominant. Even within these geographic regions there were significant gradients, as exemplified by the decreasing frequency profile of the B allele from Great Britain over Germany to Slovakia. Thus, DYS 19 emerges as a useful tool for studying the structure and dynamics of human populations.     

Immobilization of lipase on chitin and its use in nonconventional biocatalysis

Chitin was functionalized with hexamethylenediamine followed by glutaraldehyde activation, and its capacity to bind Candida rugosa lipase was investigated. The loading of 250 units g(-1) support showed to be effective, resulting in a uniform enzyme fixation with high catalytic activity. Both free and immobilized lipases were characterized by determining the activity profile as a function of pH, temperature, and thermal stability. For the immobilized lipase, the influence of the reaction temperature and substrate polarity in nonconventional biocatalysis was also analyzed. Production of butyl esters was found to be dependent on the substrate partition coefficient, which accounts the greatest value for the system butanol and butyric acid. The highest enzyme activity was found for the system butanol and caprylic acid at a reaction temperature of 40 degrees C. Under such conditions, the operational stability tests indicated that a small enzyme deactivation occurs after 12 batches, revealing a biocatalyst half-life of 426.7 h.     

Parasitism Behavior of Tetrastichus howardi (Hymenoptera: Eulophidae) on Larvae and Pupae of Sugarcane Borers

Journal of Insect Behavior - Control of the sugarcane borers, Diatraea saccharalis and Diatraea impersonatella (= D. flavipennella) (Lepidoptera: Crambidae), in Brazil, is based on mass release of...     

The effect of riverine networks on fish β-diversity patterns in a Neotropical system

Hydrobiologia - We investigated how the riverine network influences taxonomic and functional beta diversity patterns of fish assemblages in the mainstem/headwater (lateral) and upstream/downstream...     

The Role of Historical Barriers in the Diversification Processes in Open Vegetation Formations during the Miocene/Pliocene Using an Ancient Rodent Lineage as a Model

The Neotropics harbors a high diversity of species and several hypotheses have been proposed to account for this pattern. However, while species of forested domains are frequently studied, less is known of species from open vegetation formations occupying, altogether, a larger area than the Amazon Forest. Here we evaluate the role of historical barriers and the riverine hypothesis in the speciation patterns of small mammals by analyzing an ancient rodent lineage (Thrichomys, Hystricomorpha). Phylogenetic and biogeographic analyses were carried out with mitochondrial and nuclear DNA markers to analyze the evolutionary relationships between Thrichomys lineages occurring in dry domains along both banks of the Rio São Francisco. This river is one of the longest of South America whose course and water flow have been modified by inland tectonic activities and climate changes. Molecular data showed a higher number of lineages than previously described. The T. inermis species complex with 2n = 26, FN = 48 was observed in both banks of the river showing a paraphyletic arrangement, suggesting that river crossing had occurred, from east to west. A similar pattern was also observed for the T. apereoides complex. Thrichomys speciation occurred in Late Miocene when the river followed a different course. The current geographic distribution of Thrichomys species and their phylogenetic relationships suggested the existence of frequent past connections between both banks in the middle section of the Rio São Francisco. The extensive palaeodune region found in this area has been identified as a centre of endemism of several vertebrate species and is likely to be a center of Thrichomys diversification.     

Spatial population structure of the Neotropical tiger catfish Pseudoplatystoma metaense: skull and otolith shape variation

Using geometric morphometrics, the skull and otolith of tiger catfish Pseudoplatystoma metaense were analysed to identify population structure in tributaries of the Apure River (i.e. the Sarare, Caparo, Guanare, Portuguesa and San Carlos Rivers) in the Orinoco basin, Venezuela. The analyses show uniformity in skull and otolith shapes of P. metaense within and among four tributaries, with only the Caparo River showing significant differences. Within the Apure basin, the stock of P. metaense was differentiated through spawning, refuge and nursery areas. This study concludes that populations of P. metaense from each major tributary in the Orinoco basin should be considered as part of a metapopulation system for management purposes. Human disturbances in the catchment have directly reduced the spawning areas available to this species, decreased the total biomass and changed the spatial distribution of spawning areas.     

Physiological characteristics of citrus plants infested with citrus blackfly

Aleurocanthus woglumi (Ashby, 1915) is an important agricultural pest that causes yield losses of 20–80% in citrus plants by removing plant nutrients while feeding and allowing the formation of sooty mold. The objective of this study was to evaluate physiological changes in citrus plants in response to A. woglumi infestation under field conditions. The experiment was conducted in a citrus orchard in Paço do Lumiar, Maranhão, Brazil. Thirty-two citrus plants were used, including eight of each of the following varieties: Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine. Four random plants with A. woglumi infestation and four plants free from this pest were selected from each variety. The physiological parameters evaluated were photochemical efficiency and gas exchange. Regarding photochemical efficiency, infested plants presented photoinhibition damage, with a performance index of 4.22. The gas exchange parameters of infested plants changed, with reductions in photosynthetic CO₂ assimilation of 69.7% (Tahiti), 64% (Tanjaroa), 68.8% (Nissey) and 63.3% (Ponkan). Plants infested with A. woglumi also presented physiological changes; their photosynthetic CO₂ assimilation, stomatal conductance, instantaneous transpiration, and performance indexes were affected. The infested citrus plants showed photoinhibition of photosystem II. The photosynthetic CO₂ assimilation decreased approximately 70% in Tahiti lime, Tanjaroa tangerine, Nissey tangerine, and Ponkan tangerine plants infested with A. woglumi.     

Hormonal induction of ovulation and artificial insemination in suckled beef cows under nutritional stress

The objective was to develop a program for inducing estrus (followed by insemination) of suckled beef cows under nutritional stress (poor body condition). A total of 123 cows, from 60 to 75 days postpartum, were classified according to their body condition score (BCS; range from 1 to 5, in increments of 0.5) and allocated into two groups. On Day 0 (without regard to stage of the estrous cycle), cows (n = 59) in the hormone induction (HI) treatment group were given an intravaginal device (IVD) containing 250 mg of medroxiprogesterone acetate (MAP) and an i.m. injection of 2.5 mg estradiol benzoate (EB). On Day 6, these cows were given 500 IU eCG i.m. and calves were weaned for 96 h. The IVD were removed on Day 7. Cows detected in estrus by 45 h after IVD removal were inseminated 12 h after standing estrus; cows not in estrus by 45 h after IVD removal received an i.m. injection of 100 microg gonadorelin (GnRH) and were inseminated 16-18 h later. In the control group (C), cows (n = 64) only had their calves weaned at Day 6 (for 96 h), with estrus detection and AI from Days 6 to 11. Overall, the BCS ranged from 2.0 to 3.0. In the treatment group, estrus and pregnancy rates in cows with BCS 2.0 (20 and 30%, respectively) was lower (P < 0.05) than those with BCS 3.0 (50 and 66.6%, respectively), but did not differ (P > 0.05) from BCS 2.5 (23.3 and 47.6%). In C group, only 2 of 66 cows were detected in estrus and bred (neither was pregnant). In conclusion, the program for induction of ovulation using MAP, EB, eCG and GnRH increased the pregnancy rate in beef cows in poor body condition, enabling AI to be done in a 63-h interval.     

Fish Communities in Central Amazonian White- and Blackwater Floodplains

In Amazonian floodplains, the flood cycle of the river is becoming the dominant seasonal factor, and fish communities are found to fluctuate greatly over the year. During inundation, fish migrate into floodplain forests to feed on fruits and seeds, in an area more than 300000km² in size. To document patterns of species diversity, distribution, abundance and temporal dynamics and in order to describe the ecological importance of the inundated forest, floodplain fish were captured using variously sized gill nets in white and black water areas inside and outside the floodplain forests during low, rising, high and falling water level in 1990 and 1991. Dominance varies to some extent in white water between floodplain forest (0.06) and open water (0.11) while it is unchanged in black water (0.04). Black water fish communities were more diverse. Most abundant among white water fish were Liposarcus pardalis, Pygocentrus nattereri, and Pellona flavipinnis, for example, or Plagioscion squamsissimus, Serrasalmus rhombeus, and Serrasalmus manueli in black water. Among the most abundant white water fish, Colossoma macropomum, Mylossoma duriventre and Osteoglossum bicirrhosum occurred almost exclusively in inundated forests. Of the black water species there were a large number of species which were captured only in inundated forest, such as Geophagus cf. altifrons, Hoplias malabaricus, Osteoglossum bicirrhosum and Uaru amphiacanthoides. Catches varied with sample site, water level and direction of water level change. The average CPUE in white and black water was 190 and 41g fishm^–2 and day, respectively, with maximum yields at low water and minimum yields at high water. Comparing rising and falling water levels, a significantly higher quantity of fishes was captured at falling water level. In black water, fish catches from the floodplain forest exceeded the open water catch by 183 to 550%, depending on season. Differences in respect of white water are smaller (106–281%). Fish communities in the area under investigation seem to be stochastically assembled, with significant differences between white and black water only. Many fishes move into the floodplain forest not only to feed but probably also for other reasons – to seek shelter, for example.