Ecological drivers of fish metacommunities: Environmental and spatial factors surpass predation in structuring metacommunities of intermittent rivers

Metacommunity theory is a new approach for explaining how local and regional processes contribute to community organisation and integrative studies are needed to fully characterise the processes underlying its structure and function. We analysed, through variation partitioning and distance decay relationships, how metacommunities of fish in pools of intermittent rivers are structured by environmental, species interaction and spatial factors. The results indicate that both species sorting and dispersal limitation (spatial factors) were important in shaping fish metacommunities. Species sorting was the most influential driver within fish metacommunities, but predation was much less relevant and did not show any pure effect in metacommunity structure. However, environmental factors were determinant among metacommunity patches.     

Effect of l‐glutamic acid supplementation on performance and nitrogen balance of broilers fed low protein diets

The aim of this study was to evaluate the effect of protein reduction and supplementation of l ‐glutamic acid in male broiler diets. A total of 648 chicks of the Cobb 500 strain were distributed in a completely randomized design with six treatments and six replications with eighteen birds per experimental unit. The study comprised pre‐starter (1–7 days), starter (8–21 days), growth (22–35 days) and final (36–45 days) phases. The first treatment consisted of a control diet formulated according to the requirements of essential amino acids for each rearing phase. The second and third treatments had crude protein (CP) reduced by 1.8 and 3.6 percentage points (pp) in relation to the control diet respectively. In the fourth treatment, l ‐glutamic acid was added to provide the same glutamate level as the control diet, and in the last two treatments, the broilers were supplemented with 1 and 2 pp of glutamate above that of the control diet respectively. The reduction in CP decreased the performance of broilers and the supplementation of l ‐glutamic acid did not influence performance when supplied in the diets with excess of glutamate. The lowest excreted nitrogen values were observed in the control diet, and treatments 2 and 3, respectively, in comparison with treatments with the use of l ‐glutamic acid (5 and 6). Retention efficiency of nitrogen was better in the control diet and in the treatment with a reduction of 1.8 pp of CP. It was verified that the serum uric acid level decreased with the CP reduction. A reduction in CP levels of up to 21.3%, 18.8%, 18.32% and 17.57% is recommended in phases from 1 to 7, 8 to 21, 22 to 35 and at 36 to 42 days, respectively, with a level of glutamate at 5.32%, 4.73%, 4.57%, 4.38%, also in these phases.     

Dexmedetomidine low dose followed by constant rate infusion and antagonism by atipamezole in isoflurane-anesthetized cats: an echocardiographic study

Objective

To investigate the effects of a low dose of dexmedetomidine (DEX) followed by constant rate infusion (CRI) and reversal with atipamezole on systolic and diastolic functions in isoflurane-anesthetized healthy cats.

Seeds Collected from Different Ziziphus joazeiro Plants Are Differently Affected by Gibberellic Acid

Ziziphus joazeiro is a tree endemic to Caatinga, Northeastern Brazil, with great economic potential. However, its commercial production is still limited due to low and non-uniform germination of seeds. Recently we demonstrated that gibberellic acid (GA₃) stimulates the emergence and uniformity of seedlings in this species. In its natural habitat, however, great morphological diversity between Z. joazeiro trees is found, suggesting great genetic variability. Therefore, it was necessary to test if the GA₃ effect is a general response. We collected seeds from four plants maintained in a collection. The plants were selected according to contrasting morphological characteristics. After breaking impermeability with 98% sulfuric acid, the seeds were treated with 2 mmol L^?1 GA₃ or a control with distillated water for 24 h. Effects ranged from great, low, and no effect of GA₃ stimulating the percentage and rapidity of emergence between genotypes tested. For reforestation, thus, the GA₃ treatment of Z. joazeiro seeds might reduce its genetic variability; but for economic production, it will be an adequate and simple treatment to increase the quantity and uniformity of seedlings.     

Identification of a bisegmented double-stranded RNA virus (picobirnavirus) in calf faeces

To determine the incidence of rotavirus infection among dairy herds in the State of S?o Paulo, Brazil, 576 faecal samples obtained from calves aged 1-45 days with and without diarrhoea, reared on 63 dairy cattle farms, were analyzed. Polyacrylamide gel electrophoresis (PAGE) identified 28 samples positive for group A rotavirus, while four samples, two diarrhoeic and two non-diarrhoeic, showed a bisegmented genome with a typical picobirnavirus pattern. Electron microscopy revealed spherical virus particles with a diameter of 37 nm and without a defined surface structure. The present study is the first report of a bisegmented virus identified in cattle in Brazil.     

The ecology of horse cyathostomin infective larvae (Nematoda-Cyathostominae) in tropical southeast Brazil

Experimental studies about the recovery, survival and migration to pasture of cyathostomin infective larvae (L(3)) from fresh feces depositions were conducted from February 2005 to March 2007 in a tropical region of southeast Brazil. Grass and feces were collected weekly at 8 a.m., 1 and 5 p.m. and processed by the Baermann technique. Multivariate analysis (principal components method) showed the influence of time and environmental variables on the number of infective larvae recovered from the feces and pasture. In the rainy period (October-March), more infective larvae were recovered on the feces and grass apex. In contrast, in the dry period (April-September), the recovery was higher only on the grass base, as well as the L(3) survival on feces and grass. More larvae were recovered at 8 a.m., except from the grass apex, where the highest recovery was at 1 p.m. Few studies investigating the seasonal transmission of equine cyathostomin have been conducted in South American tropical climates. These results demonstrate that in tropical conditions L(3) are available on feces and pasture throughout the year. Knowledge of climatic influences on the development and survival of L(3) is crucial to designing integrated parasite control programs that provide effective protection while slowing the development of anthelmintic resistance.     

Long-lasting systematic roguing for effective management of CABMV in passion flower orchards through maintenance of separated plants

In Brazil, passion flower is grown across almost the entire country. The predominant disease of the passion flower crop is passion fruit woodiness, caused by the potyvirus cowpea aphid-borne mosaic virus (CABMV), and transmitted by aphids in a nonpersistent manner. The disease reduces the useful life of the orchard from 36 months to approximately 18 months. Up to now, there has not been an efficient method for disease management. The aim of this work was to evaluate the efficiency of systematic roguing of diseased plants through weekly inspections, for disease management in the field. The latent and incubation periods of CABMV in passion flower vines were determined in order to optimize roguing efficiency. Passion fruit plants inoculated with CABMV started to act as sources of inoculum from 3 days after inoculation (DAI), and the symptoms were expressed, on average, at 8 DAI. Five field experiments, conducted in the states of São Paulo and Bahia, Brazil, demonstrated that systematic roguing of diseased plants was significantly efficient for managing passion fruit woodiness disease. In order to facilitate identification and subsequent removal of the infected plants, they need to be grown separately. This cultural practice can be recommended for managing passion fruit woodiness disease, provided it is applied on a regional scale by all passion fruit growers. The development of some pilot plantings for the application of roguing in a passion flower-producing region is recommended to validate the use of this technique for managing passion fruit woodiness disease.     

Subtidal macrozoobenthic assemblages along the River Minho estuarine gradient (north‐west Iberian Peninsula)

• 1. The community composition and spatial distribution of the macrobenthic fauna in relation to abiotic factors was investigated at 20 sites along the River Minho estuarine gradient, in the north‐west Iberian Peninsula.
• 2. A total of 68 taxa were identified and the non‐indigenous invasive species Corbicula fluminea dominated both numerically (43.1%) and by biomass (97.7%).
• 3. Multivariate analysis identified spatial differences in structure and composition of assemblages and suggests a continuum between five distinct assemblages along the length of the estuary. This situation fits the two‐ecocline model in which an ecocline from the sea to mid‐estuary overlaps with an ecocline from freshwater to mid‐estuary.
• 4. Each assemblage was found in a particular physico‐chemical environment and had a specific composition. The distribution and diversity patterns were linked to salinity. However, inside each assemblage the sediment characteristics (granulometry and organic matter content) played an important role.
• 5. The highest abundances, biomasses and total species numbers were recorded from upstream freshwater tidal areas, indicating the importance of these habitats within estuarine ecosystems.

Copyright © 2007 John Wiley & Sons, Ltd.