Short‐term environmental changes in Lake Morenito (41°S, 71°W,Patagonia, Argentina) from the analysis of sub‐fossil chironomids     

Julieta Massaferro  Sergio Ribeiro Guevara  Andrea Rizzo  María Arribre 《水产资源保护:海洋与淡水生态系统》2005,15(1):23-30

• 1. A short sediment core from Lake Morenito was studied to assess the impact of environmental changes on chironomid communities occurring during the last ca 100 yr.
• 2. Lake Morenito (41°S, 71°W) is located 20 km west of the city of Bariloche, in northern Patagonia, Argentina. Before 1960, this lake was a branch of Lake Moreno; by that time, an artificial dam closed the system, establishing the new lake. Another human disturbance that took place during the time span of the core was the introduction of salmonids to the area ca 1910.
• 3. The most important natural events that occurred in the area during the last 100 yr were related to volcanic episodes. One of them, occured in Chile in 1960 affecting the Argentinian side, coincided with the dam's construction.
• 4. Changes in the chironomid community were recorded by studying the sub‐fossil remains (the chitinized head capsule of the larvae) present in the sedimentary sequence. The results show that volcanic tephra layers deposited along the core led to a sharp instantaneous drop in the diversity and abundance of chironomid assemblages. Human activities are also associated with a change in chironomid community composition.
• 5. Chironomus reached its maximum abundance values in 1910 and 1960. The organic matter content also increased at the same time. The increase of Chironomus after 1910 is clearly related to an increase in the trophic status of the lake. However, owing to the synchronicity of events in 1960, i.e. the volcanic event and the dam's construction, it is difficult to establish whether the change in the chironomid assemblage was in response to an increase in trophic enrichment, to natural disturbance, or both.

Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Cryogenic preservation of spermatozoa from Prochilodus scrofa and Salminus maxillosus     

Ana Maria Coser  Hugo Godinho  Dirceu Ribeiro 《Aquaculture (Amsterdam, Netherlands)》1984,37(4):387-390

This paper reports an initial trial to cryopreserve semen from two freshwater South American fishes, the curimbatá (Prochilodus scrofa) and the dourado (Salminus maxillosus). Motility and duration of motility were observed in curimbatá and dourado fresh sperm. Semen mixed with extender (0.8% NaCl) was frozen using vials (1 ml) with subsequent storage in liquid nitrogen. Samples were thawed in 1% NaHCO₃ or in 0.8% NaCl solutions. Post-thawing motility and duration of motility were verified. A simple extender consisting of 0.8% NaCl plus 10% DMSO was able to initiate motility in fresh spermatozoa. The percentage of motile cells and duration of motility were similar in both thawing solutions, but lower than in fresh sperm.  相似文献   

Improving weaning strategies for Senegalese sole: effects of body weight and digestive capacity   总被引：2，自引：0，他引：2  

Sofia Engrola  Luís E C Conceição  Lurdes Dias  Ricardo Pereira  Laura Ribeiro  & Maria Teresa Dinis 《Aquaculture Research》2007,38(7):696-707

To optimize Senegalese sole‐weaning strategies, three experiments were performed. The first trial tested four weaning strategies with a 10 mg sole. Artemia‐fed sole grew threefold less than fish fed an inert diet. Sudden weaning (abrupt change from Artemia to inert diet) and weaning with co‐feeding produced larger sole than did a late weaning treatment; delayed weaning negatively affected fish growth. In the second experiment, the digestive capacity of early‐weaned 1, 2 and 4 mg sole was investigated. The highest growth was observed in sole weaned at 4 mg. Digestive enzyme profiles suggest that sole have an adaptation period to inert diets, with reduced feed intake. This adaptation period is inversely proportional to post‐larvae weight. The third experiment examined weaning with co‐feeding at different weights (2, 5 and 11 mg). These studies demonstrate that sole of 5–10 mg can be weaned, with high survival rates. On the basis of the digestive enzyme profiles, the early introduction of inert diets in co‐feeding with Artemia seems to affect intestinal processes in smaller postlarvae. This study also suggests that trypsin and alkaline phosphatase may be used as indicators of nutritional status in sole of <5 mg.  相似文献   

Above- and belowground biomass in a Brazilian Cerrado   总被引：1，自引：0，他引：1  

Sabina Cerruto Ribeiro  Lutz Fehrmann  Carlos Pedro Boechat Soares 《Forest Ecology and Management》2011,262(3):491-499

Cerrado is a biome that occupies about 25% of the Brazilian territory and is characterized by a gradient of grassland to savanna and forest formations and by high species richness. It has been severely affected by degradation and deforestation and has been heavily fragmented over the past 4-5 decades. Despite the recognized overall ecological importance of the Cerrado, there are only few studies focusing on the quantification of biomass in this biome. We conducted such a case study in the South-East of Brazil in a cerrado sensu stricto (cerrado s.s.) with the goal to produce estimates of above- and belowground biomass and to develop allometric equations. A number of 120 trees from 18 species were destructively sampled and partitioned into the components: leaves, branches and bole. Five models with DBH (D), height (H), D²H and wood density (WD) as independent variables were tested for the development of allometric models for individual tree aboveground biomass (leaves + branches + bole). One model based on basal area (BA) as a stand parameter was also tested as an alternative approach for predicting aboveground biomass in the stand level. Belowground biomass was estimated by subsampling on 10 sample plots. Mean aboveground tree biomass (bole, branches and leaves) was estimated to be 62,965.5 kg ha⁻¹(SE = 14.6%) and belowground biomass accounted for 37,501.8 kg ha⁻¹ (SE = 23%). The best-fit equation for the estimation of individual tree aboveground biomass include DBH and wood density as explanatory variables (R² = 0.898; SEE = 0.371) and is applicable for the diameter range of this study (5.0-27.6 cm) and in environments with similar conditions of the cerrado s.s. sampled. In the stand level, the model tested presented a higher goodness of fit than the single tree models (R² = 0.934; SEE = 0.224). Our estimates of aboveground biomass are higher than reported by other studies developed in the same physiognomy, but the estimates of belowground biomass are within the range of values reported in other studies from sites in cerrado s.s. Both biomass estimates, however, exhibit relatively large standard errors. The root-to-shoot ratio of the sample trees is in the magnitude of reported values for savanna ecosystems, but smaller than estimated from other studies in the cerrado s.s.  相似文献   

Leaf-level responses to light in two co-occurring <Emphasis Type="Italic">Quercus</Emphasis> (<Emphasis Type="Italic">Quercus ilex</Emphasis> and <Emphasis Type="Italic">Quercus suber</Emphasis>): leaf structure,chemical composition and photosynthesis     

M. Vaz  J. Maroco  N. Ribeiro  L. C. Gazarini  J. S. Pereira  M. M. Chaves 《Agroforestry Systems》2011,82(2):173-181

We studied morphological, biochemical and physiological leaf acclimation to incident Photon-Photosynthetic-Flux-Density (PPFD) in Quercus ilex (holm oak) and Quercus suber (cork oak) at Mediterranean evergreen oak woodlands of southern Portugal. Specific leaf area (SLA) decreased exponentially with increasing PPFD in both species. Q. ilex had lower SLA values than Q. suber. Leaf nitrogen, cellulose and lignin concentration (leaf area-based) scaled positively with PPFD. Maximum rate of carboxylation (V_cmax), capacity for maximum photosynthetic electron transport (J_max), rate of triose-P utilization (V_TPU) and the rate of nonphotorespiratory light respiration (Rd) were also positively correlated with PPFD in both Quercus species, when expressed in leaf area but not on leaf mass basis. Q suber showed to have higher photosynthetic potential (V_cmax, J_max^m and V_TPU^m) and a higher nitrogen efficient nitrogen use than Q.ilex. Leaf chlorophyll concentration increased with decreasing PPFD, improving apparent quantum use efficiency (Φ) in both Quercus species. We concluded that, in Q.ilex and Q.suber, leaf structural plasticity is a stronger determinant for leaf acclimation to PPFD than biochemical and physiological plasticity.  相似文献   

Fatty acid profile and qualitative characteristics of meat from zebu steers fed with different oilseeds     

Oliveira DM  Ladeira MM  Chizzotti ML  Machado Neto OR  Ramos EM  Gonçalves TM  Bassi MS  Lanna DP  Ribeiro JS 《Journal of animal science》2011,89(8):2546-2555

The objective of this study was to evaluate the effects of dietary addition of ground oilseed sources on the quality, fatty acid profile, and CLA content of meat from zebu steers. Thirty-one zebu steers with an initial average age of 23 mo and an initial BW of 365 kg were used in this study. The experimental period was 84 d, which was preceded by an adaption period of 28 d. The diet was provided ad libitum with a forage:concentrate ratio of 40:60. Corn silage was used as the forage source. Four different concentrates were formulated for each treatment: without additional lipids (control) or with ground soybeans (SB), ground cottonseed (CS), or ground linseed (LS). The SB, CS, and LS diets were formulated to have 6.5% ether extract on a total dietary DM basis. The experiment was set up as a completely randomized design. After slaughter, samples were taken from the longissimus thoracis muscle for the measurement of fatty acid concentration and the evaluation of meat quality. The luminosity index was greater in the control and LS diets (P < 0.01). The greatest percentages of myristic acid (C14:0), palmitic acid (C16:0), trans octadecenoic acid (C18:1 trans-10, trans-11, or trans-12), and SFA in the subcutaneous fat were observed in the CS treatment (P < 0.01). Moreover, the least percentages of oleic acid (C18:1 cis-9) and total unsaturated fatty acids in the subcutaneous fat were observed in the CS diet (P < 0.01). The meat linoleic acid and α-linolenic acid percentages were greatest in the SB and LS treatments, respectively (P < 0.001). The unsaturated fatty acid:SFA ratio was smallest for the CS diet (P < 0.01). A gradual increase in oxidation was observed as a function of storage time; however, the diets did not affect the rancidity of the meat (P > 0.05). The fatty acid profile of subcutaneous fat was impaired by the addition of CS. Supplying ground oilseeds did not increase the content of CLA in the meat.  相似文献   

Dogs mean arterial pressure and heart rate responses during high propofol plasma concentrations estimated by a pharmacokinetic model     

Silva A  Ribeiro LM  Bressan N  Oliveira P  Ferreira DA  Antunes LM 《Research in veterinary science》2011,91(2):278-280

Propofol total intravenous anesthesia should provide stability of the cardiovascular system. In this study, mean arterial pressure and heart rate were evaluated in eight healthy dogs anesthetized with increasing rates of propofol. The cerebral state index (CSI) was studied as an additional parameter. Although the estimated propofol plasma concentration reached a maximal value of 15.3 μg ml⁻¹, no hypotension or bradycardia were observed. Exploration of each animal’s data revealed high inter-individual variability regarding mean arterial pressure and heart rate. Considering the logarithmic of the concentration, a moderate depressant effect of propofol on mean arterial pressure was revealed in five dogs but the effect was not followed on heart rate.  相似文献   

Biological control of <Emphasis Type="Italic">Ascaris suum</Emphasis> eggs by <Emphasis Type="Italic">Pochonia chlamydosporia</Emphasis> fungus     

Ferreira SR  de Araújo JV  Braga FR  Araujo JM  Frassy LN  Ferreira AS 《Veterinary research communications》2011,35(8):553-558

Ascaris suum is a gastrointestinal nematode parasite of swines. The aim of this study was to observe Pochonia chlamydosporia fungus on biological control of A. suum eggs after fungus passage through swines gastrointestinal tract. Eighteen pigs, previously dewormed, were randomly divided into three groups: group 1, treated with the fungus isolate VC4; group 2, treated with the fungus isolate VC1 and group 3 did not receive fungus (control). In the treated groups, each animal received a 9 g single dose of mycelium mass containing P. chlamydosporia (VC1 or VC4). Thereafter, animal fecal samples were collected at the following intervals: 8, 12, 24, 36, 48, 72 and 96 h after treatment beginning and these were poured in Petri dishes containing 2% water-agar culture medium. Then, 1,000 A. suum eggs were poured into each dish and kept in an incubator at 26°C and in the dark for 30 days. After this period, approximately 100 eggs were removed from each Petri dish and morphologically analyzed under light microscopy following the ovicidal activity parameters. The higher percentage observed for isolated VC4 eggs destruction was 57.5% (36 h) after fungus administration and for isolate VC1 this percentage was 45.8% (24 h and 72 h) (p > 0.01). P. chlamydosporia remained viable after passing through the gastrointestinal tract of swines, maintaining its ability of destroying A. suum eggs.  相似文献   

Biological control of cyathostomin (Nematoda: Cyathostominae) with nematophagous fungus Monacrosporium thaumasium in tropical southeastern Brazil     

Tavela Ade O  Araújo JV  Braga FR  Silva AR  Carvalho RO  Araujo JM  Ferreira SR  Carvalho GR 《Veterinary parasitology》2011,175(1-2):92-96

Horses are hosts to a wide variety of helminthes; the most important are the cyathostomin, or small strongyles. The viability of a fungal formulation (pellets) using the nematode-trapping fungus Monacrosporium thaumasium was assessed in biological control of horse cyathostomin. Two groups (fungus-treated and control) consisted of six mares in each group, crossbred (ages of 2.5 and 3.5 years), were placed in pastures of Cynodon sp. naturally infected with horse cyathostomin larvae. In the treated group, each animal received 1g/10 kg body weight (0.2g/10 kg live weight of fungus) of pellets of sodium alginate matrix containing the fungus M. thaumasium orally, twice a week for 6 months. In the control group, animals received (1g/10 kg body weight) of pellets without fungus. The egg count per gram of feces showed difference (p<0.01) in the animals treated with the fungus in relation to the control animals during all months of the experiment. The EPG percentage decrease were 87.5%, 89.7%, 68.3%, 58.7%, 52.5% and 35.2% during June, July, August, September, October and November, respectively. In faecal cultures, there was difference (p<0.05) among animals treated with fungus was found in relation to the control animals during all the experiment month, with percentage reduction of 67.5%, 61.4% and 31.8% in September, October and November, respectively. Difference (p<0.01) was observed in the recovery of infective larvae from pastures that were collected up to 20 cm from the dung pats in pastures in the group treated with the fungus in relation to the control group with a reduction of 60.9% and between 0-20 and 0-40 cm from the faecal pat reduction (p<0.01) was about 56% in the group treated with the fungus M. thaumasium in relation to the control group pasture. There was no difference (p>0.05) between the average weight gains in both animal groups. The treatment of horses with pellets containing the nematophagous fungus M. thaumasium can be effective in controlling cyathostomin in the tropical region of southeastern Brazil.  相似文献   

Towards allelic diversity in the storage proteins of old and currently growing tetraploid and hexaploid wheats in Portugal     

Miguel Ribeiro  Carlos Carvalho  Valdemar Carnide  H. Guedes-Pinto  Gilberto Igrejas 《Genetic Resources and Crop Evolution》2011,58(7):1051-1073

Using sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE), the different alleles encoded at the 6 glutenin loci and 3 ω-gliadin loci were identified from a set of 134 hexaploid and 128 tetraploid wheat accessions mainly grown in Portugal. In the hexaploid wheats (T. aestivum L.), a total of 56, 42 and 36 patterns were observed for high molecular weight-glutenin subunits (HMW-GS), low molecular weight-glutenin subunits (LMW-GS) and ω-gliadins respectively. For HMW-GS encoded at Glu-A1, Glu-B1 and Glu-D1 loci, 4, 10 and 6 alleles were observed, respectively. LMW-GS displayed similar polymorphism, as Glu-A3, Glu-B3 and Glu-D3 loci, which comprises 5, 9 and 3 alleles. Twenty-four alleles were observed for ω-gliadins found at Gli-A1, Gli-B1 and Gli-D1 loci with, 5, 16 and 3 alleles respectively. For tetraploid collection fifty different alleles were identified for the seven loci studied Glu-A1 (3), Glu-B1 (13), Glu-A3 (6), Glu-B3 (7), Glu-B2 (2), Gli-A1 (5) and Gli-B1 (14). The genetic distances within hexaploid and tetraploid wheats were presented using cluster representation. The mean value of genetic variation indices (H) for wheat storage protein loci was slightly lower in current commercially available varieties (0.592) and highest for old varieties (0.574).  相似文献