Search

Bumble bees are essential, efficient pollinators of numerous crops, and scientists are increasingly concerned about their global decline. Although several potential causes have been put forward, the concurrent modification of landscape structure and pesticide use by agriculture are often pointed out as the main drivers of the decline. Yet, the mechanisms through which these factors cause species to decline remain elusive. Most field studies have been conducted at the individual level, and the few studies that addressed higher levels of organization only covered narrow ecological conditions. We undertook a field experiment in spring 2016 to overcome these limitations by placing four commercial Bombus impatiens colonies in each of 20 sites located along a gradient of agricultural intensity in southern Québec, Canada. We hypothesized that landscape habitat composition and configuration, as well as local floral resources, would affect colony development. We expected colonies surrounded by low‐intensity and/or flowering crops in heterogeneous landscapes to develop better and live longer, partly linked to more abundant and diversified food resources, than colonies embedded in landscapes dominated by high‐intensity crops. Colonies were weighed once a week, and workers were captured to assess pollen load diversity. Final colony weight, queen production, and presence of depredators (Aphomia sociella, Lepidoptera: Pyralidae) were also recorded. Landscape habitat composition and configuration were characterized within 1 km of colonies. Local availability of floral resources was assessed within 100 m of colonies every two weeks. As predicted, colony weight and longevity decreased with the proportion of intensive crops and increased with the amount of flowering crops, but queen production and the occurrence of A. sociella were not affected by landscape composition. Contrary to our prediction, local availability of floral resources also did not affect colonies. The pollen richness brought back to colonies decreased with the proportion of flowering crops and varied according to the proportion of intensive crops interacting with local floral resources. Our work contributes to generalize the more restrictive conclusion of local‐scale, crop‐specific studies that intensive crop farming undermines bumble bee colony development and that it may thus play a role in the large‐scale population decline of these insects. [ABSTRACT FROM AUTHOR]

The article discusses a 2021 report on the infection of strawberry plants in Quebec by a new subgroup of Candidatus Phytoplasma asteris (16Srl) linked to strawberry green petal disease (SbGP). It states that infected plants had the symptoms of reddened leaves and sepals, flower greening and phyllody linked to strawberry green petal disease phytoplasma. Also noted is the first occurrence of a new 16Srl subgroup linked to SbGP in Quebec in the report.

A 9-week feeding trial was conducted to investigate the effects of dietary supplementation with protein hydrolysates on growth, innate immunity and disease resistance of olive flounder. A fishmeal ( FM)-based diet was regarded as a control, and three diets were prepared by partial replacement of FM with krill hydrolysate, shrimp hydrolysate or tilapia hydrolysate (designated as Con, KH, SH and TH, respectively). Triplicate groups of fish (24.5 ± 0.3 g) were fed one of the diets to apparent satiation twice daily for 9 weeks and then challenged by Edwarsellia tarda. Fish-fed KH diet showed significantly ( P < 0.05) higher growth performance and feed utilization compared with the Con diet. Dry matter digestibility of the diets was significantly increased by KH and TH supplementation. All the examined innate immune responses were significantly increased in fish fed KH diet. Significantly, higher respiratory burst and superoxide dismutase ( SOD) activities were found in fish-fed SH diet. Lysozyme and SOD activities were significantly increased in fish-fed TH diet. However, no significant effect was found on fish disease resistance. This study indicates that dietary supplementation of the hydrolysates, particularly KH, can improve growth performance, feed utilization and innate immunity of olive flounder. [ABSTRACT FROM AUTHOR]

Interactions between headwater aquifers and peatlands have received limited scientific attention. Hydrological stresses, including those related to climate change, may adversely impact these interactions. In this study, the dynamics of a southern Québec headwater system where a peatland is present is simulated under current conditions and with climate change. The model is calibrated in steady state on field-measured data and provides satisfactory results for transient-state conditions. Under current conditions, simulations confirm that the peatland is fed by the fractured bedrock aquifer year-round and provides continuous baseflow to its outlets. Climate change is simulated through its impact on groundwater recharge. Predicted precipitation and temperature data from a suite of regional climate model scenarios provide a net precipitation variation range from +10% to −30% for the 2041-2070 horizon. Calibrated recharge is modified within this range to perform a sensitivity analysis of the headwater model to recharge variations (+10%, −15% and −30%). Total contribution from the aquifer to rivers and streams varies from +14% to −44% of the baseline for +10% to −30% recharge changes from spring 2010 data, for example. With higher recharge, the peatland receives more groundwater, which could significantly change its vegetation pattern and eventually ecosystem functions. For a −30% recharge, the peatland becomes perched above the aquifer during the summer, fall and winter. Recharge reductions also induce sharp declines in groundwater levels and drying streams. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The reproduction of lowbush blueberry (Vaccinium angustifolium Aiton) is closely tied to insect pollination, owing to self-incompatibility. Many species are known to have greater pollination efficiency than the introduced Apis mellifera L., commonly used for commercial purposes. In this study, we measured the pollen loads of several antophilous insect species, mostly Apoidea and Syrphidae, present in four lowbush blueberry fields in Lac-St-Jean, Québec. To measure pollen loads and species specificity toward V. angustifolium, we net-collected 627 specimens of pollinators, retrieved their pollen loads, identified pollen taxa, and counted pollen grains. We found that the sizes of pollen loads were highly variable among species, ranging from a few hundred to more than 118,000 pollen grains per individual. Bombus and Andrena species in particular carried large amounts of Vaccinium pollen and thus may have greater pollination efficiency. Also, two species (Andrena bradleyi Viereck and Andrena carolina Viereck) showed nearly monolectic behavior toward lowbush blueberry. Finally, we identified alternative forage plants visited by native pollinators, notably species of Acer, Rubus, Ilex mucronata, Ledum groenlandicum, and Taraxacum. Protecting these flowering plants should be part of management practices to maintain healthy pollinator communities in a lowbush blueberry agroecosystem. [ABSTRACT FROM AUTHOR]

The pupal development of Aethina tumida Murray (Coleoptera: Nitidulidae) was studied at various combinations of thermo-hygrometric soil conditions (temperatures of 16, 18, and 20°C and soil water content levels of 0.37, 0.56, and 0.73 m3 water per cubic meter of dry soil) representative of southeastern Canada. Survivorship and development duration of A. tumida pupae, as well as sex ratio and life span of emerging adults, were assessed. Assays were conducted in growth chambers on an average of 50 third-instar larvae per thermo-hygrometric combination. Results show that survivorship of pupae decreased with lower temperature and higher soil water content. Pupal development time shortened as temperature increased (69-78 d at 16°C, 47-54 d at 18°C, and 36-39 d at 20°C), but was longer in dryer soil. Optimal soil water content for pupal development was 0.56 m3 water per cubic meter of soil. We estimated that the minimum development temperature for pupae is between 10.2 and 13.2°C, depending on soil water content. The sex ratio of emerging adults was influenced by soil water content. We measured one female to one male for dry and intermediately wet soils and three females to one male for wet soils. Higher soil water content reduced the life span of emerging adults by half. This study contributes to a better understanding of A. tumida population dynamics in eastern Canada. [ABSTRACT FROM AUTHOR]

Summary: Objectives: The purpose of this open multicenter study was to evaluate the value of a new starch-thickened formula in infants with regurgitations in ambulatory pediatric practice. Population and methods: The study population comprised full-term infants with an age at inclusion of 1–90 days, who were bottle-fed and presented regurgitations. The formula tested was an infant formula-thickened with starch (2g/100mL). The primary endpoint was the frequency of bottles regurgitated, expressed in percentage of meals per day after 15 days of feeding with the preparation studied. Secondary endpoints were the assessment of regurgitations using the Vandenplas’ score, as well as the daily increase in weight, height, and cranial circumference, overall and gastrointestinal tolerance, and formula acceptability. Results: Sixty-four infants presenting regurgitation were included. The frequency of bottles regurgitated estimated at 80.3% at inclusion significantly decreased at D3, D15, and D30 to 40.1, 40.2 and 37.2% (P <0.0001), respectively. Thirty percent of infants did not present regurgitations at all at D30. Similarly, a significant decrease in the Vandenplas’ score was observed from 1.9 at D0 to 0.9 at D30 (P <0.0001). Infant growth was similar to the French and European growth curves. Conclusion: The results showed rapid and lasting improvement in decreasing the frequency of feeding-bottles regurgitated by 50% from the first 3 days of using this new starch-thickened formula (2g/100mL). These satisfying results encourage the use of the tested formula in cases of infant regurgitation, in line with the European Society of Gastroenterology, Hepatology and Nutrition (ESPGHAN) recommendations. [Copyright &y& Elsevier]

The article compares the suitability of various rotation crops as nonhosts or poor hosts to Pratylenchus penetrans over a three-year rotation sequence including both forage pearl millet and the grain pearl millet hybrid and to measure their effect on the subsequent potato crop under field microplot conditions. The population densities of Pratylenchus increased under rye, potato, oats and Indian mustard and decreased under both forage and grain pearl millets.

A study was designed to evaluate the maximum level of substitution of fish meal in diets for turbot when a mixture of feedstuffs of plant origin was used and when the amino acid profile was adjusted to reflect amino acid profile of a reference fish meal based diet. Five diets were formulated: a reference diet (FM40) containing 40% fish meal and four other diets (FM30, FM20, FM10 and FM0) in which protein from fish meal was substituted by protein from lupin, corn gluten and wheat gluten meal. Amino acids profile of each diet was balanced by addition of crystalline amino acids. Turbot, initially weighing 26 g were fed these diets for 12 weeks and growth parameters were recorded. Protein (96%), energy (83%) and dry matter (73%) digestibility were very high in all diets tested. Feed intake was significantly decreased by the incorporation of plant protein in diets (from 10.2 g/kg ABW/day to 8.2 g/kg ABW/day in fish fed diets FM40 and FM0, respectively), growth rate was only affected in fish fed diets FM10 and FM0 (respectively, 2.2 and 1.9%/day against an average of 2.4%/day for the other treatments) and no effect on feed utilisation was observed. The whole body composition of fish and the nitrogen retention were significantly negatively affected when dietary fish meal incorporation was equal or less than 20% diet. Activities of alanine amino transferase (ALAT) were significantly increased by the dietary incorporation of plant protein. These results suggest that a sizeable amount of fish meal can be replaced by plant feedstuffs in diets of turbot when an adequate mixture of plant feedstuffs along with amino acid supplementation are used. [Copyright &y& Elsevier]

The aim of the study was to evaluate the effects of dietary arginine (Arg) supplementation to either a plant protein-based diet or a fish meal-based diet on nitrogen (N) utilisation and ureogenesis in turbot and rainbow trout. Juvenile turbot (7.4 g) and rainbow trout (9.3 g) were fed for 12 weeks two types of diets (plant protein-based (PM) and fish meal-based (FM)) containing different levels of Arg (1.6%, 3% and 4% diet for PM diets and, 3% and 4% for FM diets). Besides, measurement of growth parameters and protein utilisation, ammonia and urea excretion rates were monitored. Plasma ammonia and urea concentrations and activities of selected enzymes of ornithine urea cycle (carbamoyl phosphate synthetase III, ornithine carbamoyltransferase and arginase) were measured.Both species fed PM-based diets had reduced growth performance compared to fish fed FM-based diets. Amino acid imbalance of the PM-based diets had a significant effect on plasma ammonia levels and ammonia excretion. Dietary Arg supplementation did not lead to any improvement in N utilisation or on ammoniogenesis. In both species, there was a linear relationship between dietary Arg and urea excretion. Our data confirm that ornithine urea cycle is incomplete in the liver and that argininolysis plays a major role in ureogenesis in both species. [Copyright &y& Elsevier]

Recent studies indicate that urea excretion is responsive to protein intake and that turbot, Psetta maxima, appear to differ from other species by their urea excretion pattern and levels. This study was undertaken to evaluate the influence of dietary nitrogen and arginine on ureagenesis and excretion in turbot. Juvenile turbot (29 g) were fed semi-purified diets containing graded levels of nitrogen (0–8% dry matter) and arginine (0–3% dry matter) for 6 weeks. Growth data showed that turbot have high dietary nitrogen (123 mg/kg metabolic body weight/day) and very low dietary arginine (9.3 mg/kg metabolic body weight/day) requirements for maintenance. Requirements for unit body protein accretion were 0.31 g and 0.15 g for nitrogen and arginine respectively. Post-prandial plasma urea levels and urea excretion rates showed that urea production was significantly (P<0.05) influenced by dietary arginine levels. While hepatic arginase (EC 3.5.3.1) activity increased significantly (P<0.05) with increasing dietary arginine levels, activities of other enzymes of the ornithine urea cycle were very low. Our data strongly suggest that the ornithine urea cycle is not active in the turbot liver and that dietary arginine degradation is a major pathway of ureagenesis in turbot. [Copyright &y& Elsevier]

Besides being an indispensable amino acid for protein synthesis, arginine (Arg) is also involved in a number of other physiological functions. Available data on the quantitative requirement for Arg in different teleosts appear to show much variability. So far, there are very limited data on the maintenance requirements of indispensable amino acids (IAA) in fish. In the present study, we compared N and Arg requirements for maintenance and growth of four finfish species: rainbow trout (Oncorhynchus mykiss), turbot (Psetta maxima), gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Groups of fish having an initial body weight close to 5???7 g were fed semi-purified diets containing graded levels of N (0 to 8 % DM) and Arg (0 to 3 % DM) over 4 to 6 weeks. For each species, N and Arg requirements for maintenance and for growth were calculated regressing daily N gain against daily N or Arg intakes. N requirement for maintenance was estimated to be 37??8, 127??3, 84??7 and 45??1 mg/kg metabolic body weight per d and 2??3, 2??2, 2??6 and 2??5 g for 1 g N accretion, in rainbow trout, turbot, gilthead seabream and European seabass respectively. The four species studied appear to have very low or no dietary Arg requirements for maintenance. Arg requirement for g N accretion was calculated to be 0??86 g in rainbow trout and between 1??04???1??11 g in the three marine species. Turbot required more N for maintenance than the other three species, possibly explaining its reputedly high overall dietary protein requirement. Data suggest a small but sufficient endogenous Arg synthesis to maintain whole body N balance and differences between freshwater and marine species as regards Arg requirement. It is worth verifying this tendency with other IAA. [ABSTRACT FROM PUBLISHER]

Our main objective was to verify whether the dietary ascorbic acid (AA) requirement of juvenile European sea bass (Dicentrarchus labrax) varies as a function of different physiological needs. Practical diets with eight (0, 5, 10, 20, 40, 80, 160, 320 mg AA/kg diet) levels of ascorbic acid polyphosphate were fed to sea bass (mean weight: 0.7 g) for 15 wk. At the beginning and at the end of the feeding trial, tissues were sampled for vitamin C and hydroxyproline (HyPro) analysis. Dose-dependent responses of skin and whole body HyPro concentrations and hepatic AA concentration to dietary vitamin C levels were observed. Skin and whole body HyPro concentrations were low in sea bass fed AA-deficient diet, 217 and 15 nmol/g tissue, respectively. HyPro levels increased with increasing dietary levels, reaching plateaus of 297 and 45 nmol/g tissue in the skin and whole body at dietary vitamin C levels of at least 5 and 31 mg AA/kg. Hepatic AA level increased with increasing dietary levels, reaching a plateau of 474 pmol/g tissue in juveniles fed at least 121 mg of AA/kg. We concluded that hepatic AA saturation is the most stringent response criterion for determination of the vitamin C requirement in juvenile European sea bass. [ABSTRACT FROM AUTHOR]

The paper draws on the Chicago School's conceptualization of career and on Personal Construct Psychology to examine the relationships between graduates' construction systems and patterns of career development during the first 4 years of employment. It seeks to identify differences in trends of constructive revision between 'successful' and 'less successful' graduates. The study is based on 33 graduates who completed repertory grids on entering employment (T1), 6 months later (T2), and 4 years later (T3), re-eliciting constructs each time. The results show some significant change in the nature of the constructs elicited by graduates over the 4 years; in particular, graduates made greater use of constructs related to achievement, cynicism, and organizational politics. Graduates whose career was more 'successful' (i.e., who experienced one or two promotions during the 4 years of the study and felt generally satisfied with their careers) were more likely to use constructs related to social behavior and flexibility at T1, while graduates whose career was 'less successful' (i.e., no promotion and felt dissatisfied with their careers) were more likely to construe themselves in terms of achievement and work competence at T1. Four years on, successful' graduates tended to rely more on constructs related to achievement and flexibility, while 'less successful' graduates were more likely to use constructs related to social behavior. The significance and implications of these results for organizational recruitment and development practices are discussed. [ABSTRACT FROM AUTHOR]

The objective of our research was to identify alternatives to synthetic pesticide treatments to prevent aphid outbreaks in greenhouse lettuce crops. In the laboratory, we determined the susceptibility of three lettuce-infesting aphid species, Macrosiphum euphorbiae (Thomas),Myzus persicae (Sulzer), and Nasonovia ribisnigri (Mosley), to the hyphomycete Verticillium lecanii (Viegas) (strain Vertalec), the planttriterpenoid molecule azadirachtin (BioNeem), and an insecticidal soap (Safer's). Estimated LC50 and LT50 obtained in the laboratory indicated that the three aphid species were susceptible to the entomopathogenic fungus, the plant extract, and the soap.Under greenhouse conditions, we assessed the potential of the three pesticides to reduce aphid populations and compared it with that of asynthetic insecticide, the organophosphate Malathion. Greenhouse experiments demonstrated that all three pesticides significantly reducedthe population of each aphid species compared with the untreated plants. This study also revealed differences in aphid susceptibility between aphid species and between laboratory bioassays and greenhouse trials. The high initial aphid densities, difficulties to reach the aphids on the undersurface of leaves, stains left by Vertalec on the harvested lettuce, and high cosmetic standards for lettuce mitigated theperformance of the insecticides. The potential of using Vertalec, BioNeem, and Safer's soap for the control of lettuce aphids is discussed in relation to aphid species and crop management. [ABSTRACT FROM AUTHOR]

Abstract: The role of dietary arginine in affecting nitrogen utilisation and excretion was studied in juvenile European sea bass (Dicentrarchus labrax) fed for 72 days with diets differing in protein sources (plant protein-based (PM) and fish-meal-based (FM)). Fish growth performance and nitrogen utilisation revealed that dietary Arg surplus was beneficial only in PM diets. Dietary Arg level significantly affected postprandial plasma urea concentrations. Hepatic arginase activity increased (P <0.05) in response to dietary Arg surplus in fish fed plant protein diets; conversely ornithine transcarbamylase activity was very low and inversely related to arginine intake. No hepatic carbamoyl phosphate synthetase III activity was detected. Dietary arginine levels did not affect glutamate dehydrogenase activity. A strong linear relationship was found between liver arginase activity and daily urea-N excretion. Dietary Arg excess reduced the proportion of total ammonia nitrogen excreted and increased the contribution of urea-N over the total N excretion irrespective of dietary protein source. Plasma and excretion data combined with enzyme activities suggest that dietary Arg degradation via hepatic arginase is a major pathway for ureagenesis and that ornithine-urea cycle is not completely functional in juvenile sea bass liver. [Copyright &y& Elsevier]