Natural cortisol production is not linked to the sexual fate of European sea bass

Fish Physiology and Biochemistry - In this study, we aimed to investigate the relationship between cortisol and the determination of sexual fate in the commercially important European sea bass...     

Spatio-temporal distribution of mutton snapper and dog snapper spawning aggregations in the South-west Atlantic

1. Sites and periods of spawning aggregations of two important fishery resources, the mutton snapper, Lutjanus analis, and the dog snapper, Lutjanus jocu, were identified and validated along the Brazilian north-east coast (latitude 8–15°S) using exploratory analysis of catch per unit effort (CPUE) data, gonadosomatic index analysis, and gonad histology.
2. The CPUE analysis for both species allowed the identification of outliers and far outliers, representing fisheries with exceptional catches, which were used as proxies of possible aggregation.
3. The presence of pre-spawning and recent spawning signs (hydrated oocytes and post-ovulatory follicles) in the ovary of females caught at sites with recurrent records of high CPUE allowed the validation of spawning activity at those specific sites for each species. All aggregation sites identified in this study were located on the outer shelf, close to the shelf break, a region that has been declared an Ecologically and Biologically Significant Marine Area.
4. Comparison of two subregions showed significant differences in size structure of the fish sampled during landings, suggesting a fishing depletion effect in the north region.
5. For both species, reproduction peaked twice in all regions studied, with a more marked peak during summer. However, spawning activity was observed in almost every month of the year, suggesting that seasonal closures could be more effective if combined with spatial measures.
6. In the northern part of the study range, spawning grounds were found to lie just outside the boundaries of one of Brazil's largest marine protected areas. Inclusion of those grounds in the marine protected area would increase protection of these species and also mean increased protection of an Ecologically and Biologically Significant Marine Area, encompassing mesophotic reefs.
7. The identification of these spawning aggregations sites on the north-east coast of Brazil was conducted in collaboration with local fishers that traditionally use bottom handline. Co-management approaches are suggested in view of the importance of these fishing sites for traditional fishing communities that may also face threats due to encroachment of mobile fleets.

     

Yield and grain protein concentration in bread wheat: how to use the negative relationship between the two characters to identify favourable genotypes?

A study of the relationship between grain yield (GY) and grain protein concentration (GPC) in bread wheat was carried out on a 11-year series of trials conducted by the Groupement d’Etude des Variétés Et Semences (GEVES) for the registration of new cultivars on the French National List. Values for GY and GPC came from 458 individual trials, grouped together in 21 series of bi-annual and multi-site data. The correlations between the two characters, calculated environment by environment, appeared highly variable due to high “genotype × environment” interactions for GY and GPC. The use of mean values, calculated on the 21 series of GEVES trials, enabled a better assessment of the relationship between the two characters, and an algorithm was proposed to avoid bias due to potential outliers. Using the well-assessed relationship obtained, grain protein deviations (GPDs) were defined as the standardized residuals of the regression of GPC on GY. These deviations appeared to have a partly genetic basis, as the lines with high deviations were about the same in the two independent datasets constituted by the two consecutive years of GEVES experiments. Some lines used as standards in GEVES trials obtained significant GPD for different series of bi-annual and multi-site trials, confirming the genetic origin of high-GPD. Simulations made to determine the minimum experimental design, showed that at least five sites per year for two consecutive years, were necessary to have a good assessment of the GY–GPC relationship, and hence reliable estimates of GPD.     

DNA sequence polymorphisms and their application to bread wheat quality

Single-nucleotide polymorphisms (SNPs) constitute an abundant source of DNA polymorphisms, which have been successfully used to identify loci that are associated with a particular phenotype. Additionally, such markers could be efficiently used in combination with doubled haploid technology to improve the efficiency of breeding programmes. Information on such markers in plants is still scarce. For bread wheat, SNP data are restricted to a few genes. This can be explained by the hexaploidy of Triticum aestivum which makes SNP discovery difficult. We developed a novel method for SNP discovery in bread wheat. The strategy is based on the development of highly specific PCR-primers, which were used to sequence 27 lines. SNPs were discovered from sequence alignment data. Some SNPs were identified by mass spectrometry in a collection of 113 lines, which were both evaluated for agronomic traits and genotyped at 42 neutral microsatellite loci. Traits investigated include: protein content, the quantity of high-molecular-weight glutenins and that of the GluBx subunit. The 42 markers were used to infer population structure, which was included in linear models for association studies. The results of this preliminary study showed 89 SNPs in approximately 20 kbp, i.e., one SNP every 223 bp on average. Six SNPs were genotyped: three were located along the sequence of Glu-B1-1, while three non-synonymous SNPs were located along the sequence of the B homoeologous gene coding for SPA (Storage Protein Activator). The SNPs from Glu-B1-1 had a significant effect on the studied variables, whereas those of SPA had no effect. Such results might indicate that some haplotypes for Glu-B1-1 are linked to higher protein content, through an increased amount of high-molecular-weight glutenins, especially the GluBx subunit.     

Modelling the effects of temperature and leaf wetness on monocyclic infection in a tropical fungal pathosystem

Modelling the epidemiology of water yam anthracnose (Dioscorea alata) caused by the fungus Colletotrichum gloeosporioides is an important research goal, as it will allow the investigation of a wide range of scenarios of new practices to reduce the disease impact before experimentation in the field. Developing such a model requires a prior knowledge of the fungus’s response to the environmental conditions, which will be affected by pest management. In this work, we first measured the response of the fungus to the main physical environmental factors controlling its development, namely temperature (ranging from 18 °C to 36 °C) and wetness duration (from 2 h to 72 h). As response variables, we measured the percentage of formed appressoria (relative to the total number of spores), the length of the latent period (time lag between inoculation and first symptoms observed), and the rate of necrotic lesion extension (percentage of diseased leaf surface at different time steps). These variables allow us to estimate the effects of temperature and wetness duration on the success of infection (appressoria formation) and the subsequent rate of disease development (latent period length and lesion extension rate). The data were fitted to non-linear models chosen for their ability to describe the observed patterns. From our data and model analyses, we were able to estimate parameters such as the optimal and maximal temperatures (25–28 °C and 36 °C, respectively), the required wetness duration to reach 20 % of infection success and the time to reach 5 % disease severity as a function of temperature.     

Effect of pea canopy architecture on microclimate and consequences on ascochyta blight infection under field conditions

In order to investigate the impact of pea canopy architecture and development on microclimate and infection by Mycosphaerella pinodes, two field experiments were conducted in 2009 and 2010 at Le Rheu (France) to obtain canopies contrasted in height, closure dynamic, leaf area index (LAI) and leaf area density (LAD). Three pea cultivars (Athos, Antares, Gregor) were sown at two (80 and 40 seeds/m² in 2009) and three densities (80, 40 and 30 seeds/m² in 2010) and microclimatic sensors were located inside the canopy (at the bottom and in the middle) and outside. Two main sources of wetness were identified: rainfall and dew. During rainfall periods, average daily leaf wetness duration (LWD) was about 15 h, and 3 to 10 h longer inside than outside the canopies. LWD was positively correlated with LAI until canopy closure during these periods. During dry periods when dew was the only source of leaf wetness, average daily LWD was short, decreasing as the canopy developed. Shorter LWDs were observed at the base than at the mid-level of the canopies and longer LWDs were observed outside the canopy and inside the less dense canopies irrespective of the cultivar. LWD was negatively correlated with canopy height and LAI during these periods. Slow wind speeds were recorded inside the canopies (less than 0.5 km/h) and no significant canopy effect was observed on air temperature. An infection model was developed and showed that only rainfall periods which induced long LWDs inside the canopy, were favourable to M. pinodes infection under our climatic conditions and suggested a more favourable microclimate inside dense canopies.     

Liquid chromatography-tandem mass spectrometry for the determination of sphingomyelin species from calf brain, ox liver, egg yolk, and krill oil

In this study, molecular species of sphingomyelin (SM) in egg yolk, calf brain, ox liver, and krill oil were investigated. Classes of phospholipids (PLs) were purified, identified, and quantified by normal phase semipreparative high-performance liquid chromatography (HPLC) combined with evaporative light scattering detectors (ELSD). For SM molecular species identification, pure SM collected through a flow splitter was loaded to HPLC-electrospray ionization-tandem mass spectrometry (LC-ESI-MS(2)), with 100% methanol containing 5 mM ammonium formate as mobile phase. In addition to classes of PLs, the used approach allowed the determination of profiles of SM species in egg yolk, ox liver, and calf brain, whereas krill oil turned out not to contain any SM. It also allowed the separation and identification of SM subclasses, as well as tentative identification of species with the same molecular mass, including isomers. The results showed that egg yolk contained the highest proportion of (d18:1-16:0)SM (94.1%). The major SM molecular species in ox liver were (d18:1-16:0)SM (25.5%), (d18:1-23:0)SM (19.7%), (d18:1-24:0)SM (13.2%), and (d18:1-22:0)SM (12.5%). Calf brain SM was rich in species such as (d18:1-18:0)SM (40.7%), (d18:1-24:1)SM (17.1%), and (d18:1-20:0)SM (10.8%).     

Mars surface diversity as revealed by the OMEGA/Mars Express observations

The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) investigation, on board the European Space Agency Mars Express mission, is mapping the surface composition of Mars at a 0.3- to 5-kilometer resolution by means of visible-near-infrared hyperspectral reflectance imagery. The data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy, offering key insights into the evolution of Mars. OMEGA has identified and mapped mafic iron-bearing silicates of both the northern and southern crust, localized concentrations of hydrated phyllosilicates and sulfates but no carbonates, and ices and frosts with a water-ice composition of the north polar perennial cap, as for the south cap, covered by a thin carbon dioxide-ice veneer.     

Toxicity survey of Canadian Arctic marine sediments

Purpose

This paper reports a toxicity survey of Canadian Arctic marine sediments. During the Amundsen scientific cruise, eight sites distributed across the Canadian Arctic and sub-Arctic regions were selected to highlight sensitive areas affected by either atmospheric deposition, ocean current, river drainage, or anthropogenic activities. As part of the Canadian-led ArcticNet research program, this study aims to monitor and to better understand potential changes likely to impact the Arctic.

Materials and methods

Surface sediments were investigated with bioanalytical tests to assess sediment toxicity. Testing of sediment elutriates was undertaken with the ARTOXKIT M, Microtox liquid phase (MLPA), and ROTOXKIT M toxicity assays, while whole sediment testing was carried out with the Microtox solid phase assay (MSPA) toxicity test procedure. Sediment mercury (Hg) content was also determined in each sample since Hg transport and toxicity is specifically an important issue in the Arctic and is generally a key indicator of the pollution status in many aquatic ecosystems.

Results and discussion

Based on bioassay results and sediment granulometric criteria, these Arctic sediments must be considered nontoxic. However, based on MSPA half maximal inhibitory concentrations (IC50s) and/or MLPA threshold effect concentration (TEC) values, some degree of toxicity may be measureable particularly in the sediments located in southern and northeast Hudson Bay. The Hudson Bay watershed drains 30% of Canadian rivers and extends to northern USA. Despite the large Hg concern in the Arctic, the input of local or long-range Hg sources does not appear to be a contributing factor to sediment toxicity.

Conclusions

These initial results are valuable in that they set baseline quality levels for these sediments as of 2005. As such, future comparisons can be made to assess temporal and spatial trends. Human activity and climate change is expected to impact these regions in the future, resulting in further reduction of sea ice extent, access to new Arctic seaways, and drilling associated with the exploitation of natural resources.