Bayesian estimation of diagnostic sensitivity and specificity of a qPCR and a bacteriological culture method for Piscirickettsia salmonis in farmed Atlantic salmon (Salmo salar L.) in Chile

Early detection of piscirickettsiosis is an important purpose of government- and industry-based surveillance for the disease in Atlantic salmon farms in Chile. Real-time qPCRs are currently used for surveillance because bacterial isolation is inadequately sensitive or rapid enough for routine use. Since no perfect tests exist, we used Bayesian latent class models to estimate diagnostic sensitivity (DSe) and specificity (DSp) of qPCR and culture using separate two-test, single-population models for three farms (n = 148, 151, 44). Informative priors were used for DSp (culture (beta(999,1); qPCR (beta(98,2)), and flat priors (beta 1,1) for DSe and prevalence. Models were run for liver and kidney tissues combined and separately, based on the presence of selected gross-pathological signs. Across all models, qPCR DSe was 5- to 30-fold greater than for culture. Combined-tissue qPCR median DSe was highest in Farm 3 (sampled during P. salmonis outbreak (DSe = 97.6%)) versus Farm 1 (DSe = 85.6%) or Farm 2 (DSe = 83.5%), both sampled before clinical disease. Median DSe of qPCR was similar for liver and kidney, but higher when gross-pathological signs were evident at necropsy. High DSe and DSp and rapid turnaround-time indicate that the qPCR is fit for surveillance programmes and diagnosis during an outbreak. Targeted testing of salmon with gross-pathological signs can enhance DSe.     

Dietary n‐3/n‐6 ratio affects the biochemical composition of Eurasian perch (Perca fluviatilis) semen but not indicators of sperm quality

In general, the effects of dietary fatty acids (FA) on sperm quality have received less attention than egg quality, and were never studied in perch. This study investigated the effects of dietary FAs on the quality and chemical composition of sperm in Eurasian perch (Perca fluviatilis). Two experimental diets containing 16% lipids and 45% proteins were compared. The n‐3/n‐6 ratios tested were 0.2 for diet 1 (D1) and 7.0 for diet 2 (D2). No significant effects of the n‐3/n‐6 ratio were observed on the sperm characteristics, either in terms of the sperm volume (around 1.2 mL) and density, spermatozoa motility (94%) and velocity, or the sperm osmolality. All these parameters corresponded to semen of good quality in Eurasian perch. Interestingly, both the FA composition and the lipid class profile of the semen were correlated to the tested diet. However, basal levels of certain highly unsaturated FAs such as eicosapentaenoic acid, 20:5 n‐3 and docosahexaenoic acid, 22:6 n‐3, were maintained in the sperm irrespective of the diet tested. Perch semen was characterized by high levels of cholesterol, phosphatidylethanolamine and phosphatidylcholine. In conclusion, the dietary n‐3/n‐6 ratio affects the lipid composition of perch semen but not the indicators of sperm quality.     

A Practical Approach for Sexing Zebrafish,Danio rerio

This study aimed at a simple, rapid, reliable, practical, and non-destructive sexing technique for mature zebrafish (0.61 ± 0.011 g each). In the first experiment, 36 fish of each sex were selected on the basis of the presence of a prominent genital papilla on mature females and bred randomly. All the couples laid fertilized eggs with a mean fecundity of 304 eggs per female, for a 100% sexing accuracy. In the second experiment, 140 mature zebrafish were randomly selected and individually sexed like in the first experiment. Each fish was then dissected in order to confirm the reliability of this sexing technique through the observation of either the ovaries or the testes. Upon dissection, an accuracy of 100% was recorded. This study demonstrates that sexing mature zebrafish only on the basis of the presence of a prominent genital papilla on the mature female is a reliable technique.     

Fate of polyphenols and antioxidant activity of barley throughout malting and brewing

Phenolic contents of barley and malt extracts and their corresponding antioxidant activities were investigated using a chromatographic online antioxidant detection system. Ethyl acetate extracts of barley and malt were separated using reverse phase HPLC and compounds eluting from the column were submitted to two UV–visible detections: one for the phenolic compounds; and the other for the reduced form of the radical cation 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+) after the compounds were allowed to react online with it. Prodelphinidin B3 and procyanidin B3 were identified as two major contributors in the antioxidant activity of barley, in addition to catechin. Malting had a dramatic impact on these three compounds by resulting in a sharp decrease in their detected amounts and the associated antioxidant activities. Two other antioxidants, ferulic and sinapic acids, showed a better ability to withstand not only malting but also brewing steps. As for the overall phenolic content and antioxidant capacity, the study showed that malting allowed a better release and/or extraction of phenolic compounds, while the first brewing step caused the most significant damage by drastically decreasing the total polyphenols and their activity. Hopping however did not significantly affect neither the phenolic content nor the antioxidant activity.     

Effect of natural root grafting on growth response of jack pine (Pinus banksiana) after commercial thinning

Commercial thinning is a silvicultural treatment used to increase the merchantable yield of residual trees. Growth response to thinning, however, is highly variable and discrepancies between studies remain largely unexplained. The objective of this study was to demonstrate the effect of natural root grafting on growth response after thinning. We excavated root systems of jack pine (Pinus banksiana) in five naturally regenerated stands, in which three had been commercially thinned 6 and 9 years earlier. Radial growth before and after thinning was examined using dendrochronological techniques. Thinning increased radial growth of trees, however growth increments were significantly less for trees that had root grafts with removed trees, while growth of grafted trees was better in unthinned stands. Furthermore, radial growth response of trees grafted to removed trees was smaller than that of non-grafted trees 4 years and more post-thinning. On average, non-grafted stumps survived less than 1 year (0.4 year), while grafted stumps lived 2.0 years after the stem was removed. Differences in growth response to thinning between grafted and non-grafted trees thus appear to be linked to the support of roots and stumps of removed trees by live residual trees.     

VisEgg: a robust phenotyping tool to assess rainbow trout egg features and viability

Fish Physiology and Biochemistry - Assessing female fish reproductive success requires a thorough evaluation of egg characteristics, including egg number, size, and variability as well as egg...     

Antimalarial Activity of Axidjiferosides,New β-Galactosylceramides from the African Sponge Axinyssa djiferi

The marine sponge, Axinyssa djiferi, collected on mangrove tree roots in Senegal, was investigated for glycolipids. A mixture containing new glycosphingolipids, named axidjiferoside-A, -B and -C, accounted for 0.07% of sponge biomass (dry weight) and for 2.16% of total lipids. It showed a significant antimalarial activity, with a 50% inhibitory concentration (IC₅₀) of 0.53 ± 0.2 μM against a chloroquine-resistant strain of Plasmodium falciparum. They were identified as homologous β-galactopyranosylceramides composed of 2-amino-(6E)-octadec-6-en-1,3,4-triol, and the major one, axidjiferoside-A (around 60%), contained 2-hydroxytetracosanoic acid. Cytotoxicity was studied in vitro on human cancer cell lines (multiple myeloma, colorectal adenocarcinoma, glioblastoma and two lung cancer NSCLC-N6 and A549). Results of this investigation showed that axidjiferosides are of interest, because they proved a good antiplasmodial activity, with only a low cytotoxicity against various human cell lines and no significant antitrypanosomal and antileishmanial activity. Thus, it seems that galactosylceramides with a β anomeric configuration may be suitable in searching for new antimalarial drugs.     

Evaluation of dried macrophytes as an alternative diet for the rearing of the sea urchin Paracentrotus lividus (Lamarck, 1816)

The aim of this work was to assess the potential use of different dried macroalgae as food in the rearing of Paracentrotus lividus. Growth, consumption and food conversions were compared in adult sea urchins fed with fresh or dried thalli of four macroalgae species. Six experimental diets were tested: (a) fresh Palmaria palmata; (b) fresh Saccharina latissima; (c) dry P. palmata; (d) dry S. latissima; (e) dry Laminaria digitata and (f) dry Grateloupia turuturu. Linear growth rates were similar for all treatments. Specific growth rate was higher in sea urchins fed with fresh P. palmata, but no difference was found between animals fed with fresh S. latissima and those fed with dried diets. Regarding daily food consumption (DFC), sea urchins consumed the same amount of dried macroalgae as fresh but exhibited a higher food conversion efficiency (FCE) when fed with fresh P. palmata. However, this FCE was only significantly higher when compared to sea urchins fed with dry L. digitata. Dried G. turuturu is not a suitable diet due to its rapid degradation after rehydration. The results suggest that P. lividus adults can be reared on dried macroalgae thalli without detriment to their somatic growth, especially over short periods. The low cost of feeding sea urchins with this diet could help small shellfish farmers to diversify their production into echinoculture.