Some effects of light intensity and photoperiod on the sea bass larvae (Dicentrarchus labrax (L.)) reared at the Centre Oceanologique de Bretagne

Four experiments were performed to determine the effects of light intensity on the growth and survival of sea bass larvae; two experiments dealt with the photoperiod and two with the combined effects of light intensity and the photoperiod. Recently hatched larvae from the same spawning were used within each experiment.The light intensity experiments show that there is better growth but poorer survival at higher light intensities. The photoperiod experiments show a better growth at 18 h photoperiod and a better survival at 12 h exposure to light. The study of the combined effects of light intensity and photoperiod confirmed the hypothesis that strong light intensities are lethal to newly hatched larvae (with no pigmentation). If the light intensity is lowered during the first week, the best rearing conditions were found to be continuous lighting relative to survival rate, and 14–16 h photoperiod relative to growth.     

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.     

Evidence for an expanded host range ofFusarium oxysporum f.sp.raphani

The pathogenicity of four isolates ofFusarium oxysporum obtained from infected cultivated rocket (Eruca vesicaria) and wild (sand) rocket (Diplotaxis tenuifolia) was tested on the following cruciferous hosts: stock, radish, wild and cultivated rockets, and various species in the cabbage tribe: cabbage (Brassica oleracea var.sabauda), cauliflower (Brassica oleracea var.botrytis), Brussels sprouts (Brassica oleracea var.gemmifera), broccoli (Brassica oleracea var.italica), turnip (Brassica rapa var.rapa). The results indicated that isolates ofF. oxysporum from cultivated and wild rocket belong to theforma specialis raphani. The isolates from rocket were pathogenic on cabbage, Brussels sprouts, broccoli, turnip, radish and stock; isolates ofF. oxysporum conglutinans from cabbage and radish, and the isolate ofF. oxysporum f.sp.raphani from rape obtained from the ATCC collection, were pathogenic on both cultivated and wild rocket.     

Evaluation of non-chemical seed treatment methods for the control of Alternaria dauci and A. radicina on carrot seeds

The current study was initiated to evaluate the efficacy of physical methods (hot water, aerated steam, electron treatment) and agents of natural origin (resistance inducers, plant derived products, micro-organisms) as seed treatments of carrots for control of Alternaria dauci and A. radicina. Control of both Alternaria species by seed treatment with the resistance inducers was generally poor. Results were also not satisfactory with most of the formulated commercial micro-organism preparations. Based on the average of five field trials, one of these, BA 2552 (Pseudomonas chlororaphis), provided a low but significant increase in plant stand. Among the experimental micro-organisms, the best results were obtained with Pseudomonas sp. strain MF 416 and Clonostachys rosea strain IK726. A similar level of efficacy was provided by seed treatment with an emulsion (1%) of thyme oil in water. Good and consistent control was generally achieved with the physical methods aerated steam, hot water and electron treatment. Aerated steam treatment was, apart from the thiram-containing chemical standard, the best single treatment, and its performance may at least partially be due to extensive pre-testing, resulting in dosages optimally adapted to the respective seed lot. In some of the experiments the effect of the hot water treatment, which was tested at a fixed, not specifically adapted dosage, was significantly improved when combined with a Pseudomonas sp. MF 416 or C. rosea IK726 treatment. The results are discussed in relation to the outcome of experiments in which the same seed treatment methods and agents were tested in other seed-borne vegetable pathosystems.     

Tissue distribution of Red Spotted Grouper Nervous Necrosis Virus (RGNNV) genome in experimentally infected juvenile European seabass (Dicentrarchus labrax)

The distribution of viral genome in the tissues of juvenile European seabass (Dicentrarchus labrax) during the course of a Red Spotted Grouper Nervous Necrosis Virus (RGNNV) infection has not yet been described. The present study addresses this and indicates which target organs may be involved in viral replication. This information should enable more accurate detection of virus in asymptomatic carriers, and in turn help to control the spread of the disease. The aim of this study was to examine the pattern of expression of viral genomic segments RNA1 and RNA2, using two absolute real-time PCRs (RT-qPCR), over the course of a RGNNV infection after administering the virus by intramuscular injection. In situ hybridization was also used to locate the RNA2 viral segment in different organs throughout the infection. The experimental challenge provoked an acute form of viral nervous necrosis (VNN), with a resulting cumulative mortality of 37%. The RT-qPCRs designed allowed the detection of both genomic segments in all the organs tested (nervous and non-nervous tissues) at all sampling times examined. The highest viral RNA copy number was found in eyes, although viral replication appeared to begin in the brain. Viral replication was also recorded in pooled internal organs and in caudal fin. However, the increase in the viral RNA copy number in these organs did not result in an increased viral titre, which may indicate that a productive infection does not take place in non-nervous tissues, possibly due to a failure in a viral post-replication step.     

Initial cooling time before freezing affects post‐thaw quality and reproductive performance of rabbit semen

The aim of this study was to investigate the effect of initial cooling time at 5°C during semen cryopreservation on post‐thaw quality and reproductive performance of rabbit semen. Pooled semen samples (n = 6) were divided into two subsamples and cooled at 5°C for 45 or 90 min. After cooling, the semen samples were diluted to a ratio of 1:1 (v:v) with a freezing extender composed of Tris‐citrate‐glucose (TCG) containing 16% of dimethylsulfoxide and 0.1 mol/L sucrose. The semen was subsequently loaded in 0.25 ml straws, equilibrated at 5°C and frozen in liquid nitrogen vapor. After thawing, sperm motility, viability, osmotic resistance, acrosome and DNA integrity were assessed. Our results indicate that the longer cooling time, that is, 90 min before cryopreservation significantly improves sperm post‐thaw viability, motility and fertility. In fact, reproductive performances obtained with semen frozen after a 90 min cooling time were similar to those produced by fresh semen insemination. Hence, the present research provides an effective freezing protocol for rabbit semen that will allow for the creation of a sperm cryobank for the conservation of Italian rabbit genetic resources, as well as the use of frozen semen doses in commercial farms.     

Pseudomonas fluorescens contamination of a feline packed red blood cell unit and studies of canine units

Background: While screening programs have reduced the risk of infectious disease transmission by donors in human and veterinary blood banking, bacterial contamination of blood products has emerged as a major complication in human medicine. Objectives: To describe a Pseudomonas fluorescens (Pf)‐contaminated feline packed RBC (pRBC) unit and experimentally investigate Pf‐contaminated canine pRBCs. Methods: Canine pRBCs were inoculated with Pf‐rich pRBCs from the sentinel feline unit and stored at 4°C or 20°C for 72 hours. Aliquots from the pRBCs were serially evaluated by microscopy, culture, and a eubacterial 16S rRNA real‐time PCR assay. Results: One Pf‐contaminated feline unit turned black after 22 days of storage and was removed from the blood bank; a source was not found, and no other contaminated units were identified. Canine pRBCs spiked with 5 or 25 μL of the sentinel unit became culture‐ and/or 16S PCR‐positive at ≥8 hours at 20°C and 48 hours at 4°C and developed a color change at ≥24 hours. Sensitivity studies indicated that without incubation, inoculation of ≥100 μL Pf‐rich pRBCs was necessary for a positive 16S PCR test result. Conclusions: P. fluorescens grows in stored pRBCs slowly at 4°C and rapidly at 20°C. Screening of blood products for color change, estimating bacterial concentration with microscopy, and 16S PCR testing are simple and fast ways to detect bacteria in stored blood. Aseptic collection, temperature‐controlled storage, and regular visual monitoring of stored units is recommended. Discolored units should not be transfused, but examined for bacterial contamination or other blood product quality problems.     

Seroprevalence and risk factors for Neospora caninum in sheep in the state Minas Gerais, southeastern Brazil

The aim of this study was to determine the prevalence and risk factors associated with infection due to Neospora caninum in serum samples from 488 sheep originating from 63 farms in 63 municipalities distributed across eight of the twelve mesoregions of the state Minas Gerais, southeastern Brazil. For detection of N. caninum the sheep serum samples were subjected to the indirect fluorescence antibody test (IFAT ≥ 50). To identify the risk factors associated with infection due to N. caninum a questionnaire was filled out for each herd by interviewing, the individual responsible for the herd, demanding information on the general characteristics of the property. Sixty-four sheep sera (13.1%; 95% CI=10.3-16.4) presented IgG-specific anti-N. caninum antibodies with the following titers: 50 (49; 76.6%), 100 (7; 10.9%), 200 (4; 6.2%), 400 (3; 4.7%) and 800 (1; 1.6%). The prevalence of infected sheep per mesoregion ranged from 0 to 28.1%. Out of the 63 farms sampled, 31 (49.2%; 95% CI=36.4-62.1) presented at least one seropositive sheep. No significant association was found between the presence of anti-N. caninum antibodies and the risk factors evaluated on the farms, except for the mesoregion variable (p=0.004; OR=0.429; CI95%=0.182-1.008). These results indicate that there is a need for additional research to define the epidemiological importance of this parasite as a cause of reproductive problems in sheep herds in Minas Gerais.     

Food resources and cyprinid diet in permanent and temporary Mediterranean rivers with natural and regulated flow

This study addresses the differences in food availability, diet and feeding activity of the Iberian barbel, between permanent and temporary nonregulated rivers, and the effect of flow regulation on feeding parameters. A total of 267 adult barbels were seasonally collected in four nonregulated and regulated rivers from permanent and temporary basins, and their gut content was analysed. Locally available food sources were evaluated across sites and seasons. Barbels from the permanent nonregulated river exhibit a more variable and diversified diet in which invertebrates assumed a large importance, especially during high flows. Barbels from the temporary nonregulated river presented a more uniform diet composed of plant material and detritus, particularly in drought seasons. Flow regulation affected different flow components in both systems, but the effects on food resources and barbels' diet were similar, resulting in an intra‐annual stabilisation of resource availability and fish diet, with a higher consumption of plants and detritus. Changes in fish diet and feeding activity in both nonregulated and regulated rivers were strongly associated with the seasonal variability of streamflow components, particularly between low‐ and high‐flow periods, and with the reduction in flow variability in the case of dam regulation. Results from this study can be used to improve guidelines for flow requirement implementation.