Studies on the pathogenesis of Vibrio spp infection in Penaeus monodon Fabricius

Vibrio infections are one of the principal final causes of serious production losses in penaeid shrimp farming. The pathogenesis of experimental Vibrio spp infections in Penaeus monodon has been investigated using an immunohistochemical technique. A Vibrio spp isolate was obtained from a disease outbreak in Thailand and identified using biochemical tests and SDS-PAGE. The isolate was identified as gelatine negative Vibrio vulnificus biotype I with variable urease activity. A polyclonal antiserum was raised in rabbits against the bacterium and its specificity tested by means of agglutination, immunoblot and ELISA tests. This antiserum was used to identify the 31KD protein and a 90-99KD LPS fraction responsible for the immune response using a Western-blot technique. P. monodon juveniles were experimentally infected with the bacterium either by injection, ingestion or bath challenge method. In a time course study, an indirect immunoperoxidase technique was employed to trace the presence of the bacterium in the tissue of the challenged shrimps. The penetration of the bacteria differed between the three challenge methods, the clearance mechanisms of bacteria converged into common routes. Bacterial cells penetrated through damaged gill cuticle, body cuticle or through the insertion of the cuticular setae. Haemocytes were observed to phagocytose the bacterial cells and migrate through connective tissue and be transported with the haemolymph, accumulating around hepatopancreas, midgut caecum, gills and antennal gland. Once the phagocytic haemocytes reached the heart, they were distributed to lymphoid organ. Bacterial material appeared to accumulate in heart and lymphoid organ. Bacteria entering through the mouth were broken down and only soluble material filtered through gastric sieves passed into the hepatopancreas. This soluble material then diffused through the hepatopancreatic tubules into the haemolymph and then to gills and antennal gland. Once this material reached the heart it was distributed to lymphoid organ accumulating in the heart and lymphoid organ as previously described. Finally, bacterial material was released to the exterior in two steps. Initially through the gills and later through hepatopancreatic B-cell vacuoles and branchial and subcuticular podocytes. This mechanism and its implications are discussed

Standardized white spot syndrome virus (WSSV) inoculation procedures for intramuscular or oral routes

In the past, strategies to control white spot syndrome virus (WSSV) were mostly tested by infectivity trials in vivo using immersion or per os inoculation of undefined WSSV infectious doses, which complicated comparisons between experiments. In this study, the reproducibility of 3 defined doses (10, 30 and 90 shrimp infectious doses 50% endpoint [SID50] of WSSV was determined in 3 experiments using intramuscular (i.m.) or oral inoculation in specific pathogen-free (SPF) Litopenaeus vannamei. Reproducibility was determined by the time of onset of disease, cumulative mortality, and median lethal time (LT50). By i.m. route, the 3 doses induced disease between 24 and 36 h post inoculation (hpi). Cumulative mortality was 100% at 84 hpi with doses of 30 and 90 SID50 and 108 hpi with a dose of 10 SID50. The LT50 of the doses 10, 30 and 90 SID50 were 52, 51 and 49 hpi and were not significantly different (p > 0.05). Shrimp orally inoculated with 10, 30 or 90 SID50 developed disease between 24 and 36 hpi. Cumulative mortality was 100% at 108 hpi with doses of 30 and 90 SID50 and 120 hpi with a dose of 10 SID50. The LT50 of 10, 30 and 90 SID50 were 65, 57 and 50 hpi; these were significantly different from each other (p 50 was selected as the standard for further WSSV challenges by i.m. or oral routes. These standardized inoculation procedures may be applied to other crustacea and WSSV strains in order to achieve comparable results among experiment

European aquaculture competitiveness: Limitations and possible strategies

This study examines the competitiveness of the EU aquaculture sector, as a contribution to the wider review of EU aquaculture policy being carried out by the European Community institutions. EU aquaculture competes with its international equivalents, with outputs from capture fisheries, and more fundamentally within global food markets. With small exceptions, the sector invests in production within the EU, and as little of its product is exported, competition is so far primarily defined within EU markets. Whilst EU aquatic food consumption has risen over the past 10 years, with stable or declining capture fisheries supply, most of this increase has come from imports rather than growth of EU aquaculture. To substantially increase aquaculture production at competitive prices for mainstream EU markets will require larger entities capable of scale economies, although small and micro-enterprises can also provide niche products and help sustain rural and coastal livelihoods. As spatial expansion is highly constrained by environmental regulation and conflicts with other resource users, productivity gains will be important in increasing output. Technological solutions are emerging, but are costly, so under current conditions, investments are more likely to be made in lower-cost production systems in third countries that export to the EU

Tracing sulfate recycling in the hypersaline Pétrola lake (SE Spain): A combined isotopic and microbiological approach

Sulfur (S) plays a significant role in saline environments, and sulfate (SO4 2−) is an important component of the biogeochemical S-cycle since it acts as the main electron acceptor in anoxic sediments. The purpose of this paper is to evaluate the fate of S, its origin, and processes affecting sulfate outcome in the hypersaline Pétrola Lake in the Castilla-La Mancha region (High Segura Basin, SE Spain). The lake is the terminal discharge zone of an endorheic basin with considerable anthropogenic pressures. Anthropogenic activities (mainly agricultural inputs and wastewater discharge), together with bedrock leaching of sulfate and sulfide-rich sediments, increase dissolved SO4 2− in surface and groundwater up to 123,000 mg/L. The source and fate of sulfate in this environment was investigated coupling hydrochemistry, including hydrogen sulfide (H2S) microprofiles, isotopic analyses (δ34S, δ18OSO4, δ2HH2O, δ18OH2O, and tritium), mineralogical determinations, and molecular biology tools (16S rDNA amplification and sequencing). The origin of dissolved SO4 2− in water is related to pyrite oxidation from Lower Cretaceous sediments, and secondary gypsum dissolution. Under the lake, dissolved SO4 2− decreases with depth, controlled by three main processes: (1) seasonal evaporation cycles, (2) hydrodynamic instability caused by the different density-driven groundwater flow, and (3) sulfate-reduction processes, i.e. dissimilatory bacterial sulfate reduction (BSR). These processes control the continuous recycling of sulfur in the system. Lake water and groundwater are in hydraulic connection, and a density-driven flow (DDF) is able to transport reactive organic matter and dissolved SO4 2− towards the underlying aquifer. Hydrochemical evolution in depth, H2S production (up to 0.024 nmol/cm3·s) and the presence of sulfate-reducing bacteria suggest the existence of BSR processes. However, isotope techniques are insufficient to elucidate BSR processes since their isotopic effect is masked by low isotope fractionation and high SO4 2− concentrations. The pattern here described may be found in other saline basins worldwide

A Multi-isotopic approach to investigate the influence of land use on nitrate removal in a highly saline lake-aquifer system

Endorheic or closed drainage basins in arid and semi-arid regions are vulnerable to pollution. Nonetheless, in the freshwater-saltwater interface of endorheic saline lakes, oxidation-reduction (redox) reactions can attenuate pollutants such as nitrate (NO3- ). This study traces the ways of nitrogen (N) removal in the Pétrola lake- aquifer system (central Spain), an endorheic basin contaminated with NO3- (up to 99.2 mg/L in groundwater). This basin was declared vulnerable to NO3- pollution in 1998 due to the high anthropogenic pressures (mainly agriculture and wastewaters). Hydrochemical, multi-isotopic (δ18ONO3, δ15NNO3, δ13CDIC, δ18OH2O, and δ2HH2O) and geophysical techniques (electrical resistivity tomography) were applied to identify the main redox processes at the freshwater-saltwater interface. The results showed that the geometry of this interface is influenced by land use, causing spatial variability of nitrogen biogeochemical processes over the basin. In the underlying aquifer, NO3- showed an average concentration of 38.5 mg/L (n = 73) and was mainly derived from agricultural inputs. Natural attenuation of NO3- was observed in dryland farming areas (up to 72%) and in irrigation areas (up to 66%). In the Pétrola Lake, mineralization and organic matter degradation in lake sediment play an important role in NO3- reduction. Our findings are a major step forward in understanding freshwater-saltwater interfaces as reactive zones for NO3- attenuation. We further emphasize the importance of including a land use perspective when studying water quality-environmental relationships in hydrogeological systems dominated by density- driven circulation