Haematological and immunological responses of sea bass (Dicentrarchus labrax) to a short-term exposure to increased water levels of nitrate

Fish reared under intensive culture conditions very often face stressful adverse conditions which either do not exist in nature, for example living in extremely high stocking densities, or they are quite unlikely, for example increased water ammonia levels (Huntingford et al. 2006).Nitrate (NO3 −) which is the ionized form of nitric acid (Cheng and Chen, 2002) and salts, like sodium nitrate, are readily soluble in water and completely dissociated. It is produced by a two-step process called ‘nitrification’ (Hargreaves and Tucker, 2004). During this process, ammonia, which is either excreted from fish or produced by the decomposition of the organic matter in the water, is first oxidized to nitrite (NO2 –) and subsequently to nitrate (NO3–). The nitrification rate can be affected by many factors such as water temperature and available diluted oxygen (Hargreaves and Tucker, 2004)

Transcriptional Responses of Resistant and Susceptible Fish Clones to the Bacterial Pathogen Flavobacterium psychrophilum

Flavobacterium psychrophilum is a bacterial species that represents one of the most important pathogens for aquaculture worldwide, especially for salmonids. To gain insights into the genetic basis of the natural resistance to F. psychrophilum, we selected homozygous clones of rainbow trout with contrasted susceptibility to the infection. We compared the transcriptional response to the bacteria in the pronephros of a susceptible and a resistant line by micro-array analysis five days after infection. While the basal transcriptome of healthy fish was significantly different in the resistant and susceptible lines, the transcriptome modifications induced by the bacteria involved essentially the same genes and pathways. The response to F. psychrophilum involved antimicrobial peptides, complement, and a number of enzymes and chemokines. The matrix metalloproteases mmp9 and mmp13 were among the most highly induced genes in both genetic backgrounds. Key genes of both pro- and anti-inflammatory response such as IL1 and IL10, were up-regulated with a greater magnitude in susceptible animals where the bacterial load was also much higher. While higher resistance to F. psychrophilum does not seem to be based on extensive differences in the orientation of the immune response, several genes including complement C3 showed stronger induction in the resistant fish. They may be important for the variation of susceptibility to the infection

Evaluation of Six Anesthetics for Use with the Mediterranean Mussel, Mytilus galloprovincialis

An effective anesthetic scheme would significantly contribute to the investigation of disease in the Mediterranean mussel (Mytilus galloprovincialis), especially when biopsy is required. In this study, we evaluated the efficacy of six anesthetics: 2-phenoxyethanol (2 ml/l), ΜS222 (0.4 and 1 g/l), MgCl2 (20 and 50 g/l), clove oil (1.5 ml/l), benzocaine (1.5 g/l), and 1-phenoxy-2-propanol (2.5 ml/l) when used to anesthetize Mediterranean mussel. For this purpose, 810 mussels were allocated to nine groups of 90 mussels each (three replicates of 30 individuals in each group). Each group was exposed to one of the above concentrations of anesthetics for 24 h, except for one group kept as the control. Mussels were considered anesthetized when they did not close their valves after tapping them with a pair of forceps. The most effective anesthesia was MS222 at the concentration of 1 g/l; it induced anesthesia in 58.8±1.92% of the exposed mussels with negligible mortality (5.7±5.8%) of the anesthetized mussels one week after anesthesia. Further, when using MS222 there was no correlation between the number of anesthetized mussels and temperature. However, the number significantly increased as the size of the mussels decreased. MgCl2 at the concentration of 20 g/l resulted in notable retardation of valve movement

Persistence of Flavobacterium psychrophilum in the aquatic environment

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Standardizing the microbiota of fish used in research

Author's accepted version (post-print).Little attention has been paid to the effects of fish microbiotas on the reproducibility and comparability of fish studies so far. Extrinsic and intrinsic factors, such as water quality, environmental microbial populations, diet, host genetic profile, gender, age and stress status, affect fish microbiotas and create significant inter- and intra-species variations. Fish microbiotas play critical roles in many key aspects of host physiology, such as protection against pathogens, digestion and development of the digestive tract and the local immune system. Thus, greater effort should be invested in standardizing the microbiological profiles of research fish. In this context, issues requiring consideration include the establishment of isogenic and isobiotic fish lines, the standardization of rearing conditions and the development of appropriate tests to adequately describe microbial populations. There are many challenges involved in each of these issues, and the research community must decide which aspects should be standardized for each species and each type of research. For all studies in which microbiota is expected to exert an influence, thorough reporting is of paramount importance. Every step towards standardization increases study quality and simultaneously contributes to reducing the number of fish used in research, which is a legal and ethical obligation