Effects of poly-β-hydroxybutyrate (PHB) on Siberian sturgeon (Acipenser baerii) fingerlings performance and its gastrointestinal tract microbial community

Poly-β-hydroxybutyrate (PHB) is a natural polymer that can be depolymerized into water-soluble short-chain fatty acid monomers. These monomers can act as microbial control agents. In this study, the effects of partially replacing the diet of Siberian sturgeon fingerlings with 2% and 5% PHB were investigated. Replacing 2% of the diet with PHB improved weight gain, specific growth rate (SGR) and survival in the sturgeon fingerlings during the 10-week experimental period. Community-level physiological profiling and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) were used to analyze the microbial community diversity and community organization in the sturgeon gastrointestinal tract. DGGE analysis revealed that PHB affected the intestinal microbial species richness and diversity. The highest species richness was observed with 2% PHB. DNA sequencing of the dominant bands in 2% and 5% PHB treatments revealed that PHB stimulated bacteria belonging to the genera Bacillus and Ruminococcaceae. Principal component analysis, Lorenz curves and the Shannon index of Biolog Ecoplate data revealed that aerobic metabolic potential of the bacterial community was different in the PHB-treated fishes as compared with the control situation. Overall, our results indicate that PHB act as microbial control agents and replacement of 2% of Siberian sturgeon fingerling diet with PHB has beneficial effects.     

Quality evaluation of brine shrimpArtemia cysts produced in Asian salt ponds

Artemia cysts produced in inoculated salt ponds in the Philippines, Thailand and India, were analyzed in comparison with the parental strains used for the inoculations. Cyst hatching efficiency, hatching rate and color changed significantly after inoculation, whereas the cyst's diameters, nauplius survival and nauplius growth remained fairly constant. The nutritional value of theArtemia nauplii was determined in a standard culture test withMysidopsis bahia juveniles as test animals. Production results were compared with the fatty acid profiles of theArtemia nauplii. Low levels of the essential fatty acid 20:53 in one of the produced cyst batches were probably caused by inadequate food conditions in the pond and resulted in poorer growth of theMysidopsis juveniles. Based on the results of this study a distinction is made between essential and nonessential strain selection-criteria forArtemia inoculations and transplantations.     

International study on Artemia. XXXII. Combined effects of temperature and salinity on the survival of Artemia of various geographical origin

The brine shrimp inhabits geographically isolated biotopes with specific biotic and abiotic conditions. This has resulted in various geographical strains between which marked genetical, biological and chemical differentiation exists. The response of 13 different Artemia strains to the combined effect of temperature and salinity has been studied. Experimental temperatures tested ranged from 18 to 34°C and salinities from 5 to 120%..

Except for Chaplin Lake (itCanada) Artemia, all strains showed high survival over a wide range of salinities (35–110%.). For all strains the common temperature optimum was between 20 and 25°C. Interaction 7between temperature and salinity was negligible or very limited. Substantial differences in tolerance were recorded in particular at the lower end of the range of experimental salinities and at the upper end of the range of temperatures. Resistance to high temperature seems to be related to the genetic classification of the Artemia strains in different sibling species. Differences, however, also exist among strains from the same sibling species. Genetic adaptation to high temperature seems to take place in Artemia.

The data obtained provide a first guideline for strain selection for specific aquacultural purposes.     

Non-lethal heat shock protects gnotobiotic Artemia franciscana larvae against virulent Vibrios

Brine shrimp Artemia were exposed under gnotobiotic conditions to a non-lethal heat shock (NLHS) from 28 to 32, 37 and 40 degrees C. Different recovery periods (2, 6, 12 and 24h) and different heat-exposure times (15, 30, 45 and 60 min) were tested. After these NLHS, Artemia was subsequently challenged with Vibrio. Challenge tests were performed in stressed and unstressed nauplii at concentrations of 10(7) cells ml(-1) of pathogenic bacteria, Vibrio campbellii and Vibrio proteolyticus. A NLHS with an optimal treatment of 37 degrees C for 30 min and a subsequent 6h recovery period resulted in a cross-protection against pathogenic Vibrio. A 100% increase in the larval survival (P < 0.05) was observed. We have also demonstrated by Western blot that a NLHS increases the expression of HSP-70 in heat-shocked (HS) treated animals. This report is the first to reveal a cross protection of a NLHS against deleterious bacterial challenges in living crustaceans. The putative role of heat shock proteins (HSPs) in this process is discussed.     

Influence of different yeast cell-wall mutants on performance and protection against pathogenic bacteria (Vibrio campbellii) in gnotobiotically-grown Artemia

A selection of isogenic yeast strains (with deletion for genes involved in cell-wall synthesis) was used to evaluate their nutritional and immunostimulatory characteristics for gnotobiotically-grown Artemia. In the first set of experiments the nutritional value of isogenic yeast strains (effected in mannoproteins, glucan, chitin and cell-wall bound protein synthesis) for gnotobiotically-grown Artemia was studied. Yeast cell-wall mutants were always better feed for Artemia than the isogenic wild type mainly because they supported a higher survival but not a stronger individual growth. The difference in Artemia performance between WT and mutants feeding was reduced when stationary-phase grown cells were used. These results suggest that any mutation affecting the yeast cell-wall make-up is sufficient to improve the digestibility in Artemia. The second set of experiments, investigates the use of a small amount of yeast cells in gnotobiotic Artemia to overcome pathogenicity of Vibrio campbellii (VC). Among all yeast cell strains used in this study, only mnn9 yeast (less cell-wall bound mannoproteins and more glucan and chitin) seems to completely protect Artemia against the pathogen. Incomplete protection against the pathogen was obtained by the gas1 and chs3 mutants, which are lacking the gene for a particular cell-wall protein and chitin synthesis, respectively, resulting in more glucan. The result with the chs3 mutant is of particular interest, as its nutritional value for Artemia is comparable to the wild type. Hence, only with the chs3 strain, in contrast to the gas1 or mnn9 strains, the temporary protection to VC is not concomitant with a better growth performance under non-challenged conditions, suggesting non-interference of general nutritional effects.     

Characterization of brine shrimp Artemia from Cam Ranh Bay in Central Vietnam

Artemia cysts collected from inoculation experiments in Cam Ranh salterns are evaluated for their potential use in aquaculture. Cyst biometrics, hatching quality, naupliar fatty acid profile and naupliar growth were measured and compared to reference Artemia strains. Cyst characteristics reveal that the parthenogenetic strain (PR China) used in inoculations, was eliminated from the environment and that the remaining brine shrimp are likely to be composed of Macau and Great Salt Lake Artemia strains, and of their cross-breds. Differences in cyst diapause deactivation characteristics between Macau and Great Salt Lake Artemia may have resulted in the disappearance of Macau Artemia during the rainy season and the persistence of Great Salt Lake Artemia during the following dry season.     

The bacterial storage compound poly-beta-hydroxybutyrate protects Artemia franciscana from pathogenic Vibrio campbellii

Infections caused by antibiotic-resistant luminescent Vibrios can cause dramatic losses in aquaculture. In this study, the short-chain fatty acid beta-hydroxybutyrate and its polymer poly-beta-hydroxybutyrate were investigated as possible new biocontrol agents. beta-Hydroxybutyrate was shown to completely inhibit the growth of pathogenic Vibrio campbelli at 100 mM. Moreover, the addition of 100 mM of this fatty acid to the culture water of Artemia nauplii infected with the V. campbelli strain significantly increased the survival of the nauplii. As Artemia is a non-selective and particle filter feeder, we also investigated whether poly-beta-hydroxybutyrate particles could be used to protect Artemia from the pathogenic V. campbellii. The addition of 100 mg l(-1) poly-beta-hydroxybutyrate or more to the Artemia culture water offered a preventive and curative protection from the pathogen as a significantly enhanced survival was noticed. If added as a preventive treatment, a complete protection of infected nauplii (no significant mortality compared with uninfected nauplii) was observed at 1000 mg l(-1) poly-beta-hydroxybutyrate. Our data indicate that the use of poly-beta-hydroxybutyrate might constitute an ecologically and economically sustainable alternative strategy to fight infections in aquaculture.     

Live food mediated vitamin C transfer to Dicentrarchus labrax and Clarias gariepinus

Live food enrichment techniques, using formulated diets and emulsions for improving the nutritional quality of Brachionus and Artemia , were studied as a tool for transferring ascorbic acid (AA) to fish larvae.
Artemia nauplii enriched for 24 h with an experimental emulsion containing 20% HUFA and 0%, 10% and 20% ascorbyl palmitate (AP) were administered to catfish larvae in a 20-day feeding trial. Survival was not affected by the dietary AA, but from day 7 onwards a significantly positive effect of supplemental AA on growth was demonstrated. At the end of the experiment the 20% AP group weighed 30% more than the control (0% AP), i.e. 9.5 and 6.3 mg DW, respectively. Evaluation of the physiological condition was demonstrated by salinity tests. In all three treatments larval growth was relatively low, and it still has to be verified if extra vitamin C in the diet really promotes growth. Seabass larvae fed on AP-enriched rotifers (days 4–12) and Artemia nauplii (days 13–46) showed no significant differences in production characteristics nor in stress resistance, however, for all salinity stress tests the 20% AP group performed better. AA was well incorporated into the predator larvae from the Brachionus feeding onwards.