Interactions between parasite, host and host-associated microbiota are increasingly understood as important determinants of disease progression and morbidity. Salmon lice, including the parasitic copepod Lepeophtheirus salmonis and related species, are perhaps the most important problem facing Atlantic Salmon aquaculture after feed sustainability. Salmon lice parasitize the surface of the fish, feeding off mucus, scales and underlying tissue. Secondary bacterial infections are a major source of associated morbidity. In this study we tracked the diversity and composition of Salmo salar skin surface microbiota throughout a complete L. salmonis infection cycle among 800 post-smolts as compared to healthy controls. Among infected fish we observed a significant reduction in microbial richness (Chao1, P = 0.0136), raised diversity (Shannon, P < 7.86e-06) as well as highly significant destabilisation of microbial community composition (Pairwise Unifrac, beta-diversity, P < 1.86e-05; P = 0.0132) by comparison to controls. While undetectable on an individual level, network analysis of microbial taxa on infected fish revealed the association of multiple pathogenic genera (Vibrio, Flavobacterium, Tenacibaculum, Pseudomonas) with high louse burdens. We discuss our findings in the context of ecological theory and colonisation resistance, in addition to the role microbiota in driving primary and secondary pathology in the host.
We evaluated the effects of enriched rotifers on growth, survival and on the lipid composition of haddock larvae. The treatments tested were (1) AlgaMac 2000 Ò , (2) AquaGrow Ò Advantage and (3) Pavlova sp. paste and AlgaMac 2000 Ò . The treatments did not influence larval growth rate throughout the experimental period (P = 0.70). Larvae from all treatments grew approximately 8% of their dry weight per day between 1 and 29 days post hatch (dph). Treatment 3 resulted in the best survival, estimated to be 3 on a scale from 0 to 5, whereas for the two other groups the survival estimates were 0 and 2. Rotifers from treatment 1 had low sterol concentrations, high eicosapentaenoic acid/arachidonic acid ratio and their feeding resulted in high larval mortality. Rotifers enriched with Pavlova sp. had the lowest proportions of the sum of saturated fatty acids, docosahexaenoic acid and sum of x3 and the highest proportions of the sum of monounsaturated fatty acids (SMUFA). This was partially reflected in larvae from treatment 3 in that they had the highest proportions of SMUFA and the lowest proportions of Sx3 (P < 0.0001 for both analyses). In addition, these larvae had the highest and lowest SC 20 and SC 22 polyunsaturated fatty acids (PUFA) respectively (P < 0.0001 for both analyses). We suggest that more research with x3 and x6 PUFA can lead to improvements in the rearing of haddock larvae produced in hatcheries.
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