Gene expression profiling of trout muscle during flesh quality recovery following spawning

Background Sexual maturation causes loss of fish muscle mass and deterioration of fillet quality attributes that prevent market success. We recently showed that fillet yield and flesh quality recover in female trout after spawning. To gain insight into the molecular mechanisms regulating flesh quality recovery, we used an Agilent-based microarray platform to conduct a large-scale time course analysis of gene expression in female trout white muscle from spawning to 33 weeks post-spawning. Results In sharp contrast to the situation at spawning, muscle transcriptome of female trout at 33 weeks after spawning was highly similar to that of female trout of the same cohort that did not spawn, which is consistent with the post-spawning flesh quality recovery. Large-scale time course analysis of gene expression in trout muscle during flesh quality recovery following spawning led to the identification of approximately 3340 unique differentially expressed genes that segregated into four major clusters with distinct temporal expression profiles and functional categories. The first cluster contained approximately 1350 genes with high expression at spawning and downregulation after spawning and was enriched with genes linked to mitochondrial ATP synthesis, fatty acid catabolism and proteolysis. A second cluster of approximately 540 genes with transient upregulation 2 to 8 weeks after spawning was enriched with genes involved in transcription, RNA processing, translation, ribosome biogenesis and protein folding. A third cluster containing approximately 300 genes upregulated 4 to 13 weeks after spawning was enriched with genes encoding ribosomal subunits or regulating protein folding. Finally, a fourth cluster that contained approximately 940 genes with upregulation 8 to 24 weeks after spawning, was dominated by genes encoding myofibrillar proteins and extracellular matrix components and genes involved in glycolysis. Conclusion Overall, our study indicates that white muscle tissue restoration and flesh quality recovery after spawning are associated with transcriptional changes promoting anaerobic ATP production, muscle fibre hypertrophic growth and extracellular matrix remodelling. The generation of the first database of genes associated with post-spawning muscle recovery may provide insights into the molecular and cellular mechanisms controlling muscle yield and fillet quality in fish and provide a useful list of potential genetic markers for these traits.

The Quality of Rainbow Trout (Oncorhynchus Mykiss) Cultured in Various Polish Regions

There is a lack of regulations regarding labeling of the place of cultivation of freshwater fish, even though some research indicates that environmental factors can influence the quality of rainbow trout meat. The purpose of this study was to assess the necessity of such regulations and to determine the meat quality of rainbow trout cultivated in different regions of Poland. The analysis of color measurement, fatty acid profile, sensory evaluation and microbiological analysis of trout muscle were performed to assess the influence of cultivation region on the quality of trout meat. The place of cultivation did not influence the redness (a*) and yellowness (b*) of fillet, but had impact on lightness (L*). The microbiological analysis showed no pathogenic microorganisms on the fish surface. The fatty acids composition differed highly significantly (P<0.01) depending on the place of cultivation. Since there are significant differences in quality and nutritional value between studied samples, the necessity of labeling the place of cultivation of rainbow trout for the final consumer should be implemented.

Heavy Metal Contamination of Landscape Componets in Surroundings of Closed Mercury Deposit in Malachov (Slovakia) / Kontamince Krajinných Složek Ťěžkými Kovy V Okolí Uzavřeného Dolu Na Rtuť V Malachově (Slovensko)

The present study investigates mercury contamination of soil, groundwater, surface water, vegetation and food commodities (fruit, vegetable, mushroom, and fish) close to the abandoned Hg deposit in Malachov, Central Slovakia. The soil was classified as cambi-soil (rendzina). Maximum concentrations of Hg (44.24 ppm) were found in the soil from the area nearby old mining activities in the Veľká Studňa locality. In the groundwater, 0.84 μg.L-1, and in the surface water, even 394 μg.L-1 of Hg content was found. Also plant tissues and mushrooms are Hg-contaminated (in the root of Salix fragilis, the Hg content was 22 mg.kg-1). The Hg concentration decreases in general in the following order: root, branch/stem, and leaf/needle. In the food commodities, the Hg content does not exceed the Slovak law limits. The Hg content in trout muscle (from the local Malachovský brook) is 252 μg.kg-1 and in liver 402 μg.kg-1. The calculation of an AMD formation potential (neutralisation potential, total acidity production, net neutralisation potential) is discussed as well. The value of the total acidity production potential (sensu Sobek et al., 1978) is low (1.562 - 3.125; with exception of a single sample, in which it increased to 9.375). On the other hand, the abundant presence of dolomite rocks causes a high neutralization potential value (up to 812.84). This result suggests that the assumption of the AMD production is excluded and the environmental risk from this viewpoint might be neglected

Introduced lake trout exhibit life history and morphological divergence with depth

We found that an introduced population of lake trout (Salvelinus namaycush) in Flathead Lake, Montana, USA, exhibited divergent life history, diet, and morphology after the invasion of Mysis diluviana. A correspondence between stable isotopes (δ13C and δ15N) in lake trout muscle and their prey suggests that individual lake trout exhibited depth preferences. Lake trout 451–600 mm total length showed morphological distinctness between shallow (0–25 m) and deep (60–100 m) collections wherein the latter had deeper bodies and larger eyes. Furthermore, these deep lake trout fed more heavily on Mysis, grew slower, and matured at a smaller size. Lack of genetic divergence between depth groups and the rapid divergence of life histories after Mysis invasion suggest a strong role for environment in producing the observed ecotypic variation. Our research supports resource partitioning by depth and diet as a drivers of phenotypic diversity in lake trout, providing insights into the origins of morphotypes and guidance for conservation of native populations.