The gut microbiome is a highly intricate ecosystem that exerts a pivotal influence on the host’s physiology. Characterizing fish microbiomes is critical to understanding fish physiology and health, ...but little is known about the ecology and colonization dynamics of microorganisms inhabiting fish species. In this study, we investigated the bacterial communities of two small-bodied fish species,
Cyprinella lutrensis
(red shiner) and
Notropis stramineus
(sand shiner), two fish species where gut microbiomes have not been investigated previously and surrounding waters, collected from rivers in Nebraska, USA. Our study focused on evaluating microbial diversity in small-bodied fish and identifying autochthonous microbes present within these species irrespective of location to better understand bacterial community composition and possible roles of such bacterial species. Our results revealed that both red shiner and sand shiner exhibited gut bacterial communities dominated by typical bacterial phyla found in freshwater fish. The phylum Bacteroidota was minimally abundant in both species and significantly lower in relative abundance compared to the surrounding water microbial community. Furthermore, we found that the gut microbiomes of red shiner and sand shiner differed from the microbial community in the surrounding water, suggesting that these fish species contain host-associated bacterial species that may provide benefits to the host such as nutrient digestion and colonization resistance of environmental pathogens. The fish gut bacterial communities were sensitive to environmental conditions such as turbidity, dissolved oxygen, temperature, and total nitrogen. Our findings also show bacterial community differences between fish species; although they shared notable similarities in bacterial taxa at phyla level composition, ASV level analysis of bacterial taxa displayed compositional differences. These findings contribute to a better understanding of the gut bacterial composition of wild, freshwater, small-bodied fish and highlight the influence of intrinsic (host) and environmental factors on shaping the bacterial composition.
Vitamin D
(ergocalciferol) and vitamin D
(cholecalciferol) are fat-soluble secosteroid hormones obtained from plant and animal sources, respectively. Fish incorporates vitamin D
and D
through the ...diet. In mammals, vitamin D forms are involved in mineral metabolism, cell growth, tissue differentiation, and antibacterial immune response. Vitamin D is an essential nutrient in aquafeeds for finfish. However, the influence of vitamin D on fish cell immunity has not yet been explored. Here, we examined the effects of vitamin D
and vitamin D
on
primary macrophage immune response to
subspecies
infection under
conditions. We determined that high concentrations of vitamin D
(100,000 ng/ml) and D
(10,000 ng/ml) affect the growth of
and decrease the viability of
primary macrophages. In addition, we determined that primary macrophages pre-treated with a biologically relevant concentration of vitamin D
for 24 h showed a decrease of
infection. In contrast, vitamin D
did not influence the antibacterial activity of the
macrophages infected with
. Vitamin D
and D
did not influence the expression of canonical genes related to innate immune response. On the other hand, we found that
up-regulated the expression of several canonical genes and suppressed the expression of
(
) gene, involved in neutrophil recruitment. Primary macrophages pre-treated for 24 h with vitamin D
counteracted this immune suppression and up-regulated the transcription of
. Our results suggest that vitamin D
affects
attachment to the
primary macrophages, and as a consequence, the
invasion decreased. Moreover, our study shows that the positive effects of vitamin D
on fish cell immunity seem to be related to the
innate immunity mechanisms. We did not identify positive effects of vitamin D
on fish cell immunity. In conclusion, we determined that the inactive form of vitamin D
, cholecalciferol, induced anti-bacterial innate immunity pathways in Atlantic salmon primary macrophages, suggesting that its utilization as a component of a healthy aquafeed diet in Atlantic salmon could enhance the immune response against
.
In the present manuscript, various by-products (heads, trimmings, and frames) generated from salmonids (rainbow trout and salmon) processing were evaluated as substrates for the production of fish ...protein hydrolysates (FPHs), potentially adequate as protein ingredients of aquaculture feeds. Initially, enzymatic conditions of hydrolysis were optimized using second order rotatable designs and multivariable statistical analysis. The optimal conditions for the Alcalase hydrolysis of heads were 0.1% (v/w) of enzyme concentration, pH 8.27, 56.2°C, ratio (Solid:Liquid = 1:1), 3 h of hydrolysis, and agitation of 200 rpm for rainbow trout and 0.2% (v/w) of enzyme, pH 8.98, 64.2 °C, 200 rpm, 3 h of hydrolysis, and S:L = 1:1 for salmon. These conditions obtained at 100 mL-reactor scale were then validated at 5L-reactor scale. The hydrolytic capacity of Alcalase and the protein quality of FPHs were excellent in terms of digestion of wastes (V
> 84%), high degrees of hydrolysis (
> 30%), high concentration of soluble protein (Prs > 48 g/L), good balance of amino acids, and almost full
digestibility (Dig > 93%). Fish oils were recovered from wastes jointly with FPHs and bioactive properties of hydrolysates (antioxidant and antihypertensive) were also determined. The salmon FPHs from trimmings + frames (TF) showed the higher protein content in comparison to the rest of FPHs from salmonids. Average molecular weights of salmonid-FPHs ranged from 1.4 to 2.0 kDa and the peptide sizes distribution indicated that hydrolysates of rainbow trout heads and salmon TF led to the highest percentages of small peptides (0-500 Da).
In Norway, x-cell parasites associated with disease in farmed salmonids have been known as a rare phenomenon for two decades. These parasites cause systemic infections in farmed rainbow trout ...(Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), but have so far not been characterized and described.
The x-cells from several cases of diseased fish were studied using light and electron microscopy, and by phylogenetic analysis based on small subunit ribosomal RNA (SSU rRNA) gene sequences.
We describe here the x-cell parasite as a new species in a new genus, Salmoxcellia vastator n. gen., n. sp. Phylogenetic analyses placed Salmoxcellia n. gen. together with Gadixcellia among the xcelliids, a group of perkinsozoan alveolates. The new genus and species were found to have vacuolate plasmodial x-cells filled with lipid droplets, and an electron-dense alveolar pellicle. Electron-dense cytoplasmic inclusions, which are characteristic of the other xcelliid genera Xcellia and Gadixcellia, are lacking in Salmoxcellia n. gen. These x-cell plasmodia divide by plasmotomy and occur as aggregates in the host tissues, particularly in blood-rich tissues such as those of the kidney, red musculature, heart and liver. Host reaction and the refractive lipid droplets in the x-cells result in S. vastator n. gen., n. sp. aggregates appearing as white patches in the tissues.
We describe a new genus and species of xcelliid protist parasites from two very important farmed fish species and provide molecular methods for detection. The new parasite is associated with disease, but more importantly it has a spoiling effect on farmed salmonid fillets, rendering them unsuitable for sale. Consequently, this parasite represents a threat to the aquaculture industry.
Long‐term conservation planning for diadromous fishes would benefit from a better understanding of both the role of connectivity among environments and habitat variability in the expression of ...life‐history diversity. Most of the scientific knowledge on habitat fragmentation and connectivity has been developed in terrestrial systems in the discipline of landscape ecology. Research on habitat connectivity in aquatic systems (e.g., salmonid research that spans the spectrum of habitats from freshwater to the sea) is uncommon and largely focused on barriers to fish passage. Here, we present a review of the literature characterizing current research patterns on habitat connectivity within and among environments for Pacific salmon. We found this topic is still incipient: the literature is dominated by studies of freshwaters, with few articles focusing on habitat needs in estuary and marine systems. Pan‐environment studies are rare, pointing to a gap in our understanding of complex habitat relationships that might be significant in the development of long‐term conservation and restoration plans for Pacific salmon, particularly in light of the potential impact of climate change.
Research Impact Statement: Science supporting Pacific salmon habitat connectivity is dominated by freshwater studies with limited marine and estuary work that is also critical for effective conservation planning.
Two feeding experiments were conducted to develop non‐fish meal and non‐fish oil diet for yellowtail with plant protein sources and Schizochytrium meal. For the first experiment, three ...iso‐nitrogenous and iso‐lipidic diets were prepared. Control diet was composed with fishmeal and fish oil and the other diet was formulated with plant protein sources and fish oil FO. Fish oil in FO diet was totally substituted by rapeseed oil and Schizochytrium sp., which was rich in DHA NFO1. Duplicate groups of yellowtails (Seriola quinqueradiata, 190.6 g) were fed the diets for 99 days. NFO1 group showed the lowest palatability and growth. However, fatty acid profile of NFO1 group showed the similar trend to FO. Four non‐fish meal diets were prepared for the second experiment with increased amount of feed attractant. 100FO diet was formulated similar to FO diet in the first experiment though higher amount of bonito peptide was contained. The other diets gradually employed Schizochytrium meal to substitute fish oil in 100FO diet for 35, 70 and 100%, respectively 65FO, 30FO, NFO2. Duplicated groups of yellowtails (186.0 g) were fed the diets for 84 days. The growth result was improved by increasement of bonito peptide; however, it was inversely proportional to employment rate of algae meal. The results suggest possibility for developing non‐fish meal diet for yellowtail with plant protein sources and Schizochytrium sp. by inducing enough amount of feed attractant. Moreover, it needs further study on essential fatty acid utilization for yellowtail while developing non‐fish meal and non‐fish oil diet with microalgae.
Species‐to‐species and species‐to‐environment interactions are key drivers of community dynamics. Disentangling these drivers in species‐rich assemblages is challenging due to the high number of ...potentially interacting species (the ‘curse of dimensionality’). We develop a process‐based model that quantifies how intraspecific and interspecific interactions, and species’ covarying responses to environmental fluctuations, jointly drive community dynamics. We fit the model to reef fish abundance time series from 41 reefs of Australia's Great Barrier Reef. We found that fluctuating relative abundances are driven by species’ heterogenous responses to environmental fluctuations, whereas interspecific interactions are negligible. Species differences in long‐term average abundances are driven by interspecific variation in the magnitudes of both conspecific density‐dependence and density‐independent growth rates. This study introduces a novel approach to overcoming the curse of dimensionality, which reveals highly individualistic dynamics in coral reef fish communities that imply a high level of niche structure.
Species‐to‐species and species‐to‐environment interactions play a crucial role in community dynamics. However, disentangling these interactions in species‐rich communities is challenging due to the ‘curse of dimensionality’. We have developed a novel approach to overcoming this problem, which reveals highly individualistic dynamics in coral reef fish communities.
Mandarin fish (Siniperca chuatsi) is a universally farmed fish species in China and has a large farming scale and economic value. With the high-density cultural mode in mandarin fish, viral diseases, ...such as infectious spleen and kidney necrosis virus (ISKNV) and Siniperca chuatsi rhabdovirus (SCRV), have increased loss, which has seriously restricted the development of aquaculture. Y-Box binding protein 1 (YB-1) is a member of cold shock protein family that regulates multiple cellular processes. The roles of mammalian YB-1 protein in environmental stress and innate immunity have been studied well, but its roles in teleost fishes remain unknown. In the present study, the characteristic of S. chuatsi YB-1 (scYB-1) and its roles in cold stress and virus infection were investigated. The scYB-1 obtained an 1541 bp cDNA that contains a 903 bp open reading frame encoding a protein of 300 amino acids. Tissue distribution results showed that the scYB-1 is a ubiquitously expressed gene found among tissues from mandarin fish. Overexpression of scYB-1 can increase the expression levels of cold shock-responsive genes, such as scHsc70a, scHsc70b, and scp53. Furthermore, the role of scYB-1 in innate immunity was also investigated in mandarin fish fry (MFF-1) cells. The expression level of scYB-1 was significant change in response to poly (I:C), poly (dG:dC), PMA, ISKNV, or SCRV stimulation. The overexpression of scYB-1 can significantly increase the expression levels of NF-κB-responsive genes, including scIL-8, scTNF-α, and scIFN-h. The NF-κB-luciferase report assay results showed that the relative expression of luciferin was significantly increased in the cells overexpressed with scYB-1 compared with those in cells overexpressed with control plasmid. These results indicate that scYB-1 can induce the NF-κB signaling pathway in MFF-1 cells. Overexpressed scYB-1 can downregulate the expression of ISKNV viral major capsid protein (mcp) gene but upregulates the expression of SCRV mcp gene. Moreover, knockdown of scYB-1 using siRNA can upregulate the expression of ISKNV mcp gene but downregulates the expression of SCRV mcp gene. These results indicate that scYB-1 suppresses ISKNV infection while enhancing SCRV infection. The above observations suggest that scYB-1 is involved in cold stress and virus infection. Our study will provide an insight into the roles of teleost fish YB-1 protein in stress response and innate immunity.
•S. chuatsi YB-1 (scYB-1) is involved in the cold stress response in mandarin fish.•scYB-1 can regulate the NF-κB signaling pathway in MFF-1 cells.•scYB-1 suppresses ISKNV infection but enhances SCRV infection.
With the ongoing loss of coral cover and the associated flattening of reef architecture, understanding the links between coral habitat and reef fishes is of critical importance. Here, we investigate ...whether considering coral traits and functional diversity provides new insights into the relationship between structural complexity and reef fish communities, and whether coral traits and community composition can predict structural complexity. Across 157 sites in Seychelles, Maldives, the Chagos Archipelago, and Australia’s Great Barrier Reef, we find that structural complexity and reef zone are the strongest and most consistent predictors of reef fish abundance, biomass, species richness, and trophic structure. However, coral traits, diversity, and life histories provided additional predictive power for models of reef fish assemblages, and were key drivers of structural complexity. Our findings highlight that reef complexity relies on living corals—with different traits and life histories—continuing to build carbonate skeletons, and that these nuanced relationships between coral assemblages and habitat complexity can affect the structure of reef fish assemblages. Seascape-level estimates of structural complexity are rapid and cost effective with important implications for the structure and function of fish assemblages, and should be incorporated into monitoring programs.
Despite their evolutionary, developmental and functional importance, the origin of vertebrate paired appendages remains uncertain. In mice, a single enhancer termed ZRS is solely responsible for Shh ...expression in limbs. Here, zebrafish and mouse transgenic assays trace the functional equivalence of ZRS across the gnathostome phylogeny. CRISPR/Cas9-mediated deletion of the medaka (Oryzias latipes) ZRS and enhancer assays identify the existence of ZRS shadow enhancers in both teleost and human genomes. Deletion of both ZRS and shadow ZRS abolishes shh expression and completely truncates pectoral fin formation. Strikingly, deletion of ZRS results in an almost complete ablation of the dorsal fin. This finding indicates that a ZRS-Shh regulatory module is shared by paired and median fins and that paired fins likely emerged by the co-option of developmental programs established in the median fins of stem gnathostomes. Shh function was later reinforced in pectoral fin development with the recruitment of shadow enhancers, conferring additional robustness.
PDF
