Juvenile Largemouth Bass Micropterus Salmoides Research Articles

Effects of Five Dietary Carbohydrate Sources on Growth, Glucose Metabolism, Antioxidant Capacity and Immunity of Largemouth Bass (Micropterus salmoides).

This study investigated the effects of glucose (GLU), tapioca starch (TS), gelatinized tapioca starch (GTS), potato starch (PS) and gelatinized potato starch (GPS) on growth and physiological responses in juvenile largemouth bass Micropterus salmoides. After 8 weeks, fish fed with starch diets had better weight gain and growth rates. Counts of red blood cells and monocytes were increased in the PS and GPS groups, compared to GLU group. Contents of serum triglyceride and total cholesterol were markedly elevated in the TS, PS and GPS groups. There were lower levels of serum glucose, insulin and cholecystokinin, and higher agouti-related peptide contents in the PS group compared to GLU group. PS and GPS could enhance glycolysis and TCA cycle by increasing their enzyme activities and transcriptional levels. Additionally, starch sources markedly heightened mRNA levels of key genes involved in the respiratory electron transport chain. Additionally, elevated mRNA levels of key antioxidant genes were shown in the TS and GTS groups. Moreover, TS and PS could promote immunity by upregulating transcriptional levels of the complement system, lysozyme and hepcidin. Taken together, starch exhibited better growth via increasing glycolysis and TCA cycle compared with GLU, and PS could improve antioxidant and immune capacities in largemouth bass.

Effects of dietary n-3 LC-PUFA levels on the growth, immunity, and lipid metabolism of freshwater carnivorous teleost largemouth bass (Micropterus salmoides) juveniles

The n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) play important roles in the normal growth and metabolism of fish . In order to explore the appropriate requiremnts of n-3 LC-PUFA in juvenile largemouth bass Micropterus salmoides, a freshwater carnivorous teleost, four isoproteic (50 %) and isolipidic (11 %) diets were formulated. The control diet used fish oil (FO) as the sole lipid source, and the other three diets used mixed vegetable oil as the main lipid source and supplemented with 0.50 %, 0.80 % and 1.10 % n-3 LC-PUFA, respectively. After the juvenile largemouth bass (initial weight 12.11 ± 0.01 g) fed with the four diets for 75 days, the growth, serum and heptic biochemical indices, as well as hepatic lipid metabolism were investigated. The results showed that the growth performance of 0.50 %-1.10 % groups were high that of control group; comparing to the 1.10 % group, high weight gain, specific growth rate and daily gain, as well as muscle hardness, chewiness and gumminess were detected in the 0.80 % group (P < 0.05). With the increase of dietary n-3 LC-PUFA levels, the serum biochemical indices (total cholesterol, triglyceride, and aspartate aminotransferase activity) and hepatic triglyceride were significantly decreased, while the serum acid phosphatase and alkaline phosphatase, as well as hepatic and muscle n-3 LC-PUFA contents were significantly increased (P < 0.05). Compared with the 0.50 % group, high hepatic mRNA expression levels of anti-inflammatory genes (il-10, tgf-β) were observed in the 0.80 % group (P < 0.05); and the relatively high transcript levels of genes related to lipid transport and catabolism (hsl, pparα, fatp and mtp) and low transcript levels of genes related to lipid anabolism (accα and pparγ) were detected in the 0.80 % and 1.10 % groups, as well as high mRNA levels of accα and pparγ were measured in the 0.80 % group (P < 0.05). The results indicated that 0.80 % dietary n-3 LC-PUFA level is suitable for largemouth bass concerning the growth performance, muscle quality and hepatic lipid metabolism. When subjected the weight gain to the second-order polynomial regression analysis, the maximum value was achieved at 0.76 % n-3 LC-PUFA level, which provide a basis for the development of formula feed for largemouth bass.

Influence of habitat and other factors on Largemouth Bass abundance in Lake Okeechobee, Florida

AbstractObjectiveSubmerged aquatic vegetation (SAV) is an important part of shallow lake ecosystems. It provides protective cover and foraging habitat for age‐0 and juvenile Largemouth Bass Micropterus salmoides and other small fish, creates structure and habitat for macroinvertebrates and other fauna, and can influence the physical environment by stabilizing sediments and reducing water column turbidity.MethodsFor this study, we reviewed annual abundance data for Largemouth Bass collected via electrofishing from 2002 to 2019, along with environmental covariates that included SAV cover (habitat) and turbidity.ResultAll age‐groups of Largemouth Bass were positively correlated with vascular SAV cover. Age‐0 Largemouth Bass were most abundant when SAV cover exceeded approximately 24% (9400 ha) of the littoral and nearshore area, while the juvenile and all‐ages groups were most abundant when SAV cover exceeded 20% and 12% of the area, respectively. Following major storm events, water depth and turbidity increased, SAV cover was reduced to &lt;5% of the littoral and nearshore area, and the abundance of age‐0 Largemouth Bass was reduced more than 90%.ConclusionOnce removed from the landscape and exposed to turbid conditions, vascular SAV will reestablish only if water clarity increases and light is sufficient to support plant growth. Lowering water levels for an extended period has been shown to reduce nearshore turbidity and jumpstart the recovery of SAV in Lake Okeechobee and other shallow lakes globally. Without adequate SAV habitat, recruitment of age‐0 and juvenile Largemouth Bass will likely be suppressed. Maintaining a minimum coverage of vascular SAV (20–35%) in the littoral and nearshore area should increase the abundance of age‐0 and juvenile Largemouth Bass and provide beneficial habitat for adult Largemouth Bass and other lake fauna.

Effects of dietary starch and metformin levels on the growth performance, body composition, hepatic glycolipid metabolism, and liver histology of juvenile largemouth bass Micropterus salmoides

In this study, an 8-week feeding trial was performed to evaluate the effects of dietary metformin inclusion on the growth performance, body composition, glucose homeostasis and liver histology of juvenile largemouth bass Micropterus salmoides (LMB) fed high starch diets. Using a 2 × 2 factorial design, four isoproteinic (50%) and isolipidic (13%) diets were formulated with two starch levels (9% and 14%) with or without 0.25% metformin inclusion at each starch level. Each diet was assigned to triplicate tanks of LMB with an initial body weight of 10.8 g. The results showed that an increase of dietary starch from 9% to 14% retarded the growth performance (weight gain ratio and specific growth rate) of LMB through impairing feed utilization (feed efficiency ratio, protein efficiency ratio and protein productive value). Though feed consumption increased, the growth performance of LMB did not benefit from dietary metformin administration as a result of the impaired feed utilization. Both the glucose homeostasis (fasting blood glucose) and glucose tolerance of LMB were impaired with increasing dietary starch from 9% to 14%. However, LMB metabolically adapted well to high starch diets through stimulating glycolysis and glycogen synthesis while inhibiting gluconeogenesis in the liver at the molecular level. Moreover, an increase of dietary starch from 9% to 14% upregulated hepatic lipogenic capacities while down-regulated fatty acid oxidation thereby promoting lipid deposition in the liver and whole fish. Dietary metformin improved the glucose homeostasis and glucose tolerance of LMB through promoting glycolysis and de novo lipogenesis rather than glycogen deposition in the liver. However, dietary metformin did not mitigate the liver injuries (the activities of alanine aminotransferase and aspartate aminotransferase in the plasma along with histological appearance) in LMB fed high starch diets. In conclusion, our results demonstrated that dietary metformin inclusion did not mitigate the growth retardation and liver injury of LMB fed high starch diets, but improved the glucose homeostasis and glucose tolerance through promoting the glycolytic and lipogenic pathways in the liver.

Effects of dietary soybean lecithin on growth performances, body composition, serum biochemical parameters, digestive and metabolic abilities in largemouth bass Micropterus salmoides

We conducted an 8-week feeding trial to explore the effects of dietary soybean lecithin (SBL) on growth performance and metabolic abilities in juvenile largemouth bass Micropterus salmoides. The addition of 4 % SBL to the feed significantly increases the specific growth rate (SGR), carcass ratio (CR) and crude protein in the fish body and muscle compared with control groups (0 %) (P < 0.05). However, 4 % SBL significant declines contents of total glucose, total bile acids and blood urea nitrogen and activities of ALT and AST in the serum compared with controls (P < 0.05). And 4 % SBL markedly increased contents of serum hormones involved in metabolism and food intake including adiponectin, agouti-related peptide, apelin and insulin (P < 0.05), while decreased cholecystokinin contents compared with controls (P < 0.05). Lipase and amylase activities in the liver and intestine were both significantly increased in 4 % and 8 % SBL groups (P < 0.05). 4 % and 8 % SBL could heighten the enzyme’s activities and genes’ mRNA levels involved in glycolysis (GCK, PFK, PK, MDH) and glycogen synthase (GS) compared with controls (P < 0.05). Meanwhile, contents of AC-CoA and glycogen in the fish liver were also significantly increased in 4 % and 8 % SBL groups compared with controls (P < 0.05). However, the activities and mRNA levels of G6P and PEPCK were not influenced in the liver of tested fish fed with 4 % SBL compared with controls (P > 0.05). In addition, 4 % SBL elevated activities and mRNA levels of FAS in the fish liver compared with controls (P < 0.05). Similarly, 4 % SBL increased the transcriptional levels of genes involved in triglycerides (TG) synthesis (GK, GPAT3 and DGAT2) and lipid transport (FATP1, CD36, APOB100 and FABP10) in the fish liver compared with controls (P < 0.05). Moreover, the mRNA expression levels of up-stream regulatory elements involved in metabolic signal processing (AKT1, mTOR, SREBP1 and PPARγ) were also markedly heightened in fish fed 4 % SBL compared with controls (P < 0.05). Together with these results, it indicated 4 % dietary SBL could increase growth and digestive abilities, improve serum biochemical indicators and hormones, promote glycolysis and glycogen synthesis, and facilitate lipid synthesis and transport in juvenile largemouth bass Micropterus salmoides.

Transcriptome analysis provides insights into the molecular mechanism of liver inflammation and apoptosis in juvenile largemouth bass Micropterus salmoides fed low protein high starch diets

The present study was conducted to investigate the regulatory mechanism of liver injury in largemouth bass Micropterus salmoides (LMB) fed low protein high starch diets. Two isolipidic and isoenergetic diets were formulated with different protein and starch ratios, being named as diets P49S9 (48.8 % protein and 9.06 % starch) and P42S18 (42.4 % protein and 18.2 % starch). Each diet was fed to triplicate replicates of LMB (initial body weight, 4.65 ± 0.01 g) juveniles. Fish were fed to visual satiation for 8 weeks. The results indicated that though the P42S18 fish up-regulated the feeding ratio to meet their protein requirements, feeding efficiency ratio and growth performance were impaired in treatment P42S18 as compared to treatment P49S9. Periodic acid-Schiff (PAS) staining showed glycogen accumulated in the liver of LMB fed low protein high starch diets, and the reason should be attributed to down-regulated expression of the glycogenolytic glycogen debranching enzyme. Lower liver lipid level was associated with feeding low protein high starch diets in LMB, which should be resulted from the changes in hepatic glycerolipid metabolism regulated by lipoprotein lipase (representative of triglyceride synthesis, up-regulated) and diacylglycerol acyltransferase (representative of triglyceride breakdown, down-regulated). Though fasting plasma glucose level was comparable, treatment P42S18 performed inferior glucose tolerance to treatment P49S9. Hematoxylin-eosin (HE) and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining suggested that feeding low protein high starch diets induced disruption of structural integrity, inflammation and apoptosis in the hepatocytes of LMB. As expected, KEGG pathways analysis indicated that many of the up-regulated differentially expressed genes were enriched in AGE (advanced glycation end product)/RAGE (receptor for AGE), Toll-like receptor and apoptosis signaling pathways. Our transcriptome data revealed that feeding low protein high starch diets might promote the accumulation of AGEs in LMB, which bound to RAGE and subsequently induced PI3K/Akt signal pathway. The activation of Akt induced NF-κB translocation into the nucleus thus releasing proinflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin-8. The release of these inflammatory factors concomitantly induced T cell stimulation and natural killer cells chemotactic effects through Toll-like receptor signaling pathway. Besides mediating inflammation and immune response, TNF-α signal transduction participated in mediating apoptosis through the receptor of TNF (TNF-R1) pathway by up-regulating the expression of caspase 8 and cytochrome c. In conclusion, our results demonstrated that feeding low protein and high starch diets induced hepatocytes inflammation and apoptosis in LMB through the PI3K/Akt/NF-κB signaling pathway.

Di-(2-ethylhexyl) phthalate exacerbated the toxicity of polystyrene nanoplastics through histological damage and intestinal microbiota dysbiosis in freshwater Micropterus salmoides

Organic pollutants such as di-(2-ethylhexyl) phthalate (DEHP) interact with nanoplastics (NPs) and change their bioavailability and toxicity to aquatic organisms. This study aims to assess the ecotoxicological impacts of NPs in the presence and absence of DEHP on juvenile largemouth bass (LMB) Micropterus salmoides. Therefore, LMB was fed with diets containing various concentrations (0, 2, 10, and 40 mg/g) of polystyrene nanoplastics (PSNPs) by the weight of diets. After a 21-day of PSNPs dietary exposure, LMB was treated with DEHP at 450 μg/L through waterborne exposure for three days. Our results showed that PSNPs were accumulated in the intestinal tissues, which significantly decreased the feeding and growth rates in LMB. The histopathological analysis showed the intestine and liver of LMB were subjected to various degrees of structural damage caused by PSNPs, and DEHP-PSNP co-exposure enhanced those histopathological damages in both tissues. Additionally, the co-exposure induced oxidative stress in terms of increased activities of glutathione S-transferase, catalase, and superoxide dismutase enzymes in the liver, intestine, spleen, and serum. Furthermore, the co-exposure significantly changed the intestinal microbial composition, i.e., the decrease in the abundance of probiotics (Bacteroidetes and Proteobacteria) and the increase in pathogenic bacteria (Firmicutes) posed a great threat to fish metabolism and health. Therefore, this study highlights that the presence of DEHP enhances the toxicity of NPs on LMB in freshwater and suggests the regulated use of plastic and its additives for improving the health status of aquaculture fish for food safety in humans.

Effects of dietary non-starch polysaccharides level on the growth, intestinal flora and intestinal health of juvenile largemouth bass Micropterus salmoides

A 56-day feeding trial was conducted to evaluate the effects of dietary non-starch polysaccharide (NSPs) inclusion on the growth performance, intestinal flora and intestinal health of juvenile largemouth bass (6.00 ± 0.01 g) in quadruplicate. Seven isoproteic and isolipidic diets (crude protein 47.0%, crude lipid 12.5%) were formulated to contain 0%, 3%, 6%, 9%, 12%, 15% and 18% NSPs (each 100 g contains 32.26 g cellulose, 19.35 g arabinoxylan, 4.52 g β-glucan, 5.16 g mannan and 38.71 g pectin; named N0, N3, N6, N9, N12, N15 and N18), respectively. Weight gain rate, specific growth rate, protein efficiency ratio, protein and lipid deposition rate in the N12, N15 and N18 groups were significantly lower than in the N0 group. Plasma diamine oxidase activity and lipopolysaccharide and endothelin-1 concentration in the N15 and N18 groups were significantly higher than in the N0 group. Intestinal occludin, caludin-1, caludin-4, zonulaoccludens-1, interleukin-10, transforming growth factor-β, nuclear factor E2-related factor 2, B-cell lymphoma-2 (Bcl-2), B-cell lymphoma-xl and Bcl-2-associated athanogene expression levels and intestinal peroxidase, catalase and superoxide dismutase activities in the N15 and N18 groups were significantly lower than in the N0 group, while interleukin-8, interleukin-1β, tumor necrosis factor-α, kelch-like ECH-associated protein 1, caspase3, Bcl-2-assoxicated x protein and Bcl-2-associated death protein genes expression levels showed opposite trends. Moreover, the Shannon, Simpson, Chao and Ace indices and the abundance of Plesiomonas shigelloides, [Clostridium] dakarense and Romboutsia ilealis in the N18 group were significantly lower than in the N0 group, in contrast to the abundance of Paraclostridium bifermentans, Mycoplasma moatsii. Propionate, butyrate, valerate and total short-chain fatty acids (SCFA) contents in digesta of the N6 group were significantly higher than in the N0 group, while acetate, butyrate, valerate, caproate and total SCFA in digesta of the N18 group were significantly lower than in the N0 group. Results suggest that high NSPs diets increased intestinal permeability and abundance of pathogenic microorganisms, induced intestinal inflammation and intestinal epithelial cell apoptosis, but decreased intestinal flora α-diversity and SCFA contents, and ultimately impaired growth performance and intestinal health of juvenile largemouth bass. Conversely, low-dose NSPs inclusion had no negative effect on growth and improves intestinal health in juvenile largemouth bass, showing potential as prebiotics in aquafeed.

Dietary methionine hydroxy analogue supplementation benefits on growth, intestinal antioxidant status and microbiota in juvenile largemouth bass Micropterus salmoides

To study the possible impacts of dietary methionine hydroxy analogue (MHA) on growth, intestinal antioxidant status, and intestinal microbiota in juvenile largemouth bass (LMB) Micropterus salmoides (14.49–14.58 g), we conducted a feeding trial for 84-days. Four hundred and eighty fish were randomized into four dietary MHA treatments (0.0, 3.0, 6.0, and 9.0 g/kg diet). Results revealed that dietary MHA supplementation: (1) dramatically improved growth of juvenile LMB; (2) markedly decreased intestinal protein and lipid peroxidation, and increased intestinal antioxidant activities via Keap1/Nrf2 axis; (3) increased the richness and diversity of intestinal microbial community; (4) changed intestinal microbiota composition, increased the abundances of Proteobacteria, Bacteroidetes, and Actinobacteria, and decreased the abundances of Firmicutes and Cyanobacteria at the phylum level; increased the abundances of Bifidobacterium and Bacillus and decreased the abundance of Bacteroides at the genus level. Collectively, dietary MHA supplementation has potential benefits in growth, intestinal antioxidant capacity, and intestinal microbiota in LMB. The dietary optimal Met level of LMB (14.49–131.06 g) was recommended to be 14.49 g/kg diet, corresponding to 8.30 g/kg diet sourcing from basic diet and 4.19 g Met/kg diet sourcing from MHA based on specific growth rate.

Transcriptome analysis provides insights into the molecular mechanism of hepatocyte apoptosis in response to feeding restriction in juvenile largemouth bass Micropterus salmoides

Feeding restriction (FR) is a scientific strategy to attenuate nutrient excess-mediated liver metabolic syndromes in human beings. However, it is still unclear whether liver health could benefit from FR in cultured animals including fish. In this regard, the regulatory role of FR in liver health of juvenile largemouth bass Micropterus salmoides were investigated in this study using single-molecule real-time sequencing and next-generation sequencing. Groups of fish (20 fish per group) with an initial body weight of 6.9 g were randomly allocated into 12 rectangular tanks (250 L each) operating as a recirculating aquaculture system. The satiation (ST) fish was fed to satiation, while ration levels of the moderately restricted (MR) and highly restricted (HR) fish were maintained at 85% and 70% of the ST fish, respectively. All fish were fed a commercial extruded diet containing 49.9% crude protein and 13.2% crude lipid. After a 9-week feeding trial, growth performance of the MR fish was not affected through improving the feed utilization as compared with the ST fish. Even though feed utilization was further improved, growth of the HR fish was still impaired. The MR fish obtained superior antioxidant status in the plasma and liver (based on glutathione or malondialdehyde concentration, and total antioxidant capacity and superoxide dismutase activities) together with better liver integrity (based on HE and TUNEL staining) than the other treatments. A total of 38,909 full-length transcripts were generated from the sequencing. GO enrichment analysis of the differentially expressed genes (DEGs) showed that many terms related to immunization and wound repair were enriched in the feed restricted fish (especially the MR fish). A total of 701 DEGs were identified in the liver of the MR fish as compared with the ST fish, and the apoptosis was enriched as the prominent pathway by KEGG pathway analysis. Our results suggested that the intrinsic apoptosis pathway played an important role in the hepatocyte apoptosis inhibition in the MR fish. Specifically, the activation of Akt might mediate an anti-apoptosis role through inhibiting the release of direct IAP binding protein with low pI (DIABLO) from mitochondria and promoting the transcription of pro-survival genes such as X-linked inhibitor-of-apoptosis protein (xiap), which coordinately activated the inhibitor of apoptosis protein (IAP). Besides the intrinsic apoptosis pathway, our results indicated that the lysosome pathway and endoplasmic reticulum stress pathway might also participate in regulating hepatocyte apoptosis inhibition of the MR fish.

Effects of dietary Bacillus subtilis DSM 32315 supplementation on the growth, immunity and intestinal morphology, microbiota and inflammatory response of juvenile largemouth bass Micropterus salmoides

This study aimed at evaluating the effects of dietary inclusion of Bacillus subtilis DSM 32315 on the growth, immunity, intestinal architecture and gut microbiota of juvenile largemouth bass Micropterus salmoides (LMB). B. subtilis DSM 32315 was supplemented in the diets at the levels of 0 (control, CON), 1.5 (BS1.5, 3 × 106 CFU/g feed) and 3 g/kg (BS3, 6 × 106 CFU/g feed). Each diet was assigned to four replicate tanks of LMB juveniles (initial mean body weight, 8.32 ± 0.06 g) with 20 fish per tank for 9 weeks. The results showed that the growth and feed utilization of LMB were not sensitive to dietary modifications (p > .05). Compared with the CON fish, dietary BS supplementation did not affect the haematological parameters (white and red blood cell counts and haematocrit value) of LMB (p > .05), but the BS1.5 fish performed better than the BS3 fish. Serum innate immunity indicators (lysozyme activity and complement C3 and C4 levels) were improved with dietary BS supplementation at both doses, while higher serum IgM level was only recorded at 1.5 g/kg feed (p < .05). All the sampled fish exhibited intact intestines, but the intestinal architecture (villus height and muscular layer thickness) still benefited from dietary BS inclusion at both doses (p < .05). Although intestinal anti-inflammatory response (mRNA levels of IL-10 and TGF-β1) did not differ between the BS supplemented fish (p > .05), the BS1.5 fish obtained superior pro-inflammatory response (mRNA levels of IL-1β, IL-8, and TNF-α) over the BS3 fish (p < .05). Compared with the CON fish, the abundance of the harmful Plesiomonas shigelloides decreased in the gut microbiota of the BS1.5 fish (p < .05). Despite the BS3 fish obtained higher diversity of gut microbiota, the abundances of potential beneficial (Cetobacterium somerae and Shewanella xiamenensis) and harmful bacteria (Acinetobacter johnsonii and P. shigelloides) increased or decreased simultaneously (p < .05). Taken together, it was concluded that dietary BS DSM 32315 inclusion presented some positive effects on LMB. Although the BS1.5 fish performed better than the BS3 fish, the best supplemental dose need to be further studied.

Interactions between dietary lipid levels and chronic exposure of legal aquaculture dose of sulfamethoxazole in juvenile largemouth bass Micropterus salmoides

Antibiotics have been widely used (mainly mixed with feed) in aquaculture, while few studies have evaluated the interactions between feed composition and antibiotics. Sulfamethoxazole (SMX) is a fat-soluble antibiotic, an eight weeks feeding trial was conducted to investigate the interactions between dietary lipid levels and chronic exposure of legal aquaculture dose of sulfamethoxazole in juvenile largemouth bass Micropterus salmoides, and evaluated the possible human health risk. Six practical diets were formulated to three levels of crude lipid (11, 14.5, 18 %) and two levels of SMX (0 and 0.3 %), namely low fat (LF), moderate fat (MF), high fat (HF), low fat and SMX (LFS), moderate fat and SMX (MFS), high fat and SMX (HFS), respectively. Each diet was assigned to three tanks (20 fish per tank, average weight 30.65 ± 0.02 g). Growth and organ indices were increased by SMX. Higher malformation rate and lower hypoxia stress resistance were found in fish exposed to SMX than those not exposed. Cholesterol and bile acid synthesis related gene expressions were down-regulated by SMX exposure. Oxidative stress, inflammation and apoptosis were increased in fish exposed to SMX. Significant interactions between dietary lipid levels and SMX on renal immune response of fish were observed. Remarkable damage of intestinal histology was observed in fish fed the diet HFS. In addition, dietary SMX exposure increased pathogen susceptibility of largemouth bass and induced dysbiosis of gut microbiota. The concentrations of SMX in muscle of fish fed diets containing SMX were higher than those fed other diets, and close to the maximum residue limit (MRL) in China and international organizations. Although chronic legal aquaculture dose of dietary SMX also increased the target hazard quotient (THQ) and estimated daily intake (EDI), there is no health risk in adults and children consuming fish filet.

Lipid metabolism and plasma metabolomics of juvenile largemouth bass Micropterus salmoides were affected by dietary oxidized fish oil

During the storage, fish oil is susceptible to peroxidation to form toxic lipid derivatives, dietary intake of oxidized fish oil would induce oxidative stress and inflammation in animals, but it was not clear about the relation between oxidized fish oil intake, lipid metabolism and oxidative stress. Four isonitrogenous and isolipidic diets containing fresh fish oil (peroxide value, POV: 7.2 meq kg−1, diet FR) and oxidized fish oil (POV: 155, 275 and 564 meq kg−1, diet OX155, OX275 and OX564, respectively) were formulated to investigate the effects of dietary oxidized fish oil on growth performance, plasma metabolomics and lipid metabolism of juvenile largemouth bass, Micropterus salmoides. After the 12-week feeding trial, fish fed the OX155 obtained significantly higher (P < .05) weight gain than fish fed FR because of their higher feed intake. Malonaldehyde (MDA) levels were increased in plasma and liver of largemouth bass fed OX564 diet than those fed FR. Untargeted metabolomics ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-QTOF-MS) was performed to invest the differences of plasma metabolites in fish fed different oxidative degrees of fish oil. Lipid metabolism, especially phospholipids and sterol metabolism in largemouth bass were significantly affected by oxidized fish oil. Dietary oxidized fish oil decreased membrane phospholipids unsaturated degree and increased plasma lysophospholipid contents in largemouth bass. Several bile acids were decreased, while many cholesterols and vitamin D3 related metabolites were increased with the increasing oxidative degree of fish oil. Lipoprotein transport related genes and lipid oxidation related genes mRNA levels were increased in fish fed highly oxidized fish oil. Cholesterol synthesis related gene 7-dehydrocholesterol reductase (DHCR7) mRNA level was increased with the increasing oxidative degree of fish oil. Bile acid metabolism related gene 12a-hydroxylase (CYP8B1) was higher in fish fed OX275 diet. The increased vitamin D3 related metabolites in fish fed oxidized oil may associate with the decreased mRNA levels of RXRα and 24 - hydroxylase (CYP24A1). In conclusion, dietary oxidized fish oil may affect the health of fish through decrease the unsaturated degree of phospholipids and fatty acids, increase the contents of oxidized cholesterol and lysophospholipid in plasma, and repress the bile acid synthesis.

投喂频率和投喂量对循环水养殖大口黑鲈幼鱼生长和生理指标的影响

投喂频率和投喂量对循环水养殖大口黑鲈幼鱼生长和生理指标的影响

High dietary lipid level alters the growth, hepatic metabolism enzyme, and anti-oxidative capacity in juvenile largemouth bass Micropterus salmoides.

The present study was conducted to investigate the effects of high dietary lipid levels on growth, metabolism, antioxidant capacity, and immune responses of largemouth bass. Fish (initial body weight 13.38 ± 0.11g) were fed three isonitrogenous semi-purified diets containing 5%, 10%, and 20% lipid, respectively. The results indicated that fish fed 10% lipid diet showed significantly better final body weight, specific growth rate (SGR), protein efficiency ratio (PER), and feed conversion ratio (FCR) compared with that fed 5% lipid diet. Meanwhile, fish fed 20% lipid diet had a significantly higher viscera ratio (VR), hepatosomatic index (HSI), intraperitoneal fat ratio (IPF), and liver lipid content than those fed the other diets. Higher alanine aminotransferase (ALT) and aspartate transaminase (AST) activities, total cholesterol (TC), triglyceride (TG), free fatty acids (FFA), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) contents, and LDL-C/HDL-C value in plasma were recorded in fish fed 20% lipid diet, while higher insulin contents were obtained in fish fed 5% lipid diet. In addition, the highest carnitine palmitoyltransferase I (CPT1), AMP-activated protein kinase (AMPK), fructose-1,6-bisphosphatase (FBPase), and phosphoenolpyruvate carboxykinase (PEPCK) activities in the liver were also observed in fish fed 20% lipid diet. However, fish fed 20% lipid diet had a significantly lower superoxide dismutase (SOD) and catalase (CAT) activities and higher MDA contents in liver than those fed the other diets. The higher nitric oxide (NO) contents and inducible nitric oxide synthase (iNOS) activity in liver were recorded in fish fed 10% lipid diet. Moreover, the alkaline phosphatase (ALP), inducible nitric oxide synthase (iNOS) and lysozyme activities, and nitric oxide (NO) contents in plasma were higher in fish fed the 10% diets than the other groups. In conclusion, high dietary lipid levels could suppress growth performance and liver anti-oxidative capacity, and reduce immune responses of largemouth bass.

Effects of pressure changes induced by commercial navigation traffic on mortality of fish early life stages

Mortality of fish early life stages was measured in a pressure vessel to simulate vertical displacement within the water column. Mortality was measured for three pressure regimes for four fish species: larval bigmouth buffalo Ictiobus cyprinellus, larval blue catfish Ictalurus furcatus, juvenile bluegill Lepomis macrochirus, and juvenile largemouth bass Micropterus salmoides. The maximum pressure-change tested, 344.8 kPa, equivalent to a 35.2 m displacement of fish within the water column, did not cause significant mortality of larvae or juveniles. Since 32.5 m exceeds depths in most inland navigation channels and possibly the depth to which rapid propeller induced water mixing occurs, the range of pressure changes that could be experienced by early life stages during towboat mixing of the water column will not result in significant mortality.

Light climate and dissolved organic carbon concentration influence species-specific changes in fish zooplanktivory

Dissolved organic carbon (DOC) in lakes reduces light penetration and limits fish production in low nutrient lakes, reportedly via reduced primary and secondary production. Alternatively, DOC and light reductions could influence fish by altering their visual feeding. Previous studies report mixed effects of DOC on feeding rates of zooplanktivorous fish, but most investigators tested effects of a single concentration of DOC against clear-water, turbid, or algal treatments. We used a controlled laboratory study to quantify the effects of a DOC gradient (3–19 mg L−1) on average light climate and the zooplankton feeding rate of 3 common, north temperate fishes. Light availability, which was inversely related to DOC concentration, had a positive and linear effect on zooplankton consumption by juvenile largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus), explaining 22% and 28% of the variation in consumption, respectively. By contrast, zooplankton feeding rates by fathead minnow (Pimephales promelas) were best predicted by a nonlinear, negative influence of light (R2 = 0.13). In bluegill feeding trials we found a general trend for positive selection of larger zooplankton (Cladocera and Chaoboridae); however, the light climate did not influence the selection of prey type. Largemouth bass selected for larger-bodied zooplankton, with weak evidence that selectivity for large Cladocera changed from negative to neutral selection based on electivity values across the light gradient. Our results suggest that the effect of DOC on the light climate of lakes may directly influence fish zooplanktivory and that this influence may vary among fish species.

The Effects of Macrophyte Stem Density and Structural Complexity on Foraging Return of Invertivorous Juvenile Largemouth Bass

AbstractAquatic vegetation can impact juvenile fishes through multiple pathways. Previous studies have found that dense macrophytes can cause a trade‐off of survival for Bluegills Lepomis macrochirus, with decreased foraging efficiency in macrophytes but also decreased predation risk. For juvenile Largemouth Bass Micropterus salmoides, this phenomenon has been proposed but never experimentally tested. In addition, little information exists on the effects of vegetation on juvenile Largemouth Bass prior to the shift to piscivory, a critical period in the recruitment process. Therefore, the objective of this study was to determine if aquatic vegetation reduces the foraging ability of invertivorous (prepiscivorous) juvenile Largemouth Bass. Twenty‐four invertivorous juvenile Largemouth Bass were tested individually at each of five stem densities (0, 125, 250, 500, and 1,000 stems/m2) of artificial macrophytes within 20.8‐liter aquaria. Five treatments of a simple stem architecture (at all stem densities) and three complex stem architecture treatments (125, 250, and 500 stems/m2) were used within this experiment. Complex stem density treatments were created using a branched design which doubled the string abundance (number of strings) within the water relative to corresponding stem densities in simple vegetation treatments. Thirty chironomid larvae were used as prey during each 15‐minute foraging bout. Foraging return (number of chironomid larvae consumed/15‐minute foraging bout) was not significantly different among all stem treatments. Therefore, our results suggest the predator avoidance advantage aquatic macrophytes provide to juvenile Largemouth Bass does not come with a trade‐off in foraging efficiency (up to 1,000 stems/m2 vegetation density), at least when Largemouth Bass are prepiscivorous.Received December 15, 2015; accepted March 23, 2016 Published online July 7, 2016

Lethal Stomach Content Collection Methods Reduce Detection of Zooplankton Prey of Juvenile Largemouth Bass Compared with Nonlethal Methods

AbstractThe study of fish diets is an integral part of many fisheries research and management programs. Several studies have evaluated the effectiveness of nonlethal stomach content collection methods but none have considered the effectiveness of lethal methods that may also be biased by continued prey digestion. We compared one nonlethal and two lethal methods of stomach content collection and preservation for juvenile Largemouth Bass Micropterus salmoides ranging in size from 51–68 mm TL. Macroinvertebrates and zooplankton from stomachs of juvenile Largemouth Bass were collected using three methods, including gastric lavage (stomach contents immediately preserved), removing and preserving stomachs from fresh fish (whole stomach preserved after 3 h on ice), and removing and preserving stomachs after the fish had been frozen whole (stomach preserved after whole fish was frozen for 3 weeks at −20°C in a freezer). There were significant differences in total biomass of zooplankton and the total number of individual diet items for zooplankton among the three methods. Both cladocerans and copepods significantly differed among methods for total numbers and total biomass. In contrast, there were no differences between the different diet collection methods for any of the macroinvertebrate groups we were able to analyze (Ephemeroptera, Odonata, Diptera, and Coleoptera). These results suggest that prey in stomachs of fish continues to be digested after collection and that prey size and prey type are important factors. Our results suggest that gastric lavage yielded more accurate results of diet of juvenile Largemouth Bass than lethal methods.Received November 6, 2015; accepted March 9, 2016 Published online June 27, 2016

Evacuation Times of Radio Transmitters Consumed by Largemouth Bass

AbstractReduction in transmitter size used in telemetry studies have allowed researchers to tag and track fish that are much smaller than could have been tagged previously. Researchers seek information on juvenile or small fish movement, behavior, and survival to better understand recruitment processes. Juvenile or small‐bodied fish that have been tagged have an increased risk of predation, which results in transmitters being consumed. Knowledge about radio transmitter accumulation in a predator's gut and evacuation times are critical for interpreting locations of radio‐tagged fish and their predators. Our objective was to determine what factors influenced the evacuation time of transmitters (0.3 g), implanted in juvenile Largemouth Bass Micropterus salmoides through the digestive system of adult Largemouth Bass that had preyed upon those tagged juveniles. All transmitters ingested by the predators were evacuated within 84 h. A Poisson regression model showed that transit time decreased significantly with temperature and increased with prey length and predator length. The results of this study suggest that miniature radio transmitters (e.g., 0.3 g) do not accumulate in the digestive tract of predators and that after consumption, up to 3 d of behavior (i.e., movement and habitat use) by the predator, movements could falsely be attributed to the juvenile fish. Therefore, if a distinction cannot be made between predator and tagged juvenile Largemouth Bass, we recommend not including information from the final 3 d before cessation of movement when analyzing the behavior of tagged fish.Received June 9, 2014; accepted January 28, 2015