Effects of acute low salinity stress on the liver structure, physiology and biochemistry of juvenile Chinese sea bass (Lateolabrax maculatus)

In order to explore the effects of acute low salinity stress on the liver structure, physiology and biochemistry of the larvae of Lateolabrax maculatus, the experiment was carried out to transfer the juveniles direct from salinity 30‰ (control group) to salinity 20‰, 10‰, and 0‰, respectively. Changes in liver microstructure and related physiological and biochemical indexes at different time points were observed. The results showed that no fish died during the whole experiment and all of them returned to normal behavior within 15 minutes. The liver cells of juvenile Chinese sea bass showed pathological changes such as swelling, vacuolation and nuclear pyknosis after low salinity stress, and the lower the salinity, the earlier the abnormal phenomenon appeared. The total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) of liver showed a rapid increase and then decrease; The level of malondialdehyde (MDA) returned to normal after high fluctuations. The activity of lysozyme (LZM) in experimental groups were higher than that in control group between 12h and 48h, while there was not significantly different before 6h in each group (P>0.05), all of them returned to normal in 96 h. The activity of alkaline phosphatase (ALP) and acid phosphatase (ACP) increased firstly and then decreased during the time of stress, and there was no significant difference between each group at the same time point (P>0.05). The comprehensive analysis showed that the juvenile Chinese sea bass had strong osmotic pressure regulation ability, and the acute low salinity stress had little effect on the liver structure and physiological and biochemical indexes

Effect of replacement of fishmeal by soybean products with attractants supplementation on the growth performance, feed utilization, body composition, plasma physiological responses and hepatic antioxidant abilities of juvenile golden pompano Trachinotus ovatus

A feeding experiment was carried out to develop a practical diet with low fishmeal for juvenile golden pompano (Trachinotus ovatus) by substituting fishmeal protein with soybean products mixture. Six isocaloric (17.6 KJ g−1) diets were designed by replacing 0 (FM100), 5 (FM95), 10 (FM90), 15 (FM85), 20 (FM80), and 25% (FM75) of the fishmeal with soybean products mixture (SPM) (soybean meal and soybean protein concentrate). The experiment diets were supplemented with 1.5%, 3%, 4.5%, 6% and 7.5% squid paste as attractants or palatability enhancer. The experimental fish (6.9 g) were cultured in sea cages (1.0 m × 1.0 m × 1.5 m) with 25 fish in each cage. Fish were fed the corresponding experimental diets to satiation twice daily for 8 weeks. At the end of the feeding experiment, no differences were found in the final weight and weight gain (WG) of fish fed FM100, FM85, FM80, and FM75 diets (P > 0.05). The WG was significantly (P < 0.05) better in the fish-fed FM95 diet compared to FM100 and FM75 diets. FCR in diet FM95 and FM90 was significantly (P < 0.05) than that of FM80 and FM75, but these values were not significantly different from those in other treatments. Although the condition factor value in diets FM90, FM85, and FM80 was significantly (P < 0.05) higher than that of FM100, these values were not significantly different from the rest of the other groups. There was no statistical difference in SGR, FR, VSI, and survival rates among different dietary treatments. The plasma AST activity was significantly lower in fish fed FM90 diet compared to fish fed with control, FM85, FM80, and FM75 (P < 0.05). There was no significant difference in plasma AST among all dietary treatments except FM95 and FM90. In contrast, the plasma AKP activity showed the opposite trend. Compared with the control, the fish-fed FM80 and FM75 diets had significantly decreased plasma cholesterol, triglyceride total protein, albumin, and globulin level (P < 0.05) while significantly increasing plasma COR levels (P < 0.05). There was no significant difference in ALT, Urea and glucose values among all treatments. No statistical difference was observed among the FM100, FM80, and FM75 treatments for those of plasma LYZ activity, C3, and C4 levels. The hepatic T-AOC and SOD activities were significantly increased in fish fed the FM90 diet (P < 0.05) compared to those in fish fed with FM100 diet. According to the current experiment, it can be concluded that SPM supplemented with SP could partially substitute fishmeal (25%) for juvenile golden pompano without any adverse symptoms

Effect of Dietary Marine Red Yeast Rhodotorula mucilaginosa on the Growth Performance, and also Non-Specific Immune Responses of Juvenile Golden Pompano Trachinotus Ovatus when Challenged with Vibrio Harveyi

The present study was conducted to investigate the effects of dietary marine red yeast Rhodotorula mucilaginosa supplementation on the growth performance, non-specific immune responses, and resistance to the pathogen Vibrio harveyi in Golden Pompano Trachinotus ovatus. A basal diet was supplemented with R. mucilaginosa at 0‰ (control), 1‰, 2‰, 3‰, 4‰, and 5‰ for 8 weeks. After the 8-week feeding trial, weight gain (WG) and specific growth rate (SGR) were significantly affected by the R. mucilaginosa levels, with the highest WG and SGR occurring at the 1‰ R. mucilaginosa level (P<0.05). Compared to the control, the 4 and 5‰ R. mucilaginosa groups had significantly increased lysozyme (LYZ) and alkaline phosphatase (AKP) activity, but a decrease in nitric oxide synthase (NOS) was noted (P<0.05). Compared to the control, the 2, 3 and 4‰ R. mucilaginosa groups had significantly increased hepatic superoxide dismutase (SOD) activity (P<0.05), while hepatic malondialdehyde (MDA) content decreased significantly (P<0.05). After challenge with V. harveyi, the group supplemented with 1‰ R. mucilaginosa had 100% survival rate. In addition, compared to the control group prior to challenge, the serum C3 level significantly increased in the group supplemented with 2‰ R. Mucilaginosa (P < 0.05). Compared to the control 12 h and 48h after challenge, serum C4 levels in the 4‰ R. Mucilaginosa group increased significantly (P<0.05). Our results suggest that ingestion of a basal diet supplemented with 1-3‰ R. mucilaginosa in T. ovatus could enhance resistance against the pathogen Vibrio harveyi

Dietary Methionine Requirements of Pacific White Shrimp Litopenaeus vannamei, of Three Different Sizes

Three feeding trials were conducted to determine the dietary methionine requirements for Litopenaeus vannamei of three different sizes, small (0.55±0.01g), medium (4.18±0.05g), and large (9.77±0.08g). Seven diets were formulated with seven different levels of methionine (0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 0.6%). The greatest weight gain (WG) and specific growth rate (SGR) of small and large shrimp were observed when dietary methionine levels were 0.8%, and 0.71%, respectively (P<0.05). The highest survival rate of small and large shrimp was observed when dietary methionine levels were 0.97%, and 1.07%, respectively (P<0.05). For small and medium shrimp, the optimal dietary methionine level for maximum weight gain estimated by quadratic regression analysis was 0.91% and 0.67% of dry diet, respectively. For large shrimp, the optimal dietary methionine requirement estimated by broken-line model based on weight gain was 0.66% of dry diet

The complete mitochondrial genome of Chaetodon speculum (Chaetodontiformes, chaetodontidae)

Chaetodontidae species feeding observations showed that they mostly fed on different coral species. Among them, Chaetodon speculum (Cuvier, 1831) is one of most important genera of Chaetodontidae, C. baronessa and C. bennetti appeared to ingest annelid worms during the course of coral feeding, whereas gut contents of C. punctatofasciatus and C. speculum were dominated by crustaceans. However, the systemically classification and taxonomic studies have so far been limited. In this study, we report the complete mitochondrial genome sequence of C. speculum. The mitogenome has 16,537 base pairs (54.4% A + T content) and made up of total of 37 genes (13 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs), and a putative control region. This study will provide useful genetic information for future phylogenetic and taxonomic classification of Chaetodontidae

Effect of dietary carbohydrate on glycometabolism of juvenile golden pompano (Trachinotus ovatus) related to growth performance, hepatic histopathology, transcriptome profiles and identification of differentially expressed genes

A hepatic transcriptome was produced through the technology of RNA sequencing and short-read assembly in golden pompano Trachinotus ovatus fed with three experimental diets respectively containing low carbohydrate diet (LCD), intermediate carbohydrate diet (MCD), and high carbohydrate diet (HCD). In total, 57,217 unigenes were acquired in the current study, with average length 1182.24 bp. 21,920, 22,514 and 24,680 unigenes were acquired from LCD, MCD and HCD groups, respectively. There were 1513 differential expressed genes in LCD and MCD groups, with 676 up- and 837 down-regulated genes in LCD group; 2369 genes were differentially expressed between HCD vs MCD, containing 1397 up and 972 down-regulated genes in HCD group. 1686 differential expressed genes were observed in the comparison of HCD and LCD, containing 1044 up- and 642 down-regulated genes in HCD group. Some differential expressed genes, such as hexokinase-1-like isoform X3, pancreatic alpha-amylase-like, hexokinase-1-like isoform X1, ADP-dependent glucokinase isoform X2, fructose-bisphosphate aldolase A-like, and acetyl-CoA carboxylase isoform X8, were related to carbohydrate metabolism, indicating these genes in the golden pompano were in response to dietary carbohydrate. In this study, long-chain-fatty-acid-CoA ligase 5 was up-regulated in comparison of HCD_vs_MCD and HCD_vs_LCD, which indicated that FACL5 may be sensitive to high dietary carbohydrate. This result coincides with the pathological changes of hepatocyte morphology in the present study. The results of transcriptome analysis in this study were confirmed by RT-PCR in 14 randomly selected unigenes. This study may provide novel data and theoretical support on hepatic transcriptome information of the golden pompano, which is a vital resource for studies of bioinformatics in golden pompano. Besides, the present study identifies some pivotal genes related to dietary carbohydrate and lipid deposition, which will accumulate data on carbohydrate and/or lipid metabolism in marine fish species to support related research

The complete mitochondrial genome of Chaetodon wiebeli (Chaetodontiformes, Chaetodontidae)

Chaetodon wiebeli is one of the most important genera of Chaetodontidae. However, the systemic classification and taxonomic studies have so far been limited. In this study, we report the complete mitochondrial genome sequence of C. wiebeli. The mitogenome has 16,523 bp (54.3% A + T content) and is made up of a total of 37 genes (13 protein-coding, 22 transfer RNAs, and 2 ribosomal RNAs), and a putative control region. This study will provide useful genetic information for future phylogenetic and taxonomic classification of Chaetodontidae

The complete mitochondrial genome of Thalassoma lunare (Labriformes, Labridae)

Thalassoma lunare is one of most important genera of Labridae. However, the systemically classification and taxonomic studies have so far been limited. In this study, we report the complete mitochondrial genome sequence of T. lunare. The mitogenome has 17,073 base pairs (57.7% A + T content) and made up of total of 37 genes (13 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs), and a putative control region. This study will provide useful genetic information for future phylogenetic and taxonomic classification of Labridae

Evaluation of different lipid sources in diet of pacific white shrimp Litopenaeus vannamei at low salinity

Litopenaeus vannamei (1.98 ± 0.28 g) were fed diets containing soybean oil (SBO), beef tallow (BFT), fish oil (FIO), linseed oil (LNO), and an equal combination of SBO + BFT + FIO (SBF) or SBO + BFT + LNO (SBL) as dietary lipid source respectively for 8 weeks at low salinity of 3‰. The shrimp fed the SBL diet had the highest weight gain and survival rate. The whole body fatty acid composition including the EPA and DHA of L. vannamei generally reflected the composition of dietary fatty acids with the highest DHA and EPA found in L. vannamei fed FIO. The activities of fatty acid synthetase, acyl-CoA, diacylgycerol acyltransferase 2, elongase of long-chain fatty acids family member 6, Δ5 and Δ6 fatty acid desaturases of shrimp fed SBL were significantly lower than those fed BFT. The results indicated that fish oil could not be the only lipid source for L. vannamei cultured at low salinity, and the shrimp fed non-fish oil diet with a suitable proportion of PUFAs could obtain the same growth and survival rate as those fed diets with fish oil

The complete mitochondrial genome of Acanthurus mata (Acanthuriformes, Acanthuridae)

Acanthurus mata is one of most important genera of Acanthuridae. However, the systemically classification and taxonomic studies have so far been limited. In this study, we report the complete mitochondrial genome sequence of A. mata. The mitogenome has 15,102 base pairs (55.6% A + T content) and made up of total of 37 genes (13 protein-coding, 22 transfer RNAs and 2 ribosomal RNAs), and a putative control region. This study will provide useful genetic information for future phylogenetic and taxonomic classification of Acanthuridae