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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.

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.

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.

Experimental diets were formulated including the suitable lipid level (10%, PC), the high‐lipid level (16%, HL), and HL containing sodium acetate diets (HS). Three diets were fed golden pompano (Trachinotus ovatus) (initial body weight: 12.88 ± 0.03 g) for 8 weeks. The results showed HL diets significantly increased hepatosomatic index (HSI) and abdominal fat percentage (ASF), aggravated liver lipid deposition, and caused blood metabolic disorder and liver damage (P < 0.05). Moreover, the fish fed HL diets significantly decreased intestinal villus number (VN) and muscular layer thickness (MLT) (P < 0.05), accompanied with an increased trend in the relative abundance of intestinal pathogenic bacteria such as Mycoplasma and Photobacterium. However, the fish fed HS diets significantly decreased the HSI and AFP, relieved hepatic lipid deposition, improved blood and liver metabolism, and intestinal morphology in comparison to the fish fed HL diets (P < 0.05). More importantly, sodium acetate addition improved intestinal microbiota by inhibiting the proportion of pathogens (Mycoplasma and Vibrio) and increasing the abundance of probiotics (Bacteroidales_S24-7_group_norank, Cetobacterium, Bacteroides, and Lachnospiraceae_NK4A136_group). Furthermore, there was a strong correlation between these bacteria (Mycoplasma, Vibrio, Lachnospiraceae_NK4A136_group, Bacteroidales_S24-7_group_norank, Bacteroides, and Cetobacterium) and main physiological indices. In conclusion, sodium acetate improved blood performance, alleviated hepatic lipid deposition induced by HL diets, and boosted the growth and intestinal health for golden pompano. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the adaptive strategies and compensatory growth mechanisms of juvenile Epinephelus coioides under starvation stress. The fish with an initial body weight of 8.88 ± 0.06 g were starved for 0 day (F0, control), 3 days (F3), 6 days (F6), 9 days (F9), 12 days (F12), and 15 days (F15), followed by feeding periods of 30 days, 27 days, 24 days, 21 days, 18 days, and 15 days, respectively. The results are shown as follows: (1) E. coioides could achieve complete or partial compensatory growth by improving both feeding rate and feed conversion efficiency. (2) The viscerosomatic index and the hepatosomatic index of the test fish decreased linearly with the duration of starvation (P < 0.05), while the condition factor did not significantly decrease (P > 0.05). At the end of feeding, all the physical body indicators of the test fish recovered or exceeded the control levels. (3) The lipid and glycogen contents of the test fish decreased continuously throughout the entire starvation process, with noticeable protein consumption occurring in the later stages of starvation (P < 0.05). At the end of the feeding period, apart from a significant reduction in crude lipid contents in the F12 and F15 groups compared to the control group (P < 0.05), the biochemical composition of the test fish was restored or even surpassed that of the control group. (4) The activity of digestive enzymes could be stimulated by starvation, enabling the efficient utilization of energy storage substances. In conclusion, it is advisable to limit the period of starvation for juvenile E. coioides to 12 days, which means that the ratio of starvation period to feeding period should not exceed two‐thirds. [ABSTRACT FROM AUTHOR]

Although β-glucan has diverse benefits for fish health, the potential adverse impacts of excessive supplementation are poorly understood. This study investigated the optimal dosage of β-glucan for coral trout and explored the adverse effects of excessive supplementation. The results revealed that moderate β-glucan supplementation (1) significantly enhanced the weight gain rate and specific growth rate (SGR); (2) significantly improved the intestinal villus length (0.10%), muscle thickness (0.05–0.15%), and α-amylase and chymotrypsin activities (0.05–0.15%); (3) significantly increased liver catalase (CAT), glutathione reductase (GR), alkaline phosphatase, complement 3, immunoglobulin M (IgM), lysozyme, serum superoxide dismutase, CAT, glutathione peroxidase, GR, total antioxidant capacity, acid phosphatase, complement 4, and IgM activities and significantly reduced malondialdehyde contents; (4) upregulated genes in the liver associated with copper-zinc superoxide dismutase (SOD-1), manganese superoxide dismutase (SOD-2), CAT, GSH-Px1a, ACP6, AKP, LZ-c, IgM, C3, and C4-b. However, 0.20% β-glucan significantly inhibited the growth performance of coral trout compared with 0.10% β-glucan. Thus, 0.10% β-glucan represents the optimal dosage for promoting growth, antioxidant activity, and immune responses in coral trout, while higher β-glucan levels weakened these beneficial effects. With an SGR established by a cubic regression analysis, the optimal level of β-glucan for maximal growth of coral trout is 0.082%. This study provides new insights into the health impacts of β-glucan on fish. [ABSTRACT FROM AUTHOR]

Simple Summary: Ammonia is a major water quality factor influencing the survival and health of shrimp, among which the gill is the main effector organ for ammonia toxicity. In this study, we explored the toxicity of ammonia stress on the physiological homeostasis in the gills of Litopenaeus vannamei under seawater and low-salinity conditions. This study included four groups, namely the SC group (ammonia-N 0 mg/L, salinity 30‰), SAN group (ammonia-N 10 mg/L, salinity 30‰), LC group (ammonia-N 0 mg/L, salinity 3‰), and LAN group (ammonia-N 10 mg/L, salinity 3‰). The ammonia stress lasted for 14 days. The results show that ammonia stress caused the severe contraction of gill filaments and the deformation or even rupture of gill vessels. Ammonia stress could also influence the redox, ER function, apoptosis, detoxification, energy metabolism, and osmoregulation of the shrimp gills. These results are helpful to analyze the toxicological mechanism of ammonia stress on the seawater- and low salinity-cultured shrimp. Ammonia is a major water quality factor influencing the survival and health of shrimp, among which the gill is the main effector organ for ammonia toxicity. In this study, we chose two types of Litopenaeus vannamei that were cultured in 30‰ seawater and domesticated in 3‰ low salinity, respectively, and then separately subjected to ammonia stress for 14 days under seawater and low-salinity conditions, of which the 3‰ low salinity-cultured shrimp were domesticated from the shrimp cultured in 30‰ seawater after 27 days of gradual salinity desalination. In detail, this study included four groups, namely the SC group (ammonia-N 0 mg/L, salinity 30‰), SAN group (ammonia-N 10 mg/L, salinity 30‰), LC group (ammonia-N 0 mg/L, salinity 3‰), and LAN group (ammonia-N 10 mg/L, salinity 3‰). The ammonia stress lasted for 14 days, and then the changes in the morphological structure and physiological function of the gills were explored. The results show that ammonia stress caused the severe contraction of gill filaments and the deformation or even rupture of gill vessels. Biochemical indicators of oxidative stress, including LPO and MDA contents, as well as T-AOC and GST activities, were increased in the SAN and LAN groups, while the activities of CAT and POD and the mRNA expression levels of antioxidant-related genes (nrf2, cat, gpx, hsp70, and trx) were decreased. In addition, the mRNA expression levels of the genes involved in ER stress (ire1 and xbp1), apoptosis (casp-3, casp-9, and jnk), detoxification (gst, ugt, and sult), glucose metabolism (pdh, hk, pk, and ldh), and the tricarboxylic acid cycle (mdh, cs, idh, and odh) were decreased in the SAN and LAN groups; the levels of electron-transport chain-related genes (ndh, cco, and coi), and the bip and sdh genes were decreased in the SAN group but increased in the LAN group; and the level of the ATPase gene was decreased but the cytc gene was increased in the SAN and LAN groups. The mRNA expression levels of osmotic regulation-related genes (nka-β, ca, aqp and clc) were decreased in the SAN group, while the level of the ca gene was increased in the LAN group; the nka-α gene was decreased in both two groups. The results demonstrate that ammonia stress could influence the physiological homeostasis of the shrimp gills, possibly by damaging the tissue morphology, and affecting the redox, ER function, apoptosis, detoxification, energy metabolism, and osmoregulation. [ABSTRACT FROM AUTHOR]

The effects of three feed additives in a low fish meal diet on growth, antioxidant capacity and intestinal microbiota of Penaeus monodon were studied to enhance the understanding of these effects and to provide basic data and a reference for the formulation and optimization of feed for P. monodon. A total of 630 healthy, homogenous shrimp (4.58 ± 0.05 g) were randomly divided into seven groups with three replicates per group and 30 shrimp per replicate in a breeding barrel (500 L). The additive names and amounts were 0 (CT); vitamin B6, 100 mg/kg (V1); vitamin B6, 200 mg/kg (V2); phytase, 1000 U/kg (P1); phytase, 2000 U/kg (P2); 0.2% yucca extract (Y1); and 0.4% yucca extract (Y2). The experiment lasted 8 weeks. The results showed that compared to CT, V1 and Y1 had a significant increasing tendency toward weight gain (WG) (p < 0.05) and had a significant decreasing tendency in the food conversion ratio (FCR) (p < 0.05). P2 had a significant increasing tendency in α-amylase activity (p < 0.05), and P1 had a significant increasing tendency in total superoxide dismutase (T-SOD) (p < 0.05). The next-generation sequencing of intestinal microbiota showed that Proteobacteria was the most abundant phylum in the seven groups, accounting for 29.33%, 56.67%, 55%, 45.33%, 73%, 39.33% and 64.33% of the total. Compared to CT, the Proteobacteria was significantly high (p < 0.05) in P2 and Y2, and the Bacteroidota in all other groups decreased significantly (p < 0.05). The functional prediction of FAPROTAX indicated that there was no significant difference (p > 0.05) in functional components among all groups. According to growth performance, antioxidant capacity and effects on intestinal microbiota, vitamin B6 (100 mg/kg), phytase (2000 U/kg) and yucca extract (0.2%) can be recommended as additives for the diet of P. monodon. [ABSTRACT FROM AUTHOR]

Seven graded levels of sodium propionate (SP) diets with 0 (SP1), 0.2% (SP2), 0.4% (SP3), 0.6% (SP4), 0.8% (SP5), 1.0% (SP6), and 1.2% (SP7) were prepared to feed Trachinotus ovatus (initial body weight: 8.64 ± 0.08 g) for 56 days. The results showed that increasing dietary SP levels quadratically increased significantly final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) of T. ovatus but linearly and quadratically decreased significantly viscerosomatic index (VSI) and hepatosomatic index (HSI) of T. ovatus (P < 0.05). In the SP4 treatment, FBW, WGR, and SGR presented the highest values. Both positive linear and quadratic trends were detected between crude lipid content of whole fish, adhesiveness of dorsal muscle, white blood cell (WBC), red blood cell (RBC), hemoglobin (HGB), blood performance, high-density lipoprotein cholesterol (HDL-c), intestinal villus height, and dietary SP level, while negative linear and quadratic trends were found between firmness of dorsal muscle, triglyceride (TG), glucose (GLU), and dietary SP level (P < 0.05). The increasing SP led to quadratic increases in lymphocyte (Lym), complement 3 (C3), chymotrypsin, villus number, and muscle layer thickness, and a quadratic decrease in hepatic malondialdehyde (MDA P < 0.05). A significant negative linear trend was found between the content of glutamic-pyruvic transaminase (GPT) and dietary SP level, while significant positive linear trends were presented between C4, immunoglobulin M (IgM), α-amylase and dietary SP level (P < 0.05). The increasing SP resulted in linear and quadratic increases in superoxide dismutase (SOD), total antioxidant capacity (T-AOC) of livers and C3, C4, IgM of head kidney (P < 0.05). The expression levels of tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) were linearly and quadratically decreased, while the mRNA levels of growth factor beta (TGF-β) were linearly and quadratically increased with the increasing SP level (P < 0.05). In conclusion, SP could be considered as a beneficial feed additive for enhancing growth and immunity of fish. And dietary SP level at 0.6% is optimal for the growth of Trachinotus ovatus based on a quadratic regression model of WGR. [ABSTRACT FROM AUTHOR]