Aquaculture Research最新文献

Probiotic is regarded as an effective feed additive to increase the growth, feeding efficiency, survivability, and overall productivity of fishes in aquaculture. The following study was intended to examine the effects of multistrain probiotics on growth, blood indices, histomorphometry of gastrointestinal tract and liver, and growth hormone (GH) and insulin-like growth factors (IGFs) genes expression in rohu Labeo rohita. Probiotic containing Bacillus subtilis, B. thuringiencis, Lactobacillus plantarum, and L. buchneri was inoculated in water and three different doses, that is, 0 mL/L (control), 0.5 mL/L (lower dose, T1), and 1.0 mL/L (higher dose, T2) were used in this study. Each treatment had three replicates and fishes were reared in aquarium for 60 days. Results revealed that substantially higher weight gain (WG) and specific growth rate (SGR) along with least apparent feed conversion ratio (AFC) were documented in probiotic treated fish which was significantly different than that of control, however, higher dose (1.0 mL/L) showed best performance. Blood–biochemical indices such as red blood cell (RBC), white blood cell (WBC), hemoglobin (Hb), and glucose (Glu) level were observed statistically higher in probiotic additive culture water. Moreover, the inoculation of multispecies probiotic positively altered the intestinal histometry. Besides, immune response features of intestine were observed significantly higher in probiotic treated fish. The nucleus shape and distances between liver tissues (DLTs) were also improved with the upward doses of probiotic application. The mRNAs levels of GH in the pituitary and IGF-1 and IGF-2 in the liver were significantly higher in probiotic treated fish. In a nutshell, this study suggested that the inclusion of multistrain probiotics showed promising improvement in growth performance and feed conversion efficiency; additionally, uplifted the intestinal structure integrity, liver morphology, and GH and IGFs genes expression in rohu.

This study investigates the fabrication of algogenic zinc nanoparticles (ZnNPs), examining their biomimetic properties and potential antibacterial effectiveness against fish pathogens. The rising incidence of antibiotic resistance in aquaculture demands innovative strategies for disease management, highlighting the importance of developing biocompatible and effective antimicrobial agents. In this context, ZnNPs were synthesized using Pediastrum boryanum microalgal extract as the reducing and capping agent. Transmission electron microscopy (TEM) revealed spherical and tetragonal particles with sizes ranging from 32.84 to 26.87 nm. Fourier transform infrared spectroscopy (FTIR) demonstrated distinctive functional groups in the algal extracts and ZnNPs. X-ray diffraction (XRD) showed pure crystallinity of the fabricated ZnNPs with an average crystalline size of 57.97 nm. The algal extract had high total phenolic (TPC) and flavonoid (TFC) contents (TPC: 53.83 and TFC: 12.44 mg QE/g, respectively). The obtained ZnNPs retained a considerable amount of TPC and TFC (7.92 and 5.31 mg/g, respectively). The microalgal extract and ZnNPs exhibited considerable antioxidant capacity in the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. In addition, they elicited antibacterial efficacy against several bacterial pathogens in fish in a minimum inhibitory concentration (MIC) assay. Brine shrimp lethality assay (BSLA) revealed higher potential cytotoxicity of biosynthesized ZnNPs at 29.28 μg/mL compared to that of the algal extracts at 51.56 μg/mL. These findings highlight the potential of P. boryanum as a green factory for the nanofabrication of metallic nanoparticles (NPs) and as a promising clinical candidate for fish medicine.

The increase in fish production in aquaculture reflects the growth of the world population. However, this expansion is accompanied by challenges, such as the intensification of production systems through increased stocking density, which induces stress in fish, weakening their immune system and making them more susceptible to disease outbreaks, particularly those caused by parasites. Monogeneans are ectoparasites that attach to the external surfaces of fish and are characterised by their host-specificity. One of the emerging species in aquaculture, much appreciated in the Mediterranean region, is the meagre (Argyrosomus regius), whose production has been increasing due to its high-quality meat and excellent growth rates. However, the information available on the parasites that affect this species is limited, which makes it difficult to prevent and control disease outbreaks in aquaculture systems effectively. This study presents the first morphological and molecular characterisation of Calceostoma glandulosum, an ectoparasite of the Monopisthocotylea subclass, characterised by its lapel (L) in the cephalic area and an anchor-shaped haptor (Hp). The parasite’s life cycle, including eggs, larvae (oncomiracidium), and adults, has also been described. It was demonstrated that water temperature could influence the development of the eggs; at more favourable temperatures for the parasite, there was a higher percentage of developed and hatched eggs. The occurrence of the parasite in the farming tanks was higher when the temperature reached 20°C, and in vitro experiments have shown a hatching rate of 100% at 23°C. C. glandulosum reaches sexual maturity between 11 and 14 days and has a fertility period of 10 days. To assess the host-specificity of C. glandulosum for A. regius, eggs were investigated in other species (Sparus aurata, Diplodus sargus, and Seriola rivoliana). This work provides valuable insights into the behavior of monogeneans concerning environmental conditions and host interactions, offering critical information for implementing preventive measures in aquaculture.

The fish brain plays a crucial role in regulating growth, reproduction, development, and adaptation to environmental stress. However, there are few studies that have examined the entire fish brain transcriptome and its responses to long-term hypo- and hyper-salinity stress. Greater amberjack (Seriola dumerili) has a high commercial value in mariculture worldwide due to its high growth rate and excellent flesh quality. Consequently, high-throughput RNA-Seq was employed to elucidate the molecular regulatory mechanisms underlying salinity adaptation by identifying gene expression changes in the brain of greater amberjack exposed to elevated and/or reduced salinity environments. We subjected individuals to salinity levels of 20, 30, and 40 ppt (parts per thousand) for 30 days. A total of 272 (198 up-regulated and 74 down-regulated) differentially expressed genes (DEGs) were identified in the B30 vs. B20 group, 21 (10 up-regulated and 11 down-regulated) DEGs in the B30 vs. B40 group, and 343 (119 up-regulated and 224 down-regulated) DEGs in the B20 vs. B40 group. Transcriptomic analysis revealed that salinity stress influenced the expression of genes associated with amino acid metabolism and transport (gpt, arg2, LOC111237759, slc3a2, and slc7a5), carbohydrate metabolism (aldob, ldhba, and gapdh), and signal transduction (map3k8, map3k2, map2k7, and lepr). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that the DEGs were significantly enriched in metabolism pathways, especially in amino acid and carbohydrate metabolism, transcription, translation, et cetera. Furthermore, gene set enrichment analysis (GSEA) demonstrated that the metabolism, signal transduction, translation, immune system, and transport and catabolism pathways were more active in the brain. These findings provide a foundation for further studies to clarify the molecular mechanisms of salinity adaptation and transcriptional regulation in the brain of marine fish.

The current study was carried out to examine the effects of four different experimental salinities (T₁ = 0‰, T₂ = 5‰, T₃ = 10‰, and T₄ = 15‰) on growth, water quality, proximate composition, total bacterial (TB), and hemocyte counts of white leg shrimp (Litopenaeus vannamei) and giant prawn (Macrobrachium rosenbergii) in biofloc based nursery bi-culture system for 6 weeks. A total of 12 cylindrical plastic tanks (125 L) filled up 100 L water for rearing L. vannamei and M. rosenbergii post-larvae (PLs) at an equal ratio: (50 L. vannamei: 50 M. rosenbergii). At the end of the experiment, for L. vannamei, the significantly higher (p < 0.05) growth rate was recorded in T₄ (15‰) compared to the other treatments. For M. rosenbergii, a significantly higher (p < 0.05) growth rate was recorded in T₂ (5‰) than in other treatments. Similar to growth, the best (p < 0.05) feed conversion ratio (FCR) for -L. vannamei was found at T₄ (15‰) while it was at T₂ (5‰) forM. rosenbergii. Gross return, net profit, and benefit–cost ratio (BCR) analysis revealed higher profit T₄ (15‰) than T₃ (10‰), T₂ (5‰), and T₁ (0‰). TB counts were found to be significantly greater (p < 0.05) in T₄ than other treatments. Hemocyte counts for L. vannamei were significantly higher (p < 0.05) in T₄ (15‰) than T₃ (10‰), T₂ (5‰), and T₁ (0‰) and for M. rosenbergii hemocyte was significantly higher (p < 0.05) in T₁ (0‰) than T₂ (5 ‰), T₃ (10 ‰), and T₄ (15‰). Therefore, it can be suggested that 15‰ salinity will be the best condition for the nursery bi-culture of white leg shrimp (L. vannamei) and giant prawn (M. rosenbergii) in the biofloc system.

Daphnia carinata is an important biological live feed in aquaculture. Conventionally, D. carinata is cultivated and fed with fresh Chlorella pyrenoidosa, which is inconvenient for storage and transportation. After undergoing vacuum freeze-drying or spray-drying, C. pyrenoidosa exhibits advantages such as reduced weight and easier storage and transport. This study investigated the effects of feeding freeze-dried and spray-dried Chlorella on the reproductive performance and fatty acid composition of D. carinata. The results indicated that there was no significant difference in reproductive performance between the two groups of D. carinata fed with freeze-dried Chlorella and fresh Chlorella. However, a significant decline in reproductive performance was observed in the group fed with spray-dried Chlorella. The contents of crude fat and unsaturated fatty acids in freeze-dried Chlorella were significantly higher than in spray-dried Chlorella. Additionally, D. carinata fed with freeze-dried Chlorella exhibited significantly higher levels of unsaturated fatty acids (especially ALA and EPA) than those fed with spray-dried Chlorella. In conclusion, freeze-dried Chlorella can be used as an alternative to fresh Chlorella for cultivating D. carinata. Unsaturated fatty acids are a key factor influencing the reproductive performance of D. carinata.

The Macrobrachium genus thrives in freshwater and brackish environments. M. hainanense, a nocturnal freshwater prawn, is economically significant in China due to its delicious meat and rich nutrition. Its distribution is limited to regions like Zhejiang, Guangdong, Guangxi, Fujian, and Hainan due to breeding habits near estuaries and low-temperature tolerance. Despite its economic importance, there are limited studies on M. hainanense, particularly regarding its germplasm resources. This study investigates the growth traits, nutritional composition, enzyme activity, and genetic diversity and structure of seven M. nipponense populations and three M. hainanense populations to inform sustainable aquaculture and conservation efforts, comparing them with the new hybrid varieties of M. nipponense, which successfully cultivated, Because of its fast growth, high adaptability, and strong reproductive capacity was chosen as a control sample due to its well-established quality, economic value, reputation, ensuring competitive comparison. The amino acids, fatty acids, and physiological and biochemical indicators among M. hainanense populations and M. nipponense populations showed significant differentiation. M. hainanense populations showed minor differences in nutritional components except for total sugar and astaxanthin content that were significantly different, whereas M. nipponense populations showed almost no differences. Essential amino acids in M. hainanense comprised 34.42%–37.53% of the total amino acid content. Differences in glycine, isoleucine, and cystine were notable in M. hainanense, while glycine and proline differed in M. nipponense. Fatty acid components varied among the populations studied. Genetic diversity analysis revealed that the polymorphism information content (PIC) values for M. hainanense were higher than those for M. nipponense. The Changhua River (CH) and Nandu River (ND) populations of M. hainanense had the lowest nucleotide diversity, while the Oujiang River (OU) population had the highest. The OU population also exhibited the greatest genetic diversity, with the lowest inbreeding coefficient, while the CH population had the highest. There was slight genetic differentiation among M. hainanense populations, with geographical isolation and artificial selection contributing to genetic structure differences. This study is the first to examine population-wide genetic variability in M. hainanense, highlighting the need for comprehensive conservation and breeding strategies to maintain and enhance genetic variability in this species. The study concludes that both M. hainanense and M. nipponense have rich protein content and low-fat content, with varied genetic relationships and differentiation among populations.

A pathology characterized by multifocal reddish patches on the cuticle of shrimp has been reported by shrimp farmers in Latin America. These red patches are commonly associated with small black necrotic spots and white muscle necrosis. One significant impact of this pathology is the reduction in shrimp prices due to the appearance of the animals before and after cooking. The disease is more prevalent in areas with salinities above 5 ppt, with one farm reporting a 45% incidence in one pond. Histopathological examination revealed infiltration of hemocytes in the muscle tissue, melanosis, muscle necrosis, and the presence of Gram-negative rods in the muscle tissue. Given the presence of bacteria and negative polymerase chain reaction (PCR) results for muscle-infecting viruses such as infectious myonecrosis virus (IMNV) and Penaeus vannamei nodavirus (PvNV), this pathology is likely due to bacterial infection, though environmental stressors cannot be ruled out as contributing factors in this complex condition. Several Vibrio strains were isolated from the affected tissue and identified using API 20E and PCR. Two strains were selected for in vivo experimentation: Vibrio parahaemolyticus (C8Cg, PirAB toxin-positive) and V. alginolyticus (C3Ver, PirAB toxin-negative). Shrimp injected with both live and autoclaved bacteria showed similar histopathological changes, suggesting that the pathology is due to virulence factors within the bacterial cells that can still provoke a strong immune or toxic response even in the absence of live, actively replicating bacteria.

Recently, there has been increasing attention regarding the potential application of biodegradable nanoparticles (NPs) as adjuvants in injectable vaccines. In this study, encapsulated antigens of Aeromonas hydrophila in alginate/chitosan polymers were used as injectable vaccines in common carp. Formalin-killed bacteria and extracellular products (ECPs) of A. hydrophila were encapsulated via emulsification method. In total, 480 juvenile common carp (32.1 ± 3.64 g, mean ± SD) were randomly divided into eight triplicate groups (20 fish for each replicate). Groups 1–3 were injected with bacterin, ECP, and bacterin + ECP, respectively. Groups 4–6 were injected with encapsulated bacterin, encapsulated ECP, and encapsulated bacterin + ECP, respectively. Groups 7 and 8 as controls were injected with alginate/chitosan and phosphate-buffered saline (PBS), respectively. Blood samples were collected on days 0, 30, and 60 of the experiment. Immunological parameters, including antibody titer against A. hydrophila, serum lysozyme, bactericidal and complement activities, and nitro blue tetrazolium (NBT) reduction, as well as serum globulin and protein levels, were compared among the groups. Hematological parameters (red blood cell [RBC], white blood cell [WBC], hemoglobin [Hb], and hematocrit (Hct) were evaluated too. Remained fish were challenged with severe A. hydrophila, and mortality was recorded for 10 days. Results showed that anti-A. hydrophila antibody titer, survival rate following bacterial challenge, NBT reduction, serum lysozyme activity, globulin, and protein levels were significantly higher in encapsulated bacterin and encapsulated bacterin + ECP groups compared with the control group (p  < 0.05). Serum bactericidal and complement activity showed no significant change in different groups of sampling points. Then, it can be concluded that the encapsulation of bacterin and bacterin + ECP of A. hydrophila using chitosan/alginate NPs enhanced the protection and immune responses in common carp and this method is a promising candidate for a vaccine adjuvant in fish.

In this study, the effects of using the distiller’s dried grains with solubles (DDGS) instead of soybean meal on rainbow trout (Oncorhynchus mykiss) were investigated. Four different experimental diets were prepared with isonitrogenous (43%) and isolipidic (19%) values, incorporating DDGS at levels of 0%, 10%, 20%, and 30%. Fish were weighed (18.5–20.2 g) and randomly distributed in 12 tanks (140 L water) with 22 fish in each tank. The feeding trial lasted 60 days and was conducted in triplicate. The best weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR) were observed in the DDGS20 experimental group. While viscerosomatic index (VSI) and hepatosomatic index (HSI) values were found to be the highest in the DDGS30 experimental group, the spleen-somatic index (SSI) was found to be the highest in the DDGS10 experimental group (p  < 0.05). It was found that the nutrient digestibility ratio values and fish meat chemical composition values of the experimental diets were similar between the groups (p  > 0.05). Additionally, it was analyzed that the use of DDGS protein sources in diets did not negatively affect the coloration of the experimental fish. While DDGS percentage increased in the diet, hepatocyte nucleus diameter was decreasing (p  < 0.05). In the distal intestine, the DDGS10 and DDGS20 groups gave results that are more likely to be digestible, which depends on villi length. The results of the DDGS30 groups had no negative effects on both liver and distal intestine. The genes interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), interleukin 8 (IL-8), and superoxide dismutase 2 (SOD2) exhibited higher fold changes when DDGS2 contribution was present in the liver, whereas the interleukin 1 beta (IL-1β) gene exhibited lower fold change. Furthermore, the mean fold changes increased with the proportion of the DDGS additive in the immunoglobulin M (IgM) heavy chain and immunoglobulin T (IgT) genes but decreased in the catalase (CAT) and glutathione peroxidase 1 (GPX1) genes. TNF-α and SOD2 genes showed the lowest fold changes in the head kidney in the presence of DDGS20, whereas IL-1β and GPX1 genes exhibited the highest fold changes in the presence of DDGS10. Moreover, the utilization of feed additives extracted from DDGS in feed formulations resulted in cost reductions, thereby positively influencing the production cost per kilogram of feed. Among the trials, the incorporation of DDGS20 had the most beneficial impact on the cost per kilogram of fish due to its comparatively lower cost.