Volume 75, Issue 2, 2023

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    Effects of emodin and different protein levels on growth and immunity of the blunt snout bream (Megalobrama amblycephala) for in-pond raceway aquaculture systems
    ( 2023) Yang, Zhenfei ; Cao, Haiyue ; Liu, Bo ; Xu, Pao ; Wang, Jianguo ; Lin, Apeng ; Xiong, Liangwei ; Li, Wei ; Qi, Fugang ; Wang, Quan ; Yao, Wenxiang ; Tang, Xiaofeng
    The present study aimed to evaluate the effects of emodin and different protein levels on growth-promoting antioxidant capacity and protein utilization of blunt snout bream to in-pond raceway aquaculture systems (IPRS). The experiment was divided into three groups: low protein group (LP) (29% low protein level), high protein group (HP) (32% high protein level), and emodin group (ED) (29% protein level + 0.05% emodin). At 210 days in the late stage of culture, the weight of the ED and HP groups was higher than the LP groups (P < 0.05). Compared with the LP group, the number of hematological parameters (white blood cell, WBC; red blood cell, RBC; hemoglobin, HGB; and hematocrit, HCT), blood antioxidant enzymes (anti-superoxide anion free radical, ASAFA; glutathione peroxidase, GPx; superoxide dismutase, SOD; and nitric oxide, NO) activity in the ED group were significantly increased (P < 0.05), and the serum malondialdehyde (MDA) content were significantly reduced (P < 0.05). Besides, the content of serum triglyceride (TG) and blood antioxidant enzymes (ASAFA, GPx, and SOD) in the HP group were significantly increased compared with the LP group (P < 0.05), and the content of serum Creatinine (CREA) significantly lower than that of the control (P < 0.05). The results of this experiment indicate that emodin and appropriate protein levels can increase the content of antioxidant enzymes, enhance immunity, and promote the growth of M. amblycephala.
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    Early embryonic development of green crucian carp Carassius auratus indigentiaus subsp. nov.
    ( 2023) Zhang, Yunsheng ; Xia, Hu ; Li, Sigang ; Liu, Jiaqi ; Liu, Liangguo ; Yang, Pinhong
    The early embryonic development of the green crucian carp (Carassius auratus indigentiaus subsp. nov.) was observed to study its timing and characteristics. The fertilized eggs are round, slightly yellow, and viscous demersal. The egg diameter after water swelling was 1.47 ± 0.04 mm. Embryonic development can be divided into eight stages according to its major characteristics: blastoderm formation, mitotic, blastula, gastrula, neurula, blastopore closure, organogenetic and hatching stages. Under a water temperature of 24 ± 1 °C, salinity of 35 ± 1, and pH of 7.4 ± 0.5, the blastoderm began to form 35 min after fertilization. It entered the mitotic stage at 55 min, blastula stage at 220 min, gastrula stage at 460 min, neurula stage at 675 min, blastopore closure stage at 700 min, organogenetic stage at 900 min and hatching stage at 3390 min. The total length of newly hatched larvae was 4.07 ± 0.35 mm. Regression models of growth characteristics were obtained. The full-length growth rate was fastest from 15 to 26 days, with an average of 0.396 mm/day. Compared with other cyprinid fishes, green crucian carp exhibited some distinct characteristics in certain stages of embryonic development. The eye primordium developed before the sarcomere, and the heart rate was relatively high before the member stage. Yolk fluctuation was observed during the multi-cell phase of embryonic development. The sarcomere formed after the eye primordium. The heart rate in the hatching phase was 136 beats/min. This study provides a reference for embryonic development in green crucian carp, which will assist its large-scale cultivation.
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    Effects of two phosphorous sources in the diet on the growth performance, digestibility, and plasma physiological parameters of Pelodiscus sinensis juveniles
    ( 2023) Sun, Haoran ; Geng, Yiran ; Liu, Haiyan ; Zhang, Junjie
    Phosphorus is an essential mineral for aquatic animals to maintain the health of the skeletal system and many physiological functions. This study assessed the effects of two inorganic phosphorus sources on growth performance, apparent phosphorus digestibility, whole-body proximate composition, and physiological status in juvenile *Pelodiscus sinensis*. Two experimental diets were supplemented with 4% calcium phosphate monobasic (MCP) and 5.47% calcium phosphate dibasic (DCP), respectively, to obtain equal total dietary phosphorus (2.20%). 96 turtles (initial body weight: 5.40±0.03g) were randomly distributed into 12 tanks and fed the corresponding diets for 60d. Results showed that phosphorus sources have not significantly influenced the growth parameters, including the specific growth rate, feeding rate, and feed conversion ratio (*P*\>0.05). No significant differences were observed in the hepatosomatic index and whole-body proximate compositions between MCP and DCP groups (*P*\>0.05). The apparent digestibility coefficients of dry matter and phosphorus in MCP group (53.22%) are slightly higher than that in DCP group (48.98%) but did not reach the statistically significant level (*P* \> 0.05). Turtles in MCP and DCP groups are the same in plasma physiological parameters and have equal alkaline phosphatase activities in plasma and liver (*P*\>0.05). In conclusion, calcium phosphate monobasic and calcium phosphate dibasic had the same biological phosphorus availability in diet for juvenile *Pelodiscus sinensis*.
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    Treatment of leachate solid wastewater and protein-rich biomass production using Ceratophyllum demersum (Linnaeus, 1753)
    ( 2023) Tekoğul, Hatice
    The present study, conducted in 2018, aimed to treat landfill leachate using the Ceratophyllum demersum plant and convert the wastewater nutrients into protein-rich biomass. The experiment was carried out for 45 days in an enriched medium with ½ Hoagland nutrient solution. Regarding the experimental setups, C. demersum cultivation was performed in four different dilution ratios (100%, 75%, 50%, and 25%) in the landfill leachate. The changes in the chemical properties of the wastewater (pH, NO₄⁻-N, NO₂⁻-N, NO₃⁻-N, and o-PO₄³⁻) were measured. The values in the leachate and after treatment were measured as follows: NH₄⁺-N ranged from 18.03 to 476.2 mg/L, NO₃⁻-N ranged from 5.0 to 33.98 mg/L, NO₂⁻-N ranged from 1.49 to 7.06 mg/L, and PO₄³⁻-P ranged from 27.99 to 145.4 mg/L. The protein yield (CP prot) in the experimental groups at the end of the 45-day study was as follows: T1 = 20.90%, T2 = 36.68 %, T3 = 41.78%, T4 = 47.43% and T5c = 49.56%. These results demonstrate that aquatic plants can be utilized in wastewater treatment and as animal feed due to their high protein yield. In my research, a completely nature-friendly treatment technique was used to reduce water pollution without using any chemicals.
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    Dietary plant soot supplementation improves the intestinal health status of farmed American eels (Anguilla rostrata)
    ( 2023) Yu, Yi-yao ; Yin, Qian ; Zhang, Ming-liang ; Xi, Feng ; Zhai, Shao-wei
    The current study evaluated the effect of different dietary plant soot supplementation levels on the intestinal health status of American eels (Anguilla rostrata) cultured in concrete tanks. Nine concrete fish tanks were randomly divided into three groups and fed the diets with plant soot (PS) supplementation levels at 0, 3 g/kg, and 5 g/kg, respectively. After a feeding trial for 60 days, the intestinal tissues were sampled to measure health status parameters. The D-lactate level and DAO activity in the serum of the PS5 group were significantly lower than those of the PS0 group (P <0.05). Compared with the PS0 group, the villi length of the intestine in both PS3 group and PS5 group increased significantly (P<0.05). The muscular thickness of the intestine of the PS5 group was significantly higher than the PS0 group (P<0.05). The microvillus density of the intestine of the American eel was increased obviously in the PS5 group. The intestinal microbiota composition of plant soot groups was beneficially regulated with certain probiotics' higher relative abundances and some pathogenic bacteria' lower relative abundance. In conclusion, dietary 5 g/kg plant soot supplementation could benefit the intestinal health of farmed American eels.
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    mtCO1-based population structure and genetic diversity of Pacific oyster *Crassostrea gigas* populations acquired from two farms in South Korea
    ( 2023) Biet, Thanh T. ; Park, Su-Jin ; Park, Hong-Keun ; Park, Dongjin ; Choi, Youn-Hee
    Since the early 1990s in South Korea, climatic and anthropogenic factors have incurred the reduction of the wild seeds of the Pacific oyster, Crassostrea gigas, which raised concerns about losing genetic diversity and accelerating genetic deterioration. We assessed the genetic diversity of C. gigas populations from two farms (Tongyeong and Gadeokdo) on the southern coast, where about 80% of the cultivated oysters in Korea are produced. Tongyeong showed slightly higher diversity than Gadeokdo, but both populations had a similar genetic structure characterized by low nucleotide diversity. Comparative haplotype analyses provided data supporting genetic features of the populations that include (1) weak genotype-locality relationship, (2) low levels of gene flow between populations, and (3) possible seasonal fluctuation of genetic variation within a population. Furthermore, the highly alike haplotype network patterns were observed between the wild and farm populations as well as among the populations in neighboring countries, which suggests that the genetic structure is conserved between wild and hatchery populations, and geographic proximity has minimal influence on the genetic composition.
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    Substituting fishmeal with extruded cull chickpea meal in diets for the white leg shrimp (Litopenaeus vannamei, Boone): A preliminary study of the effect on production parameters
    ( 2023) Tejeda-Miramontes, José P. ; García-Ulloa, Manuel ; Rodríguez-Quiroz, Gerardo ; Rodríguez-González, Hervey
    Among the most typical feed ingredients for shrimp, plants represent a low-cost source in substituting for traditional high-cost feed ingredients. Extrusion is a common grains processing technique to make plant nutrients available and more digestible to animal. Different levels (15, 30, 45, and 60%) of extruded low-quality chickpea meal were included in a formulated diet for the juvenile shrimp Litopenaeus vannamei cultured in a closed system for 75 days. The growth of shrimp fed with the tested diets was similar to the control group (P > 0.05). We concluded that the use of extruded cull chickpea meal is a potential food alternative to replace fishmeal effectively in diets for L. vannamei.
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    Effects of combined rice flour and molasses use on the growth performance of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) applied biofloc technology
    ( 2023) Phuong, Ta V. ; Hoa, Nguyen V. ; Diep, Doan X. ; Vo, Van-Thanh ; Nhu, Ma B.
    A 63-day completely random experiment with three replications was carried out to compare the effects of five different combination ratios of rice flour (R) and molasses (M) on the growth and survival rates of Pacific white shrimp (Litopenaeus vannamei Boone, 1931) postlarvae applied biofloc technology. Five biofloc (BF) treatments, including R90-M10, R70-M30, R50-M50, R30-M70, and R10-M90, formed with the addition of different combination ratios of rice flour and molasses, i.e., 90% R+10% M, 70% R+30% M, 50% R+50% M, 30% R+70% M, and 10% R+90% M, respectively, with C/N ratios of 15:1, and a control (neither rice flour nor molasses applied) was randomly arranged into the 18 plastic tanks of 1.0 m3 volume (with 0.5 m3 of water) each tank and salinity of 15‰. The postlarvae (0.095 g) were stocked into the tanks at a 150 ind. m−3 density and fed pelleted feed (40% protein). There was an improvement in growth (FMW, WG, DWG, and SGR) for all treatments. Besides, treatments with more than or equal to 30% molasses have improved SR, FCR, and FB. Especially the highest SR (94.2%) was obtained at the R70-M30, which perhaps created the highest FB (1.435 kg m−3) in this treatment. The lowest FCR (1.28) was also observed in the R70-M30 and significantly differed from the control and other treatments. Besides, water quality parameters were within the ranges recommended for Pacific white shrimp health during the experimental period. Our findings indicated the benefits of shrimp culture using the BF system when different combined ratios of rice flour and molasses were applied, of which a ratio of 70% rice flour and 30% molasses was considered as the best.
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    Growth and nutritional health of Pterophyllum scalare juveniles: Unleashing the benefits of feeding with Artemia sp. in aquariums
    ( 2023) Mao, Jing ; Chen, Yu ; Lan, Shuaiqin ; Yin, Ze ; Zhang, Meng ; Gu, Zhifeng ; Yu, Feng ; Zheng, Xing ; Vasquez, Herbert E.
    Pterophyllum scalare is a popular ornamental fish species, but current rearing methods result in high mortality, low fertility, disease incidence, and slow growth in aquarium conditions. Research on co-feeding for ornamental fish at the juvenile or adult stage needs to be completed. This study implemented a "snacking" feeding strategy using Artemia sp. to evaluate changes in fish survival rate, growth performance, and enzyme activity related to digestion, antioxidants, and immunity in a recirculating aquaculture system. Two feeding strategies were tested: one group was fed a commercial diet plus Artemia sp. (0.1% of diet) as “snacking,” and another group was fed only the commercial diet as normal. “Snacking” with Artemia sp. enhanced fish's survival and growth performance, with higher relative weight rate, standard length, and total length than the control group. Specific growth rates for weight, standard length, and total length were also more significant in the supplemented group compared to the control group. The activity of amylase, superoxide dismutase, and glutathione peroxidase was substantially higher in the supplemented group. Adding Artemia sp. as a supplement under a “snacking” feeding strategy to the control diet was beneficial for P. scalare juvenile rearing and can guide managing recirculating farming activities.
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    Transcriptome analysis reveals the important roles of a two-component system, flagellar assembly, active efflux system and outer membrane proteins in the anti-quinolone ability of Vibrio harveyi from orange-spotted grouper (Epinephelus coioides)
    ( 2023) Tang, Xiaochen ; Ding, Yu
    The drug resistance of Vibrio harveyi in aquaculture became more severe because the control of Vibriosis depends majorly on the current antibiotics. Transcriptomes of a wild-type strain (VS) and its quinolone-resistant mutants (VR) of V. harveyi were respectively sequenced by RNA-seq technology. A total of 2,082 unigenes were obtained after de novo splicing and assembly. 129 genes were identified with significant differential expression in strain VR compared to strain VS, among which 65 were up-regulated and 64 down-regulated. Then, functional annotation and enrichment analysis of these differentially expressed genes (DEGs) were performed. GO enrichment results showed that DEGs focused mainly on cell structure, substance metabolism, and transporter. COG classification of the DEGs mainly focused on amino acid transport and metabolism, cell wall/membrane biosynthesis, carbohydrate transport and metabolism, ribosomal structure, and biosynthesis. KEGG pathways related to a two-component system, ABC transport system and flagellar assembly (ko02040) were enriched significantly, and 9 genes associated with quinolone-resistance ability, including genes for resistance-related transport proteins, outer membrane proteins, and DNA repair-related proteins were discovered through analysis of the drug-resistance related genes. Ten DEGs (including the above part genes of 9 drug resistance-related genes) in the transcriptome data were taken to analyze their expression with real-time qPCR. The results were the same as the changes of the above transcriptome analysis, further confirming the reliability of the transcriptome sequencing and data analysis. In a word, genes from a two-component system, flagellar assembly, active efflux system and outer membrane proteins take great roles in the quinolone-resistance of V. harveyi. These results provide enough information for further study on the molecular mechanism of quinolone-resistance and give a helpful transcriptomic resource to unravel the contact between quinolone-resistance and metabolic pathways in Vibrios.