Volume 75, Issue 2, 2023
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ItemEffect of ginger, Zingiber officinale extract on growth performance, digestive enzyme and stress tolerance of whiteleg shrimp, Litopenaeus vannamei juveniles( 2023)This study evaluated the effects of ginger extract as a feed additive on the growth performance, digestive enzymes, and resistance to environmental stress of the whiteleg shrimp, *Litopenaeus vannamei*. 1200 juveniles were randomly allocated into four groups with three replicates. Shrimps were fed diets supplemented with 0 (T0-control), 0.5 (T1), 1 (T2), and 1.5 g kg^-1^ of ginger extract (T3) for 56 days. The results indicated that shrimp fed with ginger extract had a lower feed conversion ratio (FCR) than the control. In addition, shrimp fed with 0.5 g kg^-1^ of ginger extract had significantly greater weight gain and protease activity in the intestine than those in the control group. However, dietary supplementation with ginger extract did not significantly affect survival rates. After 56 days of culture, shrimp fed with 0.5 and 1 g kg^-1^ of ginger extract had higher survival rates than the controls after 72 -- 96 h exposure to high ammonia stress (40 mg L^-1^). Based on the study's findings, ginger extract could be recommended for shrimp feed to enhance growth and resistance against stress factors, and the optimal level is 0.5 g kg^-1^.
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ItemComparative analysis of Streptococcus agalactiae S03 and S07 isolated from Schizothorax spp. with different antibiotic resistance and virulence( 2023)Streptococcus agalactiae (GBS) is an important Gram-positive pathogen of fish aquaculture worldwide. In this study, we performed a comparative analysis of GBS S03 (serotype III) and S07 (serotype Ia) isolated from Schizothorax spp.. We explored the association between phenotypic antibiotic resistance, virulence, and genomic characteristics. Antimicrobial sensitivity tests on 12 common antibiotics using the disc diffusion method revealed that the GBS S03 resisted seven antibiotics, while GBS S07 showed sensitivity to eleven antibiotics. Pathogenicity analysis demonstrated greater virulence of GBS S07 than S03. Then, the occurrence of antibiotic resistance and virulence genes were identified using the whole-genome sequence (WGS) of GBS S03 and GBS S07. Besides just GBS S03 had gyrA and parC gene mutations, there were mefE, tetO, lnuB, lsaE, APH3', and sat-4 resistance genes present only in GBS S03 genome. In addition to 51 virulence genes in both GBS S03 and S07 genomes, GBS S07 carried virulence genes associated with invasion, such as SAN1519, rfbA and cylE_ genes. There was complete concordance between genotypic evidence and phenotypic characteristics. Virulence factors and phylogenetic analysis showed that GBS S03 and human sources shared an extremely close evolutionary relationship. Our findings also provide important proof for using WGS as an effective tool for phenotypic predictions of GBS.
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ItemPopulation genetics analysis of the black rockfish Sebastes schlegelii in Northern China based on 2b-RAD simplified genome sequencing( 2023)The black rockfish Sebastes schlegelii is an important fishery species in Japan, South Korea, and China. Overfishing has severely depleted the natural resources of S. schlegelii in recent years, leading to the initiation of programs aimed at enhancing fish stock. However, the genetic structure of northern populations remains elusive, posing challenges in collecting and preserving germplasm resources. In this study, a total of 191 S. schlegelii individuals from seven populations, including one cultured population (Changdao: CDYZ) and six wild populations (Lianyungang: LYG; Qingdao: QD; Weihai: WH; Changdao: CDYS; Beidaihe: BDH) sequenced by 2b-RAD method and their population genetics was analyzed using 27,064 SNPs obtained. The results indicated low genetic diversity in both wild and cultured populations (PIC < 0.25, Ho: 0.174-0.273, He: 0.173-0.234), with the cultured population exhibiting higher diversity than the wild ones. Moderate genetic differentiation existed between the cultured population and six wild populations (0.05 < Fst < 0.25). However, the genetic differentiation was lower among the other wild populations (Fst < 0.05). The analyses of population genetic structure indicated that the wild populations clustered together first and finally with the cultured population CDYZ, which clustered separately except for one individual. Therefore, scientific breeding programs and germplasm conservation can be important in stabilizing genetic structure. In addition, gene flow among the seven populations was high (Nm > 1). This study provides a theoretical basis for conserving and rationalizing germplasm resources for S. schlegelii.
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ItemDetermination of Growth and Nutritional Composition of Nile Tilapia (Oreochromis niloticus) Fed With L-Glutamic Acid Supplemented Feeds( 2023)The study aimed to assess Nile tilapia's (Oreochromis niloticus) growth performance and body chemical composition through varying levels of L-Glutamic acid supplementation. In the experiment, four different groups of feed were prepared; the control C (0% L-Glutamic acid), G1 (1% L-Glutamic acid), G2 (2% L-Glutamic acid), and G3 (3% L-Glutamic acid). Tilapia juveniles with an average initial weight of 4.86 g were stocked into 12 fiberglass tanks (450L) with 40 individuals and three replications under controlled conditions, and the experiment was continued for a period of 60 days. At the end of the experiment, for the G2 group final weight (FW, 19.31±0.59 g), specific growth rate (SGR; 2.30±0.05), feed conversion ratio (FCR; 1.02±0.03), daily growth rate (DGR; 4.95±0.20) protein efficiency ratio (PER 2.83±0.10) and net protein utilization (NPU; 61.62±3.39) were better than the other groups (P<0.05). Nutritional composition data showed that the groups differed between protein, dry matter, and lipid compositions. The G2 group exhibited the highest whole-body protein level, recording a value of 21.24±0.52, whereas the control group demonstrated the lowest protein level at 20.17±0.15. In conclusion, incorporating 2% L-Glutamic acid into the diet of juvenile Nile tilapia is advisable for both the growth and development of the fish and for enhancing their nutritional composition.
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ItemEffects of cadmium exposure on tissue structure, antioxidant enzyme activity, serum biochemical indices and gene expression in the liver of juvenile largemouth bass (Micropterus salmoides)( 2023)This study aimed to understand the effect of various levels of waterborne cadmium exposure and associated integrated response in largemouth bass (Micropterus salmoides). The experimental fish were randomly divided into 4 groups: Group H (high concentration group): 0.25 mg/L of water (100% of the LC~50~); Group M (medium concentration group): 0.01 mg/L of water (50% of the LC~50~); group L (low concentration group): 0.05 mg/L of water (12.5% of the LC~50~) and group C (control). Experimental fish in group C (control group) were cultured in cadmium (Cd)-free tap water. After 28 days of Cd exposure, the gill and liver tissues were collected for histological analysis and antioxidant enzyme activities assay. Serum biochemical indices and the expression levels of HSP70, HSP90, Cyp1a, and MT in the liver were assayed. Results indicated Cd exposure in group H could significantly damage the gill and liver. The SOD activity of gill and liver exhibited an increasing trend with Cd concentrations increasing, and SOD activities increased significantly in group M compared to that of group C. Still, SOD activity significantly decreased in group H. MDA content increased significantly in both the gill and liver, while T-AOC activities were not significantly different in both the gill and liver. By comparison with group C, the activities of ALT and AST in serum were significantly increased in group M and group H; the contents of ALB and TP significantly decreased in group M and group H except for the content slightly increased in the group L; the contents of GLU, TG, and TC did not show significant changes in the group L and the group M, but increased significantly in the group H. The expression levels of HSP70 and HSP90 in the liver exhibited the highest level in group M, whereas the expression levels of MT and Cyp1a were highest in groups H and L, respectively. Our results are intended to provide a reference basis for the safety risk evaluation of Cd and healthy fish farming.
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ItemEffects of Mn2+ and flow speed on blood and physiological indexes of larvae GIFT tilapia (Oreochromis niloticus)( 2023)To assess the toxicological effects of heavy metal ions on fish at different flowing speeds within aquatic environments, we investigated the impact of Mn^2+^ and flow speed on the physiological parameters of juvenile GIFT tilapia (95.2±4.3g,15.1±0.21cm). The experiment design included four different levels of Mn^2+^ concentration: control group (0mg/L), 0.1mg/L, 0.5mg/L and 1mg/L, as well as three different flow speeds: control group (0 body length/second), low speed (1 body length/second), and high-speed group (2 body lengths/second). The main research findings were as follows: Mn^2+^ had varying effects on the hematological parameters of juvenile GIFT tilapia. As the levels of Mn^2+^ increased, there was a remarkable reduction in both the red blood cell (RBC) number and hemoglobin content of the fish(*P*\<0.05). The activity of SOD, CAT, the level of MDA in the liver and white blood cell (WBC) number exhibited an initial increase followed by a subsequent decrease, with the highest levels observed mostly in the 0.5mg/L group. However, With the prolongation of Mn^2+^ exposure duration, a significant decline in levels of RBC, hemoglobin, CAT and SOD was observed. In most cases, the highest values of those, as mentioned earlier four physiological parameters were recorded at 24 hours, while the lowest values were recorded at 96 hours when exposed to the same Mn^2+^ level. However, MDA levels reached their peak at 48 hours. These findings suggested that lower levels of Mn^2+^ might enhance the immune capacity of tilapia, while higher levels could impede its immune and antioxidant functions. An increase in flow speed led to a significant elevation in both the RBC number and hemoglobin content of the GIFT tilapia at 30d(*P*\<0.05), but flow speed had no significant impact on the WBC of the fish(*P*\>0.05). Its effect on the fish antioxidant parameters also showed a certain induction, and there were significant correlations between the activity of SOD, CAT, the level of MDA, and flow speed (*P*\<0.05). At the same flow speed, the prolonging water-flow-stimulus duration could not increase the levels of three antioxidant parameters(*P*\>0.05). These findings could provide fundamental data for investigating the influence of heavy metal stress on fish ecotoxicology in aquatic environments and the artificial running water breeding of GIFT tilapia in Hebei province, China.
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ItemComparison of live microalgae and Spray-dried algae powder effects on growth, digestive and antioxidant capacity of juvenile pearl oyster Pinctada maxima( 2023)The pearl production through the pearl oyster *Pinctada maxima's* culture has developed slowly over the past decades due to over-fishing of wild populations and mass mortality at juvenile stages. Indoor farming is an alternative mode for *P. maxima* juvenile cultivation to improve survival rates. In pursuit of optimizing healthy management under the indoor farming mode, the objective of this investigation was to compare the growth performance, digestion, and antioxidant capacity of juveniles fed with different microalgae-based diets (live *Isochrysis zhanjiangensis,* *Platymonas subcordiformis*, *Chaetoceros muelleri*; and spray-dried *I. zhanjiangensis*, *P. subcordiformis*, *C. muelleri* powder). The juvenile survival rates fed with spray-dried microalgae powder (except *C. muelleri* powder) were not significantly different from those fed on live microalgae. However, the growth performance of juveniles fed with spray-dried microalgae powder could have been better than the live one. The digestive enzymatic activities were consistent with growth performance, and diets affected the antioxidant capacity. The spray-dried *I. zhanjiangensis* powder can serve as a substitute for live microalga in *P. maxima* juvenile indoor farming and is recommended under controlled conditions. The findings from this study would provide essential data to improve health management for *P. maxima* juveniles in indoor farming conditions.
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ItemTranscriptome Analysis of the Cultured Hybrid Grouper (♀*Epinephelus fuscoguttatus*×♂*E. lanceolatus*) Immunized with Vibrio harveyi formalin-killed cells vaccine (FKC) combined with chitosan oligosaccharide( 2023)Grouper has become an essential mariculture species in China, while vibriosis caused by Vibrio harveyi significantly impacts its culture. Our previous study confirmed the *V. harveyi* formalin-killed cells vaccine (FKC) combined with chitosan oligosaccharide (FKC+COS) effectively prevents vibriosis. As an adjuvant, COS could significantly enhance FKC effectiveness against *V. harveyi* in grouper. In the present study, we performed transcriptome analysis of grouper spleens tissue 14 days post-immunization of PBS and FKC+COS, respectively. After assembly and annotation, 2,503 differentially expressed genes (DEGs) were obtained, including the upregulated 1,894 DEGs and downregulated 609 DEGs between the PBS group and FKC+COS group. To explore the relevance of DEGs in immunity, enrichment analysis in the KEGG database revealed that the main pathways of DEGs distribution associated with immunity were antigen processing and presentation, lysosome, the intestinal immune network for IgA production and FcγR-mediated phagocytosis. In conclusion, transcriptome analysis of spleens was performed to explore the potential mechanism of COS as an adjuvant enhancing the protection effectiveness of FKC against vibriosis in grouper.
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ItemUsing black soldier fly larvae as feed for Thai frog (Rana rugosa Temminck and Schlegel, 1838) – Preliminary study of the effect on production parameters( 2023)This study aimed to evaluate the effect of the inclusion of either fresh or dried black soldier fly larvae (BSFL) in diets on the production parameters and chemical composition of Thai frogs (Rana rugosa) cultured in net cages. Frog fingerlings have an initial weight of 20.4 g and were distributed randomly into fifteen net cages (2 x 3 x 1.5 m) at a density of 240 frog.net cage-1. Including five dietary treatments named: T1 (100% commercial feed used as a control), T2 (100% dried BSFL), T3 (50% dried BSFL + 50% commercial feed), T4 (50% fresh BSFL + 50% commercial feed), and T5 (100% fresh BSFL) with three replicates for each treatment. The results showed that the survival rate of frogs ranged from 64.3% to 87.0%, improved feed conversion ratio (1.43 to 1.90%), increased live weight (194.7 – 244.6 g), daily weight gain (2.9 – 3.7 g.day-1), and frog’s yield (6.30 – 7.96 kg.m-2). The contents of crude protein (18.21 – 23.19%), ether extract (0.28 – 0.53%), and total ash (0.99 – 1.05%) of frog meat in this study were affected by the inclusion of either fresh or dried BSFL in the diets of frogs. In recommendation, the diet comprised from 50% fresh BSFL + 50% commercial feed could be applied successfully in Thai frog cage production.
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ItemEffects of replacing dietary fishmeal with zymolytic black soldier fly larvae on the growth performance of the mud crab (scylla paramamosain) larvae( 2023)Black soldier fly have been shown to be one of the optimal alternatives to fishmeal, but there are few reports on the effects of zymolytic black soldier fly larvae (ZBSFL) on the growth and digestion of crustaceans. An 8-week feeding trial was conducted to evaluate the effects of different replacement levels of ZBFLS on growth performance, body composition, and digestive enzyme activity of the mud crab larvae. Four diets were formulated by replacing fishmeal with 0%, 5%, 10% and 15% ZBSFL in the basal diet. Crab larvae were randomly divided into four groups of three replicates each and fed twice daily. The results showed that the SR of crab larvae was higher than that of the no-substitution group when the substitution rate reached 5% (P < 0.05). There was no significant change in SR when the substitution rate was further increased. Weight growth rate and Specific growth rate were similar, both highest at 10% substitution ratio. The crude protein content of whole crab larvae gradually increased as the proportion of FM substituted by ZBSFL increased. The lipid content of whole crab larvae in the 5% substitution ratio group was significantly higher than that in all other groups (P < 0.05). Meanwhile. The activities of amylase, protease and lipase gradually increased. In this experiment, when the percentage of ZBSFL substitution for FM reached 10%, its growth performance was optimal, with higher SR, less negative effects and more balanced indicators in all aspects. When the substitution rate was further increased, it might increase the digestive burden of the crab and negatively affect its growth.
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