Volume 72, 2020

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https://hdl.handle.net/10524/63209

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Effect of salinity on growth performance and resistance of the clam Cyclina sinensis against Vibrio parahaemolyticus infection
(2021) Ni, Qian; Li, Wenqian; Jia, Xuewen; Dong, Zhiguo; Ge, Hongxing
We examined the growth performance, immune parameters and the susceptibility to Vibrio parahaemolyticus in the clam Cyclina sinensis, which had been reared at different salinity levels of 10‰, 20‰ and 30‰ for 60 days. At the end of the feeding experiment, the biggest shell length and body weight was found in 20‰, followed by 30‰ and 10‰. No significant differences in superoxide dismutase (SOD) activity were observed among the clams held in 10‰, 20‰ and 30‰. Na+/K+ -ATPase (NKA) activity of the clams held in 20‰ and 30‰ were significantly lower than that in group 10‰. The lowest activities of lysozyme (LZM) and glutamic-pyruvic transaminase (GPT) were found in group 10‰. The Integrated Biomarker Response index (IBR) values of the clams had an inverse relationship with salinity: 11.28, 3.40 and 2.85 in 10‰, 20‰ and 30‰, respectively. At the end of the feeding experiment, the clams were infected with V. parahaemolyticus. As time after infection goes on, the survival rate of clams reared in 20‰ was not significantly different with the other two treatments from 24 to 48h after infection. However, from 72 to 120h after infection, it was significantly lower than those reared in 10‰, while it was significantly higher than those reared in 30‰. It is concluded that the clam C. sinensis reared in 10‰ seawater may reduce growth performance and immune ability, whereas increase resistance against V. parahaemolyticus infection.
Dietary lipid levels requirements of hybrid yellow catfish (Pelteobagrus fulvidraco × P. vachelli
(2021) Mamuru, Gobeng L.S.; Qiang, Jun; Tao, Yi-Fan; Chen, De-Ju; Bao, Jing-Wen; Ngoepe, Tlou K.; Zhu, Hao-Jun; Li, Hong-Xia; Xu, Pao
A 12-week feeding trial was conducted to determine the dietary lipid levels requirements of hybrid yellow catfish using pelleted diets containing six different lipid levels formulated to contain graded levels of 0.0% (control), 3.4%, 6.8%, 10.2%, 13.6%, and 17% of dry matter. A total of 504 juveniles with an average initial body weight of 8.77±0.012 g were randomly divided into 6 groups containing 3 triplicates with 28 fish per tank and fed each of the experimental diets. Results showed that maximal final body weight, weight gained and specific growth rate were significantly higher in the groups fed 3.4%, 6.8%, and 10.2% compared with that of groups fed 13.6% and 17.0% (P < 0.05). Feed conversion ratio and protein efficiency ratio were significantly lowered in the 6.8% and 10.2% groups (P < 0.05). The hepatosomatic index had no significant difference (P > 0.05) while the viscerosomatic index significantly decreased in 6.8% and 10.2% groups. White blood cells, red blood cells, hematocrit and platelets levels significantly increased in the decreased dietary lipids levels (P < 0.05) while hemoglobin had no observed significant difference (P > 0.05). Serum alanine aminotransferase, aspartate transaminase, total protein, total cholesterol, triglyceride and glucose were significantly influenced by the dietary lipid levels. Liver superoxide dismutase and catalase concentration decreased significantly in the 6.8% and 10.2% groups. Malondialdehyde increased in 6.8% and 10.2% groups. Glutathione peroxide showed insignificant results (P > 0.05). Study results suggested that, dietary lipid levels containing 3.4%,6.8% and 10.2% significantly influenced growth, blood function, antioxidant status and strengthened immune response in hybrid yellow catfish while higher dietary lipid levels (13.6% and 17.0%) decreased body weight and weakened immunity.
Aeromonas veronii, a potential pathogen of enteritis in snakehead fish Ophiocephalus argus
(2020) Wang, Huicong; Gu, Ying; Luo, Guilan; Cao, Haipeng
Enteritis is known as a major disease in snakehead fish Ophiocephalus argus aquaculture and has resulted in large economic losses. Yet only scarce information is available on Aeromonas veronii as a causal agent for enteritis in O. argus. In this study, a virulent strain, temporarily named HY2, was isolated from diseased snakehead fish suffering from enteritis, and was identified as A. veronii through molecular and phenotypic methods. In addition, the HY2 isolate showed an LD50 value of 2.8×105 CFU mL-1, and was highly sensitive to aminoglycosides, macrolides, polypeptides, quinolones, sulfonamides and tetracyclines antibiotics. To the best of our knowledge, this is the first report of A. veronii as a potential pathogen of enteritis in snakehead fish.
Effects of dietary P:E ratio and Rhizoclonium in two stocking densities on growth and profitability of Nile tilapia in intensive pond culture
(2020) Jumah, Yashier U.; Tumbokon, Barry L.M.; Serrano Jr, Augusto E.
Two onsite tests were carried out to determine the effects of varying dietary protein to energy (P:E) ratio in intensive culture of Nile tilapia in two different places at two stocking densities. In both field trials, three diets were used namely commercial (CM) diet, control (CO) diet containing no Rhizoclonium and a diet containing Rhizoclonium replacing 52% of soybean meal (RLP); the diets contained decreasing P:E ratio of 21, 16 and 12 gMJ-1, respectively. The first trial was conducted in Aklan, Philippines at a stocking density of 17 fishm-2 while the second was in Pangasinan, Philippines at 27 fishm-2. In both trials, the three diets were fed for 2 months to 3 replicate cages of Nile tilapia, all of which were randomly placed in about 1.0 ha fresh water fish pond. In the first trial in Aklan, at 17 fish m-2 stocking density, no significant differences in the parameters were observed except in the absolute growth rate (AGR) in which the RLP dietary treatment exhibited a higher value than did either the CM or the CO diet. In Pangasinan, at 27 fish m-2 stocking density, significant differences in TFI, DFI and SGR were observed, all the other parameters were statistically similar. The RLP group exhibited lower total feed intake (TFI) and daily feed intake (DFI) but higher specific growth rate (SGR) than did either the CM or CO diet. In either stocking densities, feed cost was the main determinant of profitability in which the RLP group resulted in significantly highest profitability i.e., lowest total production cost, highest gross income and highest profit and profit margin. Although profit was significantly higher in the higher stocking density, profit margin was significantly higher in the lower stocking density. There was no statistical interaction between dietary treatment and stocking density as analyzed by two-way analysis of variance.
The secondary bacterial infection caused by WSSV outbreaks impacts shrimp Marsupenaeus japonicus’ growth as well as its intestinal microbiota’s composition and function
(2020) He, Zihao; Zhao, Jichen; Liao, Xuzheng; Chen, Xieyan; Fu, Zhibin; Sun, Chengbo; Ni, Zuotao
Intestinal microbiota homeostasis is a complex ecosystem and is essential for promoting aquatic animals’ growth. Invading pathogens can cause dynamical composition and structure change in the hosts’ microbiota due to this affecting their functions. WSSV is one of the most common and dangerous shrimp pathogens, which leads to white spot disease with too high mortality. A few studies on shrimp intestinal microbiota mainly focused on the changes during acute infection stage. Marsupenaeus japonicus is one of the most cultured shrimp with a decent ability to cope with environmental changes. In the current research, using M. japonicus as a model, we compared the differences of intestinal microbiota between healthy shrimp and the shrimp that survived through the WSSV outbreak. Our study showed that compared to the healthy M. japonicus, the WSSV outbreak disrupted intestinal microbiota structure in the survived shrimp: There was less potential beneficial bacteria and more harmful bacteria. Furthermore, the diversity and total abundance of intestinal microbiota in WSSV-survived shrimp increased significantly. On top of that, a metagenomic analysis by PICRUSt suggested that the changed intestinal microbiota could help the host to combat the secondary bacterial infections caused by WSSV outbreaks by regulating cell growth and death, reducing cell motility, improving energy metabolism, and increasing intestinal enzyme activities regardless the smaller sizes of WSSV-survived shrimp. This could be a result of excessive energy consumption and reduced nutrient-absorbing intestinal microbiota. Our study indicated that shrimp intestinal microbiota plays a fundamental role in combating against secondary infections and regulating the hosts’ growth post WSSV outbreaks. The eventual goal is to development of more efficient diagnostics and therapeutic strategies.
Effects of feeding strategies on growth，body composition, intestine digestive enzymes activities and intestine histology of Megalobrama pellegrini (Tchang, 1930) early juveniles raised in flow-through system
(2020) Qu, Huantoao; Chen, Lei; Yang, Jinyuan; Liao, Jianxin; Wei, Dai; Lu, Xuebao
To determine the effects of feeding rate and feeding frequency on growth performance, digestive enzymes activities, and intestine development of Megalobrama pellegrini in a replicated flow-through system, we conducted a 42-day experiment. We designed three feeding rates (5%, 6.5%, and 8% body weight/day, BW/d) and two feeding frequencies (2 and 3 meals/day; m/d) in this experiment. Fish (0.57 ± 0.01 g) were distributed into 18 tanks with 70 individuals and fed with a commercial diet (33% crude protein, 4% total lipid). Results showed that the highest weight gain was found in the fish fed diet with 6.5% BW/day and 3 m/d, which was significantly higher in comparison with that of other feeding rate groups (5% BW/d and 6.5% BW/d) at both feeding frequency (2 and 3 m/d). Fish growth performance was significantly affected by the feeding rate but not by the feeding frequency. The significantly higher feed conversion ratio (FCR) was recorded at 8% BW/d with 3 m/d than other treatments. Furthermore, fish fed diet at 8% BW/d with 2 m/d had significantly high mortality during the middle of this trial. In contrast, we found that other fish groups' survival rates were higher (over 90%), and there were no significant differences among them. We saw a significantly lower whole-body crude protein, lipid, and intestinal digestive enzymes in fish fed at a ratio of 8% BW/d with 3 m/d compared with other treatments. Moreover, our findings revealed intestinal villi fusion and exfoliation in this group compared with other treatments. In conclusion, the Megalobrama pellegrini received a feeding rate of 6.5% BW/d, and a feeding frequency of 2 m/d may be the optimum feeding regime for raising Megalobrama pellegrini in a flow-through system.
Effects of Dietary Wheat Gluten Meal on Growth, Intestinal Morphology, and Microbiome in Juvenile Large Yellow croaker Larimichthys crocea
(2020) Fan, X.J.; Yin, H.; Chai, R.Y.; Shui, X.M.; Huang, J.; Wang, P.
Wheat gluten meal (WGM) was evaluated as a replacement for fish meal (FM) for juvenile Larimichthys crocea．FM was replaced by 0%, 25%, 50%, 75%, and 100% of WGM (WGM0, WGM25, WGM50, WGM75, and WGM100, respectively). In addition, all diets except the control group were supplemented with amino acids. Fish were fed twice daily for 56 days. There were no significant differences in survival and feed conversion ratio (FCR) among all treatments (P>0.05). WGM25, WGM50, and WGM75 groups had significantly higher specific growth rate (SGR) and weight gain ratio (WGR) than those fed with WGM0 (P<0.05). There were no significant differences in mucosal thickness (MT), lamina propria width (LW), mucosal fold height (MH), and goblet cell quantity of single hair (GC) for all the diets (P>0.05). The indexes of Chao1, Shannon, Simpson, and Good coverage in fish fed with WGM0, WGM50, and WGM100 were not significantly affected (P>0.05). Firmicutes (81.03~94.03%) were the dominant bacterial community in juvenile large yellow croaker. Compared with the WGM0 group, the abundance of Firmicutes increased significantly, and Proteobacteria decreased significantly in the WGM100 group (P<0.05). These results suggested that WGM could replace 366.3 g kg-1 FM of the juvenile large yellow croaker diet.
Effects of Dietary Lipid Levels on Growth Performance, Whole Body Composition and Digestive Enzyme Activity of Juvenile Bighead Carp (Aristichthys nobilis)
(2020) Cai, Fangfang; Wang, Yan; Hu, Xiangin; Huang, Feng; Wang, Fucheng; Liu, Hongming
A 60-day study was conducted to investigate the effects of dietary lipid levels on growth, whole body composition and digestive enzyme activity of bighead carp (Aristichthys nobilis) with initial average weight (3.28 ± 0.11) g. Six isonitrogenous (40.25% crude protein) diets were formulated to contain graded contents of lipid (4.72%, 7.31%, 11.02%, 14.90%, 17.14%, and 19.37%) using corn oil and soybean oil as main lipid source. The results showed that the maximum weight gain (WG) and specific growth rate (SGR) were recorded at 11.02% dietary lipid level. Significant alterations were demonstrated on whole-body composition by different dietary lipid levels. Crude lipid content of whole body increased in parallel with the increase of dietary lipid levels. Fish fed diet with 11.02% lipid level showed lowest moisture and ash content. The activities of amylase and protease initially increased before decreasing, and the highest activities of amylase and protease were obtained in individuals fed the 11.02% lipid content diet. There were no significant differences in condition factor (CF) and hepatosomatic index (HSI) (P >0.05). Based on the polynomial regression analysis of WG and SGR, this study suggested that the optimum dietary lipid requirement of juvenile bighead carp was estimated to be 7.77%~8.31%.
Effects of dietary P:E ratio and Rhizoclonium in two stocking densities on growth and profitability of Nile tilapia in intensive pond culture
(2020) Serrano Jr, Augusto E.; Tumbokon, Barry L.M.; Abalos, Rosie S.; de la Pena, Raul; Bohulano, Nenia N.; Binh, Mac N.
Two onsite tests were carried out to determine the effects of varying dietary protein to energy (P:E) ratio in intensive culture of Nile tilapia in two different places at two stocking densities. In both field trials, three diets were used namely commercial (CM) diet, control (CO) diet containing no Rhizoclonium and a diet containing Rhizoclonium replacing 52% of soybean meal (RLP); the diets contained decreasing P:E ratio of 21, 16 and 12 gMJ-1, respectively. The first trial was conducted in Aklan, Philippines at a stocking density of 17 fishm-2 while the second was in Pangasinan, Philippines at 27 fishm-2. In both trials, the three diets were fed for 2 months to 3 replicate cages of Nile tilapia, all of which were randomly placed in about 1.0 ha fresh water fish pond. In the first trial in Aklan, at 17 fish m-2 stocking density, no significant differences in the parameters were observed except in the absolute growth rate (AGR) in which the RLP dietary treatment exhibited a higher value than did either the CM or the CO diet. In Pangasinan, at 27 fish m-2 stocking density, significant differences in TFI, DFI and SGR were observed, all the other parameters were statistically similar. The RLP group exhibited lower total feed intake (TFI) and daily feed intake (DFI) but higher specific growth rate (SGR) than did either the CM or CO diet. In either stocking densities, feed cost was the main determinant of profitability in which the RLP group resulted in significantly highest profitability i.e., lowest total production cost, highest gross income and highest profit and profit margin. Although profit was significantly higher in the higher stocking density, profit margin was significantly higher in the lower stocking density. There was no statistical interaction between dietary treatment and stocking density as analyzed by two-way analysis of variance.
The use of otolith shape to identify stocks of Konosirus punctatus
(2020) Li, Songzhang; Wang, Xianwen; Wang, Haixia; Wu, Chunzhi; Zhan, Huixiang; Su, Shengqi; Gao, Tianxiang; He, Tao
Konosirus punctatus is an important economic fish in the Northwest Pacific Ocean, especially along the coast of China, and an important substitute in the marine ecosystem. The aim of this study is to quantify the variation of sagittal shapes to discriminate the K. punctatus stocks between China coasts (Wei Hai, Yan Tai, Zhou Shan, Wen Zhou, Dong Ying, Hai Kou and Qing Dao) and Aomori (Am) in Japan by comparing the sagittal morphometric features. The sagitta variation of eight K. punctatus stocks was examined using nine shape indices (Roundness, Circularity, Form-factor, Rectangularity, Ellipticity, Radius ratio, Feret ratio, Aspect ratio and Surface density). Multiple comparisons on shape indices showed that three shape indices (Roundness, Feret ratio and Surface density) have significant differences between nine stocks. The comprehensive judgment accuracy rate is 54.5%. Based on the Fourier coefficient eight Fourier parameters can fit the shape of sagittal. The comprehensive judgment accuracy rate is 56.1%. The results showed that the otolith morphology was not significantly different between seven China stocks, while the China stocks showed a large sagittal morphological difference from the Japanese stock. It could be related to environmental factors and geographical conditions in various sea areas.
Molecular cloning and functional analysis of type I IFNd of Chinese sea bass (Lateolabrax maculatus) under immune stimulation
(2020) Zhang, Yaqing; Yan, Lulu; Wang, Pengfei; Zhao, Chao; Fan, Sigang; Yuan, Man; Qiu, GaoFing; Qiu, Lihua
Chinese sea bass (Lateolabrax maculatus) is an economically important marine cultured species in China. Interferons (IFNs) play an essential role in innate antiviral immunity. The study on IFN immune system helps prevent and control viral diseases of L. maculatus. We have obtained cloning and characterization of the type I IFNd gene from L. maculatus (LmIFNd) in the present study. The full length of cDNA was 1190 bp, including 5'UTR (untranslated region) of 354 bp, 3'UTR of 278 bp, and an open reading frame (ORF) of 558 bp. It encodes 185 amino acids, and the first 20 amino acids are hypothetical signal peptides. The results of amino acid multiple sequence alignment and phylogenetic tree analysis showed that LmIFNd and mandarin fish (Siniperca chuatsi) IFNd were clustered into one branch, and the gene sequence similarity was as high as 88.9%. The expression of LmIFNd was tissue-specific and highly expressed in the head kidney, spleen, and gill. After infection with Rana grylio virus (RGV), and polyinosinic-polycytidylic acid [Poly(I:C)], the expression of LmIFNd in gill, spleen, and head-kidney was up-regulated significantly. Besides, the expression level of LmIFNd has increased significantly under the stimulation of Vibrio harveyi and Streptococcus iniae. The results show that LmIFNd may play a protective role in both viral and bacterial infections.
Dietary Quillaja saponin improves growth and resistance against acute hyposalinity shock in the black tiger shrimp Penaeus monodon post larvae
(2020) Jumah, Yashier U.; Tumbokon, Barry L.M.; Serrano Jr., Augusto E.
Acute hyposalinity stress in shrimp ponds is a natural occurrence during the rainy season and the provision of functional ingredients that will elicit resistance to this stress is needed. Quillaja saponin (QS), a triterpenoid saponin derived from the bark of Quillaja saponaria, is reported to trigger innate immunity in vitro and in vivo in shrimps. The present study aims to evaluate its potential as growth-promoter and its immune-enhancement effects against salinity stress. Three separate experiments were done: (a) an attractability test; (b) a 30-day feeding trial to determine optimal inclusion of QS; and (3) an acute hyposalinity stress test following feeding the experimental diets. Attractability tests showed that all the Quillaja saponin inclusions significantly attracted more shrimps than the control diet (p<0.05). In the feeding trial, 5 experimental diets containing 0.0, 0.15, 0.30, 0.45, and 0.60 g kg-1 QS (QS 0, QS 15, QS 30, QS 45 and QS 60, respectively) were fed to groups of shrimps. Results showed that the final average body weight (FABW), feed intake (FI), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) values of shrimps in the QS 30 and 45 groups were significantly higher than that of the control group; the values of those in QS 15 and 60 groups were not significantly different from those of the QS 0 group. The optimal inclusion level of dietary QS was estimated to be 0.36 g kg-1. In the acute hyposalinity stress test, shrimps were fed with the experimental diets for 2 weeks and then transferred from 24 PSU salinity media to 2 PSU. All QS groups showed lower cumulative mortality rate than that of the QS 0 group except for the QS 60; QS 30 groups exhibited significantly the lowest. The estimated level of QS that elicited the lowest cumulative mortality rate was 0.33 g kg-1. In conclusion, the diets containing QS enhanced the shrimp's attractability, promoted both growth and immune response against acute hyposalinity stress at the optimal level of 0.36 g kg-1 QS in the black tiger shrimp P. monodon.
Population Genetic Analysis of Rainbow Clam Moerella iridescens by Using rDNA
(2020) Li, Xiaoying; Zhang, Min; Lu, Guanzheng; Mao, Shuang; Wu, Ruixue; Ge, Hongxing; Meng, Xueping; Dong, Zhinguo
To assess the genetic background of the germplasm resource of rainbow clam Moerella iridescens along China coasts, population genetic structure and genetic diversity of rainbow clam from five geographical populations in the Yellow Sea and the East China Sea (Lianyungang, Chongming, Cixi, Zhoushan, and Ningde) were analyzed based on rDNA (ITS1-5.8S-ITS2) sequences. Forty-Seven rDNA haplotypes were identified among 109 rainbow clam individuals of the five populations. Gen4 and Gen21 were the dominant haplotypes, accounting for 49.5% of rDNA whole gene sequences, and shared by the five populations. Six to eight exclusive haplotypes were found in each population. The average haplotype diversity index (HD) of the five populations was 0.8733. The genetic distance among populations ranged from 0.002 to 0.004, and haplotypes from the same population were not clustered in a single clade. Molecular variance analysis (AMOVA) demonstrated that the main genetic differentiation mainly occurred within population, and the genetic differentiation coefficient (FST) among five populations was between -0.02836 and 0.01896, which meant that no genetic differentiation among populations occurred. Overall, the five geographical populations showed a high genetic diversity, but no evident genetic structure or genetic differentiation.
Effect of ammonia on the immune response of mud crab (Scylla paramamosain) and its susceptibility to mud crab reovirus
(2020) Cheng, Chang-Hong; Ma, Hong-Ling; Deng, Yi-Qin; Feng, Juan; Jie, Yu-Kun; Guo, Zhi-Xun
Ammonia is one of the major environmental pollutants that affect the growth and physiological functions of organisms. In the present study, the effects of ammonia on the immune response and pathogen resistance of mud crab reovirus (MCRV) in mud crab were investigated. Mud crab were exposed to four different ammonia concentrations (0, 2.5, 5 and 10 mg L-1 ammonia-N) for 7 d. The result showed that aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity significantly increased after 5 and 10 mg L-1 ammonia exposure. The hepatopancreas superoxide dismutase (SOD), catalase (CAT), and total antioxidative capacity (T-AOC) in ammonia-N group were significantly lower than those in the control group, while the levels of malondialdehyde (MDA) were significantly higher than those in the control group. Significant reductions in total hemocyte counts (THC) were observed after ammonia exposure. After 7d ammonia exposure, mud crabs were injected 100 μL MCRV at 105 copies/g body weight. The mortality of mud crabs in ammonia-N group were significantly higher than those in the control group. All these results suggested that ammonia in water caused a depression in the immune response, and increased susceptibility to MCRV infection.
Molecular characterization and expression of the related-male gene sox30 in the common carp Cyprinus carpio
(2020) Cao, Xianglin; Fu, Xiaozhe; Zhao, Yidi; Li, Baohua; Zhang, Huajie; Liu, Nana; Li, Ninggiu; Chen, Jianjun
The Sox (SRY-related HMG-box) family of transcription factors is involved in the regulation of embryonic development and determination of cell fate. Sox proteins serve as transcriptional regulators that are complexed with other proteins. For this study, we initially cloned and characterized the full-length cDNAs, DNA sequences, and 5′-flanking regions of the common carp Cyprinus carpio Sox30. The sequence analysis suggested that Ccsox30 carried a distinct HMG-box of the Sox family within Cyprinus carpio. Phylogenetic and gene structure analysis revealed that sox30 was homologous to mammalian Sox30, whereas chromosome synteny analysis demonstrated that the position of Cyprinus carpio Sox30 in the genome was different from that of other vertebrates. This might have been due to the split of the Sox30 flanking gene by several genes not yet found near the Ccsox30 in evolution, or because the genome sequencing data was not annotated. The results of Real Tim Quantitative-PCR (RT-qPCR) revealed that Sox30 expression was high in the testes, and the expression was traced in other tissues by researching the tissue distribution of C. carpio and ontogeny of Ccsox30 expression in the gonads. This expression pattern suggested that Ccsox30 may be involved in spermatogonial differentiation and spermatogenesis.
Histological study on development of the digestive system of longfin batfish (Platax teira)
(2020) Zeng, Chen; Liu, Bao-Suo; Zhu, Ke-Cheng; Guo, Hua-Yang; Guo, Liang; Zhang, Nan; Liu, Bo; Wang, Zhi-Yong; Zhang, Dian-Chang
The ontogeny of the digestive tract in Platax teira was studied by means of optical microscopy from hatching to 30 days post-hatching. Collect fertilized eggs from P. teira broodstock, fertilize the eggs to hatch in hatching net bags, and rear the larvae in higher-place ponds. Observe the morphology and structure of the digestive tract of larvae 1-30 days post-hatching using tissue slicing technique. The results showed that the oral cavity of the larvae was closed and had not yet begun to differentiate at 1day post-hatching. Its digestive tract was close to the abdominal wall, and the yolk sac was completely dyed dark red. At 4 days post-hatching, the oropharyngeal cavity, esophagus, and stomach of the larvae had been communicated, and their oral cavity opened and food intake begins, entering the mixed period of endogenous nutrition and exogenous nutrition. Thereafter, the yolk sac gradually decreased to disappear, the esophagus, stomach, and intestines continued to differentiate, and their functions gradually improved. During 25-30 days post-hatching, the structure of the digestive tract of the larvae didn’t change much. Due to the increase in the size of the larvae, most changes in the digestive system are related to the complexity of the tissues and the size of the organs. Specifically, the number of mucosal folds and cells in the esophagus and intestine increases, and the gastric glands and pits in the stomach increase. The number of mucous membrane folds, mucosal epithelial cells and gastric glands in the digestive tract increase with the growth of the larvae, indicating that the development of the digestive system of P. teira is consistent with the growth of larvae, morphological development, feeding, metabolism and other functions consistently, its developmental stage is also adapted to the stages of the early development stage of P. teira.
De novo transcriptome analysis of the sandworm (Sipunculus nudus) and identification of differentially expressed genes associated with body size
(2020) Cai, Xiaohui; Fang, Jing; Zhou, Yuna; Chen, Honglin; Wu, Xinzhong; Peng, Yinhui
The sandworm (Sipunculus nudus) is an aquatic species of economic importance because of its high nutritional and medicinal value. Under the same culture conditions, substantial individual growth variation is often found in populations of sandworms. However, the genetic mechanisms of individual growth variation are poorly understood. In this study, the transcriptome of the body wall muscle of the sandworm at different growth rates was analyzed by Illumina sequencing and bioinformatics analysis. A total of 185 181 unigenes were obtained after processing raw reads and about 96,824 (47.72%) of them were annotated. Among the annotated transcripts, 418 differentially expressed genes were identified, of which 207 were upregulated and 211 were downregulated in large worms relative to small worms. We identified several genes that had a possible association with individual growth variation. These results will provide insight into the growth mechanism of sandworm, and will further assist in the selective breeding of improved strains of this species.
Effects of dietary κ-carrageenan on growth and resistance to acute salinity stress in the black tiger shrimp Penaeus monodon post larvae
(2020) Jumah, Yashier U.; Tumbokon, Barry L.M.; Serrano Jr., Augusto E.
Acute salinity stress happens unnoticed in shrimp ponds and there is a need to protect the animals by providing dietary functional ingredients that will elicit resistance to this stress. k-Carrageenan, a sulfated polysaccharide from red seaweed, is reported to trigger innate immunity in vitro and in vivo in shrimps. The present study aims to evaluate its potential as growth-promoter and its immune-enhancement effects against salinity stress. Three separate experiments were done: (a) an attractability test; (b) a 30-day feeding trial to determine optimal inclusion of k-carrageenan, and (3) acute salinity stress test. Results of the attractability tests showed that all the experimental diets did not differ in their attractability to the shrimps. In the feeding trial, 5 groups of post larval shrimp were fed with 5 experimental diets containing various inclusion levels of k-carrageenan, namely, 0.0, 0.15, 0.30, 0.45, and 0.60 g kg-1. Results showed that the final average body weight (FABW), weight gain (WG), and specific growth rate (SGR) and feed conversion efficiency (FCE) values of shrimps in the 0.15 and 0.3 g kg-1 were significantly higher than that of the control group; the values of those in 0.45 and 0.60 g kg-1 groups were not significantly different from those of the control group. Protein efficiency ratio (PER) values, in contrast, were not significantly different from each group. Optimal inclusion level in the diet of k-carrageenan was 0.29 g kg-1. In the acute salinity stress test, 5 groups of shrimps were fed with the same 5 experimental diets as those in the feeding experiment for 2 weeks, transferred them from 21 ppt salinity media to 4 ppt. Results showed that the control group exhibited significantly highest mortality rate while in the 0.6 g kg-1 group the lowest; each group were significantly different from each other. Mortality rate decreased with increased dietary k-carrageenan level in a linear fashion. In conclusion, the study demonstrated that the the diets containing dietary k-carrageenan was equally as attractive as the basal/control diet and that k-carrageenan showed both growth-promoting and immune-stimulating effects against acute salinity stress in the black tiger shrimp P. monodon post larvae.
Plesiomonas shigelloides, a potential pathogen of enteritis in Ictalurus punctatus
(2020) Wang, Huicong; Gu, Ying; Zhou, Huihua; Chen, Jun; Wang, Minghua; Jiang, Hucheng; Cao, Haipeng
Enteritis has resulted in large economic losses in channel catfish aquaculture. Yet only scarce information is available on Plesiomonas shigelloides as a causal agent for this disease. In this study, a virulent strain, temporarily named BD1, was isolated from diseased channel catfish suffering from enteritis, and was identified as P. shigelloides through molecular and phenotypic methods. A phylogenetic tree was also constructed to determine its taxonomic position. In addition, the BD1 isolate has developed multiple resistances to aminoglycosides, amphenicols, quinolones, tetracyclines and sulfonamides drugs for veterinary uses in aquaculture as revealed when screened against a range of common antibiotics. To the best of our knowledge, this is the first report of P. shigelloides as a potential pathogen of enteritis in channel catfish.
Genome-wide identification and expression analysis of Bcl-2 gene family under low-temperature stress in tilapia (Oreochromis niloticus)
(2020) Yang, Changgeng; Wang, Meizi; Wen, Hua; Jiang, Ming; Tian, Juan; Lu, Xing
Low temperature stress can lead to variety of changes, including apoptosis in tilapia (Oreochromis niloticus). The B cell lymphoma-2 (Bcl-2) gene family plays an important role in the process of apoptosis. The present study conducted genome-wide characterization of the Bcl-2 family genes in tilapia and their mRNA expression profiles were analysed in different tissues of tilapia under the low temperature stress (10°C). Twenty-four Bcl-2 family genes were identified, containing 2~8 exons. These genes were classified into two subfamilies (Bcl-2 homologs and BH3-only) based on their conserved domains. Besides, these BCL-2 proteins in tilapia possess at least one of the four conserved BH domains. The phylogenetic analysis showed that the Bcl-2 family genes did not aggregate by species, demonstrating sequence conservation of different types of Bcl-2 family members. Real-time quantitative PCR (RT-qPCR) analysis showed that Bcl-2 family genes were broadly expressed in different tissues of tilapia. When reared at 10 °C, the transcriptional expression levels of most of anti-apoptotic Bcl-2 homologs subgroup members and other BH3-only subgroup members in most tissues of tilapia were higher than those at 30°C. However, most of other Bcl-2 family members revealed a lower expression. The results suggested that hypothermia had significantly induced apoptotic in tilapia.

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