Replacement of fish oil with soybean oil in diets for juvenile Chinese sucker (<Emphasis Type="Italic">Myxocyprinus asiaticus</Emphasis>): effects on liver lipid peroxidation and biochemical composition

This study was designed to evaluate the effect of the replacement of fish oil (FO) by soybean oil (SO) on growth performance, liver lipid peroxidation, and biochemical composition in juvenile Chinese sucker, Myxocyprinus asiaticus. Fish (13.7 ± 0.2 g) in triplicate were fed five experimental diets in which 0% (FO as control), 40% (SO40), 60% (SO60), 80% (SO40), and 100% (SO100) FO were replaced by SO. The body weight gain of fish fed SO40, SO60, or SO80 diet was similar to FO group, but diets that have 100% soybean oil as dietary lipid significantly reduced fish growth (P < 0.05). Although the level of SO resulted in increasing crude lipid content of the liver, the level of SO did not significantly alter the hepatosomatic index (HSI). Indicators of peroxidation, such as vitamin E (V_E) and thiobarbituric acid-reactive substance (TBARS) contents, were changed as increasing dietary SO. It was shown that the inclusion of SO in the diets increased V_E concentrations, but reduced TBARS in the liver and total cholesterol (T-CHO) in the plasma. Linoleic acid (LA) and linolenic acid (LNA) significantly increased in fish liver fed diets that contained SO, but eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and the ratio n-3/n-6 were significantly reduced by the inclusion of dietary SO (P < 0.05). Our results indicated that the inclusion of SO increased the hepatic V_E content and reduced lipid peroxidation in fish. However, diet containing 100% SO as dietary lipid could reduce growth performance. Thus, we recommended that 40–80% SO can be used as dietary lipid to replace FO for juvenile Chinese sucker.     

Effect of LED light quality on the phototaxis and locomotion behaviour of Haliotis discus hannai

Abalones were reared in a laboratory to determine the percentage response rate, response time, average crawling speed and the time taken to recover an upright posture under nine light‐emitting diode light quality treatments (red, orange, yellow, green, cyan, blue, purple, white and grey) and a dark environment. Animals were placed in the centre of an experimental device, and the tropism of each animal was continuously monitored by video. The highest percentage response rate (80% in dark adapted abalones, 60% in light adapted abalones) was observed in the dark environment, followed by red and orange light (27% and 30% in dark adapted abalones, respectively, 22% and 24% in light adapted abalones). Two induction materials (substrate and brown algae Laminaria japonica) were used to assess the effect of light quality on the tropism of abalones, with the highest percentage response rate (76% in the L. japonica treatment, 22% in the substrate treatment) also observed in the dark environment, followed by red and orange light (both 25% in the L. japonica treatment, and 26% and 32%, respectively, in the substrate treatment). The tropism order of the abalones under dark, red, orange and yellow light was as follows: dark > orange > red, yellow, but fewer abalones chose to stay in blue, green, cyan and purple light. The response time (about 700 s) in the dark environment was significantly longer than for the other light quality treatments. Compared with the average crawling speed in the other light quality treatments, abalones were relatively slower (about 3.8 mm s^?1) in red and orange light, and the dark environment. The mean time required for the recovery of an upright posture in red light and the dark environment was longer than in the other light quality treatments, with the average recovery time reaching a maximum of 60 s in the dark environment. The results demonstrate the phototaxis and locomotion behaviour of abalones, as well as confirming the necessity of a dark, orange or red environment for their management and aquaculture.     

Genetic parameters for growth‐related traits and survival with age in the Kuruma shrimp Marsupenaeus japonicus

Genetic parameters were estimated for growth‐related traits and survival of the Kuruma shrimp Marsupenaeus japonicus based on 66 families, including 30 paternal half‐sib families, which were obtained using artificial insemination of two females by each male. The variance components for growth‐related trait and survival were estimated using a single‐trait animal model and a sir‐dam model, respectively, and genetic parameters were estimated using the restricted maximum likelihood method. The coefficients of variation for growth‐related traits such as body length (BL), abdominal length (AL), and body weight (BW) were 9.36%–22.44%, 10.61%–21.92%, and 26.47%–58.33%, respectively, at different ages (45, 75, 105, 135, and 165 days). The corresponding heritability estimates for each growth trait were 0.1545–0.1951, 0.1672–0.1905, and 0.1596–0.1934, respectively, all of which were found to be at moderate levels and increased with age. The heritability of survival on day 165 was low (0.003). The genetic correlations among growth traits were positive and high (0.7316–0.9896) at the different ages, suggesting that selection to improve any single growth trait will cause positive responses in other growth traits examined in M. japonicus. The genetic correlations between growth traits and survival were also positive but low (0.005–0.087), which indicated that only selecting for growth traits may not cause a positive correlated response in the survival of the core population. According to the above results, we suggested that growth and survival traits should be taken as improving targets of breeding in M. japonicus. These results provided reference data for selective breeding and multitrait selection of M. japonicus.     

Preliminary study to evaluate the effects of dietary bile acids on growth performance and lipid metabolism of juvenile genetically improved farmed tilapia (Oreochromis niloticus) fed plant ingredient‐based diets

A 9‐week feeding experiment was conducted to investigate the effects of dietary bile acids (BAs) on juvenile genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) based on the evaluations of growth performance and parameters relevant to lipid metabolism. Each of five vegetable protein‐based diets containing BAs at a level of 0, 0.05, 0.15, 0.45 or 1.35 g/kg diet was fed to three replicates with 40 fish (8.2 g per fish). The results showed that weight gain (WG) increased significantly with the increase in BAs from 0 to 0.15 g/kg diet and then decreased significantly at a higher BA supplementation. Dietary BAs significantly reduced the crude lipid content in the whole body, muscle and liver tissue of GIFT. Fish fed diet with 1.35 g BAs/kg diet developed serious nuclear migration and vacuolization in hepatocytes. Gall bladder appeared to contain white solid and has fragile capsules. Dietary BA supplementation had significant effects on serum biochemical indices and activities of lipid metabolism enzymes in liver and intestine. In conclusion, dietary bile acid supplementation (0.15 g/kg) can facilitate the lipid metabolism and therefore promote the growth of tilapia. However, overdosed dietary BAs induced gallstone development, disrupted lipid metabolism and depressed the growth performances of GIFT.     

中草药联用对罗非鱼无乳链球菌作用的研究

本文利用BIOLOG自动微生物鉴定系统对所分离保存的罗非鱼致病菌株进行生化鉴定,确定为无乳链球菌(Streptococcus agalactiae),进而测定虎杖、五倍子、地榆、黄连、大黄、白头翁、黄芩等14种中草药单用及联用复方对该致病菌株的抑菌效果。结果表明,从14种中草药中筛选出6种中草药(中草药A、中草药B、中草药C、中草药D、中草药E、中草药F)对无乳链球菌有良好的抑制作用;随后考察此6种中草药组合成双联用、三联用及四联用复方的抑菌效果,其中双联用中的2种复方具有显著协同作用,4种复方具有协同作用;三联用中的8种复方具有显著协同作用,3种复方具有协同作用;四连用中的1种复方具有显著协同作用,1种复方具有协同作用。     

南美白对虾大棚六茬养殖试验

南美白对虾是重要的养殖虾类,目前国内养殖模式比较多是单茬养殖,主要是因为受到区域性气候的限制,所以养殖茬数较少。为了充分发挥南美白对虾养殖的优势,探索南美白对虾健康高效养殖模式,进一步提高单位产量,提高养殖设施的利用率和经济效益,我们在两茬养殖的基础上,采用三级池暂养的方法,进行了南美白对虾六茬养殖试验。     

Nitrate removal efficiency and bacterial community of polycaprolactone-packed bioreactors treating water from a recirculating aquaculture system

A denitrification reactor packed with polycaprolactone (PCL) as a carbon source and biofilm carrier was developed to remove nitrate nitrogen (\( {\mathrm{NO}}_3^{-}-\mathrm{N} \)) from the water of a recirculating aquaculture system for 115 days. The hydraulic retention time was set to 6 h, and the water flow rate was 0.95 L h^?1. The removal rates of \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) ranged from 34.67 to 155.7 g \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) m^?3 day^?1 when the effluent \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) concentrations ranged between 1.62 and 72.25 mg L^?1. No obvious changes in the Fourier transform infrared spectra of the PCL before and after use were observed. Bacterial community structure in the biofilm of the PCL granules was analyzed using Illumina MiSeq sequencing technology. Proteobacteria and Bacteroidetes were predominant in the biofilm, with relative abundances of 63.9 and 27.4%, respectively. Three genera, Acidovorax, Azospira, and Diaphorobacter, were capable of both denitrification and PCL degradation. This study indicates that PCL-packed reactors may be used and optimized for removing nitrate from aquaculture effluents.     

Plasma levels of immune factors and sex steroids in the male seahorse <Emphasis Type="Italic">Hippocampus erectus</Emphasis> during a breeding cycle

To better understand the endocrine- and immune-response pattern during reproduction in a fish species having parental care behaviors and also to accumulate the endocrine- and immune-related data for future explanations of the low reproductive efficiency in seahorse species, the variations of immune factors and sex steroids in the plasma of the male lined seahorse Hippocampus erectus at different breeding stages, i.e., pre-pregnancy, pregnancy (early, middle, and late periods), and post-pregnancy, were investigated in the present study. The immune factors included monocytes/leucocytes (M/L), leucocyte phagocytic rate (LPR), immunoglobulin M (Ig M), interleukin-2 (IL-2), interferon-α (IFN-α), and lysozyme (LZM). The sex steroids included testosterone (T), 11-ketotestosterone (11-KT), 11β-hydroxytestosterone (11β-OHT), 17α-methyltestosterone (17α-MT), 17β-estradiol (E2), and 17α-hydroxy-20β-dihydroprogesterone (17α-20β-P). Moreover, the immune metabolic activity of epithelium cells in the brood pouch at different breeding stages was also analyzed through ultrastructural observations of the abundance of cytoplasmic granules, mitochondria, endoplasmic reticulum, lysosomes, and exocytosis. The results show that a higher immune level was observed during pregnancy, particularly in the early and middle periods, and a lower immune level was noted during pre-pregnancy. Correspondingly, the epithelium cells in the brood pouch also showed a stronger immune metabolic activity during pregnancy and weaker activity during pre-pregnancy. Four sex steroids of T, 11β-OHT, 17α-MT, and E2 were higher during pre-pregnancy and lower during post-pregnancy, whereas 11-KT and 17α-20β-P, which were positively correlated with part immune factors, were higher during pregnancy. No negative correlations between sex steroids and immune factors were observed. In conclusion, the higher immune competence during pregnancy may indicate that parental care could improve immunity, which may be the major factor for no immunosuppressive effect of sex steroids during reproduction in the seahorse H. erectus, unlike noncaregiving fishes in which inhibitions of sex steroids on immunity are frequently observed. Moreover, higher 11-KT and 17α-20β-P during pregnancy than during pre-pregnancy and post-pregnancy may suggest that these two steroids are also involved in parental care regulation.     

RAPD技术在鱼类研究中的应用

RAPD(Random Amplified Polymorphic DNA, 随机引物扩增多态DNA)技术是1990年由Williams和Welsh两个研究小组同时发展起来的一项DNA多态检测技术.RAPD技术与其他分子标记技术相比具有独特的优势,在生物种群遗传结构分析、遗传多样性检测、物种亲缘进化关系鉴定、基因连锁图谱的构建和基因定位与分离等得到了广泛应用,在鱼类研究中也有了一定应用,并取得相应成果,主要表现在以下方面.     

鳗鲡仔,幼鱼年龄生长的研究

辽东半岛黄海北部沿岸河口4—6月溯河的白仔鳗,全长53.5—64.5毫米,平均58.83毫米,体长频率高峰位于57.1—59.0 毫米体长组,其体长体重呈直线相关。白仔鳗与幼鳗群体的体长、体重则是指数相关,其方程为W=1.136×10~(-7) L~(3.3871)。12尾白仔鳗耳石平均日轮数为146.3,据此对其产卵期进行了推测,观察证实,在不同生态条件下生活过的幼鳗耳石的环纹有过渡带存在。