Ontogeny of the stomach in yellow catfish (Pelteobagrus fulvidraco): detection and quantifictation of pepsinogen and H+/K+‐ATPase gene expression

Yellow catfish (Pelteobagrus fulvidraco) is an important commercial species with high aquaculture potential in China. To better understand the process of digestive functioning of gastric gland development during the larval from 1 dph (day post‐hatching) to 30 dph, real‐time PCR was used to detect and quantify the pepsinogen and H⁺/K⁺‐ATPase gene expression in P. fulvidraco. These data were also compared with the adult situation. The results showed that the expression of pepsinogen and H⁺/K⁺‐ATPase genes in P. fulvidraco larvae both started at 1 dph, though the expression level was very low until 3 dph. The quantification of pepsinogen gene expression increased significantly from 4 to 8 dph, increased fluctuantly from 8 to 23 dph and rose sharply from 23 to 30 dph. In comparison with adult fish, there were no significant differences with larvae at 5 and 23 dph. However, data of 10 and 30 dph larvae were obviously higher than those of adult group. H⁺/K⁺‐ATPase gene expression increased linearly from 1 to 30 dph. However, it was significantly lower than that of adult. The results show that P. fulvidraco larvae have an earlier functional stomach, though the function of the stomach is still not perfect. There is a gradual acidification environment within the stomach during the P. fulvidraco larvae development. Based on these results, we suggest that the weaning time for P. fulvidraco larvae would be much better after 23 dph.     

黄颡鱼早期发育阶段受精卵和鱼体磷脂含量变化

研究了黄颡鱼(Pelteobagrus fulvidraco)受精卵孵化及仔鱼发育阶段鱼体磷脂含量的变化规律.采用常规化学分析方法对黄颡鱼从鱼卵受精开始至仔鱼孵化后未投饵的7d内的磷脂含量进行测定.结果表明,孵化期间受精卵磷脂含量在受精后16h略有增加;仔鱼孵化后,鱼体磷脂含量急剧下降,从0日龄的1.32％降低到7日龄的0.14％.说明磷脂是黄颡鱼仔鱼发育阶段代谢的重要能源,是仔鱼正常生长和发育所必需的重要营养素,仔鱼对磷脂的需求量很大.     

A Comparison of the Effects of Two Prey Enrichment Media on Growth and Survival of Pacific Bluefin Tuna,Thunnus orientalis,Larvae

Three experiments were conducted to investigate the growth, survival, and standardized cohort biomass of Pacific bluefin tuna, Thunnus orientalis, larvae fed nutritionally enhanced prey during the first week of feeding using two commonly used, commercially available enrichment media, AlgaMac Enrich and Marine Glos. T. orientalis larvae exhibited exponential growth in standard length and dry weight. The daily specific growth rates in length and weight are the first reported for T. orientalis larvae and the averages ranged from 3.8 to 4.1% and 27.5%, respectively, for larvae in the AlgaMac treatment and from 4.1 to 6.1% and 31.5%, respectively, in the Marine Glos treatment. Average daily growth rates in length ranged from 0.16 to 0.23 mm/d for larvae in the AlgaMac treatment and from 0.17 to 0.27 mm/d for those in the Marine Glos treatment. Daily growth rates in length were similar to those reported for other tuna larvae reared in the laboratory but slower than most published estimates for larval tunas in situ at similar water temperatures. Mean prey number per gut was positively associated with mean prey level in the tank. Both enrichment media appear to be good sources of nutritional improvement of planktonic prey for T. orientalis larvae.     

Analysis of sinking death using video images of the swimming performance of Pacific Bluefin tuna (Thunnus orientalis) larvae

In this study, we aimed to clarify the mechanism of sinking death during the larval stage of Pacific Bluefin tuna Thunnus orientalis by investigating the effects of swimming performance on sinking death, using a behavioral approach. Swimming performance was examined 3–9 days after hatching (DAH) under day and night light conditions in cuboid experimental tanks. Swimming behavior variables such as swimming speed and swimming angle were measured under both light conditions. Larvae in the daytime experiment and larvae with inflated swim bladders at night were distributed on the surface layer of the water column. In contrast, larvae with uninflated swim bladders at night were frequently observed swimming vertically or sinking to the bottom of the tank. Larvae with inflated swim bladders at night were always distributed beneath the surface until the next morning (survival rates were 100 %). However, larvae with uninflated swim bladders at night swam upward repeatedly and later sank to the bottom of the tank (survival rates were 60 % and 38 % at 5 and 9 DAH, respectively). Larvae with uninflated swim bladders were not always able to maintain their swimming depth by swimming until the next morning. Additionally, their swimming speed and vertical swimming frequency (ratio) depended on the illumination and swim bladder conditions. Our findings show that larvae with uninflated swim bladders at night were associated with a higher risk of sinking death. The swimming energy capacity of Pacific Bluefin tuna larvae, which indicates the total amount of the energy that enables individuals to swim throughout the night without feeding, was found to be linked to sinking death.     

Development and survival of Haemonchus contortus infective larvae derived from sheep faeces under sub-tropical conditions in the Potohar region of Pakistan

Assessment on the development and survival of Haemonchus contortus larvae was made to evaluate the influence of microclimatic variables viz., relative humidity (%), temperature (°C), rainfall (mm) and intensity of sunlight (hrs). Pasture plots in a sub-tropical area, Pakistan were contaminated with H. contortus eggs at the start of every month. The plots were sampled on fortnightly basis after contamination for three consecutive months. The overall pattern indicated the most favorable conditions for survival, development and translation to herbage was during the wet season from July to October and the least favorable was during the dry season from April to June. Peak infective larvae (L₃) recovery was during the 15–45 day interval for each plot and the lowest number was during the 75–90 day interval. Herbage was collected in the morning, afternoon and evening and greatest recovery of L₃ was in the morning time and least in the afternoon. The number of L₃ on pasture was directly related to the pattern of rainfall and relative humidity with a significant (P < 0.05) positive correlation and temperature and intensity of sunshine were negatively correlated (P < 0.05). The results suggest that pastures can remain infective for up to 2 months and become relatively clean by 90 days after contamination. Thus, long pasture rest periods, especially during the high risk wet season, may be a helpful strategy to reduce the infection levels.     

不同水平的卤虫幼虫冻干粉对黄颡鱼生产性能及抗氧化能力指标的影响

为探讨饲粮中添加不同水平的卤虫幼虫冻干粉对黄颡鱼生产性能及抗氧化能力指标的影响,采用单因素设计试验,将1200尾体质量为8.0 g黄颡鱼随机分为4组,每个组3个重复,每个重复100尾,1组为空白对照组饲喂基础饵料,2、3、4组为试验组在基础饵料中分别添加卤虫幼虫冻干粉100、150、200 mg/kg,试验期为42 d,试验结束测定黄颡鱼生产性能和血清中抗氧化能力指标。结果表明:(1)试验3、4组的增重率和特定生长率较1组分别提高9.46%、8.73%、8.11%、7.43%(P < 0.05),试验2、3、4组存活率均高于1组(P > 0.05);试验3、4组的饵料系数较1组分别降低16.45%、14.29%(P < 0.05);(2)试验3、4组血清中总抗氧化能力(T-AOC)和总超氧化物歧化酶(T-SOD)的活性较1组分别提高23.65%、20.95%、11.26%、11.05%(P < 0.05),试验2、3、4组血清中过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GSH-Px)的活力均高于1组(P > 0.05);试验3、4组血清中丙二醛(MDA)的含量较1组分别降低23.76%、21.29%(P < 0.05)。综上,在饲料中添加150 mg/kg卤虫幼虫冻干粉可提高黄颡鱼生产性能和抗氧化能力。     

基于Hertz接触理论的黑水虻幼虫碰撞恢复系数测定

为建立黑水虻幼虫与收集、输送、分离等机械工作部件间发生碰撞时的碰撞模型,基于黑水虻幼虫生物特性,应用Hertz弹性碰撞理论推导了黑水虻幼虫碰撞过程动力学方程,结合运动学方程原理构建了黑水虻幼虫恢复系数的测定装置并进行了黑水虻幼虫恢复系数测定试验。试验针对第5龄期的黑水虻幼虫,采用L16(44×23)混合正交试验方案研究了碰撞材料、材料厚度、下落高度、碰撞角、跌落方向、含水率等因素对黑水虻幼虫恢复系数的影响,然后对碰撞材料、材料厚度、下落高度、碰撞角、跌落方向进行单因素试验,并获得了材料厚度、下落高度、碰撞角对恢复系数的影响规律与回归方程,且方程的决定系数均不小于0.9427。试验结果表明,影响黑水虻幼虫恢复系数的因素影响由大到小为：碰撞材料、下落高度、碰撞角、跌落方向、碰撞材料厚度、含水率,其中含水率对恢复系数影响不显著。单因素试验结果可得：黑水虻幼虫与Q235钢、铝合金、有机玻璃、橡胶等碰撞材料间的恢复系数依次降低,随下落高度的增大而逐渐减小,随材料厚度的增加而逐渐增大,恢复系数随碰撞角的增大而整体呈增大趋势,且横向跌落方向大于纵向跌落方向。该文研究结果可为黑水虻幼虫收集、输送、分离等机械相关工作部件优化设计提供参考依据。     

利用地下海水进行海湾扇贝越冬的效果研究

把5cm以上海湾扇贝亲贝按43-50个／m^3密度吊养于水泥沉淀池,利用附近井水调温：使池水温度达4℃以上。越冬两个半月,成活率84％以上,而自然海区越冬贝成活率仅70％．升温促熟后．亲贝产卵孵化率60％以上,而自然海区越冬贝仅为15．1％。地下海水越冬贝的单位水体出苗量为505万粒／m^3和544万粒／m^3,而自然海区越冬贝出苗量仅有209万粒／m^3．证明利用地下海水调温,在沉淀池进行海湾扇贝亲贝越冬,效果明显,完全可行．     

甲胺磷、90-消毒剂对欧洲鳗仔鳗的急性毒性作用

采用静水实验法进行甲胺磷乳剂,９０－消毒剂对欧洲鳗仔鳗急性毒性试验研究。结果表明：在试验浓度３２－５６ｍｇ／Ｌ范围内,欧洲鳗仔鳗中毒死亡发生在３０－４４ｈ,对甲胺磷乳剂急性中毒死亡的时间集中且持续短促;甲胺磷乳剂对欧洲鳗仔鳗的半致死浓度为３５．９ｍｇ／Ｌ,安全浓度为３．６ｍｇ／Ｌ。     

K~+、SO_4~(2-)和碳酸盐碱度对大银鱼仔鱼存活的影响

本试验观察了K~+、SO~(2-)_4和碳酸盐碱度对大银鱼仔鱼存活的影响。大银鱼仔鱼在K~+浓度10～302.4mg/L中96h成活率为95～100％;在SO~(2-)_4384～1920mg/L中96h成活率为100％,并且它们能正常生长;碳酸盐碱度低于14me/L时96h成活率为100％,当碱度升到22me/L时其成活率为80％。