Structural and Rheological Characteristics of Alginate from Sargassum cristaefolium Extracted by Twin Screw Extruder

This study aimed to investigate the effects of process extrusion on the characteristics of Sargassum cristaefolium sodium alginate (SCSA) extracted using twin-screw extruder. Box-Behnken Design (BBD) from response surface methodology (RSM) was established to understand the effects of temperature, screw speed, and pH on the multiple-responses of alginate characteristics including intrinsic viscosity, yield, and molecular weight. The results revealed that temperature, screw speed, and pH significantly affected (P < .05) all responses. The optimum extraction condition was found at temperature of 58.18°C, screw speed of 77.99 rpm, and pH 10.11. At this condition, the response of residence time distribution was 7.07 ± 0.029 min, yield of 34.01 ± 0.12%, intrinsic viscosity of 460.13 ± 14.75 mL/g, and molecular weight of 217.94 ± 7.14 × 10³ g/mol. This alginate had mannuronic acid to guluronic acid (M/G) ratio of 0.28, and the L-guluronic acid block was 0.78, which was higher than the D-mannuronic acid block. Rheological characterization of SCSA in aqueous solution was shear-thinning pseudoplastic, and alginate gel in 1 M CaCl₂ was more elastic than liquid.     

Disturbance‐induced responses of VHF and satellite tagged harbour seals

相似文献   

Should only females of giant freshwater prawn Macrobrachium rosenbergii be selected in genetic improvement programmes?

Sexual dimorphism is widely observed in almost all farmed aquatic animal species but giant freshwater pawn (GFP) is unique, with males characterized by three main morphotypes (blue claw, orange claw and small males) and females by different reproduction status (ovary, berried egg and already‐spawned females). There has been reported evidence that the effect of male morphotype may have masked genetic variation in growth‐related traits, as a result the heritability for male body weight was lower than that estimated in female. A pending question has arisen whether selection should be made in female only. To answer this question, we used an 8‐year data set from a long‐term selection programme (2008–2015) for high growth in this species comprising 106,756 individuals that were offspring of 515 sires and 810 dams. The body weight data of female and male GFP or of each morphotype was treated as a separate trait and a multi‐trait approach was used to estimate genetic correlations for homologous traits between sexes and between morphotypes. Our analysis showed that there were little differences in the heritability estimates between female and male. In female, mature ovary individual displayed higher heritability than berried egg and already‐spawned females. For male, the heritability for blue claw, orange claw and small males were 0.11, 0.06 and 0.00 respectively. Between‐sex genetic correlation was moderate (0.55 ± 0.11) for body weight, suggesting that the trait expressions in female and male may be genetically different. In female, the genetic correlations for body weight among three female types were close to one (0.91–0.94). In contrast, the genetic correlations for body weight between male morphotypes especially between blue claw or orange claw and small males were low (0.15–0.25). Furthermore, we estimated genetic gain as the difference in least square means (LSM) or estimated breeding values (EBV) between the selection line and control group. The genetic gain in body weight was smaller in females than in males. It is concluded that there is no need to run separate breeding programme for female and male GFP. A combined selection using both female and male data can achieve selection response for body weight as demonstrated in the present study.     

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.     

Combined effect of temperature,salinity and density on the growth and feed utilization of Nile tilapia juveniles (Oreochromis niloticus)

Based on Box–Behnken experimental design and response surface method, the joint effect of temperature (16–36°C), salinity (0–22 ppt) and rearing density (200–1000 fish.m^?3) on the specific growth rate (SGR) and feed conversion rate (FCR) of Nile tilapia juveniles were studied under laboratory conditions. The entire experiment lasted for 1 month (30 days). Results showed that the linear and quadratic effects of temperature, salinity on both growth and feed utilization were highly statistically significant (P < 0.01). The linear and quadratic effect of rearing density on the growth was highly significant (P < 0.01); the linear effect of rearing density on feed utilization was significant (P < 0.05), but the quadratic effect nonsignificant (P > 0.05). Interactions between temperature and salinity, and between salinity and rearing density on the growth statistically differed from zero (P < 0.05). Interactions between temperature and salinity, between temperature and density on feed utilization was significant (P < 0.05). Model equations of the growth and feed utilization on temperature, salinity and density were established, with the coefficient of determination being 98.34% for growth and 98.11% for feed utilization, and could be applied to projection. The optimal temperature/salinity/density combination was obtained utilizing statistical optimization approach: 29°C/6 ppt/500 fish.m^?3, at which the maximal specific growth and feed utilization reached 4.228%.d^?1 and 0.520 respectively, with the desirability being 0.989.     

仿刺参肠道潜在益生菌对稚参生长、免疫及抗病力的影响

以稚参期仿刺参为研究对象,探讨了分离自仿刺参肠道的潜在益生菌在稚参养殖中的应用效果。采用16S rDNA序列分析法将3株潜在益生菌分别鉴定为Bacillus sp.(GSC-1)、Bacillus sp.(GSC-2)和Enterococcus sp.(GSC-3)。分别以10³、10⁵或10⁷ CFU/mL的GSC-1、GSC-2、GSC-3或灿烂弧菌浸浴稚参以检验潜在益生菌对稚参期仿刺参的安全性,7 d后各潜在益生菌浸浴组的稚参成活率均高于同浓度的灿烂弧菌处理组;GSC-1和GSC-3在实验浓度下对稚参成活率无显著影响(P>0.05),可作为稚参的潜在益生菌;而10⁷ CFU/mL GSC-2浸浴组稚参的成活率显著低于对照组(P<0.05),因此GSC-2不适合作为稚参的潜在益生菌。将潜在益生菌GSC-1和GSC-3以10⁹ CFU/g的比例与鼠尾藻粉混合后饲养稚参20 d,潜在益生菌处理组的稚参成活率、特定生长率和变色率均高于对照组,其中GSC-1处理组稚参的成活率和变色率显著提高(P<0.05),GSC-3处理组稚参的成活率和特定生长率显著提高(P<0.05);与对照组相比,潜在益生菌GSC-1和GSC-3均有效增加了稚参的总菌数(P<0.05),GSC-1还有效降低了稚参的弧菌数(P<0.05);潜在益生菌GSC-1和GSC-3均可显著提高稚参体组织中的酚氧化酶和溶菌酶活力(P<0.05),GSC-1亦显著提高了其酸性磷酸酶和超氧化物歧化酶活力(P<0.05);GSC-1和GSC-3处理组稚参的抗灿烂弧菌感染能力均高于对照组,其中GSC-3显著降低了灿烂弧菌攻毒后稚参的死亡率(P<0.05)。综上所述,潜在益生菌GSC-1和GSC-3对稚参期刺参安全无毒,能够促进稚参的健康生长并提高其抗病能力,因而GSC-1和GSC-3均可作为益生菌应用于稚参养殖中。     

三角帆蚌外套膜表达的免疫相关基因筛选

利用三角帆蚌(Hyriopsis cumingii)外套膜cDNA文库EST序列,通过BLAST分析注释基因功能,发现35个与免疫防御功能相关的基因。根据其功能,这些免疫相关基因可划分为7类,即细胞免疫过程(2个)、蛋白酶和蛋白酶调节子(9个)、压力蛋白(7个)、抗菌肽(5个)、溶酶体酶(2个)、粘着蛋白(3个)及细胞凋亡和细胞周期调控相关基因(7个)。免疫相关基因在三角帆蚌外套膜中的广泛表达表明外套膜是重要的免疫组织。该研究为三角帆蚌外套膜分子免疫机理研究和抗病育种工作提供了基础性资料。     

CD40 induces an antimicrobial response against the intracellular pathogen Streptococcus agalactiae in Nile tilapia,Oreochromis niloticus

Streptococcus agalactiae is a Gram‐positive facultative intracellular bacterium that leads to severe economic loss of tilapia worldwide. Previous studies demonstrated that CD40 contributes to host protection against intracellular injection. In this study, CD40 was characterized from Nile tilapia (Oreochromis niloticus), named OnCD40. Sequence analysis showed that open reading frame of OnCD40 was 933 bp, containing a single peptide, a transmembrane domain and four cysteine‐rich domains. The qRT‐PCR revealed that OnCD40 was expressed in all examined tissues with the most abundant ones in spleen and thymus. After S. agalactiae stimulation, the expression of OnCD40 was significantly induced in most of the detected organs. Moreover, OnCD40‐overexpressing fish elicited significant protection against subsequent S. agalactiae challenge; approximately 10000‐fold fewer bacteria were detected in spleen of OnCD40‐overexpressing fish in comparison with control fish. Thus, CD40 had protecting function in Nile tilapia against intracellular pathogens.     

绿色巴夫藻和米氏凯伦藻对3种常见抗生素胁迫的响应研究

在微藻培养过程中加入不同质量浓度抗生素,采用吸光度法测定其生长量。试验结果表明,氨苄青霉素、卡那霉素及链霉素质量浓度小于200μg/mL,对绿色巴夫藻生长有显著促进作用,其中氨苄青霉素质量浓度为200μg/mL、培养11d,生长量最高,为对照组的2.4倍;氨苄青霉素、卡那霉素及链霉素质量浓度为200μg/mL时,绿色巴夫藻的比生长速率分别高出空白对照组45%、83%及3.6%;高于此质量浓度,则表现出微弱抑制作用;氨苄青霉素、卡那霉素及链霉素质量浓度低于800、500、200μg/mL,对米氏凯伦藻有促进作用,其中卡那霉素质量浓度为100μg/mL、培养12d,生长量最高,超过对照组31%;氨苄青霉素、卡那霉素及链霉素质量浓度为800、500、200μg/mL,比生长速率高出空白对照组6.6%、43%及39%;高于此质量浓度,则表现出显著抑制作用;试验证实,氨苄青霉素与链霉素在一定质量浓度下可以促进藻体生长,高于一定质量浓度则表现抑制,不同藻类响应程度及阈值存在较大差异。     

Heritability estimates and response to selection for growth of Nile tilapia (Oreochromis niloticus) in low-input earthen ponds

This study presents results of two generations of selection (G₁ and G₂) for growth of Nile tilapia. The selection environment consisted of earthen ponds which were fertilized daily with 50 kg dry matter (dm)/ha chicken manure. No supplementary feeds were provided. In total, 6429 fully pedigreed experimental fish were included in the analysis. Survival till harvest was highly variable ranging from 35% to 77% and was affected by initial weight, pond, and age effects. Body weight at harvest (BW) increased from a mean of 67.4 g in the grandparental (unselected) population (G₀) to 129.5 g in G₂ was affected by initial weight, pond, sex and age effects. Generations were discrete and therefore genetic parameters were estimated separately for each year. Heritability estimates for BW ranged from 0.38 to 0.60, and the heritability for survival ranged from 0.03 to 0.14. The estimated selection response was 23.4 g (34.7%) between G₀ and G₁ and 13.0 g (14.9%) between G₁ and G₂. These results demonstrate the feasibility of selection for growth of Nile tilapia in low-input environments.