Digestive proteinases and peptidases in the hepatopancreas of the southern brown shrimp (Farfantepenaeus subtilis) in two sub‐adult stages

The aim of this study was to examine proteinases and peptidases from the hepatopancreas of two sub‐adult stages of Farfantepenaeus subtilis: SAS₆ (5.93 ± 0.69 g wet weight) and SAS₁₃ (13.26 ± 0.60 g wet weight). Trypsin and chymotrypsin activity was higher in the extract from the SAS₆ individuals (P < 0.05). The highest activity among aminoacyl‐β‐naphthylamide substrates was found using alanine‐, arginine‐, leucine‐ and lysine‐β‐naphthylamide. There was a positive correlation between the recommended concentration of essential amino acids in penaeid shrimp feed and aminopeptidase activity in both sub‐adult stages. Proteolytic activity of F. subtilis was strongly inhibited by specific trypsin inhibitors. The optimal temperature for trypsin, chymotrypsin and leucine aminopeptidase activity was between 45 and 55 °C. Six and seven bands were found in caseinolytic zymograms for SAS₆ and SAS₁₃ respectively. All bands were inhibited by phenylmethylsulfonyl fluoride in both sub‐adult stages. The use of tosyl‐lysine‐chloromethyl‐ketone and benzamidine caused strong inhibition of the proteolytic bands. Trypsin and chymotrypsin activity was the main difference observed between the protease pattern of SAS₆ and SAS₁₃F. subtilis.     

Effect of dissolved oxygen and temperature on growth, survival and body composition of juvenile Farfantepenaeus californiensis (Holmes)

Survival, growth and proximal body composition of juvenile Farfantepenaeus californiensis (Holmes) were examined at two dissolved oxygen concentrations (mean 5.8 and 2.6 mg L^?1) and three temperatures (19 °C, 23 °C and 27 °C) for 50 days. Three replicate experiments were performed with a 12 h light/dark photoperiod. Survival was 68–85% at the lower dissolved oxygen level and 77–82% at the higher level and was not significantly affected by the treatments (P > 0.01). Growth at the lower oxygen concentration was significantly less (P < 0.01) than at the higher concentration, with growth rates of 2, 12 and 24 mg day^?1 from the lowest to the highest temperature and 4, 17 and 26 mg day^?1 for the three temperatures at the higher dissolved oxygen level. Body lipids were 1.2% wt/wt at the higher temperature and 2.1% wt/wt at the lower temperature, while proteins were 15.1% wt/wt at the higher temperature and 12.5% wt/wt at the lower temperature. These results indicate that low oxygen levels and low temperature significantly depress growth at this particular stage of life.     

Effect of salinity on growth, survival and oxygen consumption of juvenile brown shrimp, Farfantepenaeus californiensis (Holmes)

The brown shrimp, Farfantepenaeus californiensis (Holmes), is a species native to north‐west Mexico, where its culture potential is presently being addressed. Because of the climatic conditions prevailing in the region, salinities over 40 g L^?1 is a commonly encountered problem. In the present study, the effect of salinity on the growth and mortality of juvenile F. californiensis is described. The change in short‐term routine metabolism at different salinities was also evaluated in order to define the adaptive capacity of the shrimp and to provide insight into the changes in the pathways of energy distribution. Groups of shrimp were exposed to increasing salinity (25, 35, 45 and 55 g L^?1), and growth and survival rates after 75 days were determined in duplicate 1.8‐m³ tanks for each salinity level. Significant differences were found in final weight, growth rate and mortality of shrimp as a result of salinity level. Final mean shrimp weights at increasing salinity levels were 10.0, 9.4, 8.6 and 7.8 g. Corresponding mortality was 24.4%, 15.1%, 33.6% and 55.7%. Oxygen consumption was found to depend significantly on salinity and was equivalent to 0.0027, 0.0037, 0.0043 and 0.0053 mg g^?1 min^?1 respectively for the increasing salinities. The increased rate of oxygen consumption at high salinities reflects the response of the organism to osmoregulatory and ionic imbalances. Increased energy requirements to fulfil basic metabolic function as salinity increased resulted in a reduction in the energy that could be diverted to growth. Consequently, the culture of the brown shrimp at salinities over 35 g L^?1 would probably result in reduced yields.     

Digestive peptidases and proteinases in the midgut gland of the pink shrimp Farfantepenaeus paulensis (Crustacea, Decapoda, Penaeidae)

Proteases from the midgut gland of the Farfantepenaeus paulensis juveniles were assessed. Enzyme activity was determined using protease substrates and inhibitors. The effect of pH, temperature and calcium on proteolytic activity was assayed. Caseinolytic activity was analysed in substrate-sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Trypsin, chymotrypsin and leucine aminopeptidase activity was detected. Proteolytic activity was strongly inhibited by the specific trypsin inhibitors. Tosyl-phenylalanine chloromethyl ketone inhibited 59.3% of chymotrypsin activity. The greatest trypsin-like activity occurred at pH 8.0 and 45 °C. Chymotrypsin-like activity reached maximal values at alkaline pH (7.2–9.0) and 55 °C. CaCl₂ did not increase trypsin-like activity, but rather inhibited it at concentrations of 30 (20%), 50 (30%) and 100 mM (50%). The substrate-SDS-PAGE zymogram revealed eight proteinase bands. Two possibly thermal-resistant (85 °C, 30 min) chymotrypsin isoforms were found, which were inhibited by phenyl-methyl-sulphonyl-fluoride. Aminopeptidase activity of enzyme extracts (Arg, Leu, Lys, Phe and Val) and the recommended concentrations of these essential amino acids in penaeid shrimp diets were positively correlated ( P <0.05). Beause protein digestion involves the combined action of different enzymes, adequate knowledge of shrimp digestion and enzyme characteristics is required for the assessment of the digestive potential of different feed sources and development of in vitro digestibility protocols.     

方斑东风螺的耗氧率及饲养水中溶氧变化的初步研究

为对方斑东风螺养殖生产提供参考依据,试验测定了饥饿和饱食状态下方斑东风螺幼螺在不同水温(25℃、28℃、30℃)时的耗氧率,测定了幼螺摄食后水中溶解氧浓度的变化。结果表明,饱食后幼螺的生理代谢活动加强,耗氧率增加;随着水温的升高,耗氧率也增加。幼螺摄食后水中的溶解氧浓度随着时间的延长不断下降。试验观察发现,在方斑东风螺养殖的正常水温范围内(25℃~30℃),DO高于3mg/L时,幼螺生活正常;DO在2.40mg/L~2.35mg/L时,幼螺表现为缺氧状态;DO在1.5~1.0mg/L时,幼螺表现为严重缺氧状态。     

溶氧水平对黄颡鱼稚鱼摄食、生长及呼吸代谢的影响

在(28±0.5)℃循环水环境中设置4种溶氧水平,分别为2.92 mg/L(G1组)、4.71 mg/L(G2组)、6.77 mg/L(G3组)、9.68 mg/L(G4组),研究初始体重为(1.62±0.02)g的黄颡鱼(Pelteobagrus fulvidracoR.)稚鱼的生长、摄食及呼吸代谢规律。结果显示:G3组特定生长率(SGR)、饲料效率(FE)均显著高于其它各试验组(P<0.05)。试验鱼的耗氧率、排氨率与溶氧水平无正相关性,G3组的耗氧率、排氨率始终显著高于其它三组。第6周测定发现:摄食后1~4 h内耗氧率和排氨率均呈现迅速上升,到达最大值后再缓慢下降,二者均在09∶00和21∶00出现高峰,G3组的耗氧率高峰值分别为0.345、0.331 mg/g.h,G3组的排氨率高峰值分别为24.194、17.770μg/g.h。结果表明:不同溶氧条件下,黄颡鱼稚鱼的耗氧率、排氨率变化过程具有类似的特征,二者在能量代谢机制上相互关联;在6.77 mg/L的溶氧水平下,黄颡鱼稚鱼生长最快、呼吸代谢最为旺盛。     

Digestive enzyme activity and food ingesta in juvenile shrimp Litopenaeus vannamei (Boone, 1931) as a function of body weight

A study was conducted to evaluate variations of digestive enzyme activities in Litopenaeus vannamei (Boone) reared in commercial ponds under semi‐intensive conditions. Shrimp were collected at each body weight increase of 2 g. As the shrimp grew (2–12 g), significant increases in the activities of lipase and chymotrypsin were observed. The total protease activity decreased from 6 g onwards. Trypsin activity showed a peak at 6 g and amylase activity increased two‐fold after 2 g. Additionally, the stomach contents were analysed microscopically for shrimp between 2 and 10 g. Plant matter contributed above 30% of the total stomach content in 6‐, 8‐ and 10‐g shrimp. Detritus represented 58% and 62% of the total stomach content in 2‐ and 4‐g shrimp, respectively, decreasing to 33–43% at greater shrimp weights. Artificial feed showed a maximum contribution of 20% in 6‐g shrimp. The present results show changes in the enzyme activity after the shrimp reach 6 g in body weight, evidenced by a decrease in total protease and an increase in lipase and amylase activities. The amylase/protease ratio was 2.6 in 2‐g shrimp and increased steadily to 9.6 in 12‐g shrimp. These findings suggest an adaptation of the enzymatic activity to diets with lower protein content as body weight increases, and may be related to the variation of the different items found in the stomach.     

Growth and survival of the juvenile yellowleg shrimp Farfantepenaeus californiensis cohabiting with the green feather alga Caulerpa sertularioides at different temperatures

This study was performed to determine the growth and survival patterns of the juvenile yellowleg shrimp Farfantepenaeus californiensis cohabiting with the green feather alga Caulerpa sertularioides over a range of temperatures (18, 22, 25, 28 and 32°C) found throughout the year in the Gulf of California. From an initial weight of 46 ± 10 mg, shrimp cohabiting with green feather algae increased in weight by an average of 0.57 (±0.07), 5.44 (±0.45), 6.36 (±0.37), 7.66 (±0.26) and 5.96 (±0.59) g at 18, 22, 25, 28 and 32°C, respectively, whereas shrimp grown without seaweed increased in weight by an average of 0.28 (±0.026), 2.66 (±0.24), 3.15 (±0.49), 4.00 (±0.67), and 3.54 (±0.09) g respectively. Statistically significant differences were observed for the growth rates of juvenile yellowleg shrimp in the presence of C. sertularioides and peak growth was observed at 28°C in experiments with macroalgae. No significant differences were observed for shrimp survival except at 32°C without macroalgae, where survival was lower. These results suggest a beneficial and growth‐promoting effect of cohabitation with live C. sertularioides on F. californiensis.     

褐牙鲆幼鱼能量分配对限制溶解氧供应及恢复的响应

实验采用循环水养殖系统,通过水流量控制溶解氧供给,设计不同溶解氧供应和限制溶解氧供应及恢复两个实验来研究褐牙鲆(Paralichthys olivaceus)幼鱼生长及能量分配等指标的响应。在不同溶解氧供应实验中,溶解氧含量梯度设置为2.24 mg/L,3.14 mg/L,4.27 mg/L,5.38 mg/L,6.94 mg/L,实验结束时褐牙鲆幼鱼体重、日生长系数、摄食率、以湿重表示的饲料转化效率与溶解氧含量呈正相关(P0.05)。单尾鱼的摄食能随着溶解氧含量的下降而减少,生长能的比例在溶氧为5.38 mg/L时最高。排粪能的比例则随着溶解氧含量的下降而上升,排泄能比例随溶解氧含量下降也略有增加,代谢能的比例随着溶解氧含量的下降呈先下降后上升的趋势,在溶解氧含量为5.38 mg/L时最低(37.66%)。单位体重能量收支中,所有指标与溶解氧含量都有明显的正相关关系(P0.05),随着溶解氧含量的提高而显著提高。实验表明,低溶解氧含量下,褐牙鲆幼鱼通过减少能量供应降低摄食率和饲料转化效率,其生长受到抑制。在限制溶解氧供应及恢复实验中,经历10 d低溶解氧含量2 mg/L(S_2)和4 mg/L(S_4)胁迫的褐牙鲆幼鱼生长受到抑制,但在恢复正常溶解氧后10 d内体重即与对照组无显著差异(P0.05)。恢复期间褐牙鲆幼鱼的摄食率明显高于对照组(P0.05),饲料转化效率略高于对照组。恢复阶段不同处理在摄食能、生长能比例和呼吸能比例上没有显著差异(P0.05),但经历低溶解氧胁迫的处理摄食能和生长能比例略高于对照处理,而代谢耗能比例略低于对照处理。S2处理的排泄能比例显著低于其余2个处理(P0.05)。实验表明褐牙鲆幼鱼对短期低溶解氧含量有较强的适应能力,能够通过提高摄食率在较短的恢复期获得完全补偿生长。本研究揭示了褐牙鲆在低溶氧胁迫下的能量分配规律,为深入研究鱼类适应溶解氧波动环境的策略积累资料。     

水温、盐度和溶氧对红鳍东方鲀幼鱼游泳能力的影响

为了考查水温、盐度和溶氧对红鳍东方鲀(Takifugu rubripes)幼鱼游泳能力的影响,测定了其在不同水温[15.2、20.2、25.6(对照)和30.4℃]、盐度[0、10、20、32(对照)和40]和溶氧[2.14、4.10、5.81和7.36 mg/L(对照)]条件下的临界游速和最大游速。结果表明,水温和溶氧含量均显著影响实验鱼的临界游速和最大游速(P0.01)。随水温和溶氧含量升高,实验鱼的临界游速和最大游速均逐渐增加。水温(T,℃)与临界游速(U_(crit),cm/s)和最大游速(U_(max),cm/s)均呈二次函数关系,关系式分别为U_(crit)=-0.095T 2+5.450T-47.79,R~2=0.995(P0.01)和U_(max)=-0.018T 2+2.204 T-12.27,R~2=0.981(P0.01)。溶氧含量(DO,mg/L)与临界游速和最大游速也均呈二次函数关系,关系式分别为U_(crit)=0.230DO2+1.561DO+5.84,R~2=0.995(P0.01)和U_(max)=-0.806 DO2+11.10DO-3.919,R~2=0.985(P0.01)。不同盐度下实验鱼的临界游速和最大游速与对照组均无显著差异(P0.05)。结论认为,低温和缺氧会降低红鳍东方鲀放流苗种的游泳能力,进而降低其放流后的捕食成功率,提高被捕食概率。     

Different expressions of trypsin and chymotrypsin in relation to growth in Atlantic salmon (Salmo salar L.)

The expressions of trypsin and chymotrypsin in the pyloric caeca of Atlantic salmon (Salmo salar L.) were studied in three experiments. Two internal (trypsin phenotypes, life stages) and three common external factors (starvation, feeding, temperatures) influencing growth rates were varied. Growth was stimulated by increased temperature and higher feeding rate, and it was depressed during starvation. The interaction between trypsin phenotype and start-feeding temperature affected specific activity of trypsin, but not of chymotrypsin. Trypsin specific activity and the activity ratio of trypsin to chymotrypsin (T/C ratio) increased when growth was promoted. Chymotrypsin specific activity, on the other hand, increased when there was a reduction in growth rate whereas fish with higher growth had higher chymotrypsin specific activity resulting in lower T/C ratio value. During a rapid growth phase, trypsin specific activity did not correlate with chymotrypsin specific activity. On the other hand, a relationship between specific activities of trypsin and chymotrypsin could be observed when growth declined, such as during food deprivation. Trypsin is the sensitive key protease under conditions favouring growth and genetically and environmentally affected, while chymotrypsin plays a major role when growth is limited or depressed. Trypsin specific activity and the T/C ratio value are shown to be important factors in the digestion process affecting growth rate, and could be applicable as indicators for growth studies of fish in captive cultures and in the wild, especially when food consumption rate cannot be measured.     

水口水库养殖库湾季节性低溶解氧成因浅析

本文通过对水口水库雄江、湾口、樟湖等库湾养殖水体特点的监测分析,总结了水口水库养殖库湾水体发生低溶解氧的规律,并对低溶氧的产生的原因进行初步分析。本文认为低溶解氧产生的主要原因为:1.养殖库湾水体不分层;2.夏季水温高;3.泄洪引起的还原性物质耗氧是低溶氧死鱼事件的诱因。     

紊动对水体过饱和溶氧释放的影响初探

为探究紊动对水体中溶氧释放的促进效果,设计以潜水泵排水的方式,开展了不同水泵数量、功率、摆放方式、排水方向等工况下过饱和溶氧释放过程研究试验。结果表明,紊动对水体中溶氧释放有较好的促进效果。放入5个泵(功率20 W、纵向排水)时,水体溶氧释放系数为0.514 h~(-1),是未放入水泵时溶氧释放系数0.026 h~(-1)的19.77倍。当水泵垂直于水面排水时,溶氧释放效果较好。水泵个数越多、功率越大,溶氧释放系数越大,溶氧释放效果越好。     

曼氏无针乌贼对溶解氧耐受力的研究

在封闭的容器内,设置不同的温度梯度,进行不同规格的曼氏无针乌贼对溶解氧耐受力的实验.采用隔膜法检测实验过程中不同阶段的溶解氧,及结合乌贼养殖生产实际情况,研究其对溶解氧耐受情况.结果表明曼氏无针乌贼耗氧率与水温成正比例关系、与个体体重成反比例关系,耗氧率为146.0～431.4mg/kg·h-1,窒息点为1.96～3....     

基于STM32的溶氧监测仪设计

为解决海上浮标溶氧传感器存在功耗大、标定复杂等问题,研究设计了一种基于STM32的低功耗、高性能溶氧监测仪,并针对海上浮标提出红外标定设计,实现溶氧传感器的自动标定。利用单电源数据采集电路结合STM32多通道ADC,精确计算出溶氧值;利用STM32的输入捕获功能解码红外遥控信号,实现电压-溶氧曲线的斜率标定,最大程度避免因溶氧标定而频繁拆卸,造成浮标体内部密封性变差的风险;省电模式满足低功耗的要求,可以提高蓄电池的供电时长;集成MODBUS协议的RS485端口可实现远程通信,为远程监测打下基础。结果表明,溶氧监测仪采集精度较高,能在无光照情况下连续运行5~6 d。该设计可以提高海上浮标的稳定性和密封性,为工作人员提供了极大的便利,具有成本低、体积小、便于安装等优点。     

Influences of dissolved oxygen on juvenile largemouth bass foraging behaviour

Summer stratification often leads to large areas of hypolimnetic hypoxia in lakes and reservoirs. These areas of hypoxia alter fish behaviours and distributions as well as restrict access to valuable prey resources, yet few studies have examined foraging behaviour of fish in response to low dissolved oxygen (DO) concentrations. We observed foraging behaviour of juvenile largemouth bass, Micropterus salmoides, in response to varying DO concentrations in tanks that simulated a stratified lake water column during the summer: 28°C oxygenated epilimnion, 15°C deoxygenated hypolimnion. Compared with saturated concentrations (8.0–9.0 mg/L), hypolimnetic oxygen concentrations of 3.0 mg/L and 1.5 mg/L resulted in a drastic decrease in prey consumption, handling efficiency and time spent below the thermocline mainly due to avoidance behaviour of hypoxic conditions. However, we found at high hypolimnetic prey densities, individual fish were more willing to venture into reduced oxygen concentrations. Several unique behaviours including transporting prey above the oxycline for consumption, aquatic surface respiration and gill flaring were employed by largemouth bass foraging in low oxygen environments. Reduced hypolimnetic oxygen concentrations may influence and alter feeding strategies, especially for fish that rely on benthic prey resources.     

气升式光生物反应器培养微藻溶氧和pH值变化规律研究

为了解决在光生物反应器养殖微藻过程中,溶解氧和pH值2个培养工艺参数的控制问题,分别在80 L、350 L和900 L的3种规格气升式光生物反应器中培养湛江等鞭金藻(lsochrysis zhanjiangensis),高藻细胞浓度分别达到900×104,700×104,500×104cell/mL,测定其中溶氧和pH值的日变化。结果显示,在光照度4 000 lx以上时,湛江等鞭金藻光合作用强,表现为反应器中藻液溶氧较高,日最高溶氧分别可达17.91 mg/L、15.84 mg/L和12.7 mg/L。所测定的藻液日pH值均在7.00~9.16变化。