Ontogenetic development of digestive enzymes and effect of starvation in miiuy croaker <Emphasis Type="Italic">Miichthys miiuy</Emphasis> larvae

The ontogenetic development of the digestive enzymes amylase, lipase, trypsin, and alkaline phosphatase and the effect of starvation in miiuy croaker Miichthys miiuy larvae were studied. The activities of these enzymes were detected prior to exogenous feeding, but their developmental patterns differed remarkably. Trypsin activity continuously increased from 2 days after hatching (dah), peaked on 20 dah, and decreased to 25 dah at weaning. Alkaline phosphatase activity oscillated at low levels within a small range after the first feeding on 3 dah. In contrast, amylase and lipase activities followed the general developmental pattern that has been characterized in fish larvae, with a succession of increases or decreases. Amylase, lipase, and trypsin activities generally started to increase or decrease at transitions from endogenous to exogenous feeding or diet changes, suggesting that these enzymatic activities can be modulated by feeding modes. The activities of all the enzymes remained stable from 25 dah onwards, coinciding with the formation of gastric glands and pyloric caecum. These results imply that specific activities of these enzymes underwent changes due to morphological and physiological modifications or diet shift during larval development but that they became stable after the development of the digestive organs and associated glands was fully completed and the organs/glands functioned. Trypsin and alkaline phosphatase were more sensitive to starvation than amylase and lipase because delayed feeding up to 2 days after mouth opening was able to adversely affect their activities. Enzyme activities did not significantly differ among feeding groups during endogenous feeding; however, all activities were remarkably reduced when delayed feeding was within 3 days after mouth opening. Initiation of larvae feeding should occur within 2 days after mouth opening so that good growth and survival can be obtained in the culture.     

Histology of the developing digestive system and the effect of food deprivation in larval green sturgeon (Acipenser medirostris)

The histological development of the digestive tract in hatchery-reared green sturgeon (Acipenser medirostris) larvae and the effects of food deprivation on the digestive system organization were studied from hatching until 31 days post-hatching (dph). At hatching, the larval digestive system consisted of two rudiments: a large endodermal yolk sac and a primordial hind-gut. During the endogenous feeding phase, the wall of the yolk sac differentiated into the stomach (glandular and non-glandular regions) and the anterior and intermediate intestine, while the hind-gut primordium differentiated into the spiral valve and rectum. At the onset of exogenous feeding (15 dph at 16 °C), the organization and cytoarchitecture of the digestive system in green sturgeon larvae was generally similar to those of juveniles and adults. Larvae deprived of food exhibited a progressive deterioration, with subtle pathological changes observed after 5-d starvation: shrinkage of digestive epithelia, tissue degeneration, and necrosis were observed at 10–15 d of starvation (30 dph). No changes were observed in the mucous secretion of different regions of the digestive tract of food-deprived larvae. The histological analysis of the larval digestive system may be used to evaluate the nutritional condition of larval green sturgeon in their nursery habitats in spawning rivers, which are affected by dams and flow diversions.     

Ontogenetic Development of the Digestive System in Agastric Chinese Sucker,Myxocyprinus asiaticus,Larvae

This study was conducted to determine the ontogenetic development of the digestive tract and its accessory structures (liver, pancreas, and gall bladder) in agastric larval Chinese sucker Myxocyprinus asiaticus with the histological and ultrastructural approaches from hatching to 56 days after hatching (DAH). On the basis of its feeding mode, and analyzing the main histological features of the digestive system, larval development in Chinese sucker was divided into three stages from hatching: stage 1 (endotrophic period): 1–6 DAH; stage 2 (endoexotrophic period): 7–14 DAH; stage 3 (exclusively exotrophic period): from 15 DAH onward. At hatching, the digestive tract of the larvae consisted of an undifferentiated straight tube. At 4 DAH, the mouth opened, and the digestive tract was differentiated into buccopharyngeal cavity, esophagus and intestine. At 7 DAH, fish started to feed exogenously. Yolk sac was completely exhausted at 15 DAH. Until 56 DAH, the digestive tract of the larvae displayed regularly arranged microvilli, abundant vacuoles, and protein inclusion bodies. The pancreas, liver, and gall bladder were functional from 6 DAH, which enabled larvae to ingest, digest, and assimilate the first exogenous food. In comparison with teleosts that have a stomach, the development of the digestive tract of the agastric Chinese sucker seemed relatively slow .     

Organogenesis of the digestive system in Pacific red snapper (Lutjanus peru) larvae

This study reports the ontogenetic development of the digestive system of larval Pacific red snapper (Lutjanus peru), an important candidate species for aquaculture on the Pacific coast of Mexico. Histological sections of larvae were cut and dyed using the haematoxylin–eosin technique. The development of the digestive tract of Pacific red snapper larvae follows a general pattern of differentiation that can be divided into three stages. Stage I lasted from 1–3 days post hatching (DPH) and included the endogenous nutrition period; it was characterized by the initial differentiation of the digestive tract in preparation for the onset of exogenous feeding (3 DPH). At this time, the digestive tract was differentiated into buccopharynx, oesophagus, stomach anlage, anterior intestine, posterior intestine and a short rectum. The liver, pancreas and kidney were also present. The mouth and anus were open. Stage II occurred after first feeding, lasted for 16 days (4–23 DPH) and included both preflexion and flexion larvae. The main changes that occurred during this stage reflected the adaptation to exogenous feeding and the concomitant growth. Stage III (24–30 DPH) included post‐flexion larvae and started with the appearance of the gastric glands and pyloric caeca. The presence of the gastric glands suggests that early weaning during culture trials of the Pacific red snapper larvae may be possible at this early age.     

Histological evaluation of the elimination of Artemia nauplii from larval rearing protocols on the digestive system ontogeny of shi drum (Umbrina cirrosa L.)

The influence of the absence of Artemia nauplii from larval diet protocols on growth and digestive system ontogeny was studied using histological techniques in the shi drum (Umbrina cirrosa). One group of larvae was reared using the standard intensive rearing protocol, which offers a combination of enriched rotifers (Brachionus plicatilis), Artemia spp. nauplii and artificial diet (Std-group). Another group was reared using the same protocol, but without the offering of Artemia nauplii (group No-Artemia). The ontogenesis of the digestive system from hatching to metamorphosis was a very rapid process, and there were no differences between the two feeding regimes in the temporal appearance of the various components of the digestive system. The first organised presence of the hepatic and pancreatic tissue appeared at 2–3 d after hatching (dah), suggesting that these organs function from a very early developmental stage. In the No-Artemia larvae between 13 and 29 dah there was a reduction in the height of enterocytes in the intestinal mucosa, a progressive flattening of the primary intestinal folds in the anterior and posterior intestine and a decrease in lipid stores in the liver, suggesting a period of relative starvation. However, by the end of the study at 41 dah, there were no significant differences in body length, intestinal morphology or liver lipid stores between larvae reared under the two feeding regimes. The study suggests that the diet may influence the maturation and/or function, but not the ontogeny of the digestive system. Furthermore, the rapid differentiation of the digestive system in shi drum and the prompt recovery of the No-Artemia larvae from the symptoms of starvation by 29 dah, indicate a plasticity during ontogenesis and the ability of larvae to adapt to artificial diets at very early developmental stages.     

Ontogeny of the digestive tract in butter catfish Ompok bimaculatus (Bloch) larvae

The ontogeny of the digestive tract was studied histologically in butter catfish Ompok bimaculatus from hatching to 30?days post-hatching (dph). At hatching, the digestive tract of butter catfish consisted of a straight tube with a smooth lumen dorsally attached to the yolk sac. Between 1 and 2 dph, the mouth opened, oral valves were visible and canine-like teeth and taste buds were detected. During this period, intestine was differentiated into the anterior and posterior intestine, and the digestive accessory glands were also developed. Exogenous feeding started at 2?dph, and there was a 2-day mixed endogenous–exogenous feeding period. Most of the yolk sac reserves were consumed between 2 and 3 dph, and by 5?dph, the yolk sac was completely depleted and no longer visible in histological sections. Between 3 and 4 dph, several vacuoles (neutral lipids) were observed in the intestine and also in hepatocytes, indicating a functional absorption of nutrients from food. At 8 dph, differentiation of gastric glands was noticed, and by 9–11?dph, there were abundant gastric tubular glands arranged along numerous longitudinal folds. During the same period, pyloric sphincter appeared as an epithelial fold that separated the stomach from the anterior intestine. From 12 dph to the end of the study at 30?dph, no noticeable histological modifications were observed. The development of gastric glands is considered as the last major events in digestive tract development and their presence designates the end of larval period and the onset of the juvenile period. Hence, it is suggested that, butter catfish larvae have a morphologically complete digestive tract by 12?dph. These findings on the development of the digestive system in butter catfish may lead to a better understanding of the ontogeny and would be useful to improve the larval rearing techniques of this promising catfish species for freshwater aquaculture diversification.     

Histological study of the gastrointestinal tract in longfin yellowtail (<Emphasis Type="Italic">Seriola rivoliana</Emphasis>) larvae

This work contributes basic knowledge on larval development of Seriola rivoliana. A histological study describes the development of the digestive tract and accessory glands in S. rivoliana larvae reared under laboratory conditions at 24 °C from hatching to 30 days post-hatching (DPH). At hatching (2.6 ± 0.12 mm), larvae had an undifferentiated digestive tract with a closed straight tube and a large yolk sac with an oil globule. The liver and pancreas were observed at 1 and 2 days, and the mouth and anus opened at day 2. Enriched rotifers were visible in their digestive tract. At the beginning of the pre-flexion stage, a mixed nutritional period was observed. At day 3, exogenous feeding began; the digestive tract became differentiated into the buccopharynx, esophagus, an undifferentiated stomach, and the intestines. Zymogen granules were visible in the exocrine pancreas. At day 4, supranuclear vacuoles were present in the posterior intestine, indicating the beginning of intracellular digestion. At day 5, goblet cells were present in the esophagus and became functional at day 7 in the esophagus and intestine. The buccopharynx goblet cells developed at day 15. The presence of gastric glands and differentiation of the stomach in the fundic, cardiac, and pyloric regions during the post-flexion stage occurred at day 20. This was the onset of the juvenile period and the beginning of weaning; however, a long co-feeding phase is recommended. Pyloric caeca were observed at day 30 (13.6 ± 1.6 mm). These results provide valuable information on S. rivoliana larvae biology and digestive physiology, which should be useful to improve cultivation techniques and identify ecological features involved in ontogeny.     

褐菖鲉消化道的组织学和组织化学

褐菖鲉消化道的组织学和组织化学=Study on histology and histochemistry of digestive tract in Sebastiscus marmoratus[刊，中]/石戈（浙江海洋学院海洋科学学院，浙江 舟山 316004），王健鑫，刘雪珠，王日昕//水产学报.－2007，31（03）.－293～302 利用光镜技术对褐菖鲉消化道进行了组织学和组织化学研究。组织学研究表明：褐菖鲉消化道由口咽腔、食道、胃和肠4部分组成。口咽腔较大，上下颌，犁骨及腭骨均有细齿带,粘膜由复层鳞状上皮组成，并含有大量黏液细胞和少量杯状细胞；食道粗而短，上皮组织包括扁平上皮层区域和单层柱状上皮层区域，上皮含有大量杯状细胞和黏液分泌细胞，粘膜层的固有膜中含有腺体；胃呈Y型，包括贲门、胃体和幽门3个区域，胃粘膜由单层柱状上皮组成，在贲门和胃体部的粘膜层中有厚的结实层，上皮有大量的胃小凹和胃腺组织；胃幽门部括约肌明显，幽门上皮不含胃小凹；胃与肠相接处有8～9个指状幽门盲囊，其形态学和组织学特征与前肠类似；肠道上皮由单层柱状上皮细胞组成，丰富的微绒毛形成明显的纹状缘，上皮中含有大量杯状细胞，肠道系数为0.54。组织化学研究显示：幽门、幽门盲囊和肠上皮细胞顶端胞质和纹状缘具碱性磷酸酶活性；幽门盲囊及肠道上皮细胞顶端胞质中检测到酸性磷酸酶活性；在贲门部和胃体部的固有层以及幽门上皮还检测到酯酶活性，且酯酶定位于幽门柱状上皮细胞胞质的上半部。整个消化道的粘膜层中存在许多粘液细胞：食道上皮含大量酸性粘液细胞，胃上皮细胞均含有中性粘液，而肠道由前向后中性粘液物质逐渐减少，酸性粘液物质逐渐增多。组织学和组织化学的结果表明褐菖鲉食道有润滑和微弱的消化作用，胃有消化脂类和吸收糖类的功能；幽门和盲囊有较强的吸收脂类的功能；前肠、中肠和后肠有活跃的细胞内消化和吸收功能，整个消化道结构与其肉食性功能密切相关。图3参29     

Digestive enzyme activity at different developmental stages of blackspot seabream, Pagellus bogaraveo (Brunnich 1768)

Blackspot seabream, Pagellus bogaraveo (Brunnich), has been identified as a potential species to diversify European aquaculture production. Although rearing aspects have been widely investigated, little information exists on the nutritional requirements for this species. The aim of this study was to build up information on the activity of digestive enzymes at certain developmental stages of blackspot seabream in order to understand the nutritional needs of larvae and post larvae. Fish larvae were reared from hatching to 55 days after hatching (dah), and the feeding plan consisted in rotifers (5–35 dah), Artemia naupli (30–35 dah) metanaupli (35–45) and Gemma microdiet (45–55 dah). At 7, 11, 21, 45 and 55 days after hatching (dah), pooled samples of fish larvae were collected for analysis of trypsin, amylase, lipase, alkaline phosphatase and leucine–alanine peptidase activity. Up to 21 dah, the whole larvae body was used for enzymatic analysis, whereas in older larvae only the dissected abdominal cavity was used. Blackspot seabream body dry weight growth was exponential, increasing from 60 μg at 5 dah to 30±9.7 mg at 55 dah. Amylase specific activity decreased significantly during development, exhibiting at 11 dah (0.6 U mg^?1 protein) an average value 2.7 times lower than at 7 dah, and remaining stable between 45 and 55 dah (0.7 U mg protein^?1). Trypsin specific activity remained constant until 21 dah (between 38 and 44 mU mg protein^?1), which could be related to the larvae feeding regime. At later stages of development, lipase‐specific activity exhibited a significant increase (P<0.05), being three times higher at 55 dah (8 U mg protein^?1) than at 45 dah. The total activity of the studied digestive enzymes increased significantly during larval development (until 21 dah), whereas afterwards only lipase and leucine–alanine peptidase increased significantly between 45 and 55 dah. The pattern of digestive enzymes activity was related to organogenesis and the type of food used at different developmental stages.     

牙鲆消化道发育的组织学观察

牙鲆（Paralichthys olivaceus）肉质鲜美、营养价值高，是我国重要的海水养殖鱼类之一，同时，牙鲆二次变态显著，是研究硬骨鱼类变态发育很好的模式生物。在其变态过程前后，外型上最大的变化是其右眼的移位，内部器官如脑颅骨、骨骼肌等都发生结构和功能上的改变，而消化道的发育和分化，特别是其胃在变态前后有显著的变化。消化系统的发育关系到饵料的选择，与仔鱼成活率有直接关系，有较为重要的研究价值。[第一段]     

延迟首次投喂对乌江中华倒刺鲃仔鱼的补偿生长、消化酶活性及饵料日转化率的影响

为探究延迟首次投喂对乌江中华倒刺鲃(Spinibarbus sinensis)仔鱼补偿生长、消化酶活性及饵料日转化率的影响,对肠道贯通后的仔鱼进行了不同饥饿天数(H0、H1、H3、H5、H7、H9、H11)后补偿投喂17 d的实验。结果显示,全长和体重的损失率随饥饿时间的延长而增加。补偿投喂后,全长补偿率在H9组以后明显下降,体重补偿率在各实验组间无明显差异。各组全长和体重的特定生长率都呈波动性变化趋势,且实验后期各实验组都大于正常组都存在显著性差异。全长、体重及特定生长率的变化表明该饥饿仔鱼补偿投喂后能完成部分补偿生长。饥饿处理中,淀粉酶、碱性磷酸酶和胰蛋白酶随饥饿时间都呈下降趋势,脂肪酶呈先上升后下降趋势,补偿投喂后,除了淀粉酶呈先上升后下降外,其余三种酶都呈上升趋势。各组在饥饿处理下消化酶活性在实验后期与正常组存在显著差异,再投喂后与正常组差异不显著。各组在再投喂后的饵料日转化率随补偿时间呈不规则上升,但都无法恢复到正常投喂水平。综上,延迟首次投喂对中华倒刺鲃仔鱼补偿生长、消化酶活性及饵料转化都存在不同程度的影响。     

Ontogenetic development of digestive tract and digestive enzymatic activities in Squaliobarbus curriculus larvae

Squaliobarbus curriculus is an economically important freshwater fish. The ontogenetic development of the digestive system of S. curriculus larvae was studied histologically and enzymatically from hatching to 30 days posthatching (DPH). Amylase, lipase, alkaline phosphatase and pepsin activities were detected from the hatching stage, indicating that these enzymes were genetically preprogrammed. Marked increases in intestinal amylase, trypsin and alkaline phosphatase activities between 10 and 20 DPH corresponded to feed acquisition and transformation. Larval development in S. curriculus could be divided into three phases: phase I (endotrophic period): 1–3 DPH; phase II (endo‐exotrophic period): 4–5 DPH; and phase III (exclusively exotrophic period): from 6 DPH onward. At hatching, the digestive tract of the larvae was an undifferentiated straight tube. On 3 DPH, the digestive tract differentiated into the mouth cavity, oesophagus and intestine. On 6 DPH, feeding was totally exotrophic and the yolk sac was completely exhausted. During the growth of S. curriculus larvae, the intestinal mucosa formed and the number of goblet cells and microvilli increased, demonstrating maturation of the digestive system. The study about the digestive development of S. curriculus larvae will contribute to better larval‐rearing strategies.     

饥饿对星斑川鲽消化器官形态结构和组织学的影响

在温度(19±1)℃、盐度32±1的条件下,对相同规格体质量为(26.02±0.30)g的星斑川鲽(Platichthys stellatus)分别饥饿5、10、15 d(设为S5、S10、S15组),恢复投喂20 d。采用石蜡切片方法观察星斑川鲽消化器官形态结构,分析饥饿和再投喂对其组织学的影响。形态结构方面,S5组变化相对较小,而S10、S15组变化明显,表现在胃体积缩小,壁变薄;肠管壁变薄变透明,肠系膜因脂肪基本消失而萎缩;肝体积明显缩小,颜色由原来的粉红色变为深黄色。组织结构方面,S5组变化相对较小,而S10、S15组均有不同程度的损伤,表现在胃上皮细胞高度减小,细胞界限变得不清晰,胃腺细胞收缩,分泌颗粒减少;肠皱壁高度下降,上皮细胞高度显著降低,纹状缘高度减小甚至消失,杯状细胞有不同程度的增加;肝组织致密,肝细胞体积缩小,脂质空泡数量减少,细胞界限不明显,排列不规则,细胞内分泌颗粒减少。恢复投喂后,各实验组消化器官形态和组织结构均有不同程度的恢复,恢复投喂结束时,仅S5组恢复到对照组水平,S10、S15组均未达到对照组水平。结果表明,星斑川鲽饥饿耐受时间为5～10 d,超过此范围会对星斑川鲽消化系统组织结构造成不可修复的损害。     

Effects of delayed first feeding on larval growth,survival and development of the sea cucumber Apostichopus japonicus (Holothuroidea)

The time of first feeding is an important factor for establishing successful exogenous feeding in aquaculture hatcheries as it is crucial for larval survival and growth. The effects of delayed first feeding by the sea cucumber Apostichopus japonicus larvae were investigated. Groups of larvae were fed immediately after completion of the digestive tract (fed control) or starved for 24, 48, 72, 108 and 120 h post fertilization. The growth rates of A. japonicus larvae were the same as those of the control group when first feeding was delayed for less than 72 h. When the period of starvation was beyond 72 h, growth rates were reduced. The fed control group had the highest percentage of late auricularia larvae (70.0%) on day 11, followed by the groups starved for 24, 48, and 72 h, respectively, which had 35.00%, 43.48% and 41.67% of late auricularia larvae. When larvae were starved for more than 72 h, the percentage of late auricularia larvae never exceeded 12.0%. Most larvae halted in development and were deformed before reaching metamorphosis when starved for 108 and 120 h. Prolonged exposure to starvation (more than 48 h) resulted in a significant decrease in percentage of larvae reaching settlement. The point‐of‐no‐return (PNR) of A. japonicus larvae was calculated 110.4 h. Ratios of stomach length to total length, stomach width to total width were more sensitive to starvation than other larval morphometrics. To avoid mortality and obtain adequate growth and development, A. japonicus larvae in commercial culture should be fed within 48 h of the completion of the digestive tract.     

西伯利亚鲟消化道形态学和组织学的初步研究

对人工养殖2龄西伯利亚鲟消化道的形态解剖学和显微组织学结构进行了观察。研究结果表明,西伯利亚鲟的消化道从前至后分为口咽腔、食道、胃、幽门盲囊、十二指肠、瓣肠和直肠,食道与胃的分界不明显,形成一个"食道-胃过渡区",胃分为贲门部、胃体部和幽门部。组织学研究显示:西伯利亚鲟的消化道由内向外一般分为粘膜、粘膜下层、肌层和浆膜四层。其中食道粘膜上皮为复层扁平上皮,含杯状细胞和粘液细胞。"食道-胃过渡区"已有腺体存在。胃上皮细胞为单层柱状上皮细胞,无杯状细胞,胃的粘膜表面有许多上皮凹陷形成的胃小凹,幽门部的胃小凹较贲门部和胃体部深;贲门部和胃体部中含有大量的胃腺,幽门部无胃腺。幽门盲囊的管腔内被向内深入的肌层分割成许多完全或不完全的囊腔;粘膜褶皱和褶皱上的绒毛纵横交错,形成网状。肠上皮均为单层柱状上皮,上皮细胞间分布有大量的杯状细胞;粘膜褶皱的高度和数量、杯状细胞的数量从前至后递减:十二指肠粘膜褶皱细而高,上有许多绒毛;瓣肠粘膜和粘膜下层向管腔内突出并卷曲,形成螺旋瓣;直肠的粘膜褶皱矮且宽。     

The ontogeny of the alimentary tract during larval development in common pandora Pagellus erythrinus L.

The ontogenesis of the alimentary tract and its associated structures (liver, pancreas, gall bladder) was studied histologically in common pandora from hatching (0 DAH, days after hatching) until day 50 (50 DAH). Larvae were obtained by natural spawning from a broodstock adapted to captivity. They were stocked in 1500 l tanks supplied with Isochrysis galbana and Tetraselmis suecica from hatching until the Artemia feeding stage, at a temperature of 18.5–20 °C. Larvae were fed Selco-enriched Brachionus plicatilis from day 3, Artemia nauplii from day 28 and formulated feed from day 35. At hatching, the digestive tract was a histologically undifferentiated straight tube lying dorsally to the yolk sac. At first feeding (3–4 DAH) both the mouth and anus had opened and the digestive tract was differentiated into four portions: buccopharynx, oesophagus, incipient stomach and intestine. The pancreas, liver and gall bladder were also differentiated at this stage. Within 2 days after the commencement of exogenous feeding, the anterior intestinal epithelium showed large vacuoles indicating the capacity for absorption of lipids, whereas supranuclear ninhydrin-Schiff (NS) positive inclusions indicating protein absorption were observed in the posterior intestinal epithelium. Both the bile and main pancreatic ducts had opened in the anterior intestine, just after the pyloric sphincter, at this stage. Intestinal coiling was apparent since 4 DAH, while mucosal folding began at 10 DAH. Scattered PAS-positive mucous cells occurred in the oral cavity and the intestine, while they were largely diffused in the oesophagus. Gastric glands and pyloric caeca appeared at 28 DAH, indicating the transition from larval to juvenile stage and the acquisition of an adult mode of digestion.     

pH对大眼鳜和翘嘴鳜蛋白酶活性的影响

研究了不同pH值对大眼鳜消化道不同部位蛋白酶活性的影响及在最适pH条件下与翘嘴鳜消化道蛋白酶活力的差异。结果表明,大眼鳜消化道不同部位蛋白酶的活性强弱顺序为:幽门盲囊>胃>前肠>后肠,其最适pH分别是:10.4、2.8、9.5、10.1。翘嘴鳜的胃和幽门盲囊蛋白酶活力明显高于大眼鳜(P<0.01),而肠的蛋白酶活力略低,差异不显著(P>0.05)。     

大黄鱼消化道菌群结构、消化酶和非特异性免疫酶活力分析

为研究大黄鱼(Larimichthys crocea)消化道的菌群结构、消化酶和非特异性免疫酶活力特征,本研究采用高通量测序技术系统分析大黄鱼胃、幽门盲囊和肠道中菌群组成及分布,并对比研究工厂化养殖和网箱养殖模式下的消化道菌群;同时,结合生化分析方法解析2种模式下消化道消化酶和非特异性免疫酶活力特征。结果显示,2种养殖模式下,菌群多样性随消化道延伸呈下降趋势;乳杆菌科(Lactobacillaceae(f))、Fructobacillus、黄杆菌属(Flavobacterium)等代表的菌属为共有优势菌群。其中,拟杆菌属(Bacteroides)和Anaerostipes等的丰度随消化道延伸呈下降趋势,而乳杆菌科、E01_9C_26_marine_group(o)所代表的菌属及黄杆菌属等则相反;普氏菌属(Prevotella_9)、乳杆菌科代表的菌属为2种模式养殖大黄鱼的主要差异菌属。工厂化养殖条件下,幽门盲囊和肠道中的菌群组成及其参与营养和免疫相关代谢通路的基因数目差异不显著(P>0.05),但与胃部的菌群组成和相关代谢通路基因数目存在明显差异;而网箱养殖大黄鱼胃部与幽门盲囊和肠道的菌群结构及相关代谢通路基因数目差异相对较小。2种养殖模式下的大黄鱼消化道菌群与饲料菌群相近。另外,胃和幽门盲囊也具有非特异性免疫酶活性,说明,整个消化道还具有一定的化学免疫屏障作用。本研究结果将为大黄鱼健康养殖提供基础参考,并为消化道菌群生理功能探讨提供理论依据。     

Ontogeny of the digestive tract in mud loach Misgurnus anguillicaudatus larvae

This study on histological and mucous histochemistry characteristics of the digestive system of loach (Misgurnus anguillicaudatus) was carried out from hatching (0 day after hatching, DAH) until 45 DAH. The peculiar development of both digestion processes and air‐breathing functions of the intestine was revealed. At 3 DAH, both the mouth and anus opened along with the first feed. At 4 DAH, lipid vacuoles appeared in the anterior part of the intestine and at 5 DAH the acidophilic supranuclear vacuoles appeared in the posterior part of the intestine. Mucous cells occurred in the buccopharynx and oesophagus after mouth opening and grew both in number and size as larvae grew. At 15 DAH, blood capillaries were found in the posterior part of the intestine. At 20 DAH, as a valve appeared in the intestine, the whole intestine could be divided into anterior, mid and posterior parts. With large numbers of blood capillaries and a very thin wall, a gas–blood barrier formed in the posterior intestine, which indicated that the dual roles of intestine were formed. These results suggested that the air‐breathing function of the digestive tract formed from 15 to 20 DAH, which is a critical period for loach larvae.     

Development of digestive enzymes in larvae of Mayan cichlid Cichlasoma urophthalmus

The development of digestive enzymes during the early ontogeny of the Mayan cichlid (Cichlasoma urophthalmus) was studied using biochemical and electrophoretic techniques. From yolk absorption (6?days after hatching: dah), larvae were fed Artemia nauplii until 15?dah, afterward they were fed with commercial microparticulated trout food (45% protein and 16% lipids) from 16 to 60?dah. Several samples were collected including yolk-sac larvae (considered as day 1 after hatching) and specimens up to 60?dah. Most digestive enzymes were present from yolk absorption (5?C6?dah), except for the specific acid proteases activity (pepsin-like), which increase rapidly from 8?dah up to 20?dah. Three alkaline proteases isoforms (24.0, 24.8, 84.5?kDa) were detected at 8?dah using SDS?CPAGE zymogram, corresponding to trypsin, chymotrypsin and probably leucine aminopeptidase enzymes, and only one isoform was detected (relative electromobility, Rf?=?0.54) for acid proteases (pepsin-like) from 3?dah onwards using PAGE zymogram. We concluded that C. urophthamus is a precocious fish with a great capacity to digest all kinds of food items, including artificial diets provided from 13?dah.