胚后发育阶段军曹鱼生长和蛋白酶活性的初步研究

研究了军曹鱼胚后发育阶段不同日龄生长情况及蛋白酶活力的变化,包括胚后发育不同阶段消化酶活力最适pH的变化及昼夜变化.结果表明,军曹鱼仔、稚鱼的全长、体重与日龄之间呈幂函数相关;在胚后发育过程中,蛋白酶活力虽有波折,但整体不断增大;蛋白酶在7日龄出现1个低谷,应是一个饵料转换的关键时期.军曹鱼胚后发育不同阶段消化酶活力的昼夜变化,显示其稚鱼和幼鱼白天的蛋白酶活力远大于夜间且出现多个峰值,与其摄食情况存在一致,稚鱼和幼鱼蛋白酶都在12:00前后出现最高峰.在军曹鱼胚后发育不同阶段,鱼苗的蛋白酶最适pH值从仔鱼期的6.4逐渐升高到幼鱼期的7.5.     

大口黑鲈开口摄食与转食人工配合饲料期消化系统发育特征

本研究利用组织切片和扫描电镜技术,观察和研究了2~30日龄大口黑鲈(Micropterus salmoides)仔鱼消化系统的发育过程及组织学变化。结果显示,在水温为(23±1)℃条件下,0~4日龄仔鱼消化道初步分化,为内源性营养期;4~6日龄仔鱼消化道逐渐分化形成食道、胃和肠,胃和肠黏膜褶形成,肝胰脏细胞团出现,仔鱼具备基本摄食能力,进入混合性营养期;10~16日仔鱼消化道和消化腺结构分明,胃、幽门盲囊、肠道紧密排列,肝脏和胰脏独立,进入外源性营养期,此阶段后可逐步转食人工配合饲料。20~30日仔鱼胃腺发达,胃和肠道出现次级黏膜褶,幽门盲囊黏膜褶显著增多、增长,肝脏逐渐出现脂肪积累区,胰脏可见酶原分泌颗粒,肝胰脏组织结构近似成鱼。扫描电镜显示,30日仔鱼胃部内表皮具有丰富的网状黏膜褶,胃小凹间分布着密集的分泌孔;幽门盲囊和肠道内表面结构相似,无固定形态的黏膜褶上布满黏液细胞和分泌孔。20日龄后仔鱼具备转食人工配合饲料的能力。此外,在仔鱼开口和转食人工配合饲料过程中,部分死亡个体的胃肠组织表现出腔体扩大或皱缩,内表皮无成型的黏膜褶或黏膜层脱落,胃和肠道组织损伤。本研究可为大口黑鲈仔鱼开口和转食人工配合饲料条件的优化提供组织学基础资料。     

灰鲳仔稚鱼消化系统的发育

对出膜后1~35 d灰鲳仔稚鱼的消化系统进行了形态学和组织学观察。初孵仔鱼具有很大的卵黄囊,消化管为一简单的直形盲管。2日龄仔鱼消化系统中肠区首先开始分化,内面可见纹状缘。3日龄仔鱼胃区膨大,卵黄消失,肠道分化出小肠和直肠。侧囊在4日龄仔鱼时出现分化。5日龄仔鱼观察到幽门盲囊的初始结构,油球消失,从内源性营养向外源性营养过渡基本完成。6日龄仔鱼摄食主动。14日龄稚鱼肝脏分为两叶,体积增大,胰脏体积增大,胃弯曲呈"U"形,幽门盲囊指状分支已增加到几十个。22日龄稚鱼肠道弯曲更多,在胸腹腔中肠道盘曲程度已接近幼鱼。28日龄稚鱼侧囊背腹形成一纵隔,出现角质剌。35日龄稚鱼胃腺已十分丰富,侧囊结构也已完善,标志着灰鲳消化系统更趋完善。     

齐口裂腹鱼仔鱼饥饿试验及不可逆生长点的确定

水温17.3～21.5℃,取刚孵出的同一批齐口裂腹鱼仔鱼,暂养于2.0 m×0.8 m×0.6 m玻纤缸中,养殖到5日龄、即开口前1 d时,将仔鱼随机分为A、B、C 3组,每组500尾。6日龄A组试验鱼开口投喂,B组和C组不投喂,研究饥饿胁迫对齐口裂腹鱼仔鱼生长、发育、存活、卵黄囊吸收、摄食率及摄食强度的影响,确定齐口裂腹鱼仔鱼的不可逆生长点,即仔鱼初次摄食率低于最高初次摄食率50%时的日龄。试验结果显示,饥饿对齐口裂腹鱼仔鱼全长、体长、体高、肛前长等生长指标具有极显著影响(P0.01),对眼径、鳔等组织器官发育具有明显影响;齐口裂腹鱼仔鱼混合营养期为7 d;齐口裂腹鱼仔鱼初次摄食率约为15%,第13～14日龄仔鱼的初次摄食率达到最高值100%,17日龄仔鱼到达不可逆生长点;齐口裂腹鱼饥饿组仔鱼50%累计死亡率出现日龄为19日龄,在饥饿不可逆生长点之后。试验结果表明,齐口裂腹鱼仔鱼具有较强的饥饿耐受能力,齐口裂腹鱼最佳投喂时间为9日龄,最晚开口时间不晚于14～15日龄。     

暗纹东方鱼屯仔鱼期消化系统的组织学研究

对出膜后1～18 d的暗纹东方鲀仔鱼的消化系统进行了形态学和组织学观察.当水温为23℃时,6日龄仔鱼的上下颌已形成,开始摄食;12日龄仔鱼的卵黄囊已被吸收,此时仔鱼由混合性营养转向外源性营养.描述了消化系统发育过程的组织学结构特征,并采用图像分析比较了卵黄囊与消化器官发育的消长过程.     

暗纹东方鲀仔鱼期消化系统的组织学研究

对出膜后1～18d的暗纹东方鲀仔鱼的消化系统进行了形态学和组织学观察。当水温为23℃时，6日龄仔鱼的上下颌已形成，开始摄食；12日龄仔鱼的卵黄囊已被吸收，此时仔鱼由混合性营养转向外源性营养。描述了消化系统发育过程的组织学结构特征，并采用图像分析比较了卵黄囊与消化器官发育的消长过程。     

军曹鱼仔稚鱼脊柱和附肢骨骼的发育特征

为探明军曹鱼仔稚鱼早期脊柱及附肢骨骼的发育特征,本研究采用软骨-硬骨双染色技术,分别利用阿利新兰、茜素红对软骨、硬骨以及1～33日龄军曹鱼仔稚鱼全骨骼进行染色,系统观察并描述其脊柱和附肢骨骼的发育特征。结果显示,军曹鱼脊柱开始发育的标志为7日龄仔鱼中脉弓和神经弓的出现;13日龄稚鱼椎骨、神经弓和脉弓开始骨化;背肋、腹肋分别于17、20日龄开始骨化;29日龄稚鱼脊柱骨化完成。附肢骨骼骨化起始顺序依次为胸鳍、尾鳍、腹鳍、背鳍和臀鳍。胸鳍匙骨于4日龄出现,肩胛骨孔于12日龄出现,同时上匙骨开始骨化;乌喙骨与肩胛骨于20日龄开始骨化;第1尾下骨于5日龄出现,15日龄稚鱼尾杆骨、侧尾下骨和尾鳍鳍条开始骨化,18日龄稚鱼尾下骨开始骨化;腹鳍支鳍骨于17日龄延伸至匙骨,同时腹鳍开始骨化;臀鳍和背鳍于17日龄由前向后开始骨化。研究表明,军曹鱼在13日龄进入稚鱼期,早期发育阶段的骨骼发育特征与其功能性适应密切相关。本研究结果对研究军曹鱼早期骨骼发育与功能适应、优化养殖条件有重要作用。     

半滑舌鳎消化系统器官发生的组织学

利用形态学和连续组织切片技术,对出膜后1～30d的半滑舌鳎消化系统胚后发育的组织形态学进行了系统观察和研究。研究表明,试验水温为20．0～22．0℃时,孵化后第3天,仔鱼开口摄食,消化道上皮细胞出现分化,肝脏和胰脏开始出现,鱼体开始由内源性营养转向外源性营养。孵化后第5天,卵黄囊完全被吸收,消化道明显分化成口咽腔、食道、胃、前肠和后肠,仔鱼消化系统具备了摄食和消化外源性食物的能力。此后随着鱼体的生长,粘膜层的褶皱增加,消化道上皮细胞进一步分化,肠道分段、盘旋,消化系统从功能和结构上逐步地完善成熟。开口摄食之后,先后发现在后肠出现嗜曙红颗粒,在前肠出现空泡,表明肠上皮细胞吸收了蛋白质和脂肪。继而糖元在肝脏中不断地储存。在出膜后第23天,出现胃腺,标志着稚鱼期的开始。     

高体革鯻消化道发生的组织学观察

利用形态学和连续组织切片技术,对出膜后1～30d的高体革(鱼刺)消化系统胚后发育的组织形态学进行了系统观察和研究。结果表明,培养水温在26.6～29.7℃条件下,高体革(鱼刺)初孵仔鱼消化管为一柱形盲管,管腔狭窄,口、肛门尚未与外界接通。出膜30h仔鱼,口开始张开,消化管相通。出膜2d仔鱼肠壁出现皱褶,肠瓣将肠道分为前肠和后肠,在显微镜下可见消化管蠕动。出膜3d仔鱼可以开口摄食,消化管上皮分化,食管中出现黏液细胞,肝脏和胰脏出现,鱼体由内源性营养转入混合营养阶段。混合营养阶段仔鱼消化道明显分为口咽腔、食道、胃、前肠、直肠等,消化腺肝脏和胰脏也已形成,各部分已经有初步结构和一定的消化吸收能力。随着仔鱼的发育,仔鱼消化系统各器官也趋于完善。出膜21d稚鱼的胃壁出现胃腺,标志着稚鱼期开始。     

投喂卤虫无节幼体条件下黄颡鱼仔稚鱼生长、存活率、摄食力和体成分的变化

试验分析了投喂卤虫无节幼体条件下黄颡鱼(Pseudogrus fulvidraco)仔稚鱼生长、存活率、摄食力和体成分的变化。随着仔稚鱼的生长和发育,摄食率和胃充塞度逐渐加大,体长大于10 mm的仔鱼,摄食率都在93.3%以上,大多数个体胃充塞度都在3～5级。投喂卤虫无节幼体的黄颡鱼仔稚鱼生长较传统育苗方式生长快,存活率高。体内粗养分、氨基酸与脂肪酸含量都发生相应变化。黄颡鱼淀粉酶、蛋白酶与脂肪酶活性均在1日龄时即可检测到,开口期即5日龄时,3种消化酶比活力均达到较高值,15日龄后消化酶比活力又都降低到较低水平。卤虫无节幼体体内营养物质含量丰富,大小适口,是黄颡鱼仔稚鱼开口摄食的优质生物饵料。     

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.     

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.     

军曹鱼消化系统的形态及组织学研究

利用活体解剖和光镜技术对军曹鱼Rachycentron canadum消化系统进行形态及组织学研究。结果显示，军曹鱼消化道由口咽腔、食道、胃、幽门盲囊、前肠、中肠和后肠几部分组成。口咽腔大，粘膜上皮为复层鳞状上皮，内含少量杯状细胞。食道很短，但上皮包括复层鳞状上皮区和单层柱状上皮区。胃膨大，呈Y形，在贵门和幽门部可观测到杯状细胞，胃体粘膜层下有大量的胃腺细胞。幽门盲囊发达，肠短但分3部分，前肠、中肠和后肠，肠道系数为0．43，肠道由前向后杯状细胞和粘膜皱褶不断减少。消化腺包括肝脏和胰腺，肝小叶分界不明显，肝细胞内脂肪含量丰富，胰腺属于散在性的，其外分泌部有许多腺泡组成，胰岛分散于外分泌部间。     

斜带石斑鱼消化系统胚后发育的组织学研究

利用形态学和连续组织切片技术，对出膜后1-60d的斜带石斑鱼各期仔鱼、稚鱼和幼鱼的消化系统进行了光镜观察，描述了其消化器官发育过程和组织学特性。研究表明，实验水温为22.0-27.8℃时，孵化后第4天，上下颌形成，卵黄囊被吸收，消化系统明显分化成食道、胃、肠、直肠以及肝脏、胆囊和胰脏等，鱼体由内源性营养转向外源性摄食营养，表明其消化系统的形态变化与食性的变化相适应。此后随着鱼体的生长，其消化系统从功能和结构上逐步完善成熟。胰脏在出膜后第4天出现，是和肝脏相互分开的一个独立的器官，但是发育到第35-60天，位于肠道后部的胰脏组织内出现许多大空泡。     

Activities of digestive enzymes and histology of digestive system during larval development of devil stinger (Inimicus japonicus)

Devil stinger is a valuable demersal scorpaenid fish while the rearing of stinger larvae still relies on live prey. This study was conducted to illustrate the development of the main digestive enzymes and digestive system during larval development of this species to provide evidence for the application of artificial feeds. Enzymatic and histological assays were conducted from 1 day post hatching (dph) to 36 dph in larvae. The result showed that the selected digestive enzyme activities increased significantly after 15 dph. Specifically, the total trypsin activities increased significantly from 18 dph to 33 dph. The total pepsin and amylase activities increased significantly first and thereafter decreased significantly. The lipase activities followed the similar pattern with trypsin. With regard to the histological study, the stinger larvae open their mouth to first feeding at 3 dph and turned into totally exogenous nutritional stage at 6 dph. In addition, mucous membrane, rich in goblet cells, was widely distributed in oesophagus epithelium at 18 dph. The height and amounts of gastric gland in cardia and main body of the stomach increased gradually with the development of stinger larvae after 15 dph. The intestine length of stinger larvae was short, and goblet cell was abundant in anterior intestine after 12 dph, not the posterior intestine. The ontogeny of liver and pancreas started from newly hatched stage, and the differentiation of liver was prior to pancreas. The above findings would provide evidence for the use of artificial feeds from the larval stage of stinger larvae (at least from 21 dph).     

Morphological and histological changes in digestive tract development during starvation in the miiuy croaker

A histological method was used to describe the ontogenetic development of the digestive tract of laboratory-reared miiuy croaker (Miichthys miiuy) and to evaluate the effects of short-term food deprivation on the morphology and histology of the digestive tract. Larvae and juveniles were maintained at 24 °C in a thermostatically controlled system. Three starvation experiments were conducted during different developmental stages: 1–7 days after hatching (dah; prior to benthic swimming); 26–35 dah (during settling); and 42–53 dah (after benthic swimming). According to the structural changes in the ontogenetic development of the digestive tract, three stages were observed. The first stage was from hatching to 3 dah; the digestive tract was undifferentiated in newly hatched larvae and then showed remarkable morphological changes and differentiation. During this period, larvae depended on endogenous nutrition. The second stage (4–20 dah) was a critical period in which larvae transitioned from endogenous feeding to exogenous feeding and the digestive tract fully differentiated into the buccopharynx, oesophagus, stomach, anterior intestine and posterior intestine. Goblet cells and vacuoles appeared in the digestive tract, and pharyngeal teeth and taste buds developed. During the third stage (20–36 dah), the gastric glands developed and the stomach differentiated into the fundic, cardiac and pyloric regions. At 25 dah, pyloric caeca developed and mucosal folds and spiral valves were clearly distinguishable. After 30 dah, the digestive tract did not undergo any noticeable differentiation, indicating the complete development of the digestive system. The wet weight and SGR (specific growth rate) of miiuy croaker larvae and juveniles greatly decreased when they were deprived of food, and compensatory growth was observed in re-feeding juveniles. The livers of starved larvae and juveniles were atrophied and dark coloured, the intestines were transparent and thin, and the stomach cubages were reduced. The histological effects of starvation were mainly evident in the degeneration of cells in digestive organs, as seen in the shrinkage and separation of cells and the loss of intercellular substances in the liver, pancreas, intestine and stomach. These changes became more severe with increased duration of starvation. In addition, the histological structure of the digestive tracts of starved larvae and juveniles partly recovered after re-feeding, and the effects of starvation on miiuy croaker were age dependent.     

鲇仔、稚鱼消化系统胚后发育的组织学观察研究

通过石蜡包埋切片法对鲇(SilurusasotusL.)仔、稚鱼消化系统胚后发育进行了较系统的组织切片观察。本研究描述了全长5.0～22.5mm的鲇摄食器官、消化器官胚后发育的组织学结构特征。观察发现,1～3日龄为内源性营养阶段,卵黄囊很大,2日龄消化道出现裂缝状腔隙,3日龄基本贯通但未开始摄食;4～6日龄为混合营养阶段,卵黄囊被逐步吸收,主要靠吞食轮虫、小型枝角类等为食;6日龄以后卵黄囊消失,进入外源性营养阶段,捕食能力增强。观察还发现,鲇前咽顶壁始终平直无粘膜皱褶;颌齿和咽齿为斜生尖锥状的同型齿,数量多、排列紧密,与相应的骨骼牢固地骨性固着;后咽、食道的粘膜上皮内粘液细胞极多,深层结缔组织肌肉层发达。这些构造适应于鲇的完全吞食摄食方式。胃腔小,前肠膨大、中肠粘膜上皮细胞纹状缘发达,肝脏和胰脏发育速度较快。胃的消化功能较弱,主要储存、消化场所为前肠,吸收场所在中肠。鱼苗4～6日龄下塘适宜,6～8日龄可开始诱其摄食人工饲料。     

美洲黑石斑鱼(Centropristis striata)消化系统胚后发育的组织学观察

通过形态学与连续组织切片的方法,对美洲黑石斑鱼(Centropristis striata) 1-34 d仔鱼消化系统的胚后发育进行系统观察,分析描述鱼体消化道(食道、胃与肠道)以及消化腺(肝脏与胰腺)的发育过程.对1-15 d仔鱼连续取样,每次取样30尾,15 d后隔天取样,每次取样15尾.结果显示,在水温为(24±1)℃、盐度为30-32的条件下,初孵仔鱼卵黄囊体积很大,消化管为封闭的管状结构.美洲黑石斑鱼孵出3d后,口裂形成、开始摄食,肛门与外界连通,消化道逐渐分化形成食道、胃及肠道,肝脏、胆囊和胰腺也逐渐形成.7d后,卵黄囊与油球基本消失,食道、胃部以及肠道黏膜褶皱开始形成,消化道黏膜上皮细胞逐渐分化,肝脏出现脂肪颗粒,仔鱼具备了基本的摄食能力.11d时,仔鱼食道可见黏液细胞,随日龄的增加上皮组织中黏液细胞数量迅速增多,褶皱日益丰富;胃部分化形成贲门部、胃本体与幽门部,胃壁褶皱不断增多、伸长;肝脏血窦与中央静脉明显.20d时,鱼体胃腺形成,说明胃部消化、吸收蛋白质的能力增强;肠道次级黏膜褶皱出现,肠圈与褶皱更加复杂化;胰脏分布有大量酶原颗粒.32 d时,仔鱼消化道组织结构分明,自腔面向内依次为黏膜层、黏膜下层、肌层与浆膜层,消化道与消化腺结构和功能逐步完善.仔鱼3-7 d为内源性营养向外源性营养过渡期,应及时提供充足适口的生物饵料,仔鱼20 d后可以逐渐驯化投喂微型配合饲料.     

Precocious development of the digestive system in relation to early appearance of piscivory in striped bonito Sarda orientalis larvae

ABSTRACT: Striped bonito Sarda orientalis larvae and juveniles were reared in a laboratory from hatching to 14 days post hatching, and the development of their digestive system was investigated histologically. On day 2 (first feeding day), the larval-type digestive system was differentiated. On day 3, a blind sac with densely distributed gastric glands developed and pyloric ceca appeared, suggesting that the digestive system was attaining adult-type structure. The yolk was completely absorbed on day 4. Bonito larvae preyed on rotifers and/or Artemia nauplii on day 2, but almost the whole gut was occupied by fish larvae from day 4. In the striped bonito, the adult-type digestive system was established right after first feeding, and this precocious development was well synchronized with the appearance of piscivory.     

Ontogeny of the digestive tract in shi drum (Umbrina cirrosa L.) reared using the mesocosm larval rearing system

Histological changes of the digestive tract were studied in shi drum (Umbrina cirrosa) from hatching until 41 days post hatching (dph), when the fry had a mean (±S.D.) total length (TL) of 32 ± 2 mm and wet weight (WW) of 0.42 ± 0.07 g. Larvae were reared using the mesocosm technique, the most natural among commercially employed rearing methods for marine larvae. Shi drum opened their mouth at 2 dph (2.78 ± 0.09 mm TL), at which time 90% of the larvae already had an inflated swim bladder. The differentiation of the digestive tract into buccopharynx, esophagus, and anterior and posterior intestine was completed by 3 dph (2.82 ± 0.07 mm TL), 1 day after the onset of exogenous feeding. The alimentary canal started coiling and formed its first loop at 2 dph, while the pancreas and liver were differentiated at 3 dph. Yolk sac reserves lasted until 7 dph (4.3 ± 0.1 mm TL), suggesting a brief period of endogenous and exogenous feeding. The first esophageal goblet cells appeared at 7 dph containing acid mucins and at 8 dph taste buds appeared on the buccopharyngeal epithelium. The stomach was morphologically differentiated at 9 dph (5.5 ± 0.1 mm TL) when gastric glands became abundant in the cardiac region, and the first pyloric caeca appeared at 14 dph (10.1 ± 0.9 mm TL). Supranuclear eosinophilic vacuoles were observed in the posterior intestine between 3 and 11 dph (6.3 ± 0.9 mm TL). Their number decreased as the stomach differentiated, suggesting a change in the protein digestion mechanism. The results of the study suggest a rapid development of shi drum and its digestive system and underline the possibility of weaning larvae to artificial feed even earlier than the 12 dph employed in the present study.