线纹尖塘鳢仔、稚鱼的形态发育

对池养条件下线纹尖塘鳢(Oxyeleotris lineolatus)的胚后发育进行定期观察,胚后发育大致可分为前期仔鱼、后期仔鱼、稚鱼和幼成鱼期。观察发现,线纹尖塘鳢的初孵仔鱼个体较小,仅2.875mm,前期仔鱼,包括混合营养仔鱼期,时间短,仅为5d,属较早建立起外源性营养摄食机制的鱼类;器官发育主要在后期仔鱼阶段完成;鳞的出现和鳞被形成在稚鱼发育阶段完成;在池塘自然水温26~30℃条件下,从初孵仔鱼到稚鱼发育期完成历时43~44d。     

贝氏高原鳅胚胎和仔鱼的形态发育

通过人工授精获得受精卵,对贝氏高原鳅胚胎和仔鱼的发育过程进行了观察和描述。结果表明,成熟卵淡黄色,卵径较小(直径0.94－1.10mm),遇水后产生强黏性。在水温9.0－12.8℃下,胚盘在受精后4h20min开始分裂,在19h50min和27h40min时达到囊胚期和原肠期,64h40min胚孔封闭,287h时部分胚胎开始出膜,405h30min全部出膜。初孵仔鱼全长(4.32±0.23)mm,肌节36－38对,眼和躯干部黑色素细胞明显,胸鳍原基发育良好。出膜后第5天仔鱼体侧和头部出现浓密的感觉芽。到第8天时全长(6.05±0.41)mm,卵黄吸收完全。仔鱼鳔一室和鳔二室分别于出膜后第30天和第50天形成。第55天的仔鱼全长(14.05±1.01)mm,肌节52－53对,体侧出现7－8条黑色素带,各鳍鳍条数目与成鱼基本一致,但仍有少量鳍褶存在。仔鱼的卵黄囊体积减小速度为0.027mm3/d,鱼体长度生长、鱼体长度性状间的比例关系并不相同,其中,肛后长／全长比例随胚后发育逐渐增加,由初出膜时的31%增加到最后的42％左右。     

哲罗鱼消化系统器官发生发育的组织学观察

采用形态观察与连续组织切片技术,对哲罗鱼(Hucho taimen)胚胎期(水温7~8℃)和胚后期(水温3~14℃)消化系统的发生发育进行观察和研究。结果表明,哲罗鱼受精11d形成原始的消化管。受精18d肝原基出现,U型胃雏型形成。受精30d鱼体破膜,口能自由闭合。破膜8d后,齿形成,肛门与外界相通,消化道初步形成口咽腔、食道、U型胃、肠和肛门。破膜16d,胰及瓣囊出现,仔鱼消化系统初步具备了摄食和消化外源性食物的能力。破膜24d后,鱼体开始上浮,主动摄食,由内源性营养转向混合性营养。破膜30d后,卵黄囊完全被吸收,各消化器官功能和结构逐步发育完善,鱼体由混合性营养进入外源性营养阶段。此后随着鱼体的生长消化器官逐步发育成熟,舌齿和下颌齿分别为双排,胃腺发达,形成网状结构,幽门盲囊较多,肠为直行,肝和胰为相互分开的独立器官。     

鳜消化系统器官发生的组织学

利用形态学观察和连续组织切片技术,对出膜后0-35d的鳜仔稚鱼消化系统胚后发育的组织学特征进行了系统研究.结果表明,试验水温为18.0-20.0℃时,鳜初孵仔鱼消化道仅为一段位于脊索下方、卵黄囊上方的实心细胞索,卵黄囊呈椭圆形,含有油球.孵化后第2天,口和肛门形成,消化道贯通.孵化后第4天,消化道上皮细胞出现分化,肝脏和胰脏出现,仔鱼开始由内源性营养向外源性营养转变.孵化后第5天,仔鱼开口摄食,消化道分化成口咽腔、食道、胃、前肠和后肠.孵化后第9天,卵黄囊完全被吸收.此后随着鱼体的生长,消化系统从结构和功能上逐步发育完善和成熟.孵化后第7天前肠中出现空泡,孵化后第8天仔鱼后肠中发现有嗜曙红颗粒,表明肠上皮细胞吸收了脂肪和蛋白质.在孵化后第13天,出现胃腺,标志着稚鱼期的开始.     

赤水河四川华吸鳅的早期发育

四川华吸鳅Sinogastromyzon szechuanensis为长江上游特有鱼类.为了积累其生物学资料,为相关的保护措施提供参考,于2009年通过人工授精获得四川华吸鳅受精卵,对其胚胎和仔鱼的发育过程进行了观察和描述.四川华吸鳅的受精卵呈浅黄色,卵膜径较小(1.85 mm±0.23 mm),具粘性.在水温26.3~27.8℃下,胚体经历22 h 34 min发育成仔鱼出膜;初孵仔鱼全长4.39 mm±0.21 mm,肌节37对;日龄4 d时,卵黄囊吸收完毕,进入外营养期;日龄65 d时,鳞片长齐,进入幼鱼期.整个早期发育过程历时65 d 22 h 34 min.     

西伯利亚鲟侧线神经丘发育过程的观察

研究对西伯利亚鲟(Acipenser baerii)的胚后幼鱼进行石蜡切片HE染色,同时利用荧光染料DiA4-(4-Diethylaminostyryl)-1-methylpyridinium iodide对侧线管中侧线神经丘毛细胞特异性标记的特点,示踪了西伯利亚鲟胚后仔鱼各个时期侧线神经丘分化发育的过程。结果显示,西伯利亚鲟侧线管内侧线神经丘毛细胞如纤毛状,呈竖立紧密排列。出膜3d仔鱼眼眶后神经基板发育分化活动剧烈,出膜10d的仔鱼眼眶后方的神经基板分化出眼眶上下侧线神经丘的两个分支,同时眼眶后神经基板进一步向后分化发育在眼眶后部形成躯干侧线神经丘,但整个侧线神经丘还未完全发育完成,待出膜15d时,眼眶上下和躯干侧线神经丘已基本发育完全,出膜22d的仔鱼侧线神经丘发育基本完成。研究为今后深入研究西伯利亚鲟侧线发育过程中的神经分化发育、细胞迁移奠定了初步形态学基础。       

温度对花斑副沙鳅仔鱼发育、摄食及不可逆点的影响

2011年4～5月,研究了温度对花斑副沙鳅(Parabotia fasciata)早期仔鱼的发育、初次摄食时间、群体摄食率及不可逆点(PNR)的影响。结果发现,花斑副沙鳅仔鱼出膜后2 d已开始摄食;初次群体摄食率最高值出现在卵黄囊耗尽后的1～2 d,花斑副沙鳅仔鱼的摄食强度随温度升高而增大。仔鱼抵达PNR的时间随温度升高而缩短:22℃时,仔鱼的PNR出现在出膜后的8.0～9.0 d;26℃时,PNR为7.0 d;28℃时,PNR为5.5 d;30℃时,PNR为5.0 d。最大初次摄食率至PNR之间为不可逆饥饿期,22℃时为3.5 d,30℃时仅为1.5 d,说明温度越高,仔鱼耐受饥饿的能力越差,越不利于仔鱼的存活。研究认为,温度对花斑副沙鳅仔鱼发育、摄食及不可逆点的影响较大;在苗种培育过程中,应根据温度确定投饵时间,适时投饵对仔鱼的成活显得尤其重要。     

仔鱼的开口摄食期及其饵料综述

鱼类的受精卵在完成胚胎发育的正常过程后经过脱膜孵化成为仔鱼。此时,初孵仔鱼(newly hatched larvae)一般消化道尚未与外界相通,均有较大的卵黄囊作为孵化后一段时间内继续发育的营养来源。但随着卵黄物质的逐渐消耗,消化管与口腔接通以后,仔鱼必需从外界环境中摄取必要的营养物质,以便进一步发育与生长,这就是仔鱼的开口摄食期。       

稀有鮈鲫胚后发育和幼鱼生长的初步研究

本文介绍了室养条件下稀有　鲫胚后发育与幼鱼生长的特点。稀有　鲫的胚后发育过程可分为3个阶段共11个时期,在水温24．7—31．8℃的条件下,初孵仔鱼经25—30d即可完成胚后发育。在胚后发育期间,仔鱼、稚鱼及幼鱼呈线性生长,每日增长0．52mm左右。饲养条件对生长和发育均有很大影响。在相同的饲养条件下,采于四川省汉源县、灌县及彭县的亲鱼,其后代在生长上无显著性差异。     

稀有Ju鲫胚后发育和幼鱼生长的初步研究

本文介绍了室养条件下稀有Ｊｕ鲫胚后发育与幼鱼生长的特点,稀有Ｊｕ鲫的胚后发育过程可分为３个阶段共１１个时期在水温２４．７－３１．８℃的条件下,初孵仔鱼经２５－３０ｄ即可完成胚后发育。在胚后发育期间,仔鱼,稚鱼及幼鱼呈线性生长,每日增长０．５２ｍｍ左右。饲养条件对生长和发育均有很大影响。     

Histological development of the digestive system of Mayan cichlid Cichlasoma urophthalmus (Günther 1862)

The ontogeny of the digestive tract in Cichlasoma urophthalmus was studied by means of optical microscopy from hatching to 30 days post‐hatching (dph; 855 degree days, dd). The development of the digestive system in this precocial species was a very intense and asynchronous process, which proceeded from both distal ends interiorly. At hatching, the digestive tract consisted of a straight tube with a smooth lumen dorsally attached to the yolk‐sac. The digestive accessory glands were already differentiated and eosinophilic zymogen granules were visible in the exocrine pancreas. At the onset of exogenous feeding between 5 and 6 dph (142.5–171.0 cumulative thermal units, CTU), the buccopharynx, oesophagus, intestine, liver and pancreas were almost completely differentiated, with the exception of the gastric stomach that completed its differentiation between 11 and 14 dph (313.5–399.0 CTU). The development of gastric glands at 14 dph and the differentiation of the stomach in the fundic, cardiac and pyloric regions at 19 dph (541.5 CTU) were the last major events in digestive tract development and designated the onset of the juvenile period. Remnants of yolk were still detected until 16 dph (456.0 CTU), indicating a long period of mixed nutrition that lasted between 10 and 11 days (285.0–313.5 CTU). The results of the organogenesis of larvae complement previous data on the functionality of the digestive system and represent a useful tool for establishing the functional systemic capabilities and physiological requirements of larvae to ensure optimal welfare and growth under aquaculture conditions, which might be useful for improving current larval rearing practices for this cichlid species.     

Expression and activity of trypsin and pepsin during larval development of the spotted rose snapper Lutjanus guttatus

The present study aimed to describe and understand the development of the digestive system in spotted rose snapper (Lutjanus guttatus) larvae from hatching to 40 days post-hatch (dph). The mouth opened between 2 and 3 dph, at that moment the digestive tract was barely differentiated into the anterior and posterior intestine, although the liver and pancreas were already present. Gastric glands were observed until 20 dph, followed by the differentiation of the stomach between 20 and 25 dph. Trypsinogen expression and trypsin activity were detected at hatching, increasing concomitantly to larval development and the change in the type of food. Maximum levels of trypsinogen expression were observed at 25 dph, when animals were fed with Artemia nauplii, and maximum trypsin activity was detected at 35 dph, when larvae were fed with an artificial diet. On the other hand, pepsinogen gene expression was detected at 18 dph, two days before pepsin enzymatic activity and appearance of gastric glands. Maximum pepsin activity was also observed at 35 dph. These results suggest that in this species weaning could be initiated at an earlier age than is currently practiced (between 28 and 30 dph), since larvae of spotted rose snapper develop a functional stomach between days 20 and 25 post-hatch.     

中国黄羽鹌鹑消化道嗜银细胞胚后发育的分布及形态学观察

采用Grimelius银染法,对中国黄羽鹌鹑(Coturnix aponica)消化道嗜银细胞胚后发育的分布规律和形态结构进行了观察。结果显示,口腔、食管、嗉囊和泄殖腔中未发现嗜银细胞,其余部位均有不同数量的分布,其分布呈波浪形,大多数日龄段在腺胃和结直肠中存在2个分布高峰,回肠次之,十二指肠、空肠、盲肠较少,随着日龄增加,不同部位嗜银细胞数量均先增加,后减少,在100 d时达高峰。嗜银细胞主要分布在腺胃腺叶内细胞之间、肠黏膜上皮细胞之间及固有层内,形态多呈圆形、椭圆形、锥形及梭形等。结合嗜银细胞形态与功能间的联系,发现消化道内广泛分布着4种类型的嗜银细胞。我们认为中国黄羽鹌鹑消化道的嗜银细胞具有内分泌、外分泌及旁分泌3种功能,其分布特点可能与动物的食性及生活环境有关。     

Ontogeny of the Digestive System of Atlantic Salmon (Salmo salar L.) and Effects of Soybean Meal from Start-Feeding

Despite a long history of rearing Atlantic salmon in hatcheries in Norway, knowledge of molecular and physiological aspects of juvenile development is still limited. To facilitate introduction of alternative feed ingredients and feed additives during early phases, increased knowledge regarding the ontogeny of the digestive apparatus in salmon is needed. In this study, we characterized the development of the gastrointestinal tract and accessory digestive organs for five months following hatch by using histological, biochemical and molecular methods. Furthermore, the effects of a diet containing 16.7% soybean meal (SBM) introduced at start-feeding were investigated, as compared to a fishmeal based control diet. Salmon yolk sac alevins and fry were sampled at 18 time points from hatch until 144 days post hatch (dph). Histomorphological development was investigated at 7, 27, 46, 54 and 144 dph. Ontogenetic expression patterns of genes encoding key digestive enzymes, nutrient transporters, gastrointestinal peptide hormones and T-cell markers were analyzed from 13 time points by qPCR. At 7 dph, the digestive system of Atlantic salmon alevins was morphologically distinct with an early stomach, liver, pancreas, anterior and posterior intestine. About one week before the yolk sac was internalized and exogenous feeding was started, gastric glands and developing pyloric caeca were observed, which coincided with an increase in gene expression of gastric and pancreatic enzymes and nutrient transporters. Thus, the observed organs seemed ready to digest external feed well before the yolk sac was absorbed into the abdominal cavity. In contrast to post-smolt Atlantic salmon, inclusion of SBM did not induce intestinal inflammation in the juveniles. This indicates that SBM can be used in compound feeds for salmon fry from start-feeding to at least 144 dph and/or 4-5 g body weight.     

Growth of organ systems of Dentex dentex(L) and Psetta maxima(L) during larval development

Growth in volume of common dentex Dentex dentex and turbot Psetta maxima during larval development was studied by means of a quantitative histological method. A two‐phase pattern of volume increase was recorded for both species, turbot volume being always higher than dentex volume. During the first phase, the increase was small but during the second phase volume rose sharply from 22 days post hatch (dph) and 17 dph onwards in dentex and turbot, respectively. In dentex, the specific growth rate ( G ) of the whole larva as well as that of all the structures studied (nervous tissue, trunk musculature, digestive tract, liver, pancreas, spleen and thymus) was always higher during the second phase, whereas in turbot, only total volume of the larva, trunk musculature and nervous tissue had a higher G during the same period. The pattern of allometric growth of digestive organs was similar for both species. These organs showed an initial positive allometric growth that later became near‐isometric (digestive tract and liver) or negative (pancreas). In dentex, nervous tissue and trunk musculature showed near‐isometry throughout the period studied. In turbot, nervous tissue exhibited negative allometry and trunk musculature changed from negative to positive allometry. In both species studied, the highest allometry coefficients were recorded for digestive organs before the larva switched to strict exotrophy. This would indicate the importance of the development of these organs for survival.     

Early development of New Zealand hapuku Polyprion oxygeneios eggs and larvae

This study describes for the first time the normal development of New Zealand hapuku Polyprion oxygeneios embryos and larvae reared from fertilization to 11 days post-hatch (dph) at a constant temperature. Fertilized eggs were obtained from natural spawnings from communally reared captive wild broodstock. Eggs averaged 2 mm in diameter and had single or multiple oil globules. Embryos developed following the main fish embryological stages and required an average of 1859·50 degree hours post-fertilization (dhpf) to hatch. The newly hatched larvae (4·86 mm mean total length, L(T) ) were undifferentiated, with unpigmented eyes, a single and simple alimentary tube and a finfold that covered the entire body. Larvae relied on the energy from the yolk-sac reserves until 11 dph (7·33 mm mean L(T) ), when yolk-sac reabsorption was almost completed. Some of the major developmental stages from hatching to yolk-sac reabsorption were eye pigmentation (5 dph), upper jaw formation (7 dph), lower jaw formation (8 dph) and mouth opening (8-9 dph). By 9 dph, the digestive system consisted of pancreas, liver, primordial stomach, anterior and posterior gut; therefore, P. oxygeneios larvae would be capable of feeding on live prey. The developmental, morphological and histological data described constitutes essential baseline information on P. oxygeneios biology and normal development.     

Ontogeny of gene expression of group IB phospholipase A₂ isoforms in the red sea bream, Pagrus (Chrysophrys) major

The red sea bream (Pagrus major) was previously found to express mRNAs for two group IB phospholipase A₂ (PLA₂) isoforms, DE-1 and DE-2, in the digestive organs, including the hepatopancreas, pyloric caeca, and intestine. To characterize the ontogeny of the digestive function of these PLA₂s, the present study investigated the localization and expression of DE-1 and DE-2 PLA₂ genes in red sea bream larvae/juveniles and immature adults, by in situ hybridization. In the adults, DE-1 PLA₂ mRNA was expressed in pancreatic acinar cells. By contrast, DE-2 PLA₂ mRNA was detected not only in digestive tissues, such as pancreatic acinar cells, gastric glands of the stomach, epithelial cells of the pyloric caeca, and intestinal epithelial cells, but also in non-digestive ones, including cardiac and lateral muscle fibers and the cytoplasm of the oocytes. In the larvae, both DE-1 and DE-2 PLA₂ mRNAs first appeared in pancreatic tissues at 3 days post-hatching (dph) and in intestinal tissue at 1 dph, and expression levels for both gradually increased after this point. In the juvenile stage at 32 dph, DE-1 PLA₂ mRNA was highly expressed in pancreatic tissue, and DE-2 PLA₂ mRNA was detected in almost all digestive tissues, including pancreatic tissue, gastric glands, pyloric caeca, and intestine, including the myomere of the lateral muscles. In conclusion, both DE-1 and DE-2 PLA₂ mRNAs are already expressed in the digestive organs of red sea bream larvae before first feeding, and larvae will synthesize both DE-1 and DE-2 PLA₂ proteins.     

Structure of the digestive tract of tornaria larva inEnteropneusta (Hemichordata)

The ultrastructure of the digestive tract of tornaria larva of enteropneusts was investigated. It showed that the digestive tract consists of three parts: esophagus, stomach, and intestine. The esophagus epithelium consists of two types of multiciliated epithelial cells and solitary muscle cells. Axonal tracts and neurons were found in the ventral wall of the esophagus. The cardiac sphincter contains an anterior band of strongly ciliated cells and a posterior band of cells with long vacuolized processes which partition the sphincter lumen. The stomach consists of three cell types: (1) cells with electron-opaque cytoplasm, bearing a fringed border on their apical sides; (2, 3) sparse cells with electron-light cytoplasm and different patterns of apical microvilli. Cells of the pyloric sphincter bear numerous cilia and almost no microvilli. The intestine consists of three parts. The anterior part is formed of multiciliated cells which bear the fringed border. The middle part consists of flattened cells bearing rare cilia and vast numbers of mace-like microvilli. The posterior part of the intestine is formed of cells bearing numerous cilia and few microvilli. Muscle cells were not found in either stomach or intestine epithelium. One noticed that the structure of the digestive tract of enteropneust tornaria larva differs from that of echinoid pluteus larva.     

The ontogenetic development of the digestive tract and accessory glands of sterlet (Acipenser ruthenus L.) larvae during endogenous feeding

The process of differentiation of digestive tract structures in the sterlet Acipenser ruthenus (L.) larvae was studied from hatching to the beginning of exogenous feeding [9 dph (day post hatching)] using histological procedures. On the day of hatching the digestive tract was closed and completely filled with nutrients (the yolk platelets) that were successively utilized during development. A liver primordium was present in the ventral region of the yolksac. The pancreas was observed on the 2 dph. At the same time, the mouth opening took place. Glandular and nonglandular stomach and anterior and intermediate intestine developed from the yolksac walls. Gastric glands became visible on the 7 dph. The primary intestine developed into the spiral intestine. At the moment of onset of exogenous feeding the yolk material was completely exhausted and there was not mixed feeding observed in sterlet larvae. The fish started exogenous feeding on the 9 dph, which was accompanied with evacuation of melanin plug. At the end of endogenous feeding the digestive tract of sterlet larvae was developed and functional, so they could properly utilize food.     

Functional morphology of the developing alimentary canal in the holothurian Eupentacta fraudatrix (Holothuroidea, Dendrochirota)

Development of the digestive tract of the holothurian Eupentacta fraudatrix was examined using light and transmission electron microscopy. After the blastopore closes, the gut rudiment loses its connection with the blastoderm and becomes an enclosed, tubular chamber, ending blindly at both ends. The differentiation of the digestive and coelomic epithelia is mainly completed by day 12. Since no transient cell types are observed, this differentiation is definitive. By day 20, the mouth and anal openings appear. The cuticular lining in the anterior part of the gut rudiment has an endodermal origin and differentiates before the mouth is formed. The rest of the gut lining is composed of enterocytes typical of holothuroid intestine. At the early stages of development, mitotic figures are encountered among nonspecialized cells of the gut primordium. In more developed digestive epithelium, vesicular enterocytes are capable of mitotic division. Dividing enterocytes retain secretory vacuoles; thus mitosis occurs in actually differentiated cells. After mouth and anus formation, the oesophagus, stomach, intestine and rectum can be distinguished. In the wall of the stomach, powerful musculature is formed.