【作者】 杨瑞斌；

【导师】 谢从新；

【作者基本信息】 华中农业大学 ， 湿地资源与环境， 2010， 博士

【摘要】 黄颡鱼(Pelteobagrus fulvidraco)隶属于鲇形目、鲿科、黄颡鱼属,因其肉质鲜美而深受人们喜爱。但在规模化苗种培育过程中死亡率很高,严重制约了黄颡鱼养殖的发展。本试验对黄颡鱼仔稚鱼消化系统发育进行形态学、组织学及超微结构等方面研究,以期掌握组织器官结构出现与功能完善过程,为提高仔稚鱼的成活率提供理论依据；本试验还对黄颡鱼仔稚鱼的食物组成变化、摄食节律等摄食特性及其对生长的影响进行研究,以期为规模化苗种培育制定合理的饵料投喂策略提供理论依据,同时也丰富黄颡鱼早期生活史的基础资料。主要研究结果如下：1、对仔稚鱼摄食和消化器官形态学发育特征研究表明,随着日龄的增加,眼径、头长、颌须长、颐须长、肠长随鱼体的发育而增加；眼径与体长比在16 DAH(day after hatching)最大,而后逐渐降低；颌须长、颐须长与体长比快速增加,到17 DAH继续增加但增速趋缓；颌齿在4 DAH出现,到15 DAH颌齿数目增多。这些形态学变化适于仔稚鱼在不同发育阶段对不同饵料的捕食、消化。2、利用光学显微技术和透射电镜技术对黄颡鱼仔稚鱼的消化系统发育研究表明：2 DAH仔稚鱼的消化道分化出口咽腔、食道、胃和肠；3 DAH肠道分化为前肠、中肠和后肠。3 DAH黄颡鱼开口摄食时其胃贲门部粘膜层下出现胃腺。超微结构显示3 DAH胃腺细胞中可见胃蛋白酶原颗粒和丰富的管泡系统,为典型的泌酸胃酶细胞；随日龄增加,胃蛋白酶原颗粒越来越丰富而管泡系统越来越不明显。3 DAH时前肠吸收细胞胞质中可见脂肪泡,后肠吸收细胞胞质中可见蛋白质胞饮体。直到25DAH后肠吸收细胞胞质中尚可见蛋白质胞饮体。表明黄颡鱼在3 DAH开口摄食时消化道具备细胞外消化功能,但此功能不完善,期间细胞外消化逐渐取代胞饮作用等细胞内消化,直到25-30 DAH后细胞外消化功能发育完善。3、对仔稚鱼的视网膜结构观察表明：刚孵出的黄颡鱼视网膜感受细胞主要为视锥细胞,随着机体的生长发育,视锥细胞和神经节细胞在单位面积上的分布数量逐渐降低,视杆细胞的分布数量则逐渐增加,视网膜各层次的发育逐渐完善。11-13DAH是视网膜结构及视觉特性发生较明显变化的过渡时期。黄颡鱼仔稚鱼视觉结构的变化与其从浮游生活到底栖生活的特性及饵料变化相适应。4、对池养黄颡鱼仔稚鱼及幼鱼(60 DAH前)在日过量投喂8次和投喂1次条件下的摄食节律研究表明：池塘培育仔稚鱼摄食具有明显的昼夜节律性。夜间时段摄食水平显著高于白天时段。日过量投喂8次时黄颡鱼幼鱼也表现出明显的摄食节律,夜间时段摄食率显著高于白天时段摄食率,不同时间段的摄食率差异极显著。日不同时间段过量投喂1次时,8个时间段的摄食率差异不显著。投喂8次组的日摄食率远高于1次组。综合结果表明黄颡鱼仔稚幼鱼为夜行性摄食,但投喂频率、投喂量等因素直接影响其摄食节律。5、对池养黄颡鱼仔稚鱼的食物组成研究表明：黄颡鱼早期阶段主要摄食浮游动物,以轮虫、小型枝角类、无节幼体开口,9 DAH时以裸腹蚤等枝角类为主。13 DAH时在数量上仍以秀体蚤等浮游动物为主,但在重量上已被底栖的摇蚊幼虫超过。13-21日龄大型浮游动物和小型划蝽及摇蚊幼虫等底栖动物同为黄颡鱼的主要饵料。21日龄后则以底栖动物为主要食物。6、研究了以浮游动物为饵料日饱食投喂3次、2次、1次等不同投喂频率对32DAH前黄颡鱼仔稚鱼生长和存活的影响,并比较了单独投喂浮游动物、水蚯蚓及两者混合投喂对34 DAH前黄颡鱼生长和存活的影响。结果表明：(1)投喂频率对黄颡鱼仔稚鱼生长有显著影响,29 DAH前全长和体重特定生长率与投喂频率间直线正相关,投喂越多则生长越快；(2)28 DAH后水蚯蚓为黄颡鱼更合适的饵料；(3)在本实验条件下饵料种类对34 DAH内的仔稚鱼成活率没有影响。试验表明日饱食3次更有利于黄颡鱼仔稚鱼的生长；28 DAH后投喂饵料应增加水蚯蚓。7、通过研究不同饵料密度对黄颡鱼仔鱼不可逆点及生长的影响表明：(1)以摄食强度为判断仔鱼摄食能力变化的指标,比摄食率更准确反映黄颡鱼仔鱼的不可逆点出现时间；(2)本试验饵料密度变化对黄颡鱼仔鱼的开口时间、抵达PNR的时间没有影响；(3)在不同的生长阶段,饵料密度对仔鱼的生长影响不一。5-8 DAH时,0.7 preys/mL密度组即可满足仔鱼生长的需要；8-17 DAH时,0.5-1.5 preys/mL密度组适于生长需要,密度更高反而抑制了仔鱼的正常生长。根据上述研究结果提出相应的生产实践管理建议：开口期投喂(或培育)适口且易消化的浮游生物种类；随着仔鱼发育(13 DAH)逐渐增加投喂(或培育)水蚯蚓等底栖饵料生物；待细胞外消化功能完善后(25 DAH)及时转饵或投喂人工饵料。更多还原

【Abstract】 Yellow catfish (Pelteobagrus fulvidraco) is an important commercial freshwater species in China. It has a promising market potential in China, Japan, South Korea, East and South Asia. Due to its high market value, the culture of this species has increased rapidly in recent years. However, larvae rearing became a major bottleneck because of its high mortality which caused by uncorrected culture feeding strategies simply derived from the traditional carp culture. Little is known on the early life stages of P. fulvidraco, especially on their morphological and internal development relating to functional capabilities. To date, no study has been documented on ontogeny of the digestive system in P. fulvidraco, thus correct feeding strategy related to morphological development is unknown.In order to enhance the success of larvae rearing of P. fulvidraco, we need to know the ontogeny of its digestive system thoroughly and the feeding habits. The purpose of this study was to understand the morphological structure of digestive tract and the its feeding habits during the ontogeny of P. fulvidraco. We hope that this information would provide fundamental knowledge for larvae rearing management for this species. The main results are shown as follows:1 The development morphological characteristics of feeding and digestive organs of larvae of P. fulvidraco were studied. Eye diameter, lengths of head, maxillar barbells, mandibular outer barbells and gut increased with the development of fish larvae. Ratio of eye diameter to body length reached the maximum at 16 DAH, and then gradually reduced. Ratio of length of maxillar barbells, mandibular outer barbells to body length increased rapidly to 17 DAH, and then continue to increase with slowing down growth. Jaw teeth appeared at 4 DAH. The number increases with age, arranged 2 lines in upper maxillar and 1 line in mandibular. Gill raker appeared at 6 DAH, and the morphological structure similar to adult fish gill rakers at 20 DAH. It is concluded that the visual play an important role in preying at first then the tentacles were more important when larvae converted to benthic.2 Development of the digestive tract in P. fulvidraco followed the general pattern described for other fish species with some peculiar findings. At hatching, it consisted of an undifferentiated straight tube laying over the yolk sac. The digestive tract was differentiated into buccopharynx, esophagus, primary stomach and intestine by 2 DAH. The liver and pancreas were also appeared at this time. The intestine became differentiated into anterior and posterior regions separated by the intestine bend at 3 DAH. Gastric gland appeared in cardiac stomach at 3 DAH, the earliest appearance time among fishes studied to date. Oxynticopeptic cell contained pepsinogenic granules and abundant tubulovesicular systems at 3 DAH. As larvae grew, more pepsinogenic granules but less tubulovesicular systems were found in oxynticopeptic cell. The abundant visible tubulovesicular systems suggested that oxynticopeptic cell was still in rest phase with little hydrogen chloride (HCl) secreted at the first appearance time. The ultrastructure of oxynticopeptic cell indicated the asynchronous development of acid-secreting and pepsinogen-secreting function. The epithelial absorptive cell of the anterior and posterior intestinal segment showed electron-opaque lipid droplets and heavy pinocytosis, respectively at 3 DAH. Heavy pinocytosis could be observed in the posterior intestine until 25 DAH. Lipid vacuoles accumulation appeared in liver at 13 DAH, the same time as the storage of abundant glycogen. These results suggested the development of the digestive tract of P. fulvidraco larvae was functional rapidly, however it was still incomplete at 3 DAH. The functions of digestive tract and accessory glands were developed gradually until 25 DAH.3 The retinal structure and the density of three visual cells of P. fulvidraco larvae at 0-30 DAH were examined histological during different development stages. The retinal of the newly hatched larvae has only single cone as sensory cell. Over the whole range of development the density of cones and ganglion cells decreases while the density of the rods increases correspondingly. The forms of various layers of retina gradually develop to be perfect. The data concerned shows that the structure of the retina changes apparently in the age between 11 DAH and 13 DAH, which is a transitional period in which its visual characteristics changes obviously. It is revealed that the changes of visual structure of P. fulvidraco are adapted to the ecological shift from pelagic to benthic habitats.4 The circadian feeding rhythm for larvae culturing in pond, and juvenile at different feeding frequencies was investigated. Apparent day and night feeding rhythm is observed in larvae which culturing in pond. The feed intake rate at night was higher obviously than that at day through all the experiment stage. Similar results were found in juvenile. That is, there is typical nocturnal feeding activity with the highest levels of feeding activity at 20:00 pm and the lowest levels at 8:00 am in the condition of over-feeding 8 times per 24 hour. There are different significantly feeding rate between different feeding time (P<0.01). The similar circadian feeding rhythm occurred in the condition of over-feeding only 1 time in different time per 24h. However, there is no different feeding rate between different feeding time in latter feeding condition (P>0.05). Results suggest the circadian feeding rhythm of larvae and juvenile of P. fulvidraco belong to nocturnal.5 The food composition of P. fulvidraco larvae which culturing in pond were studied at different age. During initial bait phase, the main food were zooplankton, mainly rotifers, small Clandocerans and nauplii. The proportion of large Clandocerans gradually increased with age. Zooplankton were still main food according to number percentage of prey at 13 DAH. However the zoobenthos such as Chironomus were more than zooplankton in terms of weight percentage of prey. The main food changed from zooplankton to zoobenthos after 21 DAH.6 Effect of feeding frequency and different food items on growth and survival rate of larvae and juvenile of P. fulvidraco were studied. Trial 1 were conducted to investigate the effect of different feeding frequency (satiation feeding 1 (F1),2 (F2) or 3 (F3) times/day) of zooplankton on the growth and survival. Trial 2 were conducted to investigate the effect of different food items (feeding zooplanktons (groupⅠ), feeding zoobenthos (groupⅡ) or feeding zooplanktons and zoobenthoes together (groupⅢ)) on the growth and survival. The results showed that:①During 3-29 days after hatching, with increasing feeding frequency, specific growth rate of total length and wet weight increased significantly in linear style (SGR1=1.0366D+3.2347 R2=0.9025; SGRw=3.0013D+9.4829 R2=0.8833).②During 17-25 DAH, the growth of groupⅡwas slower than groupⅠand groupⅢ. The growth of groupⅡwas still slower than groupⅢ, but there was no different between groupⅡand groupⅠup to 28 DAH. In 34 DAH, there were different among the growth of 3 groups. The growth of groupⅢwas the fastest, followed by groupⅡand groupⅠ.③There were no survival rate difference among group of feeding different food items during 3-34 DAH. It can be concluded that it is more useful that satiation feeding 3 times/day than 1 or 2 times/day, and feeding zoobenthoes is better than feeding zooplankton after 28 DAH.7 The "point of no return" (PNR) of P. fulvidraco larvae were investigated. The result indicated that feeding intensity is more suitable than feeding rate to calculate the PNR for P. fulvidraco larvae. A method of calculating the PNR via the feeding intensity index as a complement to traditional methods was presented. Under the experimental conditions, the PNR of P. fulvidraco larvae appeared at 11 DAH.Effect of prey density on growth of P. fulvidraco larvae was also studied.7 groups of different prey density (0、0.1、0.3、0.5、0.7、1.5、3.0 preys per millilitre) were arranged. There are different optimal prey density at different growth stage of larvae. The optimal prey density was 0.7 preys per millilitre before 8 DAH. While 0.5-1.5 preys per millilitre were the optimal prey density between 8 DAH and 17 DAH. The use of more than 1.5 preys per millilitre of live prey density had negative effects on larval growth.According to the development characters of P. fulvidraco larvae, a series of scientific methods to improve the surviving rate were suggested.更多还原