梭鱼仔、稚、幼鱼消化系统胚后发育的组织学观察 [中文引用][英文引用]

利用形态学和连续组织切片技术,在光镜下系统观察了出膜后1~39 d的梭鱼(Liza haematocheila)仔、稚、幼鱼各期的消化系统发育特征。结果表明,在水温20~22℃时,梭鱼受精卵经50~54 h孵化,初孵仔鱼消化道仅由一条原始的消化管组成。孵出后第4天,上下颌形成,卵黄囊被吸收,消化管盘曲,第一盘曲处形成胃雏形,第二盘曲处及之后形成前肠和后肠,肛门形成并与外界贯通。孵化后第7天,卵黄囊被完全吸收,油球渐小至消失,孵化后第8天,消化系统明显分化成食道、胃、肠、直肠以及肝和胰等,仔鱼由内源性营养向外源性摄食营养过渡。此后,随着仔鱼的生长发育,胃黏膜层的褶皱数量增加,管壁增厚,内腔增大。稚鱼后期,梭鱼苗各鳍初步形成,分化出鳍条,孵化后18 d,幽门盲囊形成,胃腺出现,标志着稚鱼开始消化外源性蛋白,同时,消化道上皮细胞进一步分化,肌层增厚,肠道分段、盘曲,稚鱼食性开始向植食性转换。在此以后,消化系统从功能和结构上逐步地完善成熟。结果表明,梭鱼消化系统的发育与仔、稚、幼鱼的生长、形态发育和消化系统功能的完善相一致。

Liza haematocheila is a fish species with potential economic value; therefore, it is important to study the development of L. haematocheila larvae, juveniles, and young. In this study, the digestive system of Liza haematocheila from 1 to 39 days post-hatching (dph) was morphologically observed by light microscopy, and developmental characteristics were described. The results showed that digestive tracts of the newly hatched larvae at 20-22℃ were composed of a single tube for digestion. At 4 dph, the upper and lower jaws appeared, and the yolk sac was absorbed. The gastrointestinal tract was generated in coils by the digestive tract. The stomachic prototype came out of the first coils, and the following coils formed into the foregut and hindgut. At 7 dph, the yolk sac was completely absorbed, and the oil globule were absorbed fairly well and disappeared; the post-larvae individuals obtained nutrition by exogenous feeding. At 8 dph, the digestive system was clearly differentiated into organs such as the esophagus, stomach, intestine, rectum, liver, and pancreas. At this time, nutritional requirements of the larvae gradually transitioned from endogenous to exogenous. Subsequently, with larval growth, the digestive tract changed to have increased wrinkles in the mucous layer, thickened walls, and a bigger cavity. From 15 dph to 18 dph, elongation of the digestive tract, deeper folds, and increase in the absorption surface were observed. At 18 dph, the pyloric caeca was formed, and gastric glands were observed, which indicates the beginning of digesting exogenous protein. Meanwhile, the intestinal epithelial cells further differentiated, the muscle continually thickened, and the intestines became segmented and circular. The larval feeding habits began to change to herbivory. Subsequently, the digestive system gradually improved both functionally and structurally. As of 18 dph, the juveniles had rapid increase in body length by exogenous nutrition. These results showed that L. haematocheila digestive system development was consistent with functional improvement.