大海马消化系统胚后发育的形态学及组织学研究

大海马Hippocampus kuda为卵胎生海洋硬骨鱼类。利用解剖和连续组织切片技术,对孵化后2、5、9日龄、1月龄和3月龄几个特殊时期大海马消化系统的形态和组织学特征进行了报道。结果表明,大海马仔鱼孵化后1日,其消化系统已经明显分化为口咽腔、食道、小肠、直肠以及肝胰脏、胆囊等器官,但是仔鱼仍然以内源与外源混合性营养为主,至5日龄仔鱼变为完全的外源性营养;仔鱼孵化后9日左右是大海马的死亡"临界点",其消化系统的组织结构更趋于复杂;1月龄大海马的消化系统在结构和功能上进一步完善,小肠前端呈"z"型结构,管壁变厚,纵、环肌发达,肝脏组织充满大部分体腔,但在小肠周围仍然不能辨认独立的胰脏实体结构;3月龄成海马已经有了成熟的消化系统组织结构,保证了最大限度地消化和吸收动物性饵料。整个胚后发育阶段大海马没有形成胃,鱼体的形态和组织结构的变化与食性的变化紧密适应。

Histological studies on post-embryonic development of digestive system of seahorse Hippocampus kuda

The post-embryonic development of the digestive system of seahorse Hippocampus kuda,an ovoviviparous teleostean,was examined histologically from one day post-hatch to three months post-hatch.The result showed that the oesophagus,intestine,rectum,liver and cholecyst had already come into being in the digestive system after hatching from brood pouch of the male parent seahorse,however, the larvae still gained essential nutrition from yolk and tiny animal baits until five days post-hatch,when the larvae depended on feed from the environment completely.There was a critical period of high mortality for the seahorse during the development,it was at the ninth day after hatching;and the histological character began to be more complex just at this stage.In contrast with the larval stage,one-month old seahorse had a more perfect digestive system.The forepart of the intestine showed a "Z" configuration,and the intestinal wall was thick,especially its muscle layer.The liver was dramatically big so as to fill up the half part of the coelom;in contrast,the pancreas was dispersed among the liver and developed into a separate organ.Generally,the digestive system of seahorse has already matured after hatching for 3 months,which guaranteed that seahorse could digest and assimilate large animal feed,such as Acetes spp.and Mysis spp.Seahorse was also found to be a non-stomach teleostean.The study demonstrated again that the morphological and histological digestive features of seahorse always benefit its feeding activity.