锯缘青蟹幼体肝胰腺的观察研究

STUDIES ON THE HEPATOPANCREAS OF LARVAL SCYLLA SERRATA

于1988年4月—1990年6月，在实验室培育锯缘青蟹幼体，从蚤状幼体Ⅰ期培养至仔蟹期。固定各期幼体，通过组织学切片和透射电镜观察研究锯缘青蟹幼体的肝胰腺。结果表明，锯缘青蟹幼体的肝胰腺由四种类型的细胞组成，这四种类型的细胞分别为：胚细胞（E－细胞）、纤维细胞（F－细胞）、吸收细胞（R－细胞）和分泌细胞（B－细胞）。不同类型的细胞显微和超微结构具有明显不同。E－细胞的细胞器不发达；F－细胞内含丰富的粗面内质网，且细胞质中可见酶原颗粒；R－细胞线粒体和滑面内质网比较丰富，呈明显的极性分布；B－细胞内含一个大的液泡，顶端存在顶端复合体，在B－细胞内可观察到胞引作用和胞内消化现象。根据对肝胰腺显微和超微结构的观察提出锯缘青蟹幼体肝胰腺细胞的分化序列，即E－细胞分化有两个趋向，一部分分化为F－细胞，由F－细胞转化为B－细胞；另一部分分化为R－细胞，R－细胞最终发生退化。

Larval Scylla serrata were cultured from the first stage of zoea to the first larval crabin every April from 1988 to 1990. For every stage, larval Scylla serrata were fixed in Bouin's fluidand 2.5% glutaraldehyde separately and their hapatopancreases were studied using light andtransmission microscopes. The result obtained through histological sections shows that thehepatopanreas of larval Scylla serrata consists of many blind tubules. With the developmnt oflarval stages, the length and amount of hepatopancreas tubules increase. The hepatopancreas cells canbe divided into four types: embryo cells (E-cells), fibrillar cells (F-cells), resorptive cells (R-cells)and blister-like cells or secretary cells (B-cells) (PlateI:1). These types locate at one thin basophilebasement. Connective tissue, blood sinus and a lot of dissociate cells fill among the hepatopancreastubules. The whole hepatopancreas is covered by a basophile membrane (PlateI:1). E-cells locate atthe blind end of tubules. A round or oval nucleus exists in E-cells. E-cells at the mitotic divisionstate can be observed sometimes; they may be involved in mitotic astivity for production of othercell types which comprise the tubule epithelium. Cytoplasmic organelles are undeveloped. Themitochondria with littie ridges appears as small spheres or rods. High amounts of rough endoplasmicreticulum (RER) exist in E-cells. Little lipid dropets and Golgi bodies were observed once (Platel:2).F-cells mainly locate in the middle region of the tubules, scattering among R-cells and B-cells. It isstrongly basophile. Plenty of RER can be observed in F-cells. The number of RER and electrondensity of mitochondria differ in F-cells located at different positions of the tubules. Golgi bodiesare very rich in F-cells and zymogen granules can be seen near them (PlateI:3). The zymogenglanules aggregate in the apical cytoplasm. F-cells are believed to be specialized for the synthsisand secretion of digestive enzymes. R-cells are the most numerous cell type. Their noclei are nearthe basement of the cells. In som R-cells, there are no vacuoles in the cytopasm while someR-cells have one or many vacuoles. At different larvae stages, the morphology of R-cells aredifferent.There is one region in the cell where no cytoplasmic organelles exist. This region is next tothe apical cell membrane. Under this region, the number of mitochondria with high electron densitymatrix and plenty of ridges is very large (PlateI:4). In the proximal cytoplasm near the base of thecell, there is a plenty of smooth endoplasmic reticulum. The number of Golgi bodies is less thanthat in F-cells, and their morphology differs from tha of F-cells. There is much lipid dropletespecially near the base of R-cells (PlateI:5). The calcium body can be observed, and its number isvery small (PlateI:6). Some R-cells show signs of degeneration. B-cells mainly locate in theproximal regions of the tubules, their volum are the biggest and shapes not regular There is a bigvacuole whose volum mny occupy 80%-90% of the whole volum of the cell. There is a then rimaround the vacuole which includes dense cytoplasm, RER and mitochondria. On the top of B-cells,there exists a top complex body consisting dense cytoplasm, pinocytotic vesicles, small mitochondriaand microvilli on the surface of B-cells (PlateI:7). Cytosis and intracellular digestive phenomenoncan be observed. Observations on the ultrastructure of B-cells show that the formation of B-cells isa progresseve process. It is transformed from F-cells. Firstly the apical cell membrane of F-cellsdevelops invagination which extend as channels deep into the cell to form pinocytotic vesicles. Thepinocytotic vesicles move toward the base of the cell and enlarge by fusion with each other to formsmall digestive bodies. The remaining two thirds of the volum of the cells contain mitochondria andrough endoplasmic reticulum (PlateI:8). Wth the transformation progressing, pinocytosis becomsincreasingly active. Under the pinocytotic system there is a subapical vacuole system. Granules insidethe vacuoles c