秀丽白虾卵母细胞不同发育阶段线粒体的变化

采用透射电镜技术观察秀丽白虾(Exopalaemon modestus)卵巢不同发育阶段卵母细胞线粒体的变化及其与卵黄发生的关系，结果显示，随着卵母细胞的发育，线粒体经历了数目以及结构上的系列变化。卵黄发生早期，卵母细胞内的线粒体数量急剧增多，形态各异，有椭圆形、圆球形等，线粒体嵴稀少；随后，细胞质中出现较多近椭圆形的线粒体群，嵴丰富，外膜光滑。连续切片观察表明，该时期线粒体尚未明显参与卵黄颗粒的形成。卵黄发生中期，卵母细胞内的线粒体的结构出现两大类群：一类线粒体呈长杆状或椭圆形，体积小，嵴丰富，内部基质暗，外膜光滑，主要功能是为卵母细胞发育提供能量；另一类线粒体体积大，呈圆球型，嵴逐渐退化，内部基质呈现电子透明状，外膜出现大小不一的波浪状。后一类线粒体膜内陷，出现明显的类似细胞内吞作用，参与卵黄颗粒的形成。被吞饮物主要为有膜性泡，包括波浪状膜的高尔基体分泌泡、光滑外膜的内质网囊泡以及小型线粒体。与此同时，卵母细胞质膜形成众多胞饮小泡，外来物质逐渐进入卵母细胞，通过高尔基体的加工，以分泌泡相互融合形式参与卵黄颗粒的形成，内吞作用所累积的卵黄颗粒占主要部分，因此在该时期卵母细胞卵黄颗粒的形成以外源性为主。在卵子发育后期，皮层区域出现具典型结构的线粒体，当这些线粒体参与皮层颗粒形成后，卵子逐渐成熟，整个卵母细胞中很难见到线粒体。卵母细胞内卵黄颗粒进一步形成并相互融合，整个卵细胞几乎全为卵黄颗粒占据，未见明显线粒体。

Mitochondrial changes during vitellogenesis in oocytes of Exopalaemon modestus

To elucidate the morphological mechanisms of vitellogenesis of caridean shrimp Exopalaemon modestus,electron microscopic technique was used.During the whole process of oogenesis,dramatic changes including numbers and structure of mitochondria occurred in the oocyte cytoplasm.At the early stage of vitellogenesis,the number of mitochondria in oocyte cytoplasm increased rapidly,and the shapes of mitochondria are ellipsoid and oval.The number of cristae in the mitochondria is small.A lot of typical ellipsoid mitochondria appeared later at this stage,and the number of cristae is increased.The outer membranes of mitochondria are smooth.The observation on continuous sections shows that mitochondria do not participate in the vitellogenesis at this stage.At mid-stage of vitellogenesis,there are two groups of mitochondria.In one of the types,the mitochondria are long-stick-like or ellipsoid with small volumes.They are rich of cristae,and the matrix in the mitochondria is dark.The outer membrane is smooth.The principal function of mitochondria at this stage is to supply energy.In the second type,the mitochondria are spherical or globular in shape,the cristae gradually disappeared,and the inner matrix is electron-transparent.The outer membrane is wave-like in shape.The inner membranes of this type of mitochondria participate in vitellogenesis directly by endocytosis.Membranous vesicles include those from Golgi apparatus,endoplasmic reticulum and even from small mitochondria.Meanwhile,exogenous vitellogenesis occurs by forming a lot of endocytosis vesicles.Exogenous pre-yolk materials were transported into oocyte.These pre-yolk materials were transported to Golgi apparatus and were modified there.Mature yolk materials were excreted by Golgi body.Most yolk was accumulated by endocytosis of oocyte.At late stage of vitellogenesis,typical mitochondria can only be seen in the cortex,and then disappeared.Yolk granules began to fuse later.The oocyte cytoplasm is full of yolk.No typical mitochondria was observed.