Studies On Karyotype, Cement Gland And Oogenesis Of Capitulum Mitella

The karyotype for Capitulum mitella was studied with its embryo by means of hot-dropping method. The diploid chromosome number of Capitulum mitella is 2n=:32 and the karyotype can be described by 8m+6sm+2st. The length of diploid metaphase chromosome(CL) is from 0.85 to 2.47μm.The sex chromosome is not found.The histology and histochemistry of the cement gland of Capitulum mitella was studied.Mature cement gland cell is about 20μm-40μm.There are collecting canals within the cytoplasm of the cement cells,which collect the cement secreted by the cell and transport it to secondary cananls,and then to primal canals,in the end, cement was discharged. There are lots of DNA,RNA,protein and a little of glycosides within the cement cells, lipids was not discovered within the cement cells.Ultrastuctural changes of oogenesis in Capitulum mitella were studied with SEM and TEM. The results showed that oogonia is small and its structure is simple,lacking organelles besides of some mitochondria,smooth endoplasmic reticulum and lots of ribosomes,but its nuclear is big. The marked changes occur in the previtellogenic oocytes and the primary vitellogenic oocytes.At previtellogenic stage, the size of oocytes become big and contain a few organelles,but electron density is low.During the vitellogenesis,the size of oocytes ripidly become larger,there are many various and developing organelles(mitochondria,lysosome, golgi apparatus,rouge endoplasmic) in the cytoplasm. At the same time, the yolk granules become more and more, the electron density become higher and higher, and there are protuberance of vitellin membrane and hole of plasma membrane.At maturation stage, the size of oocytes become larger(diameter is about 120μm), many micropores (diameter is about 1-3μm) are exist in the surface of mature oocytes and there are many various well-developed organelles in the cytoplasm. The origin of yolk was discussed. The relation between the changes of the stuctrue in oocytes and the vitellogenesis was discussed.