Study On Oviduct Strcture And The Principle Of The Oviducutal Resumer In Mcrobrachium Rosenbergii (De Man)

M. rosenbergii (Arthropoda, Crustacea, Decapoda, Carider, Palaemonidae) is a fine kind of widely fed freshwater shrimp in China. Oviduct is one of the main parts of the female reproductive system. In this research, the structures of the oviduct during spawning were examined with light microscope and electromicroscope.1. MicrostructureA pair of oviducts originates from the anterolateral part of the ovary, and endsat the female genital pores situated in the basipodite of the 3th thoracic appendage. The oviduct wall, folded in some areas, consists of a basal lamina and a layer of columnar epithelial cells. The epithelial cells show tightly each other and the nucleus is in oval shape, with one or several nucleoli. The layer of basal lamina is thin, with a few external cells attached. There is a large quantity of secreted substance in the lumen of the oviduct.2. UltrastructureThe basal lamina is 1-2 v- m thick, which is attached with a layer of epithelial cells. Near the basal lamina, epithelial cells showed finger-like protuberances. The free surface of the epithelial cells possesses long, dense microvilli. There are two types of, one with light cytoplasm and the other with dark cytoplasm. The nucleus is in oval shape, with one or several nucleoli and the cytoplasm contains abundant mitochondria and rough endoplasmic reticulums.3. The changes of the structure of the oviduct after spawningDuring spawning the oviduct wall suffers kinds of acting force, which leads the free surface of the epithelial cells break. Gradually the epithelial cells die and the structure of the oviduct changes.Under the microscope, the membranes of the epithelial cells break. The cytoplasmleaks out and the nucleolus seems unclear. Out of' lie basal lamina, there are a mass of connective tissue and plenty of cells. The layer of secreted substance disappears, with a little remained. Sometimes, there are a few dead cells in the lumen.Under the electron microscope, the basal lamina is 3-5 u m. There are more external cells attaching to it than before spawning. Some external cells pass through the basal lamina and come into the oviduct wall. The cell membranes of the free surface and the most microvilli break. The cytoplasm leaks out and lots of vacuoles appear in the cells. The nucleus and many organelles such as mitochondria show abnormal. There are plenty of cell fragments and broken microcilli in the lumen. The differences between light cells and dark cells disappear.4. The structure of the oviduct before next spawningBefore the next spawning, the oviduct wall renews and consists of the basal lamina and a new layer of epithelial cells. In very few M rosenbergii, lots of external cells encircle the oviduct wall, which looks like a new epithelial cell-layer. The primary epithelial cells move to the lumen .The basal lamina appears unclear, and the two cell-layers are separated by secreted substance.5. After spawning, most epithelial cells break and died, however, histologically, the structure of oviduct wall still remains normal. Two things play a important role in the process. One is the cellular junction. There are two kinds of cellular junctions in the oviduct of M. rosenbergii, desmosome and septate junction. When epithelial cells break, these cellular junctions remain. Another, after spawning there are a plenty of connective tissue and external cells attaching to the basal lamina and the thickness of the basal lamina increases. All of these make the stability and integrity of the oviduct.