| Eel is one of the most important economic and cultivated fish species in China. Theproduction of eels in the mainland of China takes up about70％of total world production inrecent years, and it’s foreign exchange-earning has taken the lead in the single aquatic product.In all cultivated eels, Japanese eel is the strongest resistance and the fastest growth species. Atpresent, the artificial breeding of eel is not yet succeeded, but cultivated seed is completelydependent on natural seed. With the natural seed resources is rapid failure, the seed is in shortsupply and the prices continue to rise, it’s seriously hampered the development of the eelcultivate industry. Through basic research of the eel reproductive biology to solve the problem ofartificial breeding, is the fundamental way to solve China’s eel cultivated seed. In this study, thecultivated eels in freshwater have been used as our experiment animals, the changes of gonads,kidney, gill, pituitary on microscopical and hormone levels of serum in different water salinitylevels. Study the role of salinity on gonadal development of Japanese eel. Maturation ofcultivation Japanese eel was induced by injection exogenous gonadotropin in different waterenvironments. The secretory activity of reproduction relative hormone was detected and thechanges of relative cells were studied. This study mainly studied the secretory activities ofreproduction related hormone, it established the artificial reproduction technology of Japaneseeel, it also provided theoretical basis for regulation mechanism studies of reproductive endocrineand practical basis for the successful resolution of artificial reproduction of eels.The results are as followed:1. During the process of Anguilla japonica acclimated to sea water, the glomerular diameterbecome smaller, and the vascular tuft is more compact. In fresh water, the measurement ofglomerular diameter is89～122μm, and the vascular diameter is78～116μm. In sea water(salinity is20), the glomerular diameter is84～117μm, and the vascular diameter is67～110μm.The brush border of First Proximal Tubule (P1) and Second Proximal Tubule (P2) in fresh wateris longer than in sea water. Chloride cells were not identified in nephrons that acclimated to seawater. In the initial collecting tubules and collecting ducts, phospholipids, quite abundant inFresh-Water, appear reduced in Sea Water. The changes of the epithelial cell height and thenuclear cross sectional area in the main4segments of the eel nephron are decreased in sea water.After injected hormone, the ovarian of Salinity acclimation group further development. 2. During acclimate Anguilla japonica into sea water, the number of α Chloride cell isincreased, and became columnar, from the base of blood vessels to epithelium of gill filaments.The teleblem of α Chloride cells are retracted, and Together with vice cells and squamous cellthat formed a top nest. And β Chloride cell decreased.3. In freshwater eels, the prolactin secretion area in snout of anterior pituitary is veryadvanced, while the gonadotropin secretion area in the middle of pituitary is small, prolactincells are tightly packed. After acclimation to seawater, prolactin secretion area reduced, andgonadotropin secretion zone increased.4.In the process of acclimation to seawater, the changes are observed in content oftestosterone (T), estradiol (E2), gonadotropin-releasing hormone (GnRH), follicle stimulatinghormone (FSH), luteinizing hormone (LH) both in Male and female eels. The eels in Controlgroup injected Physiological saline once a week, the experimental group injected PG(4mg)+HCG(100IU). The male eels start injected after females has been done for two weeks, theexperiment last for9weeks.5.The ovarian in fresh-water eels are in I or II period. After inject Physiological saline intosea-water eels, the testicle could develop to III period. After injected hormone, Gonad coefficientand Liver coefficient are both significantly increased, but Digestive coefficient decreased. Afterinjected hormone, the ovarian of the Salinity acclimation group are further developing, andstopped at IV period in freshwater group,1/4seaweater group,1/2seaweater group, only a feweggs can develop to V period. The eels of seaweater group could develop to V period, achievingsexual maturity. The eggs’ diameters are changing depending on the salinity and the stage ofdevelopment.6. The testis in fresh-water eels are in I or II period. After inject Physiological saline intosea-water eels, the testicle could develop to III period. After injected hormone, freshwater eelgonad development IV period,1/4seaweater group,1/2seaweater group and seaweater groupcan development Vgroup.7. The phenomenon of hermaphroditism was observed through histological observation,during the fresh water eels were injected hormones. After the third injection, there are a few eggsobserved in one male eel’s testicle which has developed in IV period. And sperm cells and spermexist in the testicle. The eggs located in ampulla cavity of testicle, and surrounded by a thin layerof mesangial so that separated from the ampulla cavity. The eggs developed in II period, and celldiameter is53.4±4.7μm. The nuclei were larger, and there is a large or several small nucleoliclose to nuclear membrane. |
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