Researches On The Artificial Induced Maturation Of Female Giant Mottled Eel (anguilla Marmorata)

Giant mottled eel (Angullia marmorata) is preserved fish specie in China. Recently, the breeding industry of giant mottled eel developed quickly in China. But all fry cultivated are wild elvers captured in estuaries. The shortage of fry has become a very serious problem in the development of breeding industry. It plays an important role in resource conservation and the healthy development of breeding industry to studies on artificial propagation of giant mottled eel. Up to now, there were no research reports about reproductive endocrine and techniques for artificial propagation of giant mottled eel yet. In this study, female giant mottled eels were induced ovarian maturation by for the first time. During this process, variations of relative tissues were detected. The main results were shown below:1. Female giant mottled eel can be induced ovarian maturation by repeated injection of carp pituitaries extract (CPE) and LHRH-A2. None of the 5 controls which were managenment with normal saline were matured, and the occytes were in stage I-II, the mean GSI was 1.18%.15 fish managed with exogenous hormone developed differently in occytes. And the GSI increased significantly.2. The mRNA expression profiles of GtHa, LHβand FSHβin pituitaries were detected. The result showed that mRNA levels of GtHα,LHp and FSHp were low (GtHa:0.65±0.44; FSHβ:0.0015±0.00056; LHβ:0.003±0.0014.); But they reached peak levels at early vitellogenic stage and decreased from mid-vitellogenic stage to migratory nucleus. The FSHβsubunit also increased in pre-vitellogenic stage, whereas, decreased more sharply than LHβsubunit from mid vitellogenic stage to migratory nucleus stage.3. Serum steroid hormone levels were detected by the RIA. Levels of serum E2 were extremely high of the controls(48.67±12.90 ng/mL) which were in previtellogenic stage. And rapidly decreased from the early vitellogenic stage(9.81±6.92 ng/mL) to migratory nucleus stage(1.27±0.95 ng/mL). While the serum T levels were too low to be detected in the controls, but changed markedly (to 0.38±0.29ng/mL) with a large variation until the LV stage. It shown a further increase (1.43±0.41 ng/mL;) at the MN stage.4. The PAS stain was used to show the glycogen in hepatocyes. The general morphology of hepatic glycogen appeared difference in four stages of the induced maturation. The hepatic cells appeared uniformly and intensely stained after PAS reaction. The strongly stained areas being observed was glycogen, and the PAS reaction weaker gradually in the hepatocyes with the developmental stage of the ovary5. The H.E stain was used to show the variations of stomach and intestine. In the maturating eels, the stomach and intestine were greatly contracted against the immature eels. The mean alimentary canal somatic index was 1.242%. And it decreased from 1.241% to 0.407% with the development of occytes. The thickness of mucous layer, submucous layer, muscle layer and serosal layer in stomach and gut decreased with the increase of GSI.