| Pelteobagrns vachelli is one kind offish with important economical value in the upper reaches of the Yangtze River. The gonad development is the basement of stability of population and wild fish resource. On the foundation of former researchers, the purpose of this experiment was to study further and complement the content of reproductive biology of Pelteobagrus vachelli, including the annual cycle of gonad development, the process of oogenesis and the difference appeared in the developing process of the oocytes in different part of the ovary. The method mainly adopted were investigation measure of classical biology and tissue section. The results were as thefollowing:l.Gonad development of Pelteobagrus vachelliFrom 7, May, 2003 to 7, April, 2004, 10 female fish were collected from the Bei-bei reach of Jia-ling river every month. The length, body weight, ovary weight and the diameter of oocyte were measured. Through integration analyzing, four results were gained. (1) Maturation index, the maturation index of Pelteobagrus vachelli had aobvious fastigium. March and April were two phases of continuing increasing, were the blooming season of nutrition accumulating in the oocytes. And descended sharply in May, implied that May is the breeding season of Pelteobagrus vachelli and the time of reproduction was relatively short. (2) Fullness, the fullness indicating the status of nutrition accumulation, which peaked at February and reached the least value at June. February was the optimal stage of nutrition accumulation, and then because enter breeding phase the nutrition was mainly used for gonad development and maturation, especially immediately before spawn the fish stopped feeding so the body fullness descended incessantly until after spawn and enter resuming phase. (3) Mean oocyte diameter, the mean oocyte diameter peaked at May indicated that May was the last stage of oocyte maturation, and the least value was found at July Implied the end of the breeding phase. Furthermore, a relative small peak value was found at October, but descended at December and increased little at November, which were probably related to the production of large quantities of new oocytes. There were so many oocytes with smaller volume, therefore lead to the descending of the mean oocyte diameter. (4)Variation coefficient of oocyte diameter, the variation coefficient peaked at April, and from April to May was the phase of sharply descending, indicated that in the last stage of oocyte maturation the oocytes hadn't mature or developed slowly could reach maturation status fleetly, so reduced the degree of the difference among the oocytes. When the breeding phase ended at May, there was almost no oocyte in the ovary, so thevariation coefficient of oocyte diameter was 0.2.Histological study on the ovary development of Pelteobagrus vachelliMethod of dissection and histological observation were used to study the process of ovary maturation of Pelteobagrus vachelli on cell level. From 7, October, 2003 to 7, May, 2004, specimens of different seasons were collected. The ovaries were observed by naked eye, anatomizing lens and microscope, morphology and stage of the ovary, range of the oocyte diameter and status of the nuclear excursion were recorded. Tissue section also had been performed to the ovaries. The results displayed the whole process of Pelteobagrus vachelli ovary maturation. Furthermore, the number of oocyte belonged to different stage in the ovary at different times were accounted, the ratio by volume and quantity of the oocyte in each stage were calculated respectively. The results indicated that, classified by volume, there were more than 90% oocyte developed synchronously and in the most matured status, and if classified by quantity, there were 10-20% oocyte developed rapidly but 60% oocyte developed slowly which delayed almost one stage than the former. This difference disappeared at the later V stage, not only classified by volume but also quantity all oocytes achieved the same criterion. Which indicated that t...
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