| Carassius auratus red variety, a variation of Crucian carp, which scatters broadly in China, is common minitype of fresh water fish in Yangtse Valley. This paper takes the artificially bred Carassius auratus red variety as study objects. Gonad, sexual steroid hormone of blood plasma and their receptors, content of serous inorganic phosphorus are studied by the methods of histological staining, immunohistochemical techniques , radioimmunoassay and biochemical methods in details. The main results and conclusions are as follows:1. Histological study on the development and annual change in the gonad of Carassius auratus red variety1.1 Stages and oocyte's change during the ovary's growthCarassius auratus red variety has a pair of ovary, scatter symmetrically at two ventral sides of the swim bladder. The color of immature ovary is white or flesh pink; the mature ovary which looks like a yellow or the orange vesicle takes up 60 ~ 70% of body-cavity, and ovum granule can be clearly observed;the degenerate ovary assumes dark red. Histological research finds that the oocyte of Carassius auratus red variety develops out of sync and spawns in batches. The development of ovary can be divided into five stages and the oocytes be divided into five phases: phase2, phase3, phase4, phase5 and phase 6 when the oocytes degenerate. Follicle and vitellin granule are varying with the development of oocytes. The reproductive period of Carassius auratus red variety is between March and May, in which the ovaries are at phase 4 to phase 5; The ovaries degenerate after ovulation from June to August, and have a rest after September from which the ovaries are at phase 2. From the beginning of December , the ovaries live through the winter with the phase 3. From the third month of next year, the ovaries come to the peak of oviposition and went into the phase 4 immediately.1.2 Stages and the spermatid change during the testicle's growth Like other teleost fishes, Carassius auratus red variety has a pair of testicles. Carassius auratus red variety's testicle is lobular type in appearance. The immature testicle b looks like pinstriped shape or flat tape shape while the mature one is big and assume white color. Be skill and accurate, foliole is full of the inferstitial cells, mechanocyte and lots of blood capillaries. Sperm experience 5 steps during its life: spermatogonium, spermatocyte, spermatocyteⅡ,spoermatid, sperm. The anniversary change from the testicle is it can be seen, testicle growth and seasonal characteristic breed the synchronism. From the beginning of March the testicle start to breed, and it degenerate after May, September to December is convalescent period, after which the sperm happens.2. Immunohistochemical study on the gonad of Carassius auratus red variety including AR, ER and aromatase.2.1 Immunohistochemical study on ER in gonadal and sexual cellsThe estrogen receptor (ER) is express in each period of development, follicle cells show strong immunopositive reaction to ER, and immunopositive reaction is observed in phase 2 oocyte's karyon as well as cytoplast, high phase oocyte's zona radiate, vitellin granule, vacuole around ovary, follicle in the phase 6 and vacuous follicle wall. During the testicle's development, immunopositive reaction of ER happens in spermatogonium, nucleolus of spermatocyte, inferstitial cells, sertoli cell. Strong expression of ER is found in early spermatogonium and space between folioles. Spermid and sperm assume immunonegative reaction to ER.2.2 Immunohistochemical study on AR in gonadal and sexual cellsAndrogen (AR) is expressed strongly in ovary's cytoplasm, karyoplasms, follicular membrane; During the vitellus period, AR is expressed in follicular membrane, zona radiate, vitellin granule, and the reaction is weakened by the development of ovary. The vacuole around ovary in the late phase 4 also finds weak immunopositive reaction. AR is strongly expressed in follicle in the phase 6 and vacuous follicle wall. As to testicle, spermatogonium, spermatocyte, spermatocyte, inferstitial cells, sperm and spermid in all phase assume immunonegative reaction to AR. Strong expression of AR is found in the space between folioles. These results indicate ER and AR play an important role in the multiplication and development of germ cell, as well as a proof of the important function of sexual steroid hormone in gonadal growth and matureness.2.3 Immunohistochemical study on aromatase in gonadal and sexual cellsStrong immunopositive reaction is found in ovary's development from the phase 2 oocytes to the phase 6 ones. The phase 2 and phase 3 oocytes'cytoplast, follicular membrane; the phase 4 oocytes'nucleus, vitellin granule, zona radiate, follicular membrane and follicle ,vacuous follicle wall in the phase 6 are all found immunopositive reaction. As for testicle, the immunopositive reaction is weakened from the phase 3 to the phase 5, even it assume immunonegative reaction to aromatase in the space between folioles, but strong expression is found in the phase 6. All these results indicate aromatase is important for Carassius auratus red variety's gonadal growth.3. Study on the seasonal changes of sexual steroid hormone in blood plasma of Carassius auratus red variety.3.1 Female Carassius auratus red variety's 17β-Estradiol and testosterone seasonal changes.Plasma testosterone(T) and 17β-Estradiol(E2) seasonal changes in female Carassius auratus red variety was detected with radio immunoassay(RIA). The results show that Plasma testosterone and 17β-Estradiol are significantly increased during the reproductive period, 17β-Estradiol's contents are up to 36.8959±6.8846 pg/ml, testosterone's contents reach 20.6011±3.6198ng/dl.E2 significantly descend and fall to the annual minimum after November, then the sexual steroid hormone will slowly ascend next year. All these results show the increase of female Carassius auratus red variety's plasma 17β-Estradiol contents, have satisfied the vitellus'formation and accumulation, even accelerate the ovary's maturation. The correlativity of testosterone and ovary also reveal they are essential for ovary's development.3.2 Male Carassius auratus red variety's 17β-Estradiol and testosterone seasonal changes.Studies on the seasonal change of testosterone(T) and 17β-Estradiol(E2) finds that the anniversary change law of testosterone and 17β-Estradiol is consistent with GSI change trend, the peak of the year is reproductive season, in which testosterone's content is 37.6000±9.0260ng/dl. Plasma 17β-Estradiol content is 11.9846±3.2606 pg/ml, and descend after propagation, then touch the lowest point till the phase 4. All these results indicate testosterone maintain high level to boost sperm's formation in the reproductive period of Carassius auratus red variety.4. Study on the anniversary change of serous inorganic phosphorus in Carassius auratus red variety.Serous inorganic phosphorus change law reflects it's correlativity to gonadal development and GSI. Significant variation of serous inorganic phosphorus is found among different periods. At reproductive phases, serous inorganic phosphorus contents increase rapidly, male fishes'serous inorganic phosphorus content is 47.4504±14.9158 mmol/L and the female's is 58.8975±13.6518mmol/L. Significant descendant happens after June, until early reproductive period serous inorganic phosphorus starts to increase. Both female and male fishes reach the peak in reproductive period, which show the phosphorus need when Carassius auratus red variety breeds. |
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