Preliminary Studies On The Reproductive Physiology In Female Verasper Moseri

In this thesis, the ovary maturation cycle,pituitary structure, sexual steroid hormone and steroid hormone recepters of barfin flounder (Verasper moseri) were studied by histological staining methods, electron microscopy technique, immunohistochemical and radioimmunoassay methods. The main results are as follows:1. Histological study on the development and annual change in the ovary of female barfin flounderThe annual ovarian maturation cycle and correlated plasma sex steroids levels variation were studied using light microscopy and morphometric methods combined radioimmunoassay. In addition, the relationships between GSI, CF, HSI, sex steroids and temperature, photoperiod were investigated using statistical analysis. The results showed that Barfin flounder features asynchronous oocyte development and batch spawnings. The oocyte growth could be divided into six phases and ovary maturation cycle was divided into six stages accordingly. Gonadosomatic index (GSI), hepatosomatic index (HSI) and condition factor (CF) were all found to increase prior to, or during the peak phase of vitellogenic growth corresponding to the gonad development. These results could highlight the reproductive cycle of captive female barfin flounder.2. Immunohistochemical study on estrogen receptor and androgen receptor in the ovary of female barfin flounderImmunohistochemical localization of estrogen receptor (ER) and androgen receptor (AR) was investigated for the first time in the ovary during development of barfin flounder using polyclonal antibodies. The results showed that both ER and AR presented in the ovary of each development period. ER showed strong immunologically positive expression at early stage of development during vitellogenesis, while expressed weakly in mature oocytes. AR existed in follicular cell during all developmental stages of the ovary, and strongly expressed in early oocytes cytoplasm and mature oocytes nuclei. The sex steroid hormone and their receptors were expressed in cytomembrane, cytoplasm, nuclear membrane or nuclear plasm at different developmental stages with different intensity respectively, which showed their special functional characters. These results provided new morphological proofs that ER and AR participate in the regulation of physiological function in ovary development of barfin flounder.3. Histological and ultrastructure study of the pituitary gland in barfin flounderPituitary gland in sexually matured barfin flounder was of dorsoventral style, which consists of neurohypophysis and adenohysis. There were neurosecretory fibres in neurohypophysis. Two of pituicytes were recognized in the neurohypophysial tissue, except for two of neuroepithelial cells. The adenohysis which was complicated in structure was divided into rostral pars distails (RPD), proximal pars distails (PPD) and pars intermedia (PI). Six types of hormone secretory cells were found in adenohypophysis. There were prolactin hormone (PROL) cell, adrenocorticotopic hormone (ACTH) cell and thyrotropic hormone (TSH) cell formed in RPD. The PPD have three types of hormone secretory cells, named as growth hormone (GH) cell, gonadotropin hormone (GtH) cell and thyrotropic (TSH) cell. The PI was conposed of melanotropic stimulating hormone (MSH) cell. One type of gonadotropin hormone (GtH) cell was found in the pituitary of matured female barfin flounder, where the two types of secreted granules existed.4. Study on the changes of plasma sex steroid hormone levels in barfin flounder in the seasonal and reproductive cyclePlasma 17β-Estradiol (E₂) and testosterone (T) in female barfin flounder were detected with radio immunoassay (RIA). E₂ level began to increase in June (stageâ…¢) and reached the first relatively lower peak in September and peaked in February, during spawning. After the spawning, it dropped down to a relative low level and maintained until the next reproductive cycle.T level achieved the first relatively higher peak in July and peaked in January, which was a month earlier than that of E₂. A positive relationship was found between E₂ and T level. Statistical analysis revealed that a positive relationship existed between temperature and E₂.