넙치, Paralichthys olivaceus(TEMMINCK et SCHLEGEL)의 性分化와 生殖巢發達 = Sex Differentiation and Development of the Gonad in the Flounder, Paralichthys olivaceus(TEMMINCK et SCHLEGEL)

국문 초록 (Abstract)

本 硏究는 넙치를 대상으로 孵化直後에서 成熟段階에 이르기까지 始原生殖細胞의 출현과 原始生殖巢의 形成, 雌雄性分化와 配偶者形成過程을 組織學的으로 조사하여, 이들의 性分化過程과 生殖巢 발달과정을 究明하였다.
1. 始原生殖細胞는 孵化後 3일 전장 3.1㎜된 前期仔漁에서 腸管과 脊索사이의 體壁中胚葉上皮에서 크기가 7.2∼7.4㎛인 2∼3개의 細胞가 纖維性 間充織에 묻혀 식별되었다.
2. 孵化 11일(전장 4.1㎜)의 後期仔魚期에 中腎管과 밀착된 體腔上皮에서 結體纖維性 生殖上皮가 분화되고, 이들 상피상에 섬유성 간충직에 쌓인 수 개의 生殖原細胞가 위치한다.
3. 孵化 22일경의 後期仔魚(전장 9.1㎜)에서 生殖原細胞들은 後復膜쪽으로 이동하며, 孵化後 43일된 着低期椎魚(전장 2.2㎝)에서는 有絲分裂중인 소수의 生殖原細胞와 풍부한 纖維性 間充織으로 구성된 線狀의 原始生殖巢가 발달한다.
4. 孵化後 46일된 椎魚(전장 2.2㎝)에서 原始生殖巢의 髓質層은 葉狀으로 分離하여 卵巢腔이 形成되고, 孵化後 78일 된 椎魚(전장 7.9㎝)에서는 卵巢小囊의 構造가 완성된다.
135일(전장 11.2㎝)이 지나면 난소소낭 구조사 성체와 유사하게 발달하고, 生殖上皮의 기능이 활발하게 되어 난원세포의 분열증식과 함께 初期卵母細胞가 출현한다.
5. 精巢의 初期 分化는 卵巢에 비해 늦어 孵化後 80일된 椎魚(전장 7.1㎝)에서 최초로 정소의 皮質層에서 精原細胞들의 分裂增殖이 식별되었고, 孵化後 135일된 개체(전장 11.9㎝)에서 精巢小囊이 형성되었다.
6. 原始生殖巢로부터 난소와 정소로 분화 발달하면서 각각 分布位置와 出現量이 다른 4종류의 體細胞性 間質細胞가 식별되었다.
7. 수컷은 만 13개월만에 完熟精子를 포함한 정소를 형성하고, 암컷은 만 2년만에 完熟卵母細胞를 가진 卵巢를 형성하였다.
8. 性分化에 따른 性比는 암수 3 : 1로 암컷의 出現率이 높았다.

다국어 초록 (Multilingual Abstract)

To study sex differentiation and process of gonadal development in the flounder, Paralichthys olivaceus, this research was conducted according to a histological method; the appearance of primordial germ cells, formation of primitive gonads, sex differentiation of female and male and process of gametogenesis from newly hatched larva to the mature stage of adult fish.
The primordial germ cell is identified as 7.2∼7.4㎛ in cell size, among 2∼3cell which are buried under fibrous mesenchymal tissue between gut duct and notochord of pre-larva, at a total length of 3.1㎜, 3days after hatching.
Germinal epithelium of fibrous connective tissue was differentiated in the epithelium of the coelom closed in the mesonephric duct, a few gonial cell were located in the germinal epithelium. covered with fibrous mesenchymal tissue of post larva, 11 days(TL 4.1㎜) after hatching.
Gonial cells migrated in the retroperitonium of the post larva, with a total length of 9.1㎜, 22 days after hatching and a few mitotic gonial cells and primitive, lineshaped gonads were composed, with fibrous mesenchyme development, at the settlement stage with a total length of 2.2㎝, 43 days after hatching.
The ovarian cavity is formed according to the medullary layer of the primitive delaminated gonad, in a juvenile with a total length of 2.2㎝, 46 days after hatching, and a total length of 7.9㎝, 78 days after hatching, construction of the ovarian sac was thus completed.
A total length of 11.2㎝, 135 days after hatching is commensurate with construction of the ovarian sac, which is now similar to that of the adult, and so the mitotic division of oogonia and early oocytes appeared, with the germinal epithelium of functional development.
Early differentiation belatedly compared the ovary with a juvenile testis whose total length was 7.1㎝, 80 days after hatching, with the testis of the cortical layer, spermatogonia of mitotic division were first recognizable.
In a juvenile with a total length of 11.9㎝, also 135 days after hatching and testis sac was developed.
Somatic interstitial cells of four different types were identified by distribution and appearance, accorking to the differentiated development of the testis and ovary in primitive gonad.
The male appeared to have a testis that contained ripe spermatozoa, 13 months after hatching and the female appeared to have an ovary that contained ripe oocytes, 2years after hatching.
According to sex differentiation, sex ratio is female 3 : male 1, the appearance of female was high.