Studies on Vitellin Accumulation in Freshwater Shrimp, Palaemon paucidens

スジエビの卵黄形成過程を成長期、卵黄形成前期、卵黄形成後期に分類し、ポリアクリルアミド濃度勾配ゲル電気泳動法、免疫学的方法で卵黄物質の蓄櫓機構を調べた。1)成長期の卵黄は卵巣指数(GSI)約1.5以下、最大卵径(MED)300μm前後以下で、卵母細胞はヘマトキシリンで染色される核と細胞質を有する。この段階の親の血リンパ中には免疫学的に卵巣ビテリンと同一の成分は検出されなかった。2)卵黄形成前期の卵巣はGSI1.5から4.5、MED250から550μmに相当し、卵細胞内に核を有し細胞質は増大してエオシン好染性に変じ、卵黄顆粒が出現し始めた。MED350μm以上の卵細胞を持つ親の血リンパには免疫学的にビテリンと同一のリポタンパク質が出現した。3)GSI4.5以上、MED550μmの卵細胞は卵黄形成後期に相当し、細胞内には核は消失してエオシン好染性の卵黄顆粒が充満した。免疫学的に卵黄ビテリン(分子量800,000)と同一の成分(分子量860,000)ビテロジェニンが血リンパ中に活発に放出された。4)GSI5、MED500μmは組織学的、電気泳動的挙動からみて卵黄形成前期から後期への移行時期と考えられ、この段階以降、卵期顆粒の蓄積が旺盛となった。

The vitellin accumulation was studies in freshwater shrimp Palaemon paucidens by electrophoretic, immunological, and histological techniques. Egg formation and vitellin accumulation proceeded as follows. Young oocyte stage was defined as the oocytes less than 1.5 in gonadosomatic index (GSI) and less than about 300μn in maximuin egg diameter (MED). The oocyte had nucleus and cytoplasin which were positive in hematoxylin staining, but did not include components immunologically identical with vitellin. Early yolk-formation stage corresponded to the ovaly ranged 1.5 to 4.5 in GSI and 250 to 550μm in MED, and was characterized by appearance of eosin-positive cytoplasm. The yolk globules consisted of lipoprotein were accumulated in the cytoplasm from the stage, A hemolymph lipoprotein immunologically identical to vitellin of mature ovary appeared in the ovary of which MED was more than 350μm. Late yolk-formation stage was defined as the ovary having more than 4.5 in GSI and 550 μm in MED. The nucleus disappeared and the cytoplasm filled with eosin-positive yolk globules. With the appearance of a vitellogenin in the hemolymph, the yolk constituents were actively accumulated in the ovary. Vitellogenin synthesized extraovarially was probably incorporated in the oocytes as vitellin after slight conforrnational changes.