ニジマス卵の過熟現象について-I : “過熟卵”の形態ならびに出現時期

概要

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It has been frequently observed that during the stripping operation of the female rainbow trout, some eggs known as “over-ripened ova” contain oil globules which form into a lump. Furthermore, the yolk of such egg is characterized by a semi-transparency. It was confirmed from the present study that these eggs are not the products of abnormal ovarian function, but instead characterize a condition caused by an extended in situ existence within the body cavity following ovulation. This process of over-ripening could be divided into four stages according to the following description: normal ova immediately following ovulation (stage I) early stage of over-ripening (staeg II), followed by over-ripened ova (stage III), which then transform into the irregularly shaped ova with considerable decrease in their material content (stage IV). The progressive formation of over-ripened eggs, stage II, III and IV eggs could be generally recognized at about the 10th, 30th and 35th day following ovulation, respectively. During this process of over-ripening, partial collapse of the cortical alveoli and formation of a blastoderm-like structure permiated with oil globules occured. In the course of water-induced activation of eggs, the collapse of the cortical alveoli was restricted and bipolar differentiation was retarded in over-ripened eggs.
公益社団法人日本水産学会の論文