フナ×コイのF_1(♀)とコイあるいはフナ(♂)の逆交雑における受精現象

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When kept under a confined condition, the carp (Cyprinus carpio) and the funa (Carassius darassius) mate and can produce hybrids. Reciprocal crosses are also possible with similar results. The hybrids grow regularly with no observed abnormalities in the course of their development. They rank intermediate betweenthe parent species in several characters. The spermatogenetic activity in the hybrid testes is greatly disturbed (Makino, Ojima and Matsui 1958), while the hybrid females laid eggs. Of important is to learn that the maturation and fertilization of the hybrid eggs proceed normally or not. The eggs were mostly fixed in Gilson's fluid and some in Allen-Bouin's mixture. Paraffin sections were made, and stained with Ehrlich's haematoxylin. Periodic acid Schiff reaction (PAS) according to McManus (1948) was applied to eggs fixed with Gilson's fluid for the demonstration of polysaccharides. Triple staining after Himes et al. (1955) was adopted for the demonstration of DNA, polysaccharides and protein. 1) Mature unfertilized hybrid eggs: Mature eggs are surrounded by a very thick membrane, being perforated by a funnel-shaped micropyle in each. Below the egg membrane, there occur small vesicular alveoli showing a strong affinity to PAS. Two types of alveoli, carp-type and funa-type, are distinguishable in appearance (Figs.5-7). The first polar division is accomplished in such mature eggs. At the time of insemination, the second maturation division of the egg persists in the stages of metaphase. 2) Fertilization in the backcross between F_1-females and carp males: Stages subsequent to the metaphase of the second division take place after the entryof the spermatozoon into the egg. About 20 minutes after insemination the second division completed, resulting in the formation of the second polar body. At the time of fertilization, the egg membrane separates from egg-body leaving a perivitelline space between them. In pure carp eggs, the separation of the egg membrane from the egg-body is remarkable, showing fine alveolar granules in the perivitelline space (Ojima 1943). In the hybrid eggs, however, the alveolar structureremains without observed shift for 1 or 2 hours. This is a feature characteristic to the hybrid eggs at fertilization (Figs.11-12). About 40 to 50 minutes after insemination, there is found at the animal pole of the egg a metamorphosed female pronucleus. As early as 50 to 60 minutes after the sperm entrance, the haed of the spermatozoon is converted into the male pronucleus of a spherical form. The male pronucleus is remarkable for its sperm-aster. After the completion of both pronuclei, they begin to move towards the deeper part of the animal pole of the egg to conjugate with each other. The conjugation of two pronuclei takes place about 1 hour after insemination. It is noticeable that in the hybrid eggs, theprocess of fertilization proceeds in rather normal manner, but no cleavage spindle was formed. 3) Fertilization in the backcross between F_1-females and Funa males: The process of fertilization took place normally and fertilized eggs formed normal cleavage spindles. They developped into healthy embryos.
社団法人日本動物学会の論文
1961-08-15

フナ×コイのF_1(♀)とコイあるいはフナ(♂)の逆交雑における受精現象

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