性ホルモン投与によるメダカ生殖巣の性分化の転換過程の形態学的観察

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The processes of normal development and sex-reversal by administration of sex steroids were observed on both gonads of the genetic female (X^rX^r) and male (X^rY^r) in the larval medaka Oryzias latipes. Methyltestosterone (30μg/g of diet) and estoradiol-17-β (20μg/g of diet) were administered to the genetic female (X^rX^r) and male (X^rY^r) per os after hatching. In the genetic female (X^rX^r), oogonia occupied the entire gonad just after hatching (body length, 4.5mm). The gonad was identified as an ovary at 6.0mm body length on the basis of the appearence of oocytes (which differentiated from a part of oogonia). In the case of methyltestosterone administration oogonia which started to develope into oocytes at body length of 6.0mm gradually degenerated. The remaining oogonia formed a cyst at 9.0mm body length, and finally the gonad grew into a perfect testis with spermatogonia, spermatocytes, spermatids, and sperm at 11.0mm body length. In the male (X^rY^r), the spermatogonia in normal gonads stated to form a cyst of gonia at 9.0mm body length and developed into all stages of spermatocytes, spermatids, and sperm at 11.0mm body length. In the case of estradiol-17-β administration, a part of spermatogonia developed into oocytes at 8.0mm body length. Thus the gonad was established as an ovary. The differentiation from gonia into oocytes began earlier than that from gonia into spermatocytes.
1973-03-15