Gonadal Sex Differentiation in Frogs: How Testes Become Shorter than Ovaries
Gonadal Sex Differentiation in Frogs: How Testes Become Shorter than Ovaries
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DOI：
10.2108/zsj.30.125
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发表时间：
2013-02-01
影响因子：
0.9
通讯作者：
Ogielska, Maria
中科院分区：
文献类型：
--
作者：
Haczkiewicz, Katarzyna;Ogielska, Maria
无尾两栖动物的睾丸分化是两个相反过程的结果：远端退化和近端发育，后者成为一个功能性的雄性性腺。未分化性腺直接分化为睾丸，没有过渡阶段。本文描述了天竺葵和木耳的睾丸发育形态，并对小叶蕨的组织学和超微结构进行了详细的研究。将发育中的睾丸分为10期（I-III期，未分化性腺，IV-X期，睾丸）。睾丸分化最早的形态学症状出现在4 ~ 5周龄的Gosner期27 ~ 28。此时，一个未分化的性腺，由6-9个元粒组成，分化成睾丸。近端节（右侧2-3个，左侧3-4个）分化为功能睾丸，远端节退化。左右性腺大小的差异一直维持到成年期（X期）。远端部变性沿前后梯度发展，开始于IV期。它首先影响生殖细胞和伴随的前体细胞，然后影响间充质细胞和成纤维细胞。最后，外上皮在几乎空的远端部分周围形成一个“套筒”。在Gosner期41（年龄74-148天），睾丸的总长度保持不变。活跃的精子发生开始于第九阶段（幼鱼第一次冬眠后），在此期间，由于精子发生的进展，远端部分最终消失，近端部分开始大量生长。
Testis differentiation in anuran amphibians is the result of two opposing processes: degeneration of the distal part, and development of the proximal part, which becomes a functional male gonad. Undifferentiated gonad differentiates directly into a testis without a transition phase. We described the morphology of developing testes in Rana temporaria and Hyla arborea, and made careful histology and ultrastructure in Pelophylax lessonae. The developing testis was divided into 10 stages (I-III, undifferentiated gonad, IV-X, testis). The earliest morphological symptoms of testis differentiation were observed in 4- to 5-week-old tadpoles at Gosner stage 27-28. At that time an undifferentiated gonad, composed of 6-9 metameres, differentiates into a testis. The proximal metameres (2-3 in the right gonad and 3-4 in the left one) differentiate into a functional testis, while the distal ones degenerate. The difference between left and right gonad size is maintained until adulthood (stage X). Degeneration of the distal part progresses along the posterior-anterior gradient and starts at stage IV. It affects first the germ cells with accompanying precursor Sertoli cells, and then the mesenchymal cells and fibroblasts. Finally the external epithelium forms a "sleeve" around the almost empty distal part. The total length of the testes stays the same until stage VIII at Gosner stage 41 (age 74-148 days). Active spermatogenesis starts at stage IX (juveniles after their first hibernation), during which the distal part eventually disappears and the proximal part starts growing considerably due to progressing spermatogenesis.