Formation and subsequent break down of ovarian germ cell (GC) cysts is a key and an evolutionary-conserved developmental event, described in phylogenetically diverse species of invertebrates and vertebrates. In mammals, cyst break down (CBD) ends at the time of, or soon after, birth with the formation of primordial follicles enclosing single oocytes, which constitute the sole reservoir of gametes available through the whole female's reproductive life. In this study, we challenge this paradigm demonstrating the constitutive presence of a large number of cysts, enclosing two-thirty GCs, in the ovary of the adult armadillo Chaetophractus villosus, belonging to the superorder Xenarthra, one of the earliest offshoots among placentals. We also describe that (a) GCs enclosed within cysts are connected by intercellular bridges-intercellular bridges-markers of their clonal origin; (b) CBD occurs through four main phases, ending with primordial follicles containing single oocytes; (c) GCs encompass meiotic prophase I stages, from leptotene to diplotene; (d) seasonal variations in the number of GCs enclosed within cysts, suggesting the presence of a GC multiplying activity. The armadillo C. villosus''s ovary emerges as an extraordinary resource to investigate folliculogenesis and to explore the evolutionary past of the mammalian ovary.

中文翻译：

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生殖细胞囊肿是哺乳动物的胎儿特征，主要存在于成年犰狳中。

卵巢生殖细胞（GC）囊肿的形成和随后的破裂是关键的且是进化保守的发育事件，在无脊椎动物和脊椎动物的系统发育多样性物种中都有描述。在哺乳动物中，囊肿破裂（CBD）在出生时或出生后不久就结束了，形成了包含单个卵母细胞的原始卵泡，卵泡构成了整个雌性生殖生活中唯一的配子储库。在这项研究中，我们挑战了这种范例，该范例证明了成虫犰狳Chaetophractus villosus的卵巢中包含大量的囊肿，其中包括两个三十三个GC，属于超阶Xenarthra，这是胎盘中最早的分支之一。我们还描述了（a）囊肿内封闭的GCs是由其克隆起源的细胞间桥-细胞间桥-标记连接的；（b）《生物多样性公约》通过四个主要阶段发生，最后是含有单个卵母细胞的原始卵泡；（c）GC包括从瘦素到二戊烯的减数分裂I阶段；（d）囊肿内封闭的GC数量的季节性变化，表明存在GC增殖活性。犰狳C. villosus的卵巢是研究卵泡发生和探索哺乳动物卵巢进化过去的非凡资源。（d）囊肿内封闭的GC数量的季节性变化，表明存在GC增殖活性。犰狳C. villosus的卵巢是研究卵泡发生和探索哺乳动物卵巢进化过去的非凡资源。（d）囊肿内封闭的GC数量的季节性变化，表明存在GC增殖活性。犰狳C. villosus的卵巢是研究卵泡发生和探索哺乳动物卵巢进化过去的非凡资源。