This study reveals the ovary micromorphology and the course of oogenesis in the leech Batracobdella algira (Glossiphoniidae). Using light, fluorescence, and electron microscopies, the paired ovaries were analyzed. At the beginning of the breeding season, the ovaries were small, but as oogenesis progressed, they increased in size significantly, broadened, and elongated. A single convoluted ovary cord was located inside each ovary. The ovary cord was composed of numerous germ cells gathered into syncytial groups, which are called germ-line cysts. During oogenesis, the clustering germ cells differentiated into two functional categories, i.e., nurse cells and oocytes, and therefore, this oogenesis was recognized as being meroistic. As a rule, each clustering germ cell had one connection in the form of a broad cytoplasmic channel (intercellular bridge) that connected it to the cytophore. There was a synchrony in the development of the clustering germ cells in the whole ovary cord. In the immature leeches, the ovary cords contained undifferentiated germ cells exclusively, from which, previtellogenic oocytes and nurse cells differentiated as the breeding season progressed. Only the oocytes grew considerably, gathered nutritive material, and protruded at the ovary cord surface. The vitellogenic oocytes subsequently detached from the cord and filled tightly the ovary sac, while the nurse cells and the cytophore degenerated. Ripe eggs were finally deposited into the cocoons. A comparison of the ovary structure and oogenesis revealed that almost all of the features that are described in the studied species were similar to those that are known from other representatives of Glossiphoniidae, which indicates their evolutionary conservatism within this family.

中文翻译：

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两栖类水蛭 Batracobdella algira（Annelida、Clitellata、Hirudinida）卵巢索组织和卵子发生的超微结构研究

这项研究揭示了水蛭 Batracobdella algira (Glossiphoniidae) 的卵巢微形态和卵子发生过程。使用光、荧光和电子显微镜，分析成对的卵巢。在繁殖季节开始时，卵巢很小，但随着卵子发生的进行，它们的大小显着增加、变宽和拉长。每个卵巢内都有一个复杂的卵巢索。卵巢索由聚集成合胞体的众多生殖细胞组成，称为生殖系囊肿。在卵子发生过程中，成簇的生殖细胞分化为两个功能类别，即护士细胞和卵母细胞，因此，这种卵子发生被认为是分裂的。按照惯例，每个成簇的生殖细胞都有一个连接，它以宽阔的细胞质通道（细胞间桥）的形式连接到细胞质。整个卵巢中成簇的生殖细胞的发育是同步的。在未成熟的水蛭中，卵巢索仅含有未分化的生殖细胞，随着繁殖季节的进行，卵黄前卵母细胞和护士细胞从中分化。只有卵母细胞显着生长，聚集营养物质，并在卵巢索表面突出。生卵白卵母细胞随后从脐带上脱离并紧紧地充满卵巢囊，而保育细胞和细胞团退化。成熟的鸡蛋最终沉积在茧中。