Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Bankowa 9, 40-007 Katowice, Poland.
Departmento de Biodiversidad, Ecología y Evolución, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, José Antonio Nováis, 12, 28040 Madrid, Spain.
Zoology (Jena). 2023 Jun;158:126081. doi: 10.1016/j.zool.2023.126081. Epub 2023 Feb 28.
There is a gap in our knowledge of microorganization and the functioning of ovaries in earthworms (Crassiclitellata) and allied taxa. Recent analyses of ovaries in microdriles and leech-like taxa revealed that they are composed of syncytial germline cysts accompanied by somatic cells. Although the pattern of cyst organization is conserved across Clitellata - each cell is connected via one intercellular bridge (ring canal) to the central and anuclear cytoplasmic mass termed the cytophore - this system shows high evolutionary plasticity. In Crassiclitellata, only the gross morphology of ovaries and their segmental localization is well known, whereas ultrastructural data are limited to lumbricids like Dendrobaena veneta. Here we present the first report about ovarian histology and ultrastructure in Hormogastridae, a small family of earthworms inhabiting the western parts of the Mediterranean sea basin. We analyzed three species from three different genera and showed that the pattern of ovary organization is the same within this taxon. Ovaries are cone-like, with a broad part connected to the septum and a narrow distal end forming an egg string. Ovaries are composed of numerous cysts uniting a small number of cells, eight in Carpetania matritensis. There is a gradient of cysts development along the long ovary axis, and three zones can be distinguished. In zone I, cysts develop in complete synchrony and unite oogonia and early meiotic cells (till diplotene). Then (zone II), the synchrony is lost, and one cell (prospective oocyte) grows faster than the rest (prospective nurse cells). In zone III, oocytes pass the growth phase and gather nutrients; at this time, their contact with the cytophore is lost. Nurse cells grow slightly, eventually die via apoptosis, and are removed by coelomocytes. The most characteristic feature of hormogastrid germ cysts is the inconspicuous cytophore in the form of thread-like thin cytoplasmic strands (reticular cytophore). We found that the ovary organization in studied hormogastrids is very similar to that described for D. veneta and propose the term "Dendrobaena" type of ovaries. We expect the same microorganization of ovaries will be found in other hormogastrids and lumbricids.
我们对环节动物（Crassiclitellata）和相关分类群的微组织和卵巢功能知之甚少。最近对微钻和类似水蛭的分类群的卵巢分析表明，它们由合胞体生殖细胞囊组成，伴有体细胞。尽管囊组织的模式在 Clitellata 中是保守的——每个细胞都通过一个细胞间桥（环道）与中央和无核细胞质团称为细胞质体相连——但这个系统显示出高度的进化可塑性。在 Crassiclitellata 中，只有卵巢的大体形态及其节段定位是众所周知的，而超微结构数据仅限于像 Dendrobaena veneta 这样的 lumbricids。在这里，我们首次报道了 Hormogastridae 的卵巢组织学和超微结构，Hormogastridae 是一种生活在地中海盆地西部的小型蚯蚓家族。我们分析了来自三个不同属的三个物种，并表明这个分类群内的卵巢组织模式是相同的。卵巢呈锥形，宽部与隔膜相连，窄部形成卵串。卵巢由许多连接少量细胞的囊组成，Carpetania matritensis 中有 8 个细胞。沿着长的卵巢轴，囊的发育存在梯度，可以区分三个区。在区 I 中，囊同步发育并联合卵原细胞和早期减数分裂细胞（至二价体）。然后（区 II），同步性丧失，一个细胞（预期卵母细胞）比其余细胞（预期滋养细胞）生长得更快。在区 III 中，卵母细胞通过生长阶段并收集营养物质；此时，它们与细胞质体的接触丢失。滋养细胞稍微生长，最终通过细胞凋亡死亡，并被体腔细胞去除。Hormogastrid 生殖囊的最显著特征是细胞质体呈线状细细胞质链（网状细胞质体）形式的不明显。我们发现研究中的 hormogastrids 的卵巢组织非常类似于描述的 D. veneta，并提出“Dendrobaena”型卵巢的术语。我们预计其他 hormogastrids 和 lumbricids 也会发现相同的卵巢微组织。
