Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland.
OD Taxonomy and Phylogeny, Royal Belgian Institute of Natural Sciences, Brussels, Belgium.
J Morphol. 2021 Jan;282(1):98-114. doi: 10.1002/jmor.21285. Epub 2020 Oct 19.
Ovaries of Haplotaxis sp. were studied in active and nonactive states, that is, in a sexually mature specimen and in specimens outside of the reproductive period. Two pairs of ovaries were found in segments XI and XII. Especially in the nonactive state, they were in close contact with copulatory glands. Each ovary was composed of germ cells interconnected with syncytial cysts, which were enveloped by a layer of somatic cells. Within cysts each germ cell had one ring canal connecting it to the common anuclear cytoplasmic mass called a cytophore. During oogenesis clustering germ cells differentiated into nurse cells and oocytes; thus, the oogenesis was recognized as meroistic. Vitellogenic oocytes were detached from the ovaries and continued yolk absorption within the body cavity. Because recent studies have shown the variety of ovaries and germ line cyst organization in clitellates and suggest their evolutionary conservatism at the family or subfamily level, the data presented here can be valid in understanding the phylogenetic relationships among Clitellata. In this context, ovaries found in Haplotaxis sp. resembled those of the "Tubifex" type. "Tubifex" ovaries are characteristic for numerous microdrile taxa (tubificines, limnodriloidines, propappids, lumbriculids, and leech-like branchiobdellids) and can be regarded as the primary character for these Clitellata in which germ-line cysts are formed during early oogenesis. As the family Haplotaxidae is currently considered to be paraphyletic and the species studied here belongs to Haplotaxidae sensu stricto, our results support the close relationship of Haplotaxidae sensu stricto to the clade consisting of Lumbriculidae, Branchiobdellida, and Hirudinida, in which lumbriculids are sister to the latter two.
研究了 Haplotaxis sp. 的卵巢，包括活跃状态和非活跃状态，即性成熟标本和非繁殖期标本。在 XI 和 XII 节段中发现了两对卵巢。特别是在非活跃状态下，它们与交配腺密切接触。每个卵巢由相互连接的生殖细胞和合胞体胞囊组成，这些胞囊被一层体细胞包围。在胞囊中，每个生殖细胞都有一个环管将其与称为细胞质团的无核细胞质共同体连接起来。在卵子发生过程中，聚集的生殖细胞分化为滋养细胞和卵母细胞；因此，卵子发生被认为是均等分裂的。卵母细胞从卵巢中分离出来，并在体腔内继续吸收卵黄。由于最近的研究表明了环节动物中卵巢和生殖线胞囊组织的多样性，并表明它们在科或亚科水平上具有进化保守性，因此这里提出的数据可以有效地理解环节动物的系统发育关系。在这种情况下，在 Haplotaxis sp. 中发现的卵巢类似于“Tubifex”类型。“Tubifex”卵巢是许多微管类群（tubificines、limnodriloidines、propappids、lumbriculids 和类似蛭类的branchiobdellids）的特征，可以被认为是这些环节动物的原始特征，在这些环节动物中，生殖线胞囊在早期卵子发生过程中形成。由于目前认为 Haplotaxidae 科是并系的，而这里研究的物种属于严格意义上的 Haplotaxidae 科，因此我们的结果支持严格意义上的 Haplotaxidae 科与包括 Lumbriculidae、Branchiobdellida 和 Hirudinida 的进化枝密切相关，其中 lumbriculids与后两者为姐妹群。
