{"title":"两种穴居栉虫属(栉虫目,栉虫科)的子房组织和卵发生。","authors":"Piotr Świątek, Łukasz Gajda, Anna Z. Urbisz","doi":"10.1016/j.ydbio.2025.09.021","DOIUrl":null,"url":null,"abstract":"<div><div>Clitellate annelids (Clitellata) are hermaphrodites with gonads localized in specific segments in the anterior body part. Localization of gonads and the structure of the reproductive systems are considered conservative traits of clitellate evolution and are used as crucial features in their taxonomy and in phylogenetic considerations. The study aimed to present the ovary morphology, histology, and ultrastructure in two <em>Delaya</em> species. The genus <em>Delaya</em> groups poorly known cave-living clitellate annelids, and their ovary organization and oogenesis are entirely unknown. Moreover, their taxonomic status is under debate. According to recent molecular analyses, <em>Delaya</em> and two other genera form the family Pelodrilidae, closely related to earthworms. To enhance our understanding of these cave-living animals' reproductive biology and provide new characters that may aid in phylogenetic considerations, the light and electron microscopic techniques were used to study the organization of the ovaries and the course of oogenesis in two species: one from a cave in Greece (<em>Delaya</em> sp. GR) and the other from a cave in France (<em>Delaya</em> sp. FR). In both species studied, two pairs of ovaries are located in two consecutive segments – XII and XIII. Each ovary consists of 3–5 functional units. The ovarian units are polarized: their apical parts (attached to the septum) contain oogonia and early meiotic cells, while the broader distal ends contain growing oocytes and nurse cells. Initially, Germline cyst formation in cells (oogonia and early meiotic cells) develop synchronously, forming syncytial cysts in which each cell is connected via a single ring canal to the central cytoplasm (cytophore). Then, during meiotic prophase (in diplotene), synchrony is lost, and it is likely that one cell per cyst begins accumulating nutrients and differentiating into an oocyte. As oocytes detach from the cyst and continue oogenesis as individual cells, the remaining cells stay interconnected, do not grow, and are regarded as nurse cells. Yolk absorption is not completed in the ovary; vitellogenic oocytes are transferred to the ovisacs, where they continue to accumulate nutrients. Ovisacs are paired, long, sac-like structures, extending through several body segments (XII-XV). <em>Delaya</em> produces mesolecithic eggs with prominent yolk spheres, lipid droplets, and glycogen granules. Only some minor differences were observed between the two studied species. The most notable difference concerns the cytophore shape and volume in cysts connecting nurse cells. In <em>Delaya</em> sp. FR, the cytophore is reticular and inconspicuous, whereas in <em>Delaya</em> sp. GR, the cytophore is more prominent and may contain nurse cell nuclei.</div><div>The obtained results confirm that the formation of the germline cysts equipped with the cytophore is a conservative phase of oogenesis in clitellates. Morphological observations suggest that in <em>Delaya,</em> the clustering cells differentiate into two subpopulations: oocyte and nurse cells, which aligns with the reports presenting oogenesis in other clitellates. Considering the differences in ovary organization between <em>Delaya</em> and other clitellates, we propose to refer to these as “Delaya-type” ovaries. The main similarities and differences between “Delaya” ovaries and other clitellate annelids are discussed. It is suggested that the presence of cysts equipped with the reticular cytophore could be an apomorphy of Pelodrilidae, earthworms, and allied taxa.</div><div>We also provide DNA barcode sequences for <em>Delaya</em> sp. FR to shed light on its taxonomic identity. Furthermore, the phylogenetic analysis that was conducted indicates that <em>Delaya</em> sp. FR occupies a basal position among its congeners for which molecular data are available.</div></div>","PeriodicalId":11070,"journal":{"name":"Developmental biology","volume":"529 ","pages":"Pages 13-34"},"PeriodicalIF":2.1000,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Ovary organization and oogenesis in two species of cave-living clitellate annelids from the genus Delaya (Clitellata, Pelodrilidae)\",\"authors\":\"Piotr Świątek, Łukasz Gajda, Anna Z. Urbisz\",\"doi\":\"10.1016/j.ydbio.2025.09.021\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Clitellate annelids (Clitellata) are hermaphrodites with gonads localized in specific segments in the anterior body part. Localization of gonads and the structure of the reproductive systems are considered conservative traits of clitellate evolution and are used as crucial features in their taxonomy and in phylogenetic considerations. The study aimed to present the ovary morphology, histology, and ultrastructure in two <em>Delaya</em> species. The genus <em>Delaya</em> groups poorly known cave-living clitellate annelids, and their ovary organization and oogenesis are entirely unknown. Moreover, their taxonomic status is under debate. According to recent molecular analyses, <em>Delaya</em> and two other genera form the family Pelodrilidae, closely related to earthworms. To enhance our understanding of these cave-living animals' reproductive biology and provide new characters that may aid in phylogenetic considerations, the light and electron microscopic techniques were used to study the organization of the ovaries and the course of oogenesis in two species: one from a cave in Greece (<em>Delaya</em> sp. GR) and the other from a cave in France (<em>Delaya</em> sp. FR). In both species studied, two pairs of ovaries are located in two consecutive segments – XII and XIII. Each ovary consists of 3–5 functional units. The ovarian units are polarized: their apical parts (attached to the septum) contain oogonia and early meiotic cells, while the broader distal ends contain growing oocytes and nurse cells. Initially, Germline cyst formation in cells (oogonia and early meiotic cells) develop synchronously, forming syncytial cysts in which each cell is connected via a single ring canal to the central cytoplasm (cytophore). Then, during meiotic prophase (in diplotene), synchrony is lost, and it is likely that one cell per cyst begins accumulating nutrients and differentiating into an oocyte. As oocytes detach from the cyst and continue oogenesis as individual cells, the remaining cells stay interconnected, do not grow, and are regarded as nurse cells. Yolk absorption is not completed in the ovary; vitellogenic oocytes are transferred to the ovisacs, where they continue to accumulate nutrients. Ovisacs are paired, long, sac-like structures, extending through several body segments (XII-XV). <em>Delaya</em> produces mesolecithic eggs with prominent yolk spheres, lipid droplets, and glycogen granules. Only some minor differences were observed between the two studied species. The most notable difference concerns the cytophore shape and volume in cysts connecting nurse cells. In <em>Delaya</em> sp. FR, the cytophore is reticular and inconspicuous, whereas in <em>Delaya</em> sp. GR, the cytophore is more prominent and may contain nurse cell nuclei.</div><div>The obtained results confirm that the formation of the germline cysts equipped with the cytophore is a conservative phase of oogenesis in clitellates. Morphological observations suggest that in <em>Delaya,</em> the clustering cells differentiate into two subpopulations: oocyte and nurse cells, which aligns with the reports presenting oogenesis in other clitellates. Considering the differences in ovary organization between <em>Delaya</em> and other clitellates, we propose to refer to these as “Delaya-type” ovaries. The main similarities and differences between “Delaya” ovaries and other clitellate annelids are discussed. It is suggested that the presence of cysts equipped with the reticular cytophore could be an apomorphy of Pelodrilidae, earthworms, and allied taxa.</div><div>We also provide DNA barcode sequences for <em>Delaya</em> sp. FR to shed light on its taxonomic identity. Furthermore, the phylogenetic analysis that was conducted indicates that <em>Delaya</em> sp. FR occupies a basal position among its congeners for which molecular data are available.</div></div>\",\"PeriodicalId\":11070,\"journal\":{\"name\":\"Developmental biology\",\"volume\":\"529 \",\"pages\":\"Pages 13-34\"},\"PeriodicalIF\":2.1000,\"publicationDate\":\"2025-09-29\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Developmental biology\",\"FirstCategoryId\":\"99\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0012160625002799\",\"RegionNum\":3,\"RegionCategory\":\"生物学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"DEVELOPMENTAL BIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Developmental biology","FirstCategoryId":"99","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012160625002799","RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"DEVELOPMENTAL BIOLOGY","Score":null,"Total":0}
Ovary organization and oogenesis in two species of cave-living clitellate annelids from the genus Delaya (Clitellata, Pelodrilidae)
Clitellate annelids (Clitellata) are hermaphrodites with gonads localized in specific segments in the anterior body part. Localization of gonads and the structure of the reproductive systems are considered conservative traits of clitellate evolution and are used as crucial features in their taxonomy and in phylogenetic considerations. The study aimed to present the ovary morphology, histology, and ultrastructure in two Delaya species. The genus Delaya groups poorly known cave-living clitellate annelids, and their ovary organization and oogenesis are entirely unknown. Moreover, their taxonomic status is under debate. According to recent molecular analyses, Delaya and two other genera form the family Pelodrilidae, closely related to earthworms. To enhance our understanding of these cave-living animals' reproductive biology and provide new characters that may aid in phylogenetic considerations, the light and electron microscopic techniques were used to study the organization of the ovaries and the course of oogenesis in two species: one from a cave in Greece (Delaya sp. GR) and the other from a cave in France (Delaya sp. FR). In both species studied, two pairs of ovaries are located in two consecutive segments – XII and XIII. Each ovary consists of 3–5 functional units. The ovarian units are polarized: their apical parts (attached to the septum) contain oogonia and early meiotic cells, while the broader distal ends contain growing oocytes and nurse cells. Initially, Germline cyst formation in cells (oogonia and early meiotic cells) develop synchronously, forming syncytial cysts in which each cell is connected via a single ring canal to the central cytoplasm (cytophore). Then, during meiotic prophase (in diplotene), synchrony is lost, and it is likely that one cell per cyst begins accumulating nutrients and differentiating into an oocyte. As oocytes detach from the cyst and continue oogenesis as individual cells, the remaining cells stay interconnected, do not grow, and are regarded as nurse cells. Yolk absorption is not completed in the ovary; vitellogenic oocytes are transferred to the ovisacs, where they continue to accumulate nutrients. Ovisacs are paired, long, sac-like structures, extending through several body segments (XII-XV). Delaya produces mesolecithic eggs with prominent yolk spheres, lipid droplets, and glycogen granules. Only some minor differences were observed between the two studied species. The most notable difference concerns the cytophore shape and volume in cysts connecting nurse cells. In Delaya sp. FR, the cytophore is reticular and inconspicuous, whereas in Delaya sp. GR, the cytophore is more prominent and may contain nurse cell nuclei.
The obtained results confirm that the formation of the germline cysts equipped with the cytophore is a conservative phase of oogenesis in clitellates. Morphological observations suggest that in Delaya, the clustering cells differentiate into two subpopulations: oocyte and nurse cells, which aligns with the reports presenting oogenesis in other clitellates. Considering the differences in ovary organization between Delaya and other clitellates, we propose to refer to these as “Delaya-type” ovaries. The main similarities and differences between “Delaya” ovaries and other clitellate annelids are discussed. It is suggested that the presence of cysts equipped with the reticular cytophore could be an apomorphy of Pelodrilidae, earthworms, and allied taxa.
We also provide DNA barcode sequences for Delaya sp. FR to shed light on its taxonomic identity. Furthermore, the phylogenetic analysis that was conducted indicates that Delaya sp. FR occupies a basal position among its congeners for which molecular data are available.
期刊介绍:
Developmental Biology (DB) publishes original research on mechanisms of development, differentiation, and growth in animals and plants at the molecular, cellular, genetic and evolutionary levels. Areas of particular emphasis include transcriptional control mechanisms, embryonic patterning, cell-cell interactions, growth factors and signal transduction, and regulatory hierarchies in developing plants and animals.