Details

Autor(en) / Beteiligte

• Świątek, Piotr
• Thounaojam, Rojen Singh
• Singh, Th. Binoy
• James, Samuel
• Gajda, Łukasz
• Małota, Karol
• Raś, Dominika
• Urbisz, Anna Z.

Titel

Ovary organization and ultrastructure in six species of Amynthas and Metaphire earthworms (Annelida, Crassiclitellata, Megascolecidae)

Ist Teil von

• Zoology (Jena), 2023-10, Vol.160, p.126109-126109, Article 126109

Ort / Verlag

Elsevier GmbH

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Ovaries in earthworms belonging to the family Megascolecidae are paired structures attached to the septum in the anterior part of the XIII segment. They are fan to rosette shaped with numerous rows of growing oocytes, known as egg strings, radiating from the ovary center towards the segmental cavity. The histological and ultrastructural ovary organization in megascolecids and the course of oogenesis remain unknown. The paper presents the results of light and electron microscopy analyses of ovaries in six megascolecid species, three from the genus Amynthas and three from Metaphire. Both parthenogenetic and sexually reproducing species were included in the study. The organization and ultrastructure of ovaries in all studied species are broadly similar. Considering the histological organization of ovaries, they could be divided into two zones. Zone I (proximal, close to the connection with the septum) is tightly packed with germline and somatic cells. Germ cells are interconnected via intercellular bridges and thin strands of the central cytoplasm (known as cytophore) and form syncytial cysts. Cysts unite oogonia, early meiotic cells (till diplotene), and clustering cells develop synchronously. During diplotene, interconnected cells lose developmental synchrony; most probably, one cell per cyst grows faster than others, detaches from the cysts, and becomes an oocyte. The remaining cells grow slightly and are still interconnected via the thin and reticular cytophore; these cells are considered nurse cells. Zone II has a form of egg strings where growing oocytes are isolated one from another by thin somatic cells and form short cords. We present the ultrastructural details of germline and somatic cells. We propose the term "Amynthas" type of ovaries for this ovary organization. We suppose that such ovaries are characteristic of other megascolecids and related families. •Paired and fan-shaped ovaries occur in segment XIII.•Oogonia and early meiotic germline cells form syncytial cysts.•During diplotene, germ cells diversify into oocytes and nurse cells.•Growing oocytes, enveloped by follicular cells, form egg strings, wheras nurse cells degenerate.•Ovary organization and oogenesis are the same in parthenogenetic and sexual species.