Oogenesis in the tardigrade Hypsibius exemplaris Gąsiorek, Stec, Morek & Michalczyk, 2018 (Eutardigrada, Hypsibiidae). (November 2021)

• Record Type: Journal Article
• Authors: Jezierska, Marta; Miernik, Aleksandra; Sojka, Julia; Student, Sebastian; Śliwińska, Małgorzata A.; Gross, Vladimir; Poprawa, Izabela
• Is Part Of: Micron. Volume 150(2021)
• Publication Date: 2021-11
• Subjects: Oogenesis -- Tardigrades -- Germ cell cluster -- Cytoplasmic bridge -- Yolk -- Egg capsule; Microscopy -- Periodicals; Electron Probe Microanalysis -- Periodicals; Microscopy -- Periodicals; Microscopie -- Périodiques; Microscopy; Periodicals; 502.82
• DOI: 10.1016/j.micron.2021.103126
• Languages: English
• ISSNs: 0968-4328

Abstract

Highlights: Branched clusters of germ cells are formed in the meroistic-polytrophic ovary of H . exemplaris . One cell in each cluster differentiates into an oocyte. The vitellogenesis is of a mixed type. The egg capsule is composed of two shells: the vitelline envelope and the three-layer chorion. Abstract: Tardigrades are small, globally widespred invertebrates that need at least a thin layer of water to be active. There are gonochoric, hermaphroditic, and parthenogenetic species among them. The main aim of this study was to analyze the structure of the ovary, the structure of female germ cell clusters, and the course of oogenesis in the parthenogenetic species Hypsibius exemplaris, which in 2007 was recognized as a model organism. The material was analyzed using light and confocal microscopy as well as transmission and scanning electron microscopy. Histochemical and immunohistochemical methods were used. Our study showed that in the meroistic-polytrophic ovary of the examined species, branched germ cell clusters are formed in which one cell differentiates into an oocyte while the remaining cells become trophocytes. Vitellogenesis is of the mixed type: the first part of the yolk is synthesized by the oocyte (autosynthesis); the second part is synthesized by trophocytes and transported to the oocyte by cytoplasmic bridges; and the third part is synthesized outside the ovary (in storage cells) and transported to the oocyte by endocytosis. At the end of oogenesis, the trophocytes die by apoptosis. Parthenogenetic female of H. exemplaris lays from one to a dozen smooth eggs into exuviae.