Oogenesis in the viviparous phoronid, Phoronis embryolabi

Abstract

The study of gametogenesis is useful for phylogenetic analysis and can also provide insight into the physiology and biology of species. This report describes oogenesis in the Phoronis embryolabi, a newly described species, which has an unusual type of development, that is, a viviparity of larvae. Phoronid oogonia are described here for the first time. Yolk formation is autoheterosynthetic. Heterosynthesis occurs in the peripheral cytoplasm via fusion of endocytosic vesicles. Simultaneously, the yolk is formed autosynthetically by rough endoplasmic reticulum in the central cytoplasm. Each developing oocyte is surrounded by the follicle of vasoperitoneal cells, whose cytoplasm is filled with glycogen particles and various inclusions. Cytoplasmic bridges connect developing oocytes and vasoperitoneal cells. These bridges and the presence of the numerous glycogen particles in the vasoperitoneal cells suggest that nutrients are transported from the follicle to oocytes. Phoronis embryolabi is just the second phoronid species in which the ultrastructure of oogenesis has been studied, and I discuss the data obtained comparing them with those in Phoronopsis harmeri. Finally, I discuss the distribution of reproductive patterns across both, molecular and morphological phylogenetic trees in Phoronida proving that parental care has evolved independently several times in this phylum.

A Microsporidian Infection in Phoronids (Phylum Phoronida): Microsporidium phoronidi n. sp. from a Phoronis embryolabi

“…In the vasoperitoneal epithelial layer, individual cells are connected with each other and with developing oocytes via desmosomes. In P. embryolabi, vasoperitoneal cells are extremely rich in glycogen granules and contain well-developed synthetic apparatuses (Temereva 2017). Microsporidia-like spores were discovered within the vasoperitoneal tissue surrounding the embryos and developing oocytes ( Fig.…”

“…The embryos develop in the posterior part of the body, which is occupied by special vasoperitoneal tissue ( Fig. 1D-F) that nurses the developing oocytes (Temereva 2017) and embryos (Temereva and Malakhov 2016). The vasoperitoneal cells arise from mesodermal cells of the trunk lining, which compose the walls of the blood vessels, and form follicles around oocytes (Temereva et al 2011).…”

“Noah’s Ark” Project: Interim Results and Outlook for Classic Collection Development

“…The result is of fundamental importance for understanding the mechanisms that ensure conservation of the structure of multicellular animals. A new type of oogenesis, autoheterosynthesis, has been described in Phoronida [103], which expands our comprehension of the diversity of ontogenetic patterns. A mechanism for the emission of sound signals has been, for the first time, discovered in representatives of a number of Orthopteran and Homopteran families, suggesting repeated formation of a similar stridulation signal during their evolution [71].…”

Spermatogenesis in the deep‐sea brachiopod Pelagodiscus atlanticus and the phylogenetic significance of spermatozoon structure

“…Accordingly, the primordial germ cells in brachiopods are thought to arise from coelothelial cells of ileo-parietal mesenteries due to epigenesis. The development of germ cells from peritoneal epithelium was also described in phoronids (Reunov & Klepal, 2004;Temereva, 2018;Temereva, Malakhov, & Yushin, 2011).…”