Early embryonic development of the mayfly Ephemera japonica McLachlan (Insecta: Ephemeroptera, Ephemeridae)

Journal of Morphology
Koji Tojo, Ryuichiro Machida

Abstract

In the newly laid egg of the mayfly Ephemera japonica, an egg nucleus (oocyte nucleus) at metaphase of the first maturation division is in the polar plasm at the mid-ventral side of the egg, and a male pronucleus lies in the periplasm beneath a micropyle situated just opposite the polar plasm or at the mid-dorsal side of egg. The maturation divisions are typical. An extensive and circuitous migration of the male pronucleus is involved in the fertilization process: it first moves anteriad in the periplasm from beneath the micropyle to the anterior pole of the egg and then turns posteriad in the yolk along the egg's long axis to the site of syngamy, near the center of the egg. Cleavage is superficial. The successive eight cleavages, of which the first five are synchronized, result in the formation of the blastoderm, and about ten primary yolk cells remain behind in the yolk. Even in the newly formed blastoderm, the thick embryonic posterior half and the thin extraembryonic anterior half areas are distinguished: the former cells are concentrated at the posterior pole of the egg to form the germ disc, and the latter cells become more flattened, forming serosa. Time-lapse VTR observations reveal a yolk stream that is in accord with ...Continue Reading

Citations

Apr 30, 2010·Development Genes and Evolution·Brigid C O'Donnell, Elizabeth L Jockusch
Apr 20, 2005·Journal of Morphology·Barbora Konopová, Jan Zrzavý
Apr 27, 2013·The Journal of Experimental Biology·Daisuke S YamamotoHiroyuki Matsuoka
Aug 4, 2021·Open Biology·Anna H York-AndersenTimothy T Weil

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