Ultrastructural changes in the avian vitelline membrane during embryonic development

The vitelline (yolk) membrane of the avian egg plays a dual role during early embryonic development; it encloses the yolk and provides a substratum for expansion of the embryo (Fig. 1). Expansion appears to be dependent upon the movement of cells at the edge of the blastoderm which is intimately associated with the inner layer of the vitelline membrane (New, 1959; Bellairs, 1963). The blastoderm (embryonic plus extraembryonic cells) has almost covered the entire surface of the yolk by the third and fourth days of incubation, and when this stage has been reached the vitelline membrane ruptures over the embryo and slips toward the vegetal pole. Rupture of the membrane during development appears to be the consequence of a decrease in its mechanical strength (Moran, 1936), which changes most rapidly at the animal pole (over the embryo).

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Roles of Cortical and Subcortical Components in Cleavage Furrow Formation in Amphibia

Journal of Cell Science ◽

10.1242/jcs.11.2.543 ◽

1972 ◽

Vol 11 (2) ◽

pp. 543-556

Author(s):

TSUYOSHI SAWAI

Keyword(s):

Surface Layer ◽

Xenopus Laevis ◽

Species Specificity ◽

Cleavage Furrow ◽

Entire Surface ◽

Animal Pole ◽

The Future ◽

Vegetal Pole ◽

Triturus Pyrrhogaster

In the eggs of the newt, Triturus pyrrhogaster, 2 separate factors are recognized which take part in cleavage furrow formation. (1) The inductive capacity for the furrow formation by the cytoplasm lying under the cortex along the cleavage furrow (FIC); and (2) the reactivity of the overlying cortex to form a furrow in response to FIC. (1) FIC. The inductive capacity is shown by the fact that FIC induces a furrow on whichever part of the surface under which FIC is transplanted. FIC is distributed along the cleavage furrow and even extends along the future furrow plane ahead of the furrow tip. The distance FIC precedes the furrow tip is about 1.0 mm in the animal hemisphere and is less in the vegetal hemisphere. In the direction at right angles to the furrow plane, FIC does not spread more than 0.1 mm. FIC is also present in the eggs of Xenopus laevis. Species specificity of FIC for induction is not found between Triturus and Xenopus. (2) Surface layer. At the onset of the first cleavage, the reactivity of the cortex to form the furrow in answer to FIC induction is localized on the animal pole region. The reactivity of the cortex propagates medially as a belt along the surface towards the vegetal pole with the advancing tip of the cleavage furrow. After the furrow is completed, the reactivity begins to be lost from the animal pole region, and eventually over the entire surface. The reactivity, however, reappears on the animal pole region simultaneously with the second cleavage.

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The Early Embryonic-Development of the Mnesarchaeid Moth, Mnesarchaea-Fusilella Walker (Lepidoptera, Mnesarchaeidae), and Its Phylogenetic Significance

Australian Journal of Zoology ◽

10.1071/zo9950479 ◽

1995 ◽

Vol 43 (5) ◽

pp. 479 ◽

Cited By ~ 2

Author(s):

Y Kobayashi ◽

GW Gibbs

Keyword(s):

Embryonic Development ◽

Early Embryonic Development ◽

Vitelline Membrane ◽

Phylogenetic Significance ◽

Inner Region

Formative processes of the blastoderm, germ disk, germ rudiment and embryonic membranes in the mnesarchaeid moth, Mnesarchaea fusilella, are described, and their phylogenetic significance is discussed. The egg is ovoid, about 0.32 mm by 0.48 mm in size. Below the thin chorion lies a very thick vitelline membrane. In the newly laid eggs, this membrane is colourless, but it becomes blackly pigmented about 30 hours after oviposition. Soon after the completion of the blastoderm, the germ disk or embryonic area forms in the posteroventral region of the egg. It then invaginates into the yolk, and becomes a sac-shaped germ rudiment. After closure of its opening, the germ rudiment separates from the rudimentary serosal or extra-embryonic area Its inner region later develops into the embryo, and its outer one into the amnion. The serosa is thick and each of its cells has two nuclei. The formative process of the germ rudiment and embryonic membranes in M. fusilella is primitive and very similar to that of the hepialid moths, Endoclita excrescens and E. sinensis. From the embryological standpoint, Mnesarchaea clearly belong to the Exoporia because of the following two synapomorphic characters: (1) formation of the thick, blackly pigmented vitelline membrane: and (2) presence of thick, bi-nucleated serosal cells.

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Embryonic development of Pachycheles chubutensis (Decapoda: Anomura)

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315409000678 ◽

2009 ◽

Vol 89 (6) ◽

pp. 1195-1202 ◽

Cited By ~ 1

Author(s):

Ximena González-Pisani ◽

Tamara Rubilar ◽

Enrique Dupré

Keyword(s):

Embryonic Development ◽

Developmental Stages ◽

Posterior Part ◽

Entire Surface ◽

Animal Pole ◽

Second Stage ◽

Oval Form ◽

Dark Pigmentation ◽

Eye Pigmentation

The different stages of embryonic development of the porcellanid crab Pachycheles chubutensis are described, along with the chronology of each stage at 16±1°C. Five different developmental stages (I–V) were recognized including: (i) early cells and 100% of the vitellum; (ii) formation of the embryonic primordium at the animal pole of the egg; (iii) presence of dark pigmentation on the posterior part of the ocular globe; (iv) appearance of chromatophores on mouth parts and in the abdominal zone; and (v) eye pigmentation in circular–oval form, filling the entire surface. The embryonic development lasts from spawning to hatching approximately 21 days, with the second stage being the longest.

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Neural fold abnormalities induced in newt embryos by a carcinogen

Canadian Journal of Zoology ◽

10.1139/z85-291 ◽

1985 ◽

Vol 63 (8) ◽

pp. 1989-1990

Author(s):

Panagiotis A. Tsonis

Keyword(s):

Embryonic Development ◽

Abnormal Development ◽

Gastrula Stage ◽

Blastula Stage ◽

Animal Pole ◽

Vegetal Pole ◽

Neurula Stage

The effects of a carcinogen, N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), on newt embryonic development were studied. When embryos are treated with MNNG before the blastula stage, abnormal development occurs. The most prominent effect is that the hinder region of the egg–embryo (vegetal pole) does not participate in the development; thus, only one hemisphere (animal pole) of the egg develops. This phenomenon is evident at the gastrula stage and becomes even more apparent during the neurula stage.

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Embryonic development in the acoel Hofstenia miamia

10.1101/2021.01.25.427674 ◽

2021 ◽

Author(s):

Julian O. Kimura ◽

Lorenzo Ricci ◽

Mansi Srivastava

Keyword(s):

Embryonic Development ◽

Transcriptome Data ◽

Genetic Studies ◽

Animal Pole ◽

Cell Internalization ◽

Vegetal Pole ◽

Summary Statement ◽

Marine Worms ◽

Developmental Staging

AbstractAcoels are marine worms that belong to the phylum Xenacoelomorpha. The phylogenetic placement of this group as a deep-diverging lineage makes acoel embryos an attractive system to study the evolution of major bilaterian traits. Thus far, acoel development has not been described in detail at the morphological and transcriptomic levels in a species where functional genetic studies are possible. Here, we present a set of developmental landmarks for embryogenesis in the highly regenerative acoel Hofstenia miamia. We generated a developmental staging atlas from zygote to hatched worm based on gross morphology, with accompanying bulk transcriptome data for each of the stages. Hofstenia embryos undergo a stereotyped cleavage program known as duet cleavage, which results in two large ‘macromeres’ at the vegetal pole and numerous small ‘micromeres’ at the animal pole. The macromeres become internalized as micromere progeny proliferate and move vegetally, enveloping the larger blastomeres. We also noted a second, previously undescribed cell internalization event at the animal pole, following which we detected tissues corresponding to all three germ layers. Our work on Hofstenia embryos provides a resource for future investigations of acoel development, which will yield insights into the evolution of development and regeneration.Summary StatementComprehensive characterization of embryonic development in the acoel worm Hofstenia miamia with accompanying transcriptome data.

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Embryonic development in the acoel Hofstenia miamia

Development ◽

10.1242/dev.188656 ◽

2021 ◽

Vol 148 (13) ◽

Author(s):

Julian O. Kimura ◽

Lorenzo Ricci ◽

Mansi Srivastava

Keyword(s):

Embryonic Development ◽

Small Animal ◽

Transcriptome Data ◽

Genetic Studies ◽

Germ Layers ◽

Animal Pole ◽

Cell Internalization ◽

Vegetal Pole ◽

Marine Worms ◽

Developmental Staging

ABSTRACT Acoels are marine worms that belong to the phylum Xenacoelomorpha, a deep-diverging bilaterian lineage. This makes acoels an attractive system for studying the evolution of major bilaterian traits. Thus far, acoel development has not been described in detail at the morphological and transcriptomic levels in a species in which functional genetic studies are possible. We present a set of developmental landmarks for embryogenesis in the highly regenerative acoel Hofstenia miamia. We generated a developmental staging atlas from zygote to hatched worm based on gross morphology, with accompanying bulk transcriptome data. Hofstenia embryos undergo a stereotyped cleavage program known as duet cleavage, which results in two large vegetal pole ‘macromeres’ and numerous small animal pole ‘micromeres’. These macromeres become internalized as micromere progeny proliferate and move vegetally. We also noted a second, previously undescribed, cell-internalization event at the animal pole, following which we detected major body axes and tissues corresponding to all three germ layers. Our work on Hofstenia embryos provides a resource for mechanistic investigations of acoel development, which will yield insights into the evolution of bilaterian development and regeneration.

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