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The stage of development in animals in which the endoderm is formed and invagination of the blastula has occurred.



one of the stages of embryonic development in multicellular animals. In the gastrula stage the embryo has a two-layer wall and cavity (gastrocoel) that communicates with the surrounding environment by means of an opening, the blastopore. The outer wall is called the ectoderm; the inner wall, the endoderm. They are the primordial embryonic layers. In the beginning the endoderm, and less frequently the ectoderm, also contains the material for a middle layer of tissue—the mesoderm. At the end of gastrulation, the mesoderm separates and becomes independent, and the embryo is transformed from a two-layer to a three-layer organization.

The transformation from the blastula to the gastrula takes place differently in different animals. Already at the gastrula stage, certain differences in the properties of the embryonic layers that are precursors of their morphological differentiation can be observed. The differences in structure of the embryos of different animals at this stage of development are determined both by the structure of the eggs and by the different modes of existence of the embryos. In most animals the embryo spends the gastrula stage in the egg envelope or in the mother’s body; in some hydrozoans the gastrula is a free-living larva. Sometimes the differences pertain to the most general features; for example, in the embryos of bony fish the gastrocoel is lacking, and in certain coelenterate gastrulae the blastopore is lacking. The presence of the gastrula stage (with its characteristic separation into embryonic tissues) in the development of all multicellular organisms was demonstrated by A. O. Kovalevskii and E. Metchnikoff and provided proof of the common origin of animals.


References in periodicals archive ?
11) However, the mitochondria activation towards aerobic metabolism at gastrula stage seems to support the assumption that these organelles probably existed in eukaryotic cells long in advance of the oxidative phosphorylation achievement.
During the gastrula stage, structures are shaped through morphogenetic movement of tissue (mesoderm), injuring and disorganizing the invaded tissue architecture, which in turn promotes consequent proliferation and differentiation.
Dorsalization of the ventral marginal zone of the Triturus gastrula.
Prospective neural crest can first be identified by the late gastrula stage (stage 12, ~13 hr after fertilization) by expression of mRNA encoding the zinc finger gene Xslug on the lateral edge of the neural plate (Mayor et al.
After introduction of 20-40 [micro]M chlorpyrifos during the period of maximum sensitivity (late blastula 1 stage, 30 hr after fertilization) anomalies became evident by the early gastrula stage, 5-6 hr after addition of chlorpyrifos (Figure 4).
Developmental Stage Time(h or days) Oviposition 0 h First division 6 [+ or -] 1 h of cleavage Four-cell stage 8 h Eight-cell stage 11 h Morula 16 h Blastula, appearance of blastocoel 2 days Gastrula 2 days Motion of larvae by velar rudiment 3 days Early veliger stage, velum visible, viscera 4 days differentiated in stomach, left and right digestive diverticulum, shell color changed to purple Hatched 6 days No.
Stages Diameter Time Unfertilized eggs 180 [micro]m 0 sec Sperm attached to egg 185 [micro]m 20-30 sec Sperm acrosome reaction 185 [micro]m ~1 min Sperm-egg membrane fusion 180 [micro]m 2-3 min Appearance of first polar body 185 [micro]m 8-9 min Appearance of second 185 [micro]m 10 min polar body First cleavage 200 [micro]m 15-20 min Second cleavage 195 [micro]m 35-40 min Morula 200 [micro]m 45-55 min Blastula 192 [micro]m 75-85 min Gastrula 192 [micro]m 85-90 min Trochophore larvae 210 [micro]m 90-250 min Early veliger 225 [micro]m 5-24 h Late veliger 228 [micro]m 28-40 h Early creeping larvae 230 [micro]m 48-72 h Creeping larvae 300 [micro]m 3-6 days Juvenile 2 [micro]m 30 days
Gastrula formation occurs at 10:00-10:35 h, with a diameter of 145 [+ or -] 5 [micro]m.
Total RNA was extracted according to the method of Chomczynski and Sacchi (1987) from the following developmental stages: egg, gastrula, early trochophore (13 h post fertilization; hpf), mid torsion (18 hpf), early veliger (24 hpf), mid veliger (40 hpf), early competent veliger (72 hpf), late competent veliger (134 hpf), 1 day post metamorphosis and 5 days post metamorphosis.
At the third division, micromeres and macromeres could be differentiated and egg development progressed to the gastrula with cell cleavage being total, unequal and spiral (stages 6-11) (Fig.
Perform a second sorting under a dissecting microscope using dissecting probes or pipettes to select normal blastulas and early gastrulas, which have numerous small cells, even dorsal pigmentation, and a cream-colored ventral region (Figure 3D).