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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 ?
5hr Blastula 3-5hr Gastrula Trochophore 16-18hr -- -- D-shaped 63-77 D1-5 64-84 26hr Umbo 74-251 D5-12 90-110 -- Eye-spot 144-267 D 12-16 -- -- Pediveliger 195-350 D12-16 274 -- Spat 490> D16> -- -- Stage Pernaviridis [13] Ensisarcuatus [17] Size Time Size Time ([micro]m) ([micro]m) 1st pb 50-60 20m 60 15m 2nd pb 2 to 32-cell 40m 6h Morula 60 >6hr Blastula 6-12h Gastrula 16h Trochophore -- -- -- 19h D-shaped 60-70 24hr 109 20-24 Umbo 90-260 D7 177 D7 Eye-spot 220-270 D13 -- -- Pediveliger 280-380 D16 283 D14 Spat 400-490 >D21 378 D20 Stage Placuna placenta [18] Size Time ([micro]m) 1st pb 50-70 15m 2nd pb 20m 2 to 32-cell 155m Morula 285 Blastula 295 Gastrula 305 Trochophore 341 D-shaped 80 18 Umbo 140 D4 Eye-spot -- -- Pediveliger 215 D7 Spat 340 D10
53-55) Brain and palp fates are specified at the gastrula stage (Fig.
El estadio de gastrula (Figura 6), se caracteriza inicialmente por movimientos celulares de involucion, convergencia y extension del blastodermo, comenzando a migrar hacia el polo vegetal.
Las celulas resultantes de dicha division se denominan blastomeros y forman una masa compacta llamada morula, a partir de la cual se forma la blastula y posteriormente la gastrula.
In this context the (almost) anaerobic metabolism at blastula stage embryo could reflect the existence of multi-cellular organisms in the deep anoxic Earth while the transition to aerobic metabolism at gastrula could be related to the evolution towards tridermic organisms around 2 billion years ago.
A Colorado beetle has a better claim to suffer than a human gastrula.
In this process, a piece of chordamesoderm (Spemann's primary organizer) from an embryo at the gastrula stage, when transplanted, induces a secondary embryo in a competent host embryo.
Twenty-four hours after mating, embryos at the early-cleavage, blastula, gastrula, neurula, and tadpole stages were collected, preserved in Bouin's fixative, sputter coated with a mixture of platinum and gold, and observed using a scanning electron microscope (S-2460N, Hitachi).
El tiempo de formacion de la morula, blastula y gastrula observados en la corvina C.