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From this moment the embryo is called a gastrula, and the concave, visible from outside, is the emerging blastopore. Over the upper edge of the blastopore, called the dorsal lip, a migration of cells occurs, which derives from the central area of the gray crescent. The process of involution takes place – the dorsal lip turns in upon itself.
The embryo during this process is called a gastrula. The germ layers are referred to as the ectoderm, mesoderm and endoderm. In diploblastic animals only the ectoderm and the endoderm are present. [8] * Among different animals, different combinations of the following processes occur to place the cells in the interior of the embryo:
This is common in molluscs, arthropods and fishes, and is found in most frogs. [1] Oviparity: fertilisation is internal, but the female lays zygotes as eggs with a substantial quantity of yolk to feed the embryo while it remains in the egg. The egg is not retained in the body, or only for a limited time. [1] Oviparity is found in insects, birds.
In most animals, the embryo is the sessile initial stage of the individual life cycle, and is followed by the emergence (that is, the hatching) of a motile stage. The zygote or the ovum itself or the sessile organic vessel containing the developing embryo may be called the egg.
Lepidobatrachus laevis, widely known as Budgett's frog, is a species of frog in the family Ceratophryidae, discovered by John Samuel Budgett. [2] It is often kept as a pet . It has acquired a number of popular nicknames, including hippo frog , [ 3 ] Freddy Krueger frog , [ 3 ] and escuerzo de agua .
Frog (Xenopus), as well as other amphibian, gastrulation serves as an excellent example of the role of convergent extension in embryogenesis. During gastrulation in frogs, the driving force of convergent extension is the morphogenic activity of the presumptive dorsal mesodermal cells; this activity is driven by the mesenchymal cells that lie ...
The cells at the medial hinge point become wedge shaped. In some contexts, such as in Xenopus frog embryos, this cell shape change appears to be due to apical constriction. [28] [29] However, in chickens and mice, bending at this hinge point is mediated by a process called basal wedging, rather than apical constriction.
A puppy is a juvenile dog, generally one less than 12-18 months old. Puppies are markedly underdeveloped and dependent on their mothers at birth (displaying altriciality), but healthy puppies grow quickly and begin walking thereafter. Puppies generally weigh 8–16 oz (0.23–0.45 kg) shortly after birth, depending on the breed. [1]