What is gastrulation explain the process of gastrulation in amphioxus?
Gastrulation in Amphioxus � begins by the flattening of the blastula, loss of the blastocoel, and formation of the archenteron – the embryonic gut cavity that is lined with endoderm. After flattening, two cell layers can be distinguished – ectoderm and endoderm.
What is the larva of amphioxus?
The amphioxus contain two larva such as Branchiostoma( around 23 species) and other one is Asymmetron(around six species).
Which type of cleavage is found in amphioxus?
holoblastic type
The egg of amphioxus is isolecithal and the cleavage is of holoblastic type. About one hour after fertilization, the egg is divided into 2 blastomeres. The plane of this first cleavage is passing through the egg axis from pole to pole.
Which type of blastula is found in amphioxus?
The blastula resulting from holoblastic equal ceavage, as in the case of echinoderms and amphioxus, is called equal coeloblastula .
What is the first stage of embryonic development?
The process of prenatal development occurs in three main stages. The first two weeks after conception are known as the germinal stage, the third through the eighth week is known as the embryonic period, and the time from the ninth week until birth is known as the fetal period.
What is the atrium in amphioxus?
In amphioxus a big space is present, called Atrium it is lined by ectoderm. It encloses pharynx, and part of intestine. It opens out through atriopore at 36 myotome in front of caudal fin. The dorsal wall of the atrium is folded.
What is the function of velum in amphioxus?
Ammocoetes, like amphioxus, is a filter feeder, but it uses the muscular velum, rather than cilia, to generate a flow of water that is the respiratory and feeding current.
What are the 4 types of cleavage?
In the absence of a large concentration of yolk, four major cleavage types can be observed: radial holoblastic, spiral holoblastic, bilateral holoblastic, and rotational holoblastic cleavage.
What is radial and spiral cleavage?
In radial cleavage, the developing embryo divided right angles to the previous division, resulting in four blastomeres situated directly above four others. In spiral cleavage, the division of cells in the developing embryo occurs in a spiral manner. This is the difference between radial and spiral cleavage.
How is the development of amphioxus?
Amphioxus have a typical bentho-pelagic life cycle (Figure 1). An embryonic period is followed by a larval period, which ends when the larva undergoes metamorphosis, which, depending on the species, takes place from a few weeks to several months after fertilization.
What is the blastula stage of embryonic development?
blastula, hollow sphere of cells, or blastomeres, produced during the development of an embryo by repeated cleavage of a fertilized egg. The cells of the blastula form an epithelial (covering) layer, called the blastoderm, enclosing a fluid-filled cavity, the blastocoel.