In this article the classification of coelom or you can say the classification of Animals on the basis of coelom is discussed.
Contents:
1. Protostomes
2. Duetrosomes
Classification of Coelomates
Coelomates are classified into two groups on the basis of development:
1. Protostomes
ii. Deuterostomes
1. Protostomes:
(Greek word proto means single or first, stome means opening or mouth) Those animals in which first opening in embryonic stages i.e., blastopore become mouth during the process of development are called protostomes.
Characteristics:
i. Mouth is developed by blastopore of gastrula during the process of development.
ii. Cleavage of zygote is spiral and determinate.
iii. Mesoderm is derived from anterior lip of blastopore.
iv. Coelom is developed by splitting of mesoderm.
v. Central nervous system Lies on the ventral side of the body.
vi. Its larva is called trochophore.
vii. They are biliterallypilot release symmetrical.
Spiral cleavage:
It is a pattern of early cleavage in which line of division is not symmetrical between poles but animal pole (small cells that divide rapidly) blastomeres are rotated with respect to those of the vegetal pole (large yolky cells that divide very slowly) or line of division is diagonal to polar axis so arrangement of the blastomeres of each upper tier over the cell junctions of the next lower tier so that the blastomeres spiral around the pole to pole axis of the embryo. This produce unequal size of blastomeres. In some mollusks, the handedness of the spiral twist is maternally inherited.
Determinate:
A type of cleavage of a zygote in which future of blastomeres is known, that which blastomere is developing which part of the body in future. Each blastomere produced by early embryonic cleavage does not have the capacity to develop into a complete embryo.
Members:
Phylum Mollusca, Annelida and Arthropoda. and Deuterostomes
Phyla Platyhelminthes and Nematoda are placed on the basis of triploblastic nature although nematode have two openings but still placed in protostomes due to maximum similarities.
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2. Deuterostomes:
(Greek word deuteron means secondary, stome means mouth)
Those animals in which anus is developed by blastopore or primary opening and mouth is produced as a secondary opening in alimentary canal at some distance from blastopore during organogenesis are called deuterostomes.
Characteristics Of Duetrostomes:
i. Anus is formed from blastopore and mouth at some distance anterior to blastopore during embryonic development.
i. Cleavage of zygotes is radial and indeterminate:
1.Radial cleavage In Deuterostomes:
The plane of cleavage is symmetrical to polar axis so arrangement of the blastomeres of each upper tier directly over those of the next lower tier resulting in radial symmetry around the pole to pole axis of the embryo
2. Indeterminate:
A type of cleavage of a zygote in which the fate of each blastomere is not determined. If one blastomere is separated and placed in a favorable environment, it can grow into a complete organism.
iii. Mesoderm is developed from walls of archenteron.
iv. Coelom develops as an out pouching of archenteron.
V. Its larva is called pleuteous.
vi. Central nervous system lies on dorsal side of the body.
Members: Deuterostomes include phylum Echinodermata, Hemichordata and chordata.
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