Differentiation between Acoelomates, Pseudocoelomates and coelomates.
ACOELOMATES:
Ø
In phylum Platyhelminthes there is no body
cavity or coelom, and the mesoderm form a loose, cellular tissue called
mesenchyma or parenchyma which fills the space between the ectoderm and
endoderm.
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It forms a packing around the internal organs of
the animals to support and protect them.
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Such animals are called acoelomates
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In acoelomates the gut is sac-type and there is
no special transport system.
Ø
Only excretory system is developed for the
transport of excretory products.
This system consists of flame cells, excretory ducts and excretory pores.
Ø However the nervous system is well developed.
PSEUDOCOELOMATES:
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In Aschelminthes the space between the body wall
and the digestive tube is called pseudocoelom (false body cavity)
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Pseudocoelom is not homologous to true coelom
because.
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It is not lined by coelomic epithelium.
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It has no relation with the reproductive and
excretory organs.
Ø
It develops from the blastocoel of the embryo
and it is bonded externally by the muscles and internally by the cuticle of the
intestine.
Ø The animals having pseudocoelom are called pseudocoelomates.
COELOMATES:
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Coelom is cavity present between the body wall
and the alimentary canal and is lined by mesoderm.
Ø
The mesoderm splits into outer parietal layer
(somatic) which under lines the body wall and the visceral layer (splanchnic)
which covers the alimentary canal and the cavity between them is the true
coelom.
Ø
It is filled with fluid called coelomic fluid.
Ø
The animals which posses coelom or true body
cavity are called coelomates e.g. animals from annelids to chordates.
Ø
In coelomates gut attains more complexity and
neuro-sensory system is well developed along with excretory system, circulatory
system, respiratory and reproductive system.
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