There
are three classes of flatworms:
1)
Class Cestoda(Tapeworm Taenia)
2)
Class Trematoda (Fasciola)
3)
Class Tubellaria(Planaria)
4)
Class Monogenea ( Dactylogyrus)
One is
free living (tubellarian) and two are parasitic.
The
free-living specimen the planarian, best exemplifies the characteristics of the
phylum.
· Commonly known as flat worms.
· They have soft, unsegmented bodies and are often quite flat
and elongated.
· Flat worms are unsegmented,
· Bilaterally symmetrical worms that have no coelom( acoelomate), but
that do have three germ layers (triploblastic).
· Many are parasitic organisms that are harmful to humans, but
some are free living.
· Excretion and osmoregulation by flatworms is regulated by
"flame cells" located in protonephridia.
· Flatworms lack a respiratory or a circulatory system; these
functions take place by absorption through the body wall.
· Digestive system with single opening (has mouth but no anus)
· Habitat: marine, fresh water, free living
· They are hermaphroditic (monoecious), possessing both male
and female sex organ
CLASS CESTODA - Taenia Saginata
•
Beef-tapeworm
•
Endoparasite: causes intestinal blockage &
nutritional deficiencies in humans
•
Scolex ( head ) has suckers ( & some with hooks )
for attachment to intestines of host
•
Has a long series of proglottids ( not real segments )
: absorb nutrients from host
•
Lacks mouth & digestive
Parasite acquires
nutrient molecules from the host, and the digestive system is reduced.
•
It is covered by a specialized body wall resistant to
host digestive juices.
•
While the tapeworm grows in the host's intestine, body
segments called proglottids bud off its head and neck regions.
•
A mature proglottid has both male & female sex
•
organs (hermaphrodite )
•
The extensive development of the reproductive system,
with the production of millions of eggs, may be associated with difficulties in
dispersing the species.
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