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Flatworms, also known as broad or broad worms, are the simplest form of the group of worms, and these worms belong to the phylum Flatworms; The phylum or group that contains the soft, usually flat invertebrates.
Flatworms have a body with bilateral symmetry and a flat center; That
is, it resembles a tape, and there are approximately 20,000 species in
this group.
Their behaviors differ from each other, as some species live freely,
while others are parasites that may be harmful; So that it lives on
another organism called the host or in it and gets nourishment from it.
These worms may be found in sea and pure water, but they do not
belong to sea slugs, and the tapeworm is one of the most famous
species among flatworms.
These organisms reproduce by dividing into two parts; As a result of
this division, a new flatworm is formed.
The right part of the body of these worms is similar to the left part of
it; This is due to its symmetry or bilateral symmetry.
t has a thin body in general, and can be seen through a microscope,
as for its length, it may reach several feet.
Flatworms contain three layers of cells which are; ectoderm; It is the
outer covering layer, and the endoderm, which is the layer that lines
the sites of digestion; It is almost similar to cnidarians, and the
mesoderm (English: Mesoderm), which is the layer between the outer
and inner layers, while tapeworms do not have a digestive system like
adults, but the surfaces of their cells are similar to the structure of
cells lining the intestine, despite that.
Flatworms are characterized by the fact that their bodies contain three layers of tissue with organs and organelles, and they do not contain internal cavities; Where it lacks a dedicated skeletal, circulatory and respiratory system, and the following is mentioned for the formation of the body of flatworms
When dissecting the body of flatworms, it can be noted that they have
a so-called blind intestine; As it has a mouth without an opening at
the lower end of the alimentary canal, but it has the so-called proton
excretory organs instead of this opening designated to remove waste
from the body; It has a mixture between the digestive and excretory
systems, so that they get food and excrete waste using the same opening.
Flatworms have no lungs or respiratory system; But it breathes as a
result of directly absorbing oxygen through the skin and delivering it
to its internal body cells, and this process is known as cutaneous
respiration, and it is worth noting that all of its internal organs are
close to the surface of the skin to receive sufficient oxygen from the
surrounding water or fluids.
Flatworms are characterized by not having a skeleton or muscle
either, but they can move or glide quickly on their abdomen using tiny
hair-like cilia that cover their body in addition to the presence of two
layers of muscle under their skin, and these worms can swim for a
good period of time in the form of waves.
Flatworms have a very simple nervous system; Her body contains
only two nerve endings at each end, and she also has two simple
brains called ganglia that consist of a bundle of nerves. As for the
vision characteristics, she has eyes that help her sense light.
Flatworms are classified under the animal kingdom; Below that falls the group of multicellular eukaryotic organisms known as the mesozoans, that is, they belong specifically to a biological branch known as the true archaea. There are three main subgroups of flatworms in this phylum as follows:
Many types of these worms are characterized by microscopic size,
most of them may be less than five millimeters in length, and the flat
worms are the largest among them, as they may reach half a meter in length.
Most types of these worms range from 1 to 10 millimeters in length,
and some may reach several centimeters.
Some members of this group may reach fifteen meters in length,
while the smallest is one millimeter in length.
Fertilized eggs are placed together or singly, and are attached to a
surface or some object with an adhesive secretory substance most of the time.
After the embryonic development stage, tiny larvae or worms capable
of swimming emerge from these eggs.
These larvae that are produced after hatching pass through several
stages and in the final stage develop into adult worms that complete
the life cycle in turn.
As for the method of reproduction, flatworms are generally
hermaphrodite; That is, each of them has male and female genitalia,
and since the method of reproduction is sexual, in most species the
same organism produces both eggs and sperm.
With regard to the citizen, it was previously mentioned that most
types of these worms are parasitic; For this reason, trematodes and
trematodes live in vertebrate hosts, including humans; Where
tapeworms live in the digestive system of the host, while flukes live in
the circulatory system or liver of the host, the parasite may need more
than one host to complete its life cycle most of the time.