Phylum Platyhelminthes : Dangerous Flatworm
Flatworm belongs to Phylum Platyhelminthes which are usually soft-bodied parasitic animals which is the simplest of animals possessing heads. They are somewhat flattened and bilaterally symmetrical and elongated. The name of the phylum comes from the Greek terms platys which means “flat” and “helmins” which means worms.
There are three main classes which are included in this phylum:
- Tapeworms, which in the adult stage are parasitic in the digestive tracts of animals even in human, constitute the Class Cestoda.
- Flukes, which are parasitic in various parts of different animals, constitute the Class Trematoda.
- Planarians, which are free-living and non-parasitic, constitute the class Turbellaria.
Free-living flatworms are found in almost every kind of environment, on land, in fresh and even in salt water. There are approximately 15 000 species as of flatworm. The outer surface which is called “ectoderm” of the free-living flatworms is covered with cilia which secrete a hardened material called cuticle. A developed musculature found under the epidermis or the skin layer allows the body to change in size/shape either to expand or contract in a remarkable degree.
Flatworms have no real body cavity it is because the spaces between the organs are filled with a compact tissue called “parenchyma”. One end of the body is specialized for sensory perception and locomotion takes place in the direction of specialization. In ventral side is the oral and genital opening, this opening is equipped with a sucker with well developed pharynx. The nervous system contains a network with a large ganglion which is the brain and different longitudal nerve cords that forms the main parts.
Flatworms has also no blood or vascular system. The specialized cells those possess’ cilia that are called flame cells allow the interior to one or more openings in the exterior by means of network tubes and this together form the excretory system. In terms of reproductive system it has a very complicated which occupies a vast portion of the interior of animals.
Although flatworms are almost all hermaphroditic the eggs and sperm are formed separately. These germ cells either leave the body by separate openings or enter a common chamber, called the genital atrium. Flatworms can also reproduce asexually both by binary fission—by gripping themselves apart to become two and through regeneration, they can produce an entire new worm from a piece that has been cut off from their body.
In all of them the bodies are flattened from the back, or dorsal side to the belly-side, or ventral side. The scientific name of this flatworm is Planaria maculata. The adult planaria is about one centimeter in length or longer.
Planarians are free-living flatworms which live in fresh water most likely dwelling in some streams with fresh water.
Flukes and Tapeworm
Flukes may live either as ectoparasites or endoparasites in different parts of the host’s body including the intestine, blood and liver. Tapeworms are endoparasites; the adults of most of them live in the intestine of the host. Not like the free-living flatworms, the bodies of flukes and tapeworms are modified for parasitic life. Flukes have a very simple digestive cavity while tapeworms, which feed on the digested food of the host, have no digestive cavity at all.
Flukes and tapeworms are easy to find in the slaughterhouse.
- Fasciola hepatica, a liver fluke, lives in the liver of cows, sheep’s, pigs and few other mammals. Squeezing the liver of one infected cow will yield enough flukes for class study; the butcher can do that for you.
- Taenia saginata, a tapeworm, is a very long ribbon-like tapeworm in the intestine of cows.
Blood flukes attacks vertebrates especially humans. There are three types of blood flukes:
- Urinary blood fluke
- Intestinal blood fluke
- Oriental blood fluke.
The diseases that are cause by this vile organisms can cause schistosomiasis that affects millions of people in Africa and East Asia. It may cause
- The death of the host whenever a flatworms or tapeworm
- Skin diseases and marks
References ; Wikipedia, the free encyclopedia , Science and Technology by Lilia M. Rabago Ph. D , Crescensia C. Joaquin Ph.D, Catherine B. Lagunzad , PH. D, Encarta