Parasitic adaptation of flatworms and diseases caused by flatworm

Last Updated on April 19, 2021 by Sagar Aryal

Parasitic adaptation of flatworms

Adaption in parasites to survive in the environment of a body of the host is called parasitic adaptation. Mainly flat-worm are parasitic except Turbellaria, so they are adapted for parasitic nature. There are two types of parasitic adaptation to suit their parasitic mode of life.

Morphological adaptations

Morphological adaptations are adaptations in body parts and systems to survive in a particular type of environment. Parasitic flatworms have the following physiological adaptation-

a. The upper covering of the body

Parasitic flatworms live inside the host body mainly in the gastrointestinal tract. Hence they have a thick integument (thick body covering).

b. Adhesion organ

To live inside an organism body flatworm have some special organ of adhesion, which help in attaching to the host. For this purpose, they have one or more sucker, hook, and spine. And some cases sucker also have spines around it

c. Locomotory organ

Locomotory organ present in free-living flatworm, parasitic flatworm do not have locomotory organ because they live where sufficient foods are present available without effort. Only some free-living larval forms of parasitic flatworm have locomotory organs such as cilia in miracidium and tail in cercaria.

d. Organ for nutrition

They mostly live in the gastrointestinal tract, directly bathing in digested food and directly absorb food from there so they do not have a complete digestive tract. Although some flatworms have incomplete digestive tract (Trematodes have incomplete digestive tract), yet some flatworms lack digestive systems (cestode do not have a digestive system).

e. Neuro and sensory system

Developed neuro and the sensory system are characters of the free-living active organism. Parasitic organisms live in a safe environment so there is no need for the developed nervous system.

f. Reproductive adaptation

This organ is a developed organ of parasitic helminths. Mostly parasitic flatworm

Physiological adaptation

Physiological adaptation is seen physiology of an organism to survive in a particular environment, parasitic flatworm show following physiological adaptation-

a. Protective mechanism

Those type of flatworm which lives in the digestive tract like tapeworm have to protect themselves from the digestive enzyme, for this purpose, they have followings mechanism- (i) stimulate the alimentary canal wall to secrete mucous, which form a protective covering around parasites. (ii) They secrete antizyme to neutralize the effects of the digestive enzyme of the host on their body. (iii) They continuously renew their protective body covering.

b. Anaerobic respiration

We all know in the environment of the gastrointestinal system there is no free oxygen are found. Hence parasites of the gastrointestinal tract have to survive without oxygen, so their respiration is anaerobic. They have to breakdown glucose and bio-molecules without oxygen.

c. Osmoregulation

Osmotic pressure among endoparasite’s body fluids is equal to host osmotic pressure, so no osmoregulation. But in intestinal parasites, as like tape-worm have slightly high osmotic pressure which helps in absorption from host digested food.

d. High fertility

Their eggs come out from the host body with faces of the host and these eggs have a very uncertain future. So passing through complex life cycle offspring face several hazards and only a few percent of total produce eggs reach to adult life. Hence they have a high reproductive rate and production of a large amount of egg to keep their existence. And during their developmental phases, several larval forms also produce multiple next larval stages as like sporocyst contain several rediae, redia contain several cercariae so intermediate also increase the number of next larval stages. Hence one egg can produce more than one offspring.

Parasitic adaptation of flatworms and diseases caused by flatworm
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Diseases Caused by flatworm

Both types of flatworms Cestodes and Trematodes cause diseases in human-

A. Diseases caused by Trematodes

1- Opisthorchiasis/Clonorchiasis

It is caused by Opisthorchis/clonorchis sinensis. Parasites mainly inhabit the bile ducts of the host. Mainly infection is caused by raw or partially cooked fish which may have metacercaria. Adult flukes live in the bile duct and provide thickness to the wall of the bile duct. In case of severe infection, cirrhosis takes place followed by death.

2- Faciolopsiasi

The causal organism of this disease is Faciolopsis in India, which is an intestinal fluke. The worm causes erosion in the lining of the intestinal wall leads to bleeding and pain followed by diarrhea, nausea, and vomiting.

3- Schistosomiasis

This disease s caused by Schistosoma mansoni, S. japonicum, and S. haematobium, which are blood flukes. The symptoms of diseases are asthmatic attacks and hepatitis, other symptoms are fever sweating, diarrhea weight loss, etc. Female lays eggs directly in the blood-stream, from where eggs reach the intestine or the urinary bladder and passes out the body by defecation or urination.

4- Paragonimiasis

This disease wide-spread in Asia, Africa, and South & Central-America. The causal organism of this disease is Paragonimus westermani. Flukes reside in the lung and eggs pass out from the body sputum. Fluke causes chronic cough and emission of bloody sputum.

b. Disease caused by Cestodes

1- Taeniasis

Taeniasis is caused by species of Taenia such as Taenia solium and Taenia saginata. Infection T. solium is caused by eating raw or partially cooked pork and infection of T. saginata is caused by eating raw or partially cooked beef. The presence of Taenia/tape-worm in the intestine causes a gastrointestinal disorder.

2- Hydatid disease 

Hydatid disease is caused by dog tapeworm Echinococcus granulosus. The primary host is mainly dogs, egg pass out with feces and develop into the onchosphere. The man got infections by eating food or drink water contaminated with the onchosphere. In man, these onchospheres develop into cysts in the liver, lung, and other tissue, these cysts cause inflammation of the tissue.

References and Sources

  • A Text-Book of Zoology Invertebrates by R.L. Kotpal tenth edition.
  • (Platyhelminthese: Classification and Parasitic adaptation | Study & Score)
  • (Parasitic Adaptation in Helminths – Biology discussion)
  • (Intestinal parasitoses. Disease caused by flatworms) – Pub Med
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