Economic importance of protozoans

              Economic importance of protozoans

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What are Protozoans?

Ø Protozoa means “first animals,” and are described as unicellular eukaryotes (Goldfuss, 1818).

Ø They are microscopic found in fresh, marine waters & damp soil.

Ø A protozoan might be defined as an organism which is made up of a mass of protoplasm not divided into cells and which carries on all vital activities of life.

Ø Protozoan are either solitary or colonial.

Economic importance

INTRODUCTION

Ø Protozoans are Ubiquitous.

Ø They live as commensals & parasites in animals & plants.

Ø Man is invariably affected by them.

Ø Some of them are beneficial, while most of them are harmful to man.

Ø Domestic animals are also affected.

 Watch this for a better understanding

A.        Beneficial protozoa

 

Ø Some protozoa are of great importance for mankind and other animals.

Ø They can be classified into following categories:

1.  Helpful in Sanitation

a)  Protozoan play an important role in sanitary betterment & improvement in keeping water safe for drinking purpose.

b) Protozoan lives in polluted water & feed upon waste organic substances & thus purify it.

c)  Some feed on bacteria & purify the water indirectly.

 

2.  Protozoa as Food

a)  Though microscopic but directly or indirectly provide a source of food to man, fish, & other animals.

b) Larvae of aquatic insects feed on aquatic protozoans, when these larvae of fish, prawns, etc. grow to adult becomes a source of food of man.

c)  Pelagic protozoan like foraminifera and Radiolaria (figure 1. & 2) sink after death to the bottom of the ocean & forms the food of deep-sea fauna.

d) Few protozoa have chlorophyll & are capable of synthesizing their own food.

foraminifera

Radiolaria

 

3.  Commensal Protozoa

a)  These protozoans are those which live on or in the body of other animals & derive some benefits from the relationship.

b) However, the other partner is neither benefited nor injured.

c)  They may be of two types: -

(i)                     Ecto-commensal Protozoa

(ii)                  Endo-commensal Protozoa

 

(i)                     Ecto-commensal Protozoa

·     They live on the surface of the host body.

·     Ciliates & Suctorians lead an ecto-commensal life on molluscs, arthropods, fishes and frogs, etc.

·     The host simply act as a substratum for these ecto-commensals.

(ii)                  Endo-commensal Protozoa

·     They live inside the body of the hosts.

For example,

a. Trichomonas, Giardia, etc., live as endo-commensal within the alimentary canal of man.

b. Entamoeba coli live as endo-commensal in alimentary canal of frogs.

c. Balantidium coli feed upon harmful bacteria in the colon. They feed on bacteria and so have beneficial effect.

 

4. Symbiotic Protozoa

a)  Those protozoan lives a symbiotic relationship with other animals.

b) In this association, the two partners become very much dependent on each other that one cannot get along with other & their separation results in the death of both.

For example: -

1. Trichonympha & colonympha are intestinal flagellates present in termites & wood roaches. They help in the digestion of cellulose which is converted to glycogen. the glycogen is then utilized by both.

 

5. Commercial use of Protozoan skeletons

a)  Skeleton of dead Foraminifera and Radiolaria sink in sea & form oceanic ooze. This solidify & covert to rock strata.

        For example: -

1.  Such rock strata are White chalk cliffs of Dover and England, and stone beds of Paris, Cairo & north America

b) Paris building are built of the limestone which is composed of shells of genus Hiliolina.

c)  Pyramids of Egypt are constructed by lime-stone deposits of Nummulite shells.

d) Sometimes, skeletal deposits are used as filtering & as abrasive.

 

6. Protozoans in soil

 

a)  They play an important role in Soil fertility.

b) They graze on soil bacteria.

c)  Protozoan also excrete Nitrogen & Phosphorus.

 

Note: Zoological importance of Protozoa

Ø Protozoans are ideal material for Cytological, cytochemical, physiological, biochemical & genetical studies, because of their small size, simple organization, quick reproduction & easy availability.

 

A.        Harmful protozoa

 

Ø Almost all harmful Protozoans lead a parasitic mode of life.

Ø They parasitize almost every plants & animals including man and various animals.

 

1.  Soil Protozoa

a)  Several species present in the soil feed upon the nitrifying bacteria, thus declining their activity & consequently decrease the amount of nitrogen in the soil.

2.  Water pollution

a)  Whereas some are helpful in sanitation, others are responsible for water contamination, Protozoan of fecal origin.

b) Uroglenopsis – pollute water by producing aromatic oily secretion with bad odor which is unfit for human consumption.

c)  CuSO4 is used to kill such protozoans.

d) Noctiluca & Gymnodinium- sometimes multiply so extensively that the water becomes red with their bodies. The phenomena are known as “Blooming” & is the cause of “red tides”.

e) Larger concentration of these leads to destruction of fish & even poisoning of edible mollusks.

3.  Pathogenic Protozoa

a)  Disease producing protozoans are termed as pathogenic protozoa.

b) More than 25 different species of parasitic protozoa live in man alone.

4.  Parasitic Protozoa

a) Parasitic protozoans live on or within the body of other organisms for sake of food, shelter and continuance of race.

b) The parasite can be classified into two categories on their occurrence.

1) Ectoparasitic Protozoa

2) Endoparasitic Protozoa

1) Ectoparasitic Protozoa

·     They live on the external surface of the host plant or anmal. o Less common.

·     For example: -

1. Hydramoeba hydroxena: ectoparasite of Hydra & feeds on ectodermal cells.

2. Ichthyophthirius multifiliis: ectoparasite of fresh water fishes cause integumentary blisters. 3. Leishmania tropica: ectoparasite of man causes oriental sores.

2. Endoparasitic Protozoa

·     They live inside the body of the host plant or animal.

·     Further classified into according to their location in the host body.

i)              Coelozoic protozoa: living in the body cavity or coelom e.g. Entamoeba, Trichomonas, Balantidium, etc.

ii)           Histozoic Protozoa: living between the cells of tissues and body organs e.g., Giardia, Eimeria, etc.

iii)         Cytozoic Protozoa: living inside the host’s body e.g., plasmodium, leishmania, Haemoproteus, etc.