What is the Difference Between Protozoa and Helminths

The main difference between protozoa and helminths is that the protozoa are unicellular protists whereas helminths are metazoa that is multicellular worms. Furthermore, protozoa undergo both asexual and sexual reproduction while helminths undergo sexual reproduction. Moreover, the main forms of protozoa are Amoebae, flagellates, ciliates, and Sporozoa while the two main forms of helminths are Platyhelminthes and Nemathelminthes or Nematoda.

Protozoa and helminths are two forms of eukaryotic organisms that are parasitic on plants and other animals.

Key Areas Covered

1. Protozoa
     – Definition, Characteristics, Classification
2. Helminths
     – Definition, Characteristics, Classification
3. What are the Similarities Between Protozoa and Helminths
     – Outline of Common Features
4. What is the Difference Between Protozoa and Helminths
     – Comparison of Key Differences

Key Terms

Endoparasites, Helminths, Multicellular, Protozoa, Unicellular

Protozoa – Definition, Characteristics, Classification

Protozoa are a large group of unicellular eukaryotes that belong to the kingdom Protista. They are single-celled organisms covered by a cell membrane. Their cytoplasm is composed of ectoplasm and endoplasm. Usually, they have a single nucleus. In some cases, multiple nuclei can be found. Additionally, some protozoa are free-living in the environment while others are endoparasitic. Some parasitic protozoa can live inside body tissues or in the blood.  

Figure 1: Resting Cyst of Ciliated Protozoan

Furthermore, the main types of protozoa include Amoebae, flagellates, ciliates, and Sporozoa. Amoebae use pseudopodia for locomotion and Entamoeba histolytica is a parasitic microorganism in the intestine. Flagellates use flagella for their locomotion. Ciliates are the protozoa that use cilia for locomotion while Sporozoa are a type of non-motile, spore-producing protozoa.

Helminths – Definition, Characteristics, Classification

Helminths are multicellular parasitic worms. They are also known as metazoan. Generally, helminths show bilateral symmetry. The outer covering of their body is the cuticle or integument. Also, they reproduce inside the host’s body. In addition, most helminths require multiple intermediate hosts to complete their life cycle. Usually, heavy worm load can follow multiple infections.

Moreover, the two main types of helminths are Platyhelminthes and Nemathelminthes. Platyhelminthes have a dorsoventrally flattened body. They do not have an alimentary canal as well. Also, they are hermaphrodites and most of them have suckers. Trematodes (flukes) and cestodes (tapeworms) are examples of Platyhelminthes. In contrast, Nemathelminthes or Nematoda have a cylindrical body with a body cavity. They have a complete alimentary canal and they do not have suckers. Moreover, they are sexually differentiated into male and female worms.

Figure 2: Ascaris lumbricoides Life Cycle

In addition, some acanthocephalans or thorny-headed worms and some species of annelids such as ringworms are parasitic; therefore, they are also considered as helminths.

Similarities Between Protozoa and Helminths

• Protozoa and helminths are two types of eukaryotic organisms with a lower organization.
• Most of them are parasitic on plants and other animals.
• Also, both are infectious microorganisms that are endoparasites.
• And, they can multiply inside the body and their transmission occurs through the fecal-oral route.

Difference Between Protozoa and Helminths

Definition

Protozoa refer to a group of phyla which comprises the single-celled microscopic organisms, belonging to the kingdom Protista, while helminths refer to the parasitic worms characterized by elongated, flat or round bodies. Thus, this is the main difference between protozoa and helminths.

Taxonomy

Protozoa make up the kingdom Protista while helminths belong to the kingdom Animalia. Hence, taxonomy is a major difference between protozoa and helminths.

Classification

The main forms of protozoa are Amoebae, flagellates, ciliates, and Sporozoa while the two main forms of helminths are Platyhelminthes and Nemathelminthes.

Cellular Organization

Also, another difference between protozoa and helminths is their cellular organization; protozoa are unicellular while helminths are multicellular.

Locomotion

Furthermore, some protozoa are non-motile and motile protozoa use either flagella or cilia for their locomotion while helminths move through muscular contractions.

Reproduction

Moreover, protozoa reproduce asexually by binary fission, schizogony or endodyogeny and sexually by gametogony while helminths reproduce sexually differentiated.

Digestion

Besides these, digestion is another difference between protozoa and helminths. The digestion of food of protozoa occurs inside the cell while some helminths have a complete alimentary canal and others absorb nutrients from their body wall.

Conclusion

Protozoa are unicellular eukaryotes that are parasitic on plants or animals. They belong to the kingdom Protista. In comparison, helminths are parasitic worms including flatworms, roundworms, and annelids. However, both of them are endoparasites. Helminths always show higher body organization than protozoa. Therefore, the main difference between protozoa and helminths is the organization of the body.

References:

1. “Parasites.” Centers for Disease Control and Prevention, 22 Apr. 2016, Available Here.

Image Courtesy:

1. “Dileptus viridis cyst” By Deuterostome – Own work (CC BY-SA 4.0) via Commons Wikimedia  
2. “Ascaris lumbricoides life cycle” By SuSanA Secretariat (CC BY 2.0) via Commons Wikimedia