Difference Between Direct Lifecycle and Indirect Lifecycle

The key difference between direct lifecycle and indirect lifecycle in the context of parasite reproduction is that, in the direct lifecycle, the simple parasite lives its lifespan and reproduces within a host once entered while in the indirect lifecycle, the complex parasites require many numbers of hosts during the completion of their lifecycles.

Parasites are small organisms that require host organisms to complete their lifecycle. Some parasitic interactions with the host are pathogenic, but some interactions are beneficial to the host. Hence, these parasites could be classified under such parameters too; not only by their life cycle. The parasitic life cycle is mainly of two divisions such as direct life cycle and indirect life cycle. Simple parasites undergo direct life cycle while complex parasites undergo indirect life cycle.

CONTENTS

1. Overview and Key Difference
2. What is Direct Lifecycle
3. What is Indirect Lifecycle
4. Similarities Between Direct Lifecycle and Indirect Lifecycle
5. Side by Side Comparison – Direct Lifecycle vs Indirect Lifecycle in Tabular Form
6. Summary

What is Direct Lifecycle?

Simple parasites spend a direct lifecycle. Here, once the parasite enters a single host, it completes its life span and reproduction processes while contained in that particular host. During this process, the parasite will obtain habitat and nutrient from the host. Therefore, this process could be harmful to the host organism.

However, some parasitic interactions provide beneficial results to the host. Since these parasites require only one host organism for their survival, they are termed as simple parasites. In fact, most of the simple parasites are harmless to the host organism. But, it mainly depends on the type of host species.

What is Indirect Lifecycle?

Complex parasites spend an indirect lifecycle. These parasites require some host organisms to complete their life cycle. They do not depend on one host organism. Their reproduction processes are carried out further with the involvement of one host. Therefore, this sophisticated lifestyle is led by complex parasites.

Moreover, since they do not limit for a single host organism, their life cycle is termed as indirect lifecycle. Also, this type of lifecycle could harm all the hosts that this parasite interacts. Therefore, they have a higher chance of becoming virulent to the host.

What are the Similarities Between Direct Lifecycle and Indirect Lifecycle?

• Both direct and indirect lifecycles are based on parasite reproduction.
• Also, both these processes ensure the survival and successful reproduction of parasites.

What is the Difference Between Direct Lifecycle and Indirect Lifecycle?

Parasites can be either simple parasites or complex parasites. Simple parasites spend a direct lifecycle while complex parasites spend an indirect lifecycle. The key difference between direct lifecycle and indirect lifecycle is that the direct lifecycle involves only one host organism while the indirect lifecycle involves more than one host organisms. Furthermore, parasites who live a direct lifecycle are more often less harmful while the parasites who live an indirect life cycle are virulent and they cause harm to host organisms. Therefore, it is another difference between direct lifecycle and indirect lifecycle.

Below infographic on the difference between direct lifecycle and indirect lifecycle presents the differences comparatively.

Summary – Direct Lifecycle vs Indirect Lifecycle

Direct lifecycle and indirect life cycle are explained in the context of parasitic reproduction. Parasites are small organisms that require host organisms to complete their lifecycles. The key difference between direct lifecycle and indirect lifecycle is that, in the direct lifecycle, the simple parasite lives their lifespan and reproduces within one host while in the indirect lifecycle, the complex parasites live in many numbers of hosts during the completion of their life cycle. Simple parasites undergo direct lifecycle while complex parasites undergo indirect lifecycle. Most of the simple parasites are harmless to the host organism. In indirect lifecycle, the parasites have more potential for virulence and a higher chance of becoming harmful to the host. Thus, this is the difference between direct lifecycle and indirect lifecycle.

Reference:

1.Parasitism: Life Cycle and Host Defences against Parasites . Available here  
2. Revolvy, LLC. “‘Parasitic Life Cycle’ on Revolvy.com.” Trivia Quizzes. Available here  

Image Courtesy:

1.”Xenopsylla cheopis flea PHIL 2069 lores”By CDC/Dr. Pratt – Centers for Disease Control and Prevention’s Public Health Image Library (PHIL), with identification number #2069. (Public Domain) via Commons Wikimedia  
2.”Babesia life cycle human en”By LadyofHats Mariana Ruiz Villarreal – Own work (Public Domain) via Commons Wikimedia