What is the Difference Between Intermediate Host and Definitive Host?

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The difference between an intermediate host and a definitive host lies in the stages of a parasite's life cycle that they support:

  • Intermediate Host: An intermediate host is a living organism in which a parasite spends a short time period of its life. Inside the intermediate host, the parasite goes through asexual or development stages, but it does not reach sexual maturity. The intermediate host often acts as a vector for the parasite to reach its definitive host. For example, mosquitoes can serve as an intermediate host for the malaria parasite.
  • Definitive Host: A definitive host is a living organism in which the parasite reaches the adult stage and reproduces sexually, if possible. The definitive host is the organism that harbors the sexually mature parasite. For example, humans can serve as the definitive host for several parasites, including pinworms, schistosomes, and tapeworms.

In summary, the intermediate host is involved in the parasite's development stages, while the definitive host supports the parasite's sexual maturity and reproduction.

Comparative Table: Intermediate Host vs Definitive Host

The main difference between intermediate and definitive hosts lies in the stage of a parasite's life cycle that occurs within each host. Here is a table comparing the two types of hosts:

Feature Intermediate Host Definitive Host
Definition An intermediate host is an organism in which a parasite spends a transition period of its life cycle, often undergoing asexual reproduction. A definitive host is a biological organism in whose body a parasite sexually multiplies and reaches sexual maturity, which is crucial for the continuation of the parasite's species.
Examples a) Humans serve as intermediate hosts for malaria parasites, which undergo asexual reproduction within the human body.
b) Mosquitoes serve as intermediate hosts for heartworm parasites, which also undergo asexual reproduction within the mosquito.
a) Female Anopheles mosquitoes serve as definitive hosts for malaria parasites, where the parasites undergo sexual reproduction.
b) Humans serve as definitive hosts for tapeworms, pinworms, and schistosomes, where the parasites undergo sexual reproduction.

In summary, intermediate hosts are organisms in which a parasite undergoes asexual reproduction, while definitive hosts are organisms where a parasite undergoes sexual reproduction and reaches sexual maturity.