Indirect life cycle

From Biology-Online Dictionary | Biology-Online Dictionary

Definition

noun

A type of parasitic life cycle wherein the parasite is transmitted indirectly from one host to the next, i.e. by requiring a vector or an intermediate host of another species


Supplement

A life cycle refers to the whole life history of an organism, usually depicted through a series of developmental stages in which an organism goes through. It entails the course of development of an organism, i.e. from the time of inception to growth to finally maturity when an organism can viably produce another of its kind. As for the parasites, they have two types of life cycle: (1) direct life cycle and (2) indirect life cycle.

An indirect life cycle is a type of a life cycle wherein a parasite is transmitted from one host to another by using a vector or by an intermediate host of another species. A parasite with an indirect life cycle would therefore require more than one type of host species to complete their life cycle. This is in contrast to a direct life cycle wherein the parasite is transmitted to a new host without requiring a vector or an intermediate species. This parasite would be able to complete its life cycle with only one host species.

In an indirect life cycle, the parasite does not reproduce sexually in an intermediate host although it develops further to another stage (infective stage) of its life cycle.

An example of a parasite with an indirect life cycle is Schistosoma japonicum and Capillaria philippinensis.


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