Miracidium larva occurs in the life history of (a) Roundworm (b) Liver fluke(c) Earthworm(d) Tapeworm

The correct answer is: (b) Liver fluke

Explanation:

The miracidium is a larval stage in the life cycle of certain parasitic flatworms, specifically those in the class Trematoda. The liver fluke, Fasciola hepatica, is an example of a trematode that has a miracidium stage in its life cycle.

Life Cycle of Liver Fluke:

The adult liver fluke resides in the liver of its host (often sheep or cattle).
Eggs are released into the environment through the host’s feces.
When the eggs reach water, they hatch into the free-swimming miracidium larva.
The miracidium seeks out and infects a specific snail species, which acts as an intermediate host.
Inside the snail, the miracidium undergoes further development and eventually forms other larval stages.
Explanation of Options:

(a) Roundworm: Roundworms, such as Ascaris lumbricoides, do not have a miracidium stage in their life cycle. They develop directly from eggs into larvae and adults.
(c) Earthworm: Earthworms are non-parasitic and do not have a miracidium stage in their life cycle.
(d) Tapeworm: Tapeworms, like Taenia species, do not have a miracidium stage; their life cycle includes different larval stages like oncosphere and cysticercus.
Thus, the miracidium larva is specifically associated with the liver fluke.