Life cycle of liver fluke is digenetic. Its intermediate hosts are fresh water snails which are

Options

A. Lymnaea and Planorbis
B. Pila and Lymnaea
C. Limax and Helix
D. Limax and Onchidium

Answer

### Step-by-Step Solution for the Life Cycle of Liver Fluke

1. **Introduction to Liver Fluke**:
- The liver fluke is scientifically known as *Fasciola hepatica*. It belongs to the phylum Platyhelminthes, which includes flatworms. The flat body structure of the liver fluke characterizes it as a flatworm.

**Hint**: Remember that the scientific name is crucial for identifying organisms in biology.

2. **Understanding Digenetic Life Cycle**:
- The term "digenetic" indicates that the liver fluke has two hosts in its life cycle. This means that it requires two different organisms to complete its development.

**Hint**: Focus on the meaning of "digenetic" as it relates to the number of hosts involved in the life cycle.

3. **Identifying Hosts**:
- The life cycle of the liver fluke involves a primary host and an intermediate host. The primary hosts are typically sheep and goats, where the adult liver fluke resides as an endoparasite in the bile ducts.

**Hint**: Distinguish between primary and intermediate hosts; the primary host is where the adult form lives.

4. **Role of Intermediate Host**:
- The intermediate hosts are freshwater snails. These snails play a crucial role in the larval development of the liver fluke.

**Hint**: Remember that the snails are essential for the larval stages of the liver fluke.

5. **Life Cycle Stages**:
- The life cycle begins when the miracidium, the first larval stage, enters the snail's body through water. Inside the snail, it develops into the cercaria, which eventually leaves the snail.

**Hint**: Track the progression of larval stages; miracidium is the first stage, followed by cercaria.

6. **Final Stage Before Primary Host**:
- After leaving the snail, the cercaria develops into metacercaria. This metacercaria is then capable of infecting the primary host, which are sheep and goats.

**Hint**: Understand the transformation from cercaria to metacercaria as a critical step before reaching the primary host.

7. **Examples of Intermediate Hosts**:
- Specific examples of freshwater snails that serve as intermediate hosts include *Lymnaea* and *Planorbis*.

**Hint**: Familiarize yourself with the names of specific snail species that act as intermediate hosts.

### Summary
The life cycle of the liver fluke (*Fasciola hepatica*) is digenetic, involving two hosts: freshwater snails as intermediate hosts and sheep or goats as primary hosts. The larval stages include miracidium, cercaria, and metacercaria, which play vital roles in its development and transmission.