Question

Slime balls of Dicrocoelium dendriticum are aggregations of

• A. Sporocyst
• B. Redia
• C. Cercaria
• D. Metacercaria

Hint:

*Dicrocoelium dendriticum* lacks the redia stage in its life cycle.
The slime ball is an evolutionary adaptation of the parasite to survive the terrestrial environment before ingestion by the ant.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Dicrocoelium dendriticum (the lancet fluke) has a unique terrestrial life cycle that does not require water.
It involves a land snail as the first intermediate host and an ant as the second intermediate host.
Detailed Explanation:
Let us look at the developmental steps inside the snail host:
- After the land snail (e.g., Zebrina or Cionella) ingests the eggs of D. dendriticum, the miracidia hatch and develop into mother sporocysts, which produce daughter sporocysts.
- The daughter sporocysts then directly produce cercariae (there is no redia stage in Dicrocoelium).
- The developed cercariae migrate to the respiratory chamber of the snail, where they cause irritation.
- To protect itself, the snail secretes a large amount of sticky mucus that clusters and encapsulates hundreds of these cercariae.
- The snail expels these mucus-bound masses onto vegetation as moist, sticky droplets known as "slime balls."
- These slime balls protect the cercariae from drying out in the dry terrestrial environment.
- An ant (Formica fusca) ingests these slime balls, and the cercariae then develop into metacercariae inside the ant.

Step 2: Final Answer:
Thus, the slime balls of Dicrocoelium dendriticum are aggregations of cercariae.