Which statement about Ascaris eggs in zinc sulfate flotation is true?

• A. Unfertilized eggs float
• B. Both float
• C. Neither floats
• D. Fertilized eggs float; unfertilized do not

Answer: (D)

Flotation relies on buoyancy: in a saturated zinc sulfate solution with a high specific gravity, eggs that are less dense than the solution will rise to the surface for detection, while denser material sits lower. Ascaris fertilized eggs have a specific internal composition and structure that makes them less dense overall in this medium, allowing them to float. Unfertilized eggs, on the other hand, tend to be denser and do not rise in the same solution, so they remain at the bottom or sink, making them not recover in the flotation film. This distinction helps differentiate fertilized from unfertilized eggs during flotation.