Question

Sperm enter the egg via

• A. Grey crescent
• B. Pronucleus
• C. Micropyle
• D. Entry point

Hint:

The micropyle is the only pathway for sperm to cross the protective chorion. Remember this structure as the "micro-gate" on the egg shell.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Insect eggs are protected by a tough, multilayered shell called the chorion.
The chorion prevents water loss and protects the developing embryo from physical damage.
However, because the chorion is tough and impermeable, it requires specialized structural adaptations to allow sperm to enter for fertilization.

Step 2: Detailed Explanation:
The micropyle is a specialized, minute pore-like opening (or a group of pores) in the chorion of the insect egg.
It is typically located at the anterior pole of the egg, close to where the female's stored sperm are released during oviposition.
The micropyle contains narrow canals that lead through the outer layers of the shell directly to the oocyte membrane.
During egg-laying, sperm stored in the female's spermatheca are deposited onto the egg.
A sperm cell must swim through the micropylar canal to reach and fertilize the female pronucleus.
This targeted entry system also helps prevent polyspermy (fertilization of an egg by more than one sperm).
Let us review the other options:
- Grey crescent: An embryonic region formed after fertilization in amphibian eggs, not involved in insect sperm entry.
- Pronucleus: The haploid nucleus of a sperm or egg before they fuse.
- Entry point: A general term rather than a specific anatomical structure.
Therefore, sperm enter the insect egg specifically through the micropyle.

Step 3: Final Answer:
The specialized opening on the insect eggshell that allows sperm entry is the micropyle.
Thus, the correct choice is (C).