Question

The sexual dimorphism occurs in which nematode?

• A. Rotylenchus
• B. Xiphinema
• C. Anguina
• D. Hoplolaimus

Hint:

In Anguina tritici, adult females are swollen, curved, and significantly larger than the smaller, more slender males, representing a clear case of sexual dimorphism.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Sexual dimorphism is a phenotypic difference between males and females of the same species.
In nematodes, this can include differences in body shape, size, or reproductive structures.

Step 2: Detailed Explanation:
Let us analyze the morphology of the nematode genera listed:
1. Rotylenchus (A), Xiphinema (B), and Hoplolaimus (D): These are migratory ectoparasites or semi-endoparasites.
Both males and females maintain a similar vermiform (worm-like) body shape throughout their life cycles, with no distinct sexual dimorphism in overall body shape.
2. Anguina (C): The wheat seed gall nematode exhibits distinct sexual dimorphism in its adult stage.
Adult females are stout, spirally curved, and significantly larger than males, with their bodies swollen with eggs.
Adult males remain smaller, more active, and less swollen.
This morphological differentiation is an adaptation to their endoparasitic lifestyle inside the developing wheat galls, where the female's primary function is reproduction.

Step 3: Final Answer:
Therefore, distinct sexual dimorphism occurs in the genus Anguina.