Question

In which of the following nematodes, dorsal oesophageal gland opens in median bulb of oesophagus?
A. Hoplolaimus
B. Pratylenchus
C. Aphelenchus
D. Aphelenchoides
Choose the correct answer from the options given below

• A. A only
• B. B only
• C. A and B only
• D. C and D only

Hint:

In Tylenchida, the dorsal esophageal gland opens near the stylet base, whereas in Aphelenchida, it opens inside the median bulb (metacorpus) anterior to the pump valve.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Plant-parasitic nematodes possess an esophagus (pharynx) with three esophageal glands (one dorsal and two subventral).
The anatomical location where the dorsal esophageal gland duct opens into the esophageal lumen is a key diagnostic feature used to differentiate the orders Tylenchida and Aphelenchida.

Step 2: Detailed Explanation:
Let us analyze the anatomical differences between the two orders:
1. Order Tylenchida (including Hoplolaimus and Pratylenchus):
In tylenchid nematodes, the dorsal esophageal gland duct opens into the lumen of the esophagus proximally to the stylet base (typically within a few micrometers of the knobs).
Therefore, this does not occur in Hoplolaimus (A) or Pratylenchus (B).
2. Order Aphelenchida (including Aphelenchus and Aphelenchoides):
In aphelenchid nematodes, the dorsal esophageal gland duct extends further down and opens directly into the lumen of the median bulb (metacorpus), just anterior to the pump chamber.
This is a defining anatomical characteristic of this order, found in both Aphelenchus (C) and Aphelenchoides (D).

Step 3: Final Answer:
Therefore, the dorsal esophageal gland opens in the median bulb in Aphelenchus and Aphelenchoides (C and D only).