A comparison of techniques useful for preparing nematodes for scanning electron microscopy

Area of Science:

• Nematology
• Microscopy techniques

Background:

• Scanning electron microscopy (SEM) is crucial for visualizing nematode ultrastructure.
• Optimizing sample preparation is essential for minimizing artifacts and enhancing image quality.

Purpose of the Study:

• To evaluate various preparation techniques for scanning electron microscopy (SEM) of second-stage juveniles of Meloidogyne incognita.
• To identify the most effective method for preserving nematode morphology with minimal artifacts.

Main Methods:

• Comparison of different fixation methods: sequential cold fixation vs. rapid room temperature fixation.
• Evaluation of fixatives: glutaraldehyde, glutaraldehyde-formalin, and formalin.
• Assessment of different drying techniques: critical point drying (CO2, Freon), air drying, and freeze drying.

Main Results:

• Sequential cold fixation was superior to rapid fixation.
• Glutaraldehyde-based fixatives outperformed formalin alone.
• Freeze drying, particularly after sequential fixation in 100% ethanol and liquid propane, produced the best-preserved specimens with the fewest artifacts.
• Freeze drying proved adequate for most nematode genera but unsatisfactory for a few.

Conclusions:

• Sequential fixation combined with freeze drying offers superior preservation for nematode SEM compared to commonly used methods.
• Specific procedural adjustments may be necessary for optimal results across different nematode genera.
• The study highlights freeze drying as a highly effective technique for high-resolution nematode imaging.