I am happy to answer your question and I hope that my information will be useful in your field of study

1. Immediate Freezing

• Process: If you have access to a freezer, immediately place the carcasses in a -20°C freezer (or colder if possible). Freezing halts microbial activity and DNA degradation, preserving the genomic material for later extraction.
• Resource Consideration: Freezing is an energy-intensive process but remains one of the best methods for preserving samples for metagenomics, especially if you’re dealing with limited funds for long-term preservation.
• Alternative: If a -20°C freezer is unavailable, consider using dry ice for short-term preservation until you can access a freezer.

2. Storage in Ethanol or Isopropanol

• Process: After collection, immerse the carcasses in 70–95% ethanol or isopropanol. This not only preserves the structural integrity of the sample but also prevents the growth of bacteria or fungi that could contaminate the metagenomic analysis.
• Resource Consideration: Ethanol is relatively inexpensive and can be found in most basic lab settings. However, you’ll need a supply of ethanol, and care must be taken to store samples in tightly sealed containers to avoid evaporation.
• Storage Duration: Samples in ethanol can be stored at room temperature, but for long-term storage, keep them in a cool, dry place to avoid evaporation.

3. Drying (Desiccation)

• Process: Another option is desiccating the carcasses. You can use silica gel or an inexpensive desiccant to absorb moisture from the samples.
• Resource Consideration: Silica gel is reusable, though it may require more preparation time. This method can be effective in areas where refrigeration is not available, and it’s an energy-efficient way to preserve specimens.
• Storage Duration: Dried samples can be stored at room temperature, though they might require more careful processing before DNA extraction since desiccation can sometimes affect DNA quality.

4. Paper-based Storage or Filter Paper

• Process: Some researchers use filter paper to collect and preserve small arthropod specimens. This method can be quite cost-effective, as you can simply place carcasses on the paper, let them dry, and store the paper in an envelope or plastic bag.
• Resource Consideration: This method is simple and highly affordable, though it requires a more extensive analysis of the impact of drying on DNA quality and potential contamination.
• Storage Duration: Stored in a dry, cool environment, these samples can last for extended periods.

5. Minimizing Contamination

While storing your samples, especially when relying on techniques such as ethanol or drying, it's essential to minimize contamination. Use clean tools, wear gloves, and use sterilized containers to avoid the introduction of external microorganisms, which may skew your metagenomic results.

6. Field Considerations

If you're working in a field setting with minimal resources:

• Carry small, portable coolers with ice packs for immediate preservation.
• Use small vials or bags to store carcasses in ethanol or alcohol swabs.
• If refrigeration is unavailable, prioritize using desiccation (e.g., small packets of silica gel) and ensure prompt processing as soon as you're able.