Pack hunting by a common soil amoeba on nematodes

Area of Science:

• Soil ecology
• Protistology
• Nematology

Background:

• Soils harbor complex eukaryotic communities, notably heterotrophic protists.
• Protists are often viewed as bacterivores, but interactions with nematodes are known.
• Direct predatory impacts of protists on nematodes remain largely uncharacterized.

Purpose of the Study:

• To investigate the direct predatory interactions between soil protists and nematodes.
• To characterize the hunting strategy and ecological role of the testate amoeba Cryptodifflugia operculata.
• To assess the prevalence and potential importance of nematophagy by protists in soil food webs.

Main Methods:

• Isolation and observation of Cryptodifflugia operculata preying on nematodes.
• Analysis of nematode community composition changes in response to amoeba predation.
• Metatranscriptomic analysis of European soil samples to detect Cryptodifflugia operculata 18S rRNA transcripts.

Main Results:

• Cryptodifflugia operculata employs a specialized pack-hunting strategy to effectively prey on bacterivorous nematodes.
• Predation by C. operculata led to species-specific reductions in nematode populations, indicating selective impact.
• C. operculata transcripts were detected in all 12 European soil samples, comprising up to 4% of the active protist community.

Conclusions:

• The testate amoeba Cryptodifflugia operculata is an effective predator of nematodes, utilizing a unique pack-hunting behavior.
• Molecular evidence suggests C. operculata is widespread and abundant in European soils, highlighting its ecological significance.
• The study establishes nematophagy by protists as a crucial, yet underappreciated, trophic link in soil ecosystems.