Unexpected Discovery: Freshwater Flatworm Forms Complex Societies With Soldier Castes

This species of freshwater flatworm has the potential to serve as a model for studying the evolution of social organization.
New findings from UC San Diego’s Scripps Institution of Oceanography reveal that a small freshwater parasite, known for causing health issues in humans, protects its colonies with a unique class of non-reproductive soldiers.

The discovery, published in the Proceedings of the National Academy of Sciences and funded by the National Institutes of Health, vaults this species of parasitic flatworm into the ranks of complex animal societies such as ants, bees, and termites, which also have distinct classes of workers and soldiers that have given up reproduction to serve their colony.