Freshwater Gastrotrichs as Prey: First Documented Evidence of Cyclopoid Copepod Predation

Gastrotrichs (Phylum Gastrotricha) are widespread and species-rich components of benthic and periphytic communities, where they are thought to contribute substantially to food-web functioning by linking the microbial loop to higher trophic levels through their feeding on detritus, bacteria, microalgae, and fungi, and serve as prey for larger animals. Despite the well-recognized role as primary consumers, their position as potential prey remains largely unresolved, with documented predators so far restricted to carnivorous protists. Here, we report the first documented case of metazoan predation on a freshwater gastrotrich, in which a cyclopoid copepod actively captures and partially consumes a chaetonotid species. The interaction was first detected under minimally disturbed conditions and subsequently replicated in controlled experimental settings. Predation was documented through in vivo video recordings and supported by species-level identification of both predator and prey. These findings expand the currently recognized trophic interactions involving freshwater gastrotrichs and provide new insight into their ecological role within aquatic food webs.