Tiny water-dwelling organisms called phytoplankton can adopt a 'stealth' mode to avoid the attentions of predators.

Many types of plankton group together into chains, and some respond to grazers by increasing their group size until the chains are too large to eat. Erik Selander of the Technical University of Denmark in Charlottenlund and his colleagues show that predators can trigger the opposite response in Alexandrium tamarense.

When exposed to small plankton-eating crustaceans called copepods, chains of Alexandrium adopt stealth behaviour, splitting into single cells or very short chains and swimming more slowly. The phytoplankton drastically reduces its encounters with grazers through this mechanism, the authors report.

Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1011870108 (2011)