Mutualism Among Sessile Invertebrates: A Mediator of Competition and Predation

Abstract

Hydroids of the genus Zanclea are epizoic on encrusting bryozoans. The bryozoans protect these hydroids with skeletal material. Zanclea polyps on the bryozoan Celleporaria brunnea sting small predators and adjacent competitors, helping Celleporaria to survive and to grow over competing species. This mutualism enables the two species to cover a larger area than they could individually