Distribution and abundance of Ophiothrix suensonii on sponge vs. non-sponge habitat at Whale Shoals patch reef, Belize

Abstract

The morphological and chemical properties of sponges can offer unique habitat opportunities to brittle stars in coral reef environments. This study tests for the existence of an association between a brittle star (Ophiothrix suensonii) and a tube sponge (Callyspongia vaginalis) in a Belizean patch reef. Frequencies of O. suensonii on paired plots with and without C. vaginalis clusters were compared. Brittle star abundance was significantly greater on plots containing C. vaginalis; individuals were densely packed within and between the sponge’s protective tubes. Few brittle stars were also found clinging to soft corals and to other Porifera. Although O. suensonii is not an obligate sponge dweller, these brittle stars are a primary inhabitant of C. vaginalis, which offers unique morphological protection from fish predation. The results of this study highlight the importance of species-specific invertebrate symbioses in Belizean patch reefs where habitat options are limited and predation is intense.