RESEARCH ARTICLE E. E. G. Clavico Æ G. Muricy Æ B. A. P. da Gama D. Batista Æ C. R. R. Ventura Æ R. C. Pereira Ecological roles of natural products from the marine sponge Geodia corticostylifera Received: 17 December 2004 / Accepted: 3 August 2005 / Published online: 29 September 2005 Ó Springer-Verlag 2005 Abstract In the Brazilian coast, high numbers of the small brittle star Ophiactis savignyi usually live associ- ated with the sponge Geodia corticostylifera (Demo- spongiae, Geodidae), but not with other sympatric sponge species. In order to check whether this associa- tion was related only with the physical shelter provided by the sponge body or was chemically mediated, the crude organic extract of G. corticostylifera was added to sponge mimics made of phytagel and spongin skeleton. Control and treated mimics were simultaneously offered to previously sponge-associated O. savignyi in both static seawater and flow-through laboratory experi- ments. Ophiuroids were allowed to move towards the preferred mimic. The defensive properties of the sponge extract against fish predation and fouling were also evaluated. Chemotaxis assays showed that symbiotic ophiuroids were able to chemically recognize its host sponge, moving significantly more towards mimics containing G. corticostylifera extract. Chemical deter- rence assays showed that the natural concentration of the extract of this sponge was also able to inhibit gen- eralist fish predation on field experiments and the attachment of the common mussel Perna perna in lab- oratory assays. These results indicate that the crude extract of G. corticostylifera plays multiple functions in the marine environment, presumably being responsible for a closer association of this sponge with O. savignyi, providing protection for this ophiuroid and inhibition of epibionts on itself. Introduction Marine sponges are conspicuous members of the marine benthos, occurring worldwide from polar and temperate to tropical seas, from the intertidal to deep-sea envi- ronments (Sara` and Vacelet 1973; Bergquist 1978; Hooper and van Soest 2002). These benthic organisms are particularly prominent, together with scleractinian and alcyonarian coelenterates, in coral reef environ- ments, which are commonly characterized by high levels of herbivory and predation (e.g., Ru¨tzler 1978; Huston 1985; Hay 1991). In Caribbean coral reefs, sponges are one of the most abundant and diverse groups of sessile invertebrates, and they represent an important group for ecological studies (Alcolado 1990; Diaz and Ru¨tzler 2001; Wulff 2001). As in the Caribbean, sponge species are very abundant along the Brazilian coast, although the majority of the species from the broad coastline of this southwestern Atlantic region remain still unknown (Hadju et al. 1999). Sponges are the major source of unusual secondary metabolites from marine organisms (Munro et al. 1999; Faulkner 2002 and previous reviews from this author). These compounds are known to exhibit a broad spectrum of biological activities, such as antitumoral, antifungal, antiviral and antibacterial (e.g., Green et al. 1990; Mur- icy et al. 1993; Garson 1994; Munro et al. 1994; Almeida et al. 1996). Despite this, only recently ecological exper- iments have cast some light upon the true ecological roles of secondary metabolites from marine sponges. Some previous studies performed feeding assays employing appropriate methodology in order to evalu- ate the effectiveness of crude extracts or pure com- pounds from sponges as defenses against predators Communicated by P.W. Sammarco, Chauvin E. E. G. Clavico Æ B. A. P. da Gama Æ D. Batista R. C. Pereira (&) Po´s-Graduac¸a˜o em Biologia Marinha, Universidade Federal Fluminense, PO Box 100.644, 24001-970 Nitero´i, Rio de Janeiro, Brazil E-mail: egbrecp@vm.uff.br Tel.: 55 21 26292311 Fax: 55 21 26292292 G. Muricy Æ C. R. R. Ventura Museu Nacional, Departamento de Invertebrados, Universidade Federal do Rio de Janeiro, 20940-040 Rio de Janeiro, Brazil Marine Biology (2006) 148: 479–488 DOI 10.1007/s00227-005-0097-z