Isolated and synergistic effects of chemical and structural defenses of two species of Tethya (Porifera: Demospongiae) Suzi Meneses Ribeiro a, ⁎, Keila Mara Cassiano b , Diana Negrão Cavalcanti a , Valéria Laneuville Teixeira a , Renato Crespo Pereira a a Pós-Graduação em Biologia Marinha, Universidade Federal Fluminense, Niterói, Brazil b Instituto de Matemática, Departamento de Estatística, Universidade Federal Fluminense, Niterói, Brazil abstract article info Article history: Received 20 December 2010 Received in revised form 19 October 2011 Accepted 10 December 2011 Available online 31 December 2011 Keywords: Chemical Ecology Chemical Defense Structural Defense Tethya South Atlantic Sponges are an important source of many interesting secondary metabolites with multiple ecological roles. Sponges can also use their spicules as a means of deterring consumers. The present study investigated the im- portance of chemicals and spicules as defensive strategies against predation for two congeneric sponge spe- cies from the Brazilian coast, Tethya rubra and Tethya maza. Crude extract and spicules differed somewhat in their effectiveness between these sponge species, with T. maza better defended than T. rubra against preda- tion by the hermit crab Calcinus tibicen and synergistic effects stronger in T. rubra. These results show that defensive strategies may be similar between sponge species possessing monophyletic origin, and reveal the importance of research on congeneric species to understand the ecology and evolution of defensive strategies. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Sponges are conspicuous organisms in marine benthic communi- ties, even in coral reefs, in which they can establish large populations in spite of the intense predation existing in these ecosystems (Alcolado, 1991; Ribeiro and Muricy, 2004; Sarmento and Correia, 2002). Marine sponges occur worldwide in a great diversity of habi- tats, probably because of their effective defense mechanisms. Howev- er, some animals are known to eat sponges, including fish (Dunlap and Pawlik, 1998; Randall and Hartman, 1968; Wulff, 1994), sea stars (McClintock et al., 1994; Schiebling, 1982; Sheild and Witman, 1993), polychaetes (Pawlik, 1983), echinoids (Birenheide et al., 1993; Santos et al., 2002), turtles (Leon and Bjorndal, 2002; Meylan, 1988, 1990), nudibranchs (Knowlton and Highsmith, 2005) and crabs (Hazlett, 1968, 1981; Schembri, 1982). Several species of marine sponges have chemical defense mecha- nisms that help protect them against certain bacterial infections, predator attacks, biofouling, and overgrowth by other sessile organ- isms (see McClintock and Baker, 2001; Paul and Puglisi, 2004; Paul et al., 2006). However, the development of chemical defenses by sponges seems to be closely related to predation pressure in the envi- ronment. For example, transplantation experiments revealed that mangrove sponges were highly vulnerable to predation when trans- planted to the coral-reef habitat, while coral-reef sponges remain re- sistant to predation when transported to mangrove areas (Pawlik, 1998; Ruzicka and Gleason, 2009). Physical defenses have been formally known in plants since the 1970s, through studies on spines (Cooper and Owen-Smith, 1986), thorns and resin ducts (Maxwell et al., 1972), siliceous phytoliths (Kaufman et al., 1981), lignified fibers (Coley, 1983) and tissue tough- ness (Howard, 1988). In the marine environment, physical defenses have been studied in several kinds of organisms, including algae, corals and sponges. Some marine macroalgae have calcified tissues which may act as a physical defense (Hay et al., 1994). Gorgonians and soft corals have calcareous sclerites in their tissues, which are im- portant structural components (Lewis and von Wallis, 1991) and also act as deterrents against some generalist predators (Harvell et al., 1988). In sponges, however, physical defenses are a controversial topic. Chanas and Pawlik (1995) found that spicules from eight highly spiculose species of Demospongiae (Cribrochalina vasculum, Geodia neptuni, Mycale laevis, Neofibularia nolitangere, Xestospongia muta, Agelas clathrodes, Chondrilla nucula, and Ectyoplasia ferox), represent- ing different spicule types, did not deter feeding by fish in laboratory or field assays. In addition, Waddell and Pawlik (2000a) found that spicules had no deterrent effect against predation by the hermit crab Paguristes punticeps. Nonetheless, Burns and Ilan (2003) found that spicules of four sponge species from the Red Sea (Diacarnus erethrianus, Hemimycale sp., Crella cystophora, and Suberites clavatus) and two from the Caribbean Sea (C. nucula and G. neptuni) deterred feeding by fish. Spicules from the temperate-zone sponges Cliona Journal of Sea Research 68 (2012) 57–62 ⁎ Corresponding author at: Museu Nacional, Universidade Federal do Rio de Janeiro. Departamento de Invertebrados. Laboratório de Biologia de Porifera. Quinta da Boa Vista s/n°, São Cristóvão, Rio de Janeiro, Zip code 20940-040, Brazil. Tel.: + 55 21 2562 6990. E-mail address: suzimr@yahoo.com.br (S.M. Ribeiro). 1385-1101/$ – see front matter © 2011 Elsevier B.V. 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