Diet and physiological responses of Spondyliosoma cantharus (Linnaeus, 1758) to the Caulerpa racemosa var. cylindracea invasion Antonio Box a, ⁎, Salud Deudero a,b , Antoni Sureda c , Andreu Blanco a , Josep Alòs d , Jorge Terrados d , Antoni Maria Grau e , Francisco Riera e a Laboratorio de Biología Marina Universidad de las Islas Baleares, Ctra Valldemossa Km 7.5 CP: 07122 Balearic Islands, Spain b Instituto Español de Oceanografia. Centro Oceanográfico de Baleares. P.O. Box 29107015, Palma de Mallorca, Spain c Sciences of the Physical Activity Laboratory, Fundamental Biology and Healthy Sciences Department, University of the Balearic Islands, Ctra. Valldemossa Km 7.5, E-07122 — Palma de Mallorca, Balearic Islands, Spain d Mediterranean Institute for Advanced Studies, IMEDEA (CSIC-UIB), C/ Miquel Marqués 21 E-07190, Esporles, Balearic Islands, Spain e Direcció General de Pesca, Govern de les Illes Balears, C/ Foners 10, 07006 Palma de Mallorca, Balearic Islands, Spain abstract article info Article history: Received 30 January 2009 Received in revised form 11 August 2009 Accepted 12 August 2009 Keywords: Antioxidant enzymes Balearic Islands Caulerpa racemosa Spondyliosoma cantharus Stable isotopes Marine invasions are a worldwide problem that involves changes in communities and the acclimation of organisms to them. The invasive Chlorophyte Caulerpa racemosa var. cylindracea is widespread in the Mediterranean and colonises large areas from 0 to 70 m in depth. The omnivorous fish Spondyliosoma cantharus presents a high frequency of occurrence of C. racemosa in the stomach contents at invaded areas (76.3%) while no presence of C. racemosa was detected in control areas. The isotopic composition of muscle differed significantly between invaded and non-invaded sites for δ 13 C(-16.67‰±0.09 and -17.67‰±0.08, respectively), δ 15 N (10.22‰± 0.22 and 9.32‰± 0.18, respectively) and the C:N ratio (2.01 ± 0.0002 and 1.96 ± 0.009, respectively). Despite the high frequency of occurrence of C. racemosa in the stomach contents of S. cantharus and its important contribution to the δ 13 C source (20.7%±16.2), the contribution of C. racemosa to the δ 15 N in S. cantharus food sources was very low (6.6%±5.8). Other invertebrate prey such as decapods and polychaetes were more important contributors to the δ 15 N source at both invaded and non-invaded sites. Activation of enzymatic pathways (catalase, superoxide dismutase, glutathione-s-tranferase, 7-ethoxy resorufin O-de-ethylase) but not a significant increase in lipid peroxidation MDA (0.49 ± 0.01 nmol/mg prot at non-invaded and 0.53 ± 0.01 nmol/ mg prot at invaded sites) was observed in S. cantharus individuals living in C. racemosa-invaded sites compared with control specimens. The low δ 15 N contribution values of C. racemosa by S. cantharus together with the toxicity demonstrated by the activation of the antioxidant defences and the important contribution of invertebrate prey to the δ 15 N could mean that the ingestion of C. racemosa by S. cantharus might be unintentional during the predation of invertebrate preys living underneath the entanglement of the C. racemosa fronds and stolons mats. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Around 100 macrophytes species are thought to have been introduced into the Mediterranean Sea (Ribera, 2002). The invasive variety of Caulerpa racemosa (Forsskal) J. Agardh (Chlorophyta, Bryopsi- dales, Caulerpaceae) was observed for the first time in the Mediterra- nean Sea in Libya in 1990 (Nizamuddin, 1991). Morphological and molecular studies indicate that the invasive variety of C. racemosa in the Mediterranean is similar to the south-west Australian endemic C. racemosa var. laetevirens f. cylindracea (Sonder) Weber-van Bosse therefore, the invasive form of C. racemosa in the Mediterranean was named as C. racemosa var. cylindracea (Sonder) Verlaque, Huisman et Boudouresque (Verlaque et al., 2003). Distance between south-west Australia and the Mediterranean points to Ship traffic and the aquaria trade as possible introduction vectors. Only 17 years after its first observation, C. racemosa var cylindracea (hereafter C. racemosa) has colonised 12 countries (Italy, Greece, Albania, Cyprus, France, Turkey, Malta, Spain, Tunisia, Croatia, Algeria and Libya) (Klein and Verlaque, 2008). C. racemosa spreads in sheltered and exposed areas, colonising all kinds of substrates ranging from 0 to 70 m in depth (Argyrou et al., 1999; Piazzi and Cinelli, 1999; Zuljevic et al., 2003; Klein and Verlaque, 2008), spreading over coralligenous bottoms and colonising important areas, constituting an important threat to such communities (Piazzi et al., 2007; Klein and Verlaque, 2008). The fish Spondyliosoma cantharus (Linnaeus, 1978) (Black seabream) is a common species in the western Mediterranean and can be found over seagrass beds, especially in the case of juvenile individuals, and rocky and sandy bottoms to about 300 m depth (Bauchot and Hureau, Journal of Experimental Marine Biology and Ecology 380 (2009) 11–19 ⁎ Corresponding author. Tel.: +34 971 17 33 52; fax: +34 971 17 31 84. E-mail address: toni.box@uib.es (A. Box). 0022-0981/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2009.08.010 Contents lists available at ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe