1. Institut de Ciències del Mar, Spanish National Research Council (CSIC), Passeig Marítim de la Barceloneta, 37, 08003 Barcelona, Spain
2. Department of Animal and Food Science, Universitat Autònoma de Barcelona, Travessera dels Turons, s/n, Cerdanyola del Vallès, 08193 Barcelona, Spain
3. Comparative Biology Centre, The Medical School, Newcastle University, Newcastle Upon Tyne NE2 4HH, Tyne & Wear, UK
4. Department of Biological & Environmental Sciences, University of Gothenburg, P.O. Box 463, SE-405 30 Gothenburg, Sweden