ARE CHEMICAL DEFENCES PRESENT IN THE LIFE-CYCLE OF EUPOLYMNIA NEBULOSA (POLYCHAETA, TEREBELLIDAE)?
Martin, D.1; Uriz, M.J. 1; Bhaud, M. 2 & Duchêne, J. C.2
1 Centre d'Estudis Avançats de Blanes (CSIC), Camí de Santa Bàrbara s/n, E-17300 Blanes (Girona), Spain
2 Laboratoire Arago, Observatoire Océanologique de Banyuls, Univesité P. et M. Curie (Paris VI), CNRS, URA 117, Fr-66651 Banyuls-sur-Mer CEDEX, France
Previous studies revealed the production of different compounds with antifungal and antibacterial activities in polychaetes (Higa & Scheuer 1975; Woodin et al. 1987; Goerke & Weber 1990; Goerke et al. 1991; Woodin et al. 1993). It is believed that these metabolites, which seem to be species-specific, may contribute 1) to reduce or avoid predation from larval to adult stages, 2) to keep clean the inner tube-surface and 3) to inhibit competitors' settlement in the vicinity of adults. Toxic and deterrent properties of populations of the terebellid Eupolymnia nebulosa (Montagu) from the Catalan Sea (NW Mediterranean) were analysed at different stages of their life cycle (i.e. eggs and mucus from the egg-masses, one month-old juveniles and adults). Toxicity of crude extracts from these stages was measured as the decrease of luminescence of the bacterium Photobacterium phosforeum (Microtox assay, Becerro et al., 1995). The existence of antipredatory mechanisms was analysed in both fied and laboratory experiments. Sympatric generalistic predators (such as the fishes Coris julis and Parablenius incognitus) as well as carnivorous polychaetes were selected for these antipredatory tests. Antibacterial activity was not detected in the mucus from the egg-masses. Conversely, eggs, one month-old juveniles and adult bodies were toxic, while the highest values occurred in adult tentacles. We can not assess how these toxicities would affect predators not deterred by E. nebulosa. However, an operative deterrent effect was evidentiated for egg-masses, one month-old juveniles and adult tentacles, which effectively serve to protect them against potential predators.