Ontogenic shifts in chemical defenses of the northwest Mediterranean sea Eupolymnia nebulosa (Polychaeta, Terebellidae)

Polychaetes are known to produce different compounds with biological activi ties. Most of these compounds appear to be species-specific and may serve e ither to deter predators, to keep clean the inner tube-surface or to inhibi t settlement of potential competitors. In this paper, toxic and deterrent p roperties of the terebellid Eupolymnia nebulosa (Montagu) fi om the Catalan Sea in the northwest Mediterranean were analyzed for: (1) different stages of their life cycle (i.e., coelomic oocytes, eggs inside the egg-masses, s wimming larvae, early benthic stages and adults), (2) external structures ( tubes and egg-masses), (3) sexes and (4) adult's body sections (tentacles, thorax and abdomen). Toxicity was assessed by measuring decreases of biolum inescence of the bacterium Photobacterium phosphoreum (Microtox(R) bioassay ) following its exposure to polychaete crude extracts. Feeding deterrence a ssays were also conducted using sympatric generalist predators such as fish (Coris julis, Aidablennius sphinx, Parablennius incognitus, Lepadogaster s p.) and crustaceans (Cenaapagurus timidus, Pisidia longimana, Alpheus sp.). The jelly egg-masses, brooded eggs and coelomic oocytes were non-toxic. Al l remaining life cycle stages and tube were toxic. No differences were foun d between sexes and body sections. Operative deterrent effects occurred for : (1) egg-masses (probably physically mediated, linked to consistence of th e mucus), and (2) early life cycle stages (i.e., swimming larvae and juveni les) and adult tentacles (probably a chemically mediated unpalatability). H owever, the results support that both types of deterrence effectively serve to protect against potential predators.