Ontogenic shifts in chemical defenses of the northwest Mediterranean Sea Eupolymnia nebulosa (Polychaeta, Terebellidae)
Abstract:Polychaetes are known to produce different compounds with biological activities. Most of these compounds appear to be species-specific and may serve either to deter predators, to keep clean the inner tube-surface or to inhibit settlement of potential competitors. In this paper, toxic and deterrent properties of the terebellid Eupolymnia nebulosa (Montagu) from 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, swimming 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 bioluminescence of the bacterium Photobacterium phosphoreum (Microtox® bioassay) following its exposure to polychaete crude extracts. Feeding deterrence assays were also conducted using sympatric generalist predators such as fish (Coris julis, Aidablennius sphinx, Parablennius incognitus, Lepadogaster sp.) and crustaceans (Centropagurus timidus, Pisidia longimana, Alpheus sp.). The jelly eggmasses, brooded eggs and coelomic oocytes were non-toxic. All remaining life cycle stages and tube were toxic. No differences were found between sexes and body sections. Operative deterrent effects occurred for: (1) egg-masses (probably physically mediated, linked to consistence of the mucus), and (2) early life cycle stages (i.e., swimming larvae and juveniles) and adult tentacles (probably a chemically mediated unpalatability). However, the results support that both types of deterrence effectively serve to protect against potential predators.
Document Type: Research Article
Publication date: 2000-07-01
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