Serpuloidea (Annelida : Polychaeta) from Milos, an island in the Aegean Sea with submarine hydrothermalism

Serpuloidea were collected by diving within 45 m depth, by indirect samplin g in deeper waters (50 and 81 m), and among the fouling settled on oceanogr aphic instruments at various depths (10, 50, 80 and 83 m depth). A total of 33 species or subspecific taxa was found. 25 Serpulidae and eight Spirorbi dae. All the species collected are already known for the western Mediterran ean and have Atlantic-Mediterranean or worldwide distribution. Several of t hese, however, may be species-complexes hiding species with restricted geog raphic ranges. No Lessepsian migrants were found. The number of species fou nd at vent sites was significantly higher than that found at non-vent sites , although no vent-obligate species were recognized. Hydrothermal vents mig ht influence serpuloidean richness through four main mechanisms: (i) increa sing food sources to these filter-feeders, due to the chemiosynthetic produ ction by vent microbiota; (ii) enhancing the development of biogenic carbon ate mounds, which provide habitats for encrusting and cryptic species; (iii ) inducing advective mechanisms that concentrate larval stages in the vicin ity of vents and thus favouring recruitment; (iv) creating, through the per iodic emission of toxic fluids, a regime of 'intermediate disturbance' that allows a larger number of species to coexist.