Microhabitat selection in a local syllid assemblage with the first record of Syllis hyllebergi (Syllinae) in the central Mediterranean

摘要

The colonization dynamic of Syllidae (Polychaeta) is described by means of a manipulative experiment carried out into the mesotrophic marine Faro Lake (NE Sicily). Small modules of artificial expanded fire-clay granules (EFCG-module) have been positioned in a shallow water experimental field from May to July 2008; they were plunged into the lake bottom or suspended in the water column. Three sampling times (15, 30, 60 days) and three treatments (heavy and moderate organic supply, plus a control) constituted the crossed factors. The natural sandy bottom was equally sampled. Both univariate and multivariate statistics have been employed to test the significance of distribution patterns at small spatio-temporal scale. Twenty-three species were identified. Since the early stage of the fouling process, buried and suspended modules were colonized by two different syllid assemblages that showed different temporal patterns, due to the relative proximity to the source habitat of adult immigrants. Organic contamination did not seem to affect the overall colonization process, although few species showed a moderate decrease from references to enriched modules. Moreover, a remarkable population of the new record Syllis hyllebergi (Licher, 1999) has been found.The population was rather patchy, mainly distributed in the upper coarser sediment with a greater content of shell debris. Morphometric assessment of most characters indicated an increase in size with respect to the holotype. The species has an actual bipolar distribution, being recorded also in the southern Brazil. According to the present record, 5. hyllebergi might spread from the Levantine Sea to the central Mediterranean, step by step throughout similar confined transitional environments.