Settlement patterns of two spirorbidae (annelida, polychaeta) species in the harbour of Ischia (Gulf of Naples, Mediterranean Sea)

Abstract

Studies on settlement rate of Neodexiospira pseudocorrugata and Simplaria pseudomilitaris (Polychaeta, Spirorbidae) in the Port of Ischia (Naples) are reported. Observations were carried out monthly, during a one-year cycle (April 1995-April 1996) at two different depths (0.5 and 1.5 m) using unglazed ceramic tiles as substrate. Both species reproduced throughout the year with maximum settlement in June and July at 1.5 m depth. On tiles exposed during June, 40% of individuals of N. pseudocorrugata, ranging between 0.8 and 1.6 mm coil diameter, were brooding, with broods smaller (6–14 eggs, egg diameter 75 um) than in most spirorbid species. Simplaria pseudomilitaris did not reach brooding size within any of the monthly exposure periods. In and after August, an algal bloom of attached brown filaments (Ectocarpa-ceae) covered the tiles and was accompanied by decreased settlement and heavy mortality of spirorbids. © 2000 Taylor & Francis Group, LLC.