New records of old species. Some pelagic polychaetes along the Italian coast

Holoplanktonic polychaetes constitute an exception within this taxon, which as adults colonize all the whole variety of brackish water and marine habitats. Nevertheless, they form a distinctive group in marine zooplankton and play an important role in the pelagic trophic nets. Pelagic worms are little studied, especially in the Mediterranean Sea, while information regarding the distribution of the families Typhloscolecidae and Iospilidae along Italian coasts is a century out of date. This paper deals with the state of knowledge of these polychaetes; it summarizes the previous records, updating them with the new records here reported from Tyrrhenian Sea, in order to check whether they have a bearing on Italian fauna. The findings reported in this paper confirm the presence of the Typhloscolecidae, with the species Sagitella kowalewskyi and Typhloscolex muelleri, and of the Iospilidae, with the species Phalacrophorus pictus and Iospilus phalacroides, along the Italian coasts, validating, in each case, their current presence in the Italian fauna. The main morphological features of these species and a dichotomous key for their identification are also reported.