The presence of the non-indigenous species, the black-pygmy mussel Xenostrobus securis, is reported here for the first time in an intense shellfish farming area off Galicia (NW Spain). Very high concentrations of this mytilid bivalve have colonized estuarine waters located at the inner part of the Ria de Vigo. The invasive role of X. securis is discussed in the context of the wide ecological tolerance of the species and the recent finding of settlements of this species on numerous colonies of the economically-important blue mussel Mytilus galloprovincialis. The mode of introduction of the black-pygmy mussel is also discussed in relation to human management activities.

Although the bryozoological fauna of Galicia (NW Spain) is probably the best known of the whole Iberian Peninsula, and perhaps one of the better known in Europe, new studies continue to provide new knowledge. A new species, Schizotheca galaica sp. nov., is described. Eleven species are newly recorded in Galicia: Aetea longicollis, Parellisina curvirostris, Copidozoum planum, Glabrilaria corbula, Haplopoma sciaphilum, Schizomavella (Schizomavella) mamillata, Fenestrulina asturiasensis, Fenestrulina barrosoi, Buffonellaria muriella, Schizotheca divisa and Dentiporella saldanhai; two of them (B. muriella and S. divisa) are also reported for the first time in Iberian waters; four others (Antarctothoa galaica, F. asturiasensis, F. barrosoi and D. saldanhai) are reported for the first time since their original descriptions, and SEM images of A. longicollis and F. asturiasensis are provided for the first time. Moreover, the range of geographical distribution of some species is expanded: the record of S. divisa is the southernmost to date, while the records of S. mamillata, F. barrosoi and D. saldanhai are the most northerly to date. The presence of other four species in Galician waters is confirmed and we document the permanence and range extension of two species recently introduced into our waters (Tricellaria inopinata and A. galaica).

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The occurrence of the alien species Anadara kagoshimensis is reported for the first time in the Ría de Arousa (Galicia, NW Spain) during 2013. Living specimens of this species have been recognized by morphological analysis. The cytochrome c oxidase subunit I gene has been partially sequenced and Maximum likelihood and Bayesian analyses carried out to confirm its identification. This new record reaffirms the presence of A. kagoshimensis, previously reported as Anadara inaequivalvis, along the Atlantic European coast extending the known distribution range in Spanish waters to the south.

The caprellid amphipod, Caprella mutica, is a well-known invasive species, originating in the Sea of Japan, which has been rapidly expanding along the coasts of North America, Europe and Oceania for the last forty years. Caprella mutica is frequently associated with man-made structures, especially those dedicated to aquaculture activities, where it can reach high densities of up to 300,000 ind./m 2 . A well-established population of C. mutica was recently found by SCUBA-divers in Galician waters (north-west Spain) at 6 different man-made floating structures along Ría de Arousa. The record of this species in this location implies a new southernmost limit of distribution, extending the known distribution range in Atlantic European waters and confirming the continuity of the colonization southwards.