Morphological and genetic investigations have led to the identification of Spiophanes adriaticus sp. nov. (Polychaeta: Spionidae) from the North Adriatic Sea (Central Mediterranean). A total of 81 specimens were recorded along the sublittoral zone between 8 and 27.5 m of depth. This species differs from other congeners by having: two pairs of black eyes, a cirriform occipital antenna, dorsal ciliated organs as thin bands usually extending to chaetigers 11–12, dorsal ciliated crests from chaetiger 14–17, undulate glandular opening on chaetigers 5–7, unhooded hooks from the 15th chaetiger and Y shaped tubes. A detailed description and illustrations are provided for the new species. Through DNA barcoding results and comparison of DNA sequences of the new species with those of other congeners available in the GenBank database, the validity of the new finding was confirmed. Spiophanes adriaticus sp. nov. represents the eighth species of Spiophanes recorded for the Mediterranean Sea. A key for the identification of Mediterranean Spiophanes species is also provided.

A new Spiogalea species is described from South-east Brazil. The specimens were collected in muddy bottoms during a large survey (15–3000 m) in southern Brazil. This genus comprised, up to now, only one species described from Capbreton Canyon (Bay of Biscay). The new species differs from the type-species, mostly in the morphology of the prostomial chitinous plate, a character restricted to the genus Spiogalea. With this new species, the generic diagnosis of the genus was amended.

Alien polychaetes belonging to the genus Marenzelleria were recorded from the mouth of the Don River and Taganrog Bay in the Sea of Azov in February–March 2014. Morphological characteristics varied greatly and matched those of two species: M. neglecta and M. arctia. Some individuals did not match the descriptions of both species. A genetic study using different sequences (primarily COI, but also 16S, 28S, cytb and nuclear histone 3a) showed that only M. neglecta was present despite some morphological mismatches. A morphological description of the species according to the new data is presented, together with a revised table of variability of the key numeric characters. Since 2014, Marenzelleria has spread swiftly and become dominant in a considerable part of the Taganrog Bay, making up to 91% of the total abundance/biomass (6800 ind. m−2 and 31.2 g m−2, respectively). Monodominant sites were also present. Its occurrence is 100% in recent surveys. Such a sharp increase seems to be due to a lack of detritophages in the bay; this is supported by the fact that M. neglecta has not formed its specific assemblage. The community structure, if M. neglecta is excluded, is equal to that before the invasion. In the Sea of Azov itself, M. neglecta is not as abundant, but occurs up to the Strait of Kertch and at some sites in the Black Sea. Its spread further into the Black Sea seems possible, as well as into the Caspian Sea via the Volga-Don Canal.

Larvae of ~100 species of benthic invertebrates were obtained from the vicinity of Tomales Bay and Dillon Beach, California, over a 6-year period (1971–1977). This study reports on larvae of 14 species in eight families of polychaetes: Micronereis nanaimoensis, Nereis vexillosa, Sthenelais fusca, Nephtys caecoides, Nephtys californiensis, Boccardia berkeleyorum, Polydora pygidialis, Polydora spongicola, Dipolydora cardalia, Mediomastus californiensis, Ampharete labrops, Phragmatopoma californica, Sabellaria cementarium and Pectinaria californiensis. Some species were cultured from embryos obtained from laboratory fertilizations or field-collected egg masses or capsules. Larvae of other species were obtained from meroplankton and some of these were cultured through metamorphosis. A summary table is presented documenting seasonal occurrence of 60 polychaete taxa in the meroplankton.

Boccardia proboscidea is recorded for the first time in UK waters. Specimens were discovered at two intertidal sites on the Isle of Skye.

During the Antarctic summers of 2002–2003 and of 2005–2006, the Spanish BENTART cruises were conducted to the Bellingshausen Sea (west Antarctica) aiming to get a complete picture of the benthic communities of the area. To achieve it, 30 stations were selected, from depths ranging from 100 to 2000 m. In order to characterize the infaunal, epifaunal and suprabenthic components of the communities various different sampling gears were used at each station. As a part of the obtained material, some spionid individuals were identified as belonging to a species never before recorded from the Austral Ocean, Aonidella cirrobranchiata.

Scolelepis (Scolelepis) lighti was described in 2006 for the coast of the Gulf of México. Few Scolelepis species have been reported for the Brazilian coast: S. (S.) chilensis, S. (S.) goodbodyi and S. (S.) squamata. The polychaetes that live in intertidal sand beaches on the coast of João Pessoa city have not been studied before and to date nothing has been published on the Scolelepis species from the north-east region of Brazil.

Eight species of polydorid polychaetes were found to inhabit mollusc shells from south-western Australian waters. Numerous individuals of Polydora uncinata were extracted for the first time from the shells of both land-based cultured abalone Haliotis laevigata and H. roei, as well as from natural subtidal H. roei and Chlamys australis. Shells of the oyster Saccostrea commercialis cultured in sea-based systems were infested by Boccardia knoxi which was first recorded in these waters. Polydora aura, Dipolydora giardi, D. armata, D. aciculata and Boccardia proboscidea were common among shells of various natural intertidal and subtidal molluscs. A small number of P. haswelli were extracted from their self-excavated burrows in shells of cultured oysters. Boccardia knoxi and D. aciculata were redescribed based on the newly collected materials. Polydora uncinata and B. knoxi exhibited similar larval development patterns (exolecithotrophy and adelphophagy), iteroparity and longer life span, suggesting a high reproductive potential. This study suggests that further monitoring of polydorid species is needed not only from the viewpoint of marine biology but also to survey the risk invasive species pose to commercially important molluscs in this region and worldwide.