IntroductionThe phylum Annelida is composed of segmented worms and includes 2 classes, namely Polychaeta (marine worms) and Clitellata (oligochaetes and leeches) (WoRMS, 2014). The current estimation of the number of annelida species revealed that 13,721 species are present in the world's oceans (Appeltans et al., 2012). The majority of species belong to polychaetes (12,632 species), followed by oligochaetes (910 species) and leeches (179 species). In the Mediterranean Sea, 1181 Annelida species have been reported to date, of which 1122 species belonged to Polychaeta and 44 to Clitellata (Oligochaeta: 35 species; Hirudinea: 9 species) (Coll et al., 2010). Some Mediterranean countries have prepared a checklist of polychaete species along their coasts; 753 species were reported from the Greek coasts (

This study reports four alien polychaete species new to the marine fauna of Greece, four of which are aliens. These species are -Pseudopolydora paucibranchiata (family Spionidae), Paraprionospio coora (family Spionidae), Marphysa disjuncta (family Eunicidae), and Chaetozone corona (family Cirratulidae). Another species of Chaetozone, though not an alien one, Chaetozone gibber is reported here from Greek waters. All of them have been currently reported from the coasts of Turkey (Aegean or Levantine Seas). Pseudopolydora paucibranchiata and Marphysa disjuncta, probably introduced to the region through ballast waters, seem to be well established in the Mediterranean Sea. Chaetozone corona and Paraprionospio coora were considered to be cryptogenic. Pseudolydora paucibranchiata was found in great densities in a very disturbed site, confirming the opportunistic character of this species. Chaetozone corona and Chaetozone gibber showed a wider distribution pattern, though their abundance increased in disturbed sites. Marphysa disjuncta was found in disturbed as well as in undisturbed sites along the coasts of Greece and Paraprionospio coora is characteristic of moderate to higher depth zones. These new findings increase the number of polychaete species from the Hellenic Seas to 777 species and the number of alien species to 33.

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IntroductionPolychaeta is one of the most diverse and abundant benthic groups in marine ecosystems: 12,632 species of polychaetes are reported in the world's oceans (Appeltans et al., 2012), while 1122 species are reported in the Mediterranean Sea (Coll et al., 2010) and 238 species in the Black Sea to date (Kurt Şahin and Çınar, 2012). The polychaetes distributed among the Turkish coasts were recently reported by Çınar et al. (2014) with 459 species from the coast of the Levantine Sea, 547 species from the coast of the Aegean Sea, 390 species from the coast of the Sea of Marmara, and 136 species from the Black Sea coast of Turkey.The Black Sea is a semiclosed sea and it is the largest (547,000 km 3 ) permanently stratified marine basin in the world (Zaitsev et al., 2002). It is connected to the Aegean region of the Mediterranean Sea by the narrowest strait of Turkey, the Bosphorus, to the south, and the Sea of Azov by the Strait of Kerch to the north. Nearly 87% of the Black Sea is entirely anoxic (without oxygen) and it contains high levels of hydrogen sulfide. Anoxic conditions occurring below 70 to 200 m limit the vertical distribution of organisms. The hydrographic regime is characterized by low salinity surface water of river origin overlying high salinity of deep water of Mediterranean origin (Bakan and Büyükgüngör, 2000). The structure of its ecosystem differs from that of the neighboring Mediterranean Sea in that species diversity is lower and the dominant organism groups are different. However, the abundance, total biomass, and productivity of the Black Sea are much higher than those in the Mediterranean Sea (Zaitsev and Alexandrov, 1998).The first studies concerning polychaetes in the Black Sea date back to the late 1800s (

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