Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Baseline First evidence of establishment of the rayed pearl oyster, Pinctada imbricata radiata (Leach, 1814), in the eastern Adriatic Sea Ana Gavrilović a , Marina Piria b,⁎ , Xiang-Zhao Guo c,d,e , Jurica Jug-Dujaković f , Ana Ljubučić g , Alen Krkić h , Neven Iveša i , Bruce A. Marshall j , Jonathan P.A. Gardner c a Juraj Dobrila University of Pula, Department of Natural and Health Sciences, Zagrebačka 30, 52100, Croatia b University of Zagreb, Faculty of Agriculture, Department of Fisheries, Beekeeping, Game Management and Special Zoology, Svetošimunska 25, 10000 Zagreb, Croatia c School of Biological Sciences, Victoria University of Wellington, P O Box 600, Wellington 6140, New Zealand d Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, College of Fisheries, Huazhong Agricultural University, Wuhan 430070, PR China e Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan 430070, PR China f Sustainable Aquaculture Systems Inc., 715 Pittstown Road, Frenchtown, NJ 08825, USA g Independent researcher, dr. Ante Sugje 2, 20 000 Dubrovnik, Croatia h Riba Mljet d.o.o., Svetog Križa 3, 20000 Dubrovnik, Croatia i Eko-Adria d.o.o., Boškovićev uspon 16, 52100 Pula, Croatia j Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand ARTICLE INFO Keywords: Alien species Mitochondrial DNA Cytochrome c oxidase I (COI) Barcode of life Lessepsian migration Island of Mljet ABSTRACT The Mediterranean Sea is increasingly under threat from invasive species that may negatively affect biodiversity and/or modify ecosystem structure and function. The bivalve mollusc Pinctada imbricata radiata is listed among the 100 most invasive species in the Mediterranean. A first finding of an established population of P. imbricata radiata in the coastal waters of the eastern Adriatic Sea, is presented in this paper. Six and then 30 live specimens were collected in 2015 and in 2017, respectively, at depths of 5 to 15 m from the island of Mljet, Croatia. DNA sequencing of the mitochondrial cytochrome c oxidase I gene (COI) revealed three different haplotypes. All samples showed greatest similarity (98 to > 99%) to P. radiata COI sequence records in GenBank (=P. imbricata radiata as used in this paper). A Neighbour Joining tree placed all Croatian samples within the 100% bootstrap supported clade for P. imbricata radiata. The Mediterranean Sea is a hotspot of biodiversity with an esti- mated 17,000 marine species that represent ~ 7.5% of world marine biodiversity (Coll et al., 2010). However, the Mediterranean Sea is in- creasingly under threat from invasive species (marine alien species, MAS) that may negatively affect biodiversity and/or modify ecosystem structure and function (Sabelli and Taviani, 2014). Presently, 821 alien species have been reported from the Mediterranean Sea, with 613 al- ready well established and 208 casual records (Zenetos et al., 2017). Whilst no extinctions of native species are known, sudden declines in abundance, and local extirpations, concurrent with the proliferation of MAS have been recorded (Galil, 2007). The rayed pearl oyster, Pinctada imbricata radiata (Leach, 1814), is among the 100 most invasive species in the Mediterranean Sea (Streftaris and Zenetos, 2006). It was the first Lessepsian bivalve re- ported in the Mediterranean Sea, in Egypt, as Meleagrina savignyi (Monterosato, 1878). According to Gofas et al. (2001) and Bouchet (2011), Pinctada imbricata radiata is the accepted name for the taxon commonly referred to as Pinctada radiata. Although a certain degree of confusion about its taxonomic status still exists (Tëmkin, 2010; Cunha et al., 2011), the trinomial P. imbricata radiata is currently the most commonly used nomenclature for this bivalve (Barbieri et al., 2016). In the present paper, in keeping with the most currently used form, we employ P. imbricata radiata. P. imbricata radiata is an Indo-Pacific subspecies that inhabits tem- perate, subtropical and tropical waters. It is widely distributed from the western Pacific Ocean (Korea and southern China), Australia, to the Indian Ocean, the Red Sea and the Persian Gulf (Gervis and Sims, 1992). P. imbricata radiata has progressively colonised new habitats in the Mediterranean Sea (Tlig-Zouari and Zaouali, 1994; Gofas and Zenetos, 2003; Zenetos et al., 2005; Tlig-Zouari et al., 2009, 2010; Katsanevakis, 2011; Derbali et al., 2009; Lodola et al., 2013; Deidun et al., 2014; Gerovasileiou et al., 2017), but most records have been reported from the eastern part of the basin (Barbieri et al., 2016). Despite being reported as “occasionally” present (i.e., not http://dx.doi.org/10.1016/j.marpolbul.2017.10.045 Received 27 June 2017; Received in revised form 5 October 2017; Accepted 20 October 2017 ⁎ Corresponding author. E-mail address: mpiria@agr.hr (M. Piria). Marine Pollution Bulletin xxx (xxxx) xxx–xxx 0025-326X/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Gavrilović, A., Marine Pollution Bulletin (2017), http://dx.doi.org/10.1016/j.marpolbul.2017.10.045