First and Northernmost Record of Diadema setosum (Leske, 1778) (Echinodermata: Echinoidea: Diadematidae) in the Sea of Marmara

In July 2018, the first population of porcupine sea urchin Diadema setosum was recorded in the Sea of Marmara, Turkey. Individuals were observed by SCUBA diving in the eastern connection area of Dardanelles through the Sea of Marmara between 4 and 6 m of depth. This alien sea urchin has invaded the Mediterranean Sea and is now extending its range of distribution (approx. 345 nautical miles) to the Sea of Marmara.