Rhopilema nomadica in the Mediterranean: molecular evidence for migration and ecological hypothesis regarding its proliferation

Abstract

Since it was first observed in Israel in the 1970s, the nomad jellyfish Rhopilema nomadica has established a reputation as one of the worst invasive species in the Mediterranean Sea. It was assumed to originate in the Red Sea, or in the Indo-Pacific region, but in the absence of additional reports of live specimens outside the Mediterranean, its origins remained a mystery. Here, via molecular analysis, we present the first verified results of the existence of R. nomadica in the Western Indian Ocean. Moreover, using additional evidence from Cassiopea andromeda and R. nomadica, we propose that the construction of the Aswan High Dam may have led to the proliferation of R. nomadica in the Levantine Basin.