Invading Aurelia aurita has established scyphistoma populations in the Caspian Sea

The Caspian Sea has no endemic Scyphozoa. In 1999, a mass accumulation of Aurelia medusae was recorded, indicating that sometime earlier, jellyfish had invaded the basin, but since then no scyphozoans have been reported in the Caspian. In the fall of 2008, we found scyphistomae (scyphoid polyps) during a cruise to the eastern Middle Caspian. The scyphistomae were numerous (100–10,000 ind. m −2 ) and occupied a depth range of 30–73 m. Genetic data ( 18S rDNA, ITS - 1 and COI ) showed that the scyphistomae belonged to the species A. aurita . The current genetic data set is insufficient to determine the source region(s) of the invasive A. aurita . It remains unclear why no moon jellies have been recorded in the Caspian in the last 10 years. Because swarming scyphomedusae are often pests, the presence of scyphistomae should be considered as a warning of a possible outbreak of A. aurita medusae in the Caspian.