Occurrence of Didemnum perlucidum Monniot F., 1983 on artificial substrates along the Mediterranean coast of Israel

Introductions of non-indigenous ascidian species are highly common nowadays due to their ability to establish successfully on artificial substrates. Didemnid species are of particular concern because of their rapid a-sexual growth and high fecundity. The colonial ascidian Didemnum perlucidum Monniot F., 1983 was first described from Guadeloupe Island in the Caribbean, although its native range remains unknown. To date, it has been recorded from numerous sites across the Indo-Pacific and Atlantic oceans. Here, having employed both classic taxonomy and genetic tools to verify its identification, we document for the first time its occurrence in the Mediterranean Sea – on two artificial substrates along the Israeli coast. The ability of D. pelucidum to establish reproductive populations despite the harsh environmental conditions of this region, with temperature fluctuations between 16–31°C and a salinity of 38–39 ppt, raises concern regarding this species’ potential for introductions at numerous sites across the Mediterranean.