Specimens of the grapsoid crabs Grapsus granulosus, Plagusia squamosa and Pachygrapsus transversus were recently collected in the Sirte Basin, on the southern rim of the Mediterranean Sea. The Erythrean alien G. granulosus is reported for the first time from the Mediterranean Sea, along with the second record in the Mediterranean of the Indo-Pacific P. squamosa, and the first record of P. transversus along the south-central Mediterranean coast. The relations between introduced grapsoid crabs, vessel traffic and climate change are dicussed.

The introduction of invasive species may be the most profound modern threat to biological communities in high-latitude regions. In the Southern Ocean, the natural transport mechanism for shallow-water marine organisms provided by kelp rafts is being increasingly augmented by plastic debris and shipping activity. Plastic debris provide additional opportunities for dispersal of invasive organisms, but dispersal routes are passive, dependent on ocean currents, and already established. In contrast, ships create novel pathways, moving across currents and often visiting many locations over short periods of time. Transportation of hull-fouling communities by vessel traffic thus poses the most likely mechanism by which exotic species may be introduced to the Southern Ocean.