First record of the Siphonophore Physalia physalis (Linnaeus, 1758) in the Gulf of Tunis (Tunisia)

Abstract

The Portuguese man-of-war Physalia physalis (Linnaeus, 1758), is a pleustonic cnidarian commonly found in the tropical and subtropical areas of the world’s oceans. To date, and to our knowledge no signalization of P. physalis has been reported in Tunisia. In this note, we report for the first time, the presence of P. physalis in Tunisian coast on April 2, 2021. One colony was stranded at Carthage Amilcar beach. Three others were collected alive by fishermen in the open sea in front of Rades and Hammam Lif coasts. The specimens showed an unsymmetrical pneumatophore with a wrinkled longitudinal ridge consisting of a transparent purple-blue membrane, between 15 and 25 cm in length. The tentacles were approximately 50 to 130 cm in length. The presence of P. physalis in the Tunis gulf has coincided with the stranding of the jellyfish Velella velella (Linnaeus, 1758). Given the potential danger of this species for humans, it is essential to integrate it into the monitoring and observation network of the coastline.