On the presence of the less known arminid nudibranch Dermatobranchus rubidus (Gould, 1852) in the Adriatic Sea

Abstract

     Two cases of the occurrence of the alien heterobranch species, Dermatobranchus rubidus (Gould, 1852) are reported for the Adriatic Sea. The first record originates from June 2019 from the island of Brač (Croatia, Middle Adriatic Sea), when a specimen was found during the collection of clams, while the second specimen was sighted at Fiesa (Gulf of Trieste, Northern Adriatic Sea) in October 2023, photographed on coarse sand bottom. These are the first records for the Adriatic Sea and indications of the possible establishment of this species in the Mediterranean Sea. Due to its cryptic behaviour and perhaps nocturnal habits, it is difficult to assess whether the species has been overlooked so far or whether it is extending its distribution in the Mediterranean.