Molecular and morphological characterization of Melanothamnus testudinis sp. nov. (Rhodophyta, Rhodomelaceae) and its distinction from Polysiphonia carettia

The association between epizoic algae and animals is well known, and turtles are among the animals that most commonly host epibiont communities. The most studied algal component of the epizoic communities found on turtles is represented by diatoms, while other algal taxa, like the Rhodophyta, are less investigated. During a survey started to study the epibionts associated with loggerhead turtles, Caretta caretta, cared for at the WWF Sea Turtle Rescue Center of Lampedusa Island (Sicily, Italy), specimens of Rhodomelaceae (Rhodophyta) were collected for taxonomic investigation. The resulting vegetative, reproductive, and molecular data of those specimens characterised the new species described here as Melanothamnus testudinis sp. nov. We also evaluated the holotype of Polysiphonia carettia Hollenberg, an epibiont of C. caretta reported from the Mediterranean Sea. This investigation confirmed the distinction of M. testudinis from P. carettia and suggested that previous Mediterranean and Canarian records of the latter species are probably M. testudinis.