Vegetative and reproductive morphology of Cladosiphon contortus, C occidentalis and C cymodoceae sp nov (Ectocarpales, Phaeophyceae) from the Canary Islands

The genus Cladosiphon is represented in the Canary Islands by three species, C. contortus, C. occidentalis, and the new species C. cymodoceae. Vegetative and reproductive morphology of macrosporophytes, as well as habitat and phenology of the Canarian individuals, are described in detail. The southern limit of distribution of the northeastern Atlantic and Mediterranean species, C. contortus, is extended to the Canary Islands, and some anatomical features that previous descriptions had apparently overlooked (large inner medullary cells and rhizoid-like perimedullary filaments, longer cortical filaments, sheathed hairs, adventitious cortical filaments, and hairs often formed from inside empty plurilocular sporangia) are documented. Unilocular sporangia of C. contortus are described here for the first time, and they agree with the characteristics of the genus. Cladosiphon occidentalis is reported for the first time in the eastern Atlantic Ocean. Specimens previously reported from the Canary Islands as Cladosiphon zosterae were found to be misidentifications of C. occidentalis. Cladosiphon cymodoceae sp. nov., known only from the Canary Islands, is an epiphytic species on leaves of the warm temperate seagrass Cymodocea nodosa. Cladosiphon cymodoceae differs from the remaining species of the genus in a unique combination of characteristics: very irregularly branched habit with relatively thick axes and abundant short branchlets, long and thin cortical filaments (to 425 mu m long and 5-8 mu m lower diameter), sheathed hairs, and plurilocular sporangia with few-celled outgrowths of mature sporangia commonly at the apices of inrolled cortical filaments. Young thalli of C. occidentalis and C. cymodoceae were observed arising from myrionematoid crusts on leaves of Cymodocea nodosa as a juvenile stage in the development of the macroscopic sporophytes.