Barrancaceae: A new green algal lineage with structural and behavioral adaptations to a fluctuating environment

Abstract

PREMISE OF THE STUDY: To enhance our knowledge of the diversity of microalgae, a phycological survey of the Canary Islands (Spain) was undertaken. Here we report the discovery of a (semi)terrestrial green fi lamentous alga isolated from a steep volcanic canyon on La Palma. This alga is continually exposed to changing weather conditions (fl oods vs. droughts) and thus provides a good opportunity to investigate possible adaptations to a semiterrestrial habitat with large fl uctuations of environmental parameters. METHODS: We used axenic cultures, simulated fl ood and drought stresses and studied their eff ect on the life history of the alga using light, confocal laser scanning and scanning electron microscopy including fl uorescent staining. Furthermore, phylogenetic analyses using rDNA sequence comparisons were performed. KEY RESULTS: Three specifi c life-history traits that likely represent adaptations to the fl uctuating environment of the canyon were observed: (1) fragmentation through “fi lament splitting”, a unique branching mechanism not reported before in algae and initiated by formation of oblique cross walls, (2) aplanospore formation, and (3) reproduction by multifl agellate zoospores with 4–24 fl agella arranged in groups of four. Phylogenetic analyses identifi ed the alga as Barranca multifl agellata gen. et sp. nov. (Barrancaceae fam. nov., Chaetophorales, Chlorophyceae). Moreover, the Chaetophoraceae Greville, 1824 was emended and a new family, Uronemataceae (fam. nov.) erected. CONCLUSIONS: The discovery of Barrancaceae fam. nov. highlights the importance of investigating nonconventional habitats to explore microalgal diversity. The reproductive versatility demonstrated by Barranca suggests adaptation to a semiterrestrial habitat with large fl uctuations in water availability.