New pelagophytes show a novel mode of algal colony development and reveal a perforated theca that may define the class. Issue 2 (1st December 2020)

• Record Type: Journal Article
• Authors: Wetherbee, Richard; Bringloe, Trevor T.; Costa, Joana F.; van de Meene, Allison; Andersen, Robert A.; Verbruggen, Heroen
• Editors: Cock, M.
• Is Part Of: Journal of phycology. Volume 57:Issue 2(2021)
• Page Start: 396
• Page End: 411
• Publication Date: 2020-12-01
• Subjects: Aureoumbra -- Gazia -- Glomerochrysis -- Sarcinochrysidaceae -- Pelagophyceae -- molecular phylogeny -- perforated theca -- sand‐dwelling; Algae -- Periodicals; 579.8
• DOI: 10.1111/jpy.13074
• Languages: English
• ISSNs: 0022-3646

Abstract

Abstract : Pelagophytes (Heterokonta) are a morphologically diverse class of marine algae historically united only by DNA sequences. We established clonal cultures of sand‐dwelling pelagophytes collected from intertidal pools around Australia. Phylogenetic trees based on nuclear 18S rDNA and plastid rbc L, psa A, psa B, psb A, and psb C sequences revealed two new genera, Gazia and Glomerochrysis, related to Aureoumbra in a distinct lineage within the Sarcinochrysidaceae (Pelagophyceae). The three new species ( Gazia saundersii, Gazia australica, and Glomerochrysis psammophila ), along with an Australian strain of Aureoumbra geitleri, are characterized by dominant benthic stages that differ significantly from one another, while occasionally producing classic heterokont zoospores. The benthic stage of Ga. saundersii has a novel development not observed in any other colonial alga, consisting of large, spherical colonies (up to 140 μm in diameter) containing c. 2, 500 cells that eventually differentiate and segregate into a large number of daughter colonies that are subsequently liberated. Alternatively, colonies may differentiate into a mass of zoospores that escape and settle to develop into new colonies. In Gl. psammophila, cubic packets of cells form large sticky clusters that bind sand together, while Ga. australica and A. geitleri are unicellular species. Using fixation by high‐pressure freezing, a distinctive perforated theca was observed by TEM in all genera of this lineage, and we hypothesize this unique covering may be the first morphological feature to characterize most, if not all, pelagophytes. This study substantiates the diverse nature of sand‐dwelling pelagophytes as well as their mechanisms for thriving in a dynamic habitat.