BOLIDOMONAS: A NEW GENUS WITH TWO SPECIES BELONGING TO A NEW ALGAL CLASS, THE BOLIDOPHYCEAE (HETEROKONTA)

Abstract

A new algal class, the Bolidophyceae (Heterokonta), is described from one genus, Bolidomonas, gen. nov., and two species, Bolidomonas pacifica, sp. nov and Bolidomonas mediterranea, sp. nov., isolated from the equatorial Pacific Ocean and the Mediterranean Sea, respectively. Both species are approximately 1.2 m in diameter and have two unequal flagella; the longer flagellum bears tubular hairs, whereas the shorter is smooth. The flagellar basal apparatus is restricted to two basal bodies, and there is no transitional helix. Cells are naked, devoid of walls or siliceous structures. The internal cellular organization is simple with a single plastid containing a ring genophore and a girdle lamella, one mitochondrion with tubular cristae, and one Golgi apparatus close to the basal bodies. The Mediterranean and the Pacific species differ in the insertion angle between their flagella and their pattern of swimming, these differences possibly being linked to each other. Analyses of the SSU rDNA gene place the two strains as a sister group to the diatoms. Moreover, pigment analyses confirm this position, as fucoxanthin is found as the major carotenoid in both lineages. These data strongly suggest that the ancestral heterokont that gave rise to the diatom lineage was probably a biflagellated unicell.

Sex is a ubiquitous, ancient, and inherent attribute of eukaryotic life

“…The first is the order Parmales, an enigmatic group of small planktonic spherical microalgae covered by siliceous plates known since the 1980s, but until recently without cultured representatives and with effectively unknown phylogenetic position (26). The second is the class Bolidophyceae comprised of minute naked marine flagellates discovered 15 y ago and shown to be a sister group of diatoms (27). In 2011, both groups were tied together by the amazing finding that the first (and thus far only) molecularly characterized parmalean species is phylogenetically nested among bolidophytes (28).…”

Evolution of the diatoms: insights from fossil, biological and molecular data

“…However, several other heterokont groups, including the Dictyochophyceae, Synurophyceae, Chrysophyceae, Parmophyceae, and Xanthophyceae (van den Hoek et al 1995;Graham & Wilcox 2000) produce silica structures. These are spread across the phylogenetic tree of heterokonts (see Guillou et al 1999;Medlin et al 2000;Kawachi et al 2002;unfortunately, no molecular data are yet available for the Parmophyceae) and so it is possible that the ability to metabolize silica is primitive among autotrophic heterokonts. However, even if this were so, it still would be necessary to examine why diatoms have retained the capacity to metabolize silica and acquired the ability to produce a silicified wall, when their closest relatives, the Bolidophyceae, have not.…”

“…The closest relatives discovered so far are the Bolidophyceae, which are picoplanktonic algae with a simplified cellular organization (Guillou et al 1999). Both diatoms and bolidomonads possess similar pigments and two transverse plates at the base of each flagellum.…”

Ecology and Diversity of Picoeukaryotes

“…Eustigmatophyceae Nannochloropsis granulata Zapata et al (2001) (Chrysochromulina), Guillou et al (1999b), and F. Rodriguez (personal communication) (Bolidophyceae), Latasa et al (2004) (Prasinophyceae), Kawachi et al (2002a, b) (Pinguiophyceae), Henley et al (2004) (Trebouxiophyceae), and Karlson et al (1996) (Eustigmatophyceae). …”