Brandtodinium gen. nov. and B. nutricula comb. Nov. (Dinophyceae), a dinoflagellate commonly found in symbiosis with polycystine radiolarians

Abstract

Symbiotic interactions between pelagic hosts and microalgae have received little attention, although they are widespread in the photic layer of the world ocean, where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders Spumellaria, Collodaria and Nassellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate Scrippsiella nutricula, a species originally described by Karl Brandt in the late nineteenth century as Zooxanthella nutricula. The free-living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free-living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine-symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free-living stage does not match that of Scrippsiella or related genera, and LSU and SSU rDNA-based molecular phylogenies place these symbionts in a distinct clade within the Peridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name Brandtodinium gen. nov. and the recombination of S. nutricula as B. nutricula comb. nov.

Eukaryotic plankton diversity in the sunlit ocean

“…In addition to their contribution to total primary production (36,38), these diverse, biologically complex, often biomineralized, and relatively long-lived giant mixotrophic protists stabilize carbon in larger size fractions and probably increase its flux to the ocean interior (38). Conversely, the microalgae that are known obligate intracellular partners in open-ocean photosymbioses (33,(40)(41)(42) (Fig. 5B) were neither very diverse nor highly abundant and occurred evenly across organismal size fractions (Fig.…”

“…4) and copepods in, respec-tively, the oligotrophic and eutrophic and mesotrophic systems. The dino-flagellates Brandtodinium and Pelagodinium are endophotosymbionts in Collodaria (33) and Foraminifera (40,42), respectively. (C) Richness and abundance of parasitic and photosymbiotic (microalgae) protists across organismal size fractions.…”

Achradina pulchra, a Unique Dinoflagellate (Amphilothales, Dinophyceae) with a Radiolarian-like Endoskeleton of Celestite (Strontium Sulfate)

“…Indeed, since the earlier plankton studies, the Radiozoa (Acantharia and Polycystinea) were known to harbor microalgal symbionts, including dinoflagellates (Anderson 2014). Few of these symbionts have been characterized by morphological and molecular methods (Probert et al 2014, Yuasa et al 2016. However, molecular surveys revealed a high diversity of these symbionts (Gast 2006;Gast andCaron 1996, 2001;Dolven et al 2007).…”

Concerning the cohabitation of animals and algae – an English translation of K. Brandt’s 1881 presentation “Ueber das Zusammenleben von Thieren und Algen”

“…Thus, ironically, zooxanthellae do not necessarily belong to the genus Zooxanthella. In fact, multiple genera such as Amphidinium (Jørgensen et al 2004), Gymnodinium (Gast and Caron 1996), Symbiodinium (Freudenthal 1962;LaJeunesse 2001), and Brandtodinium (Probert et al 2014) that associate with a range of radiolarian, anthozoan, foraminiferan, and protist hosts are all zooxanthellae, but some of them have only a distant phylogenetic relationship with Zooxanthella (Gottschling and McLean 2013). Modern molecular techniques have illustrated how phylogenetically divergent members of zooxanthellae and zoochlorellae are to each other in each group.…”