Diversity and Phylogeny of Marine Parasitic Dinoflagellates

Abstract

The dinofl agellates are an assemblage of autotrophic, myxotrophic and heterotrophic species and play important roles in marine ecosystems. Most of them are free-living, but several are known as symbionts of marine invertebrates or as parasites of aquatic animals and protists. Molecular phylogenetic studies on parasitic dinofl agellates reveal that the parasitism has evolved polyphyletically appearing several times independently within the division Dinophyta. The Dinophyta consists of "core" dinofl agellates (typical dinofl agellates) and "basal" dinofl agellates. Within the basal dinofl agellates, the parasitic clades of Perkinsea, Ellobiophyceae and Syndiniophyceae are recognized. A large portion of environmental clone sequences recovered from various parts of the oceanic environments are thought to be members of the parasitic order Syndiniales (Syndiniophyceae). Therefore, the ecological function of parasitic dinofl agellates in the ocean is now better understood. The members of parasitic genera such as Parvilucifera (Perkinsea) and Amoebophrya (Syndiniophyceae) infect other dinofl agellates; therefore, much attention has been paid, because of their possible ability to control harmful algal blooms (HABs). The parasitism has also evolved within the "core" dinofl agellates (Dinophyceae) a number of times. These include Blastodinium , Chytriodinium , Dissodinium , Haplozoon , Oodinium , Paulsenella and Tintinnophagus. Because there are already several reviews on diversity of parasitic dinofl agellates, in this volume, only recent developments in phylogenetic studies on parasitic marine dinofl agellates are mainly reviewed here.

Single cell genomics of uncultured marine alveolates shows paraphyly of basal dinoflagellates

“…They are assumed to be parasites, and the microscopic and genomic data described here are consistent with this, and in some cases identify new hosts. Their exact evolutionary relationship to dinokaryotes has also been controversial (Guillou et al, 2008;Massana et al, 2008;Horiguchi, 2015), and our data provide strong support for their paraphyly. These insights impact how we reconstruct the evolution of plastids and parasitism in MALVs and dinoflagellates.…”

“…Originally, MALVs were divided into two major groups: MALV I including Ichthyodinium and Duboscquella (Harada et al, 2007;Skovgaard et al, 2009), and MALV II, including Syndinium, Hematodinium and Amoebophrya (Skovgaard et al, 2005). Both groups were subsequently subdivided further, but the relationships between subgroups remained uncertain (Guillou et al, 2008;Skovgaard et al, 2009;Horiguchi, 2015; see also Supplementary Figure 2). The concatenated SSU/LSU tree (Figure 1) recovers four strongly-supported subgroups: MALV Ia, Ib, II and IV (following the names of Guillou et al, 2008, but distinguishing two phylogenetically distant subgroups of MALV I).…”

“…However, most MALVs are only known from these environmental SSU rRNA gene sequences, and those that have been characterized further are relatively rare and do not represent all MALV subgroups. As only SSU rRNA is generally known, the phylogenetic position of MALVs is also partially uncertain: they are typically basal to dinokaryotes (that is, dinoflagellates with permanently condensed chromosomes), but may be monophyletic or paraphyletic with dinokaryotes branching among them, and in either case the phylogenies lack support (Guillou et al, 2008;Skovgaard et al, 2009;Horiguchi, 2015). Overall, most MALV diversity is unexamined and how MALV groups are related to one another and to dinokaryotes remains poorly resolved.…”

Two divergent Symbiodinium genomes reveal conservation of a gene cluster for sunscreen biosynthesis and recently lost genes

“…Dinoflagellates are one of the major groups in the supergroup Alveolata, with an estimated ~ 2500 species [ 1 ]. They inhabit aquatic environments and nearly half are phototrophic [ 1 ].…”

A Pelagic Microbiome (Viruses to Protists) from a Small Cup of Seawater

“…Parasites of the superphylum Alveolata, specifically the marine alveolates (MALV)-I and MALV-II clusters, routinely infect members of the family Dinophyceae and can account for up to 88% of the eukaryote fraction in some locations. These two MALV clusters have recently been renamed Syndiniales groups I and II, respectively [12]. Specifically for the southwest Indian Ocean, the eukaryotic fraction was dominated by alveolates including the Dinophyceae and their Syndiniales parasites [7].…”