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Parasites and Phytoplankton, with a Special Emphasis on Dinoflagellate Infections

Abstract

ABSTRACT. Planktonic members of most algal groups are known to harbor intracellular symbionts, including viruses, bacteria, fungi, and protozoa. Among the dinoflagellates, viral and bacterial associations were recognized a quarter century ago, yet their impact on host populations remains largely unresolved. By contrast, fungal and protozoan infections of dinoflagellates are well documented and generally viewed as playing major roles in host population dynamics. Our understanding of fungal parasites is largely based on studies for freshwater diatoms and dinoflagellates, although fungal infections are known for some marine phytoplankton. In freshwater systems, fungal chytrids have been linked to mass mortalities of host organisms, suppression or retardation of phytoplankton blooms, and selective effects on species composition leading to successional changes in plankton communities. Parasitic dinoflagellates of the genus Amoebophrya and the newly described Perkinsozoa, Parvilucifera infectans, are widely distributed in coastal waters of the world where they commonly infect photosynthetic and heterotrophic dinoflagellates. Recent work indicates that these parasites can have significant impacts on host physiology, behavior, and bloom dynamics. Thus, parasitism needs to be carefully considered in developing concepts about plankton dynamics and the flow of material in marine food webs.

Chimeric viruses blur the borders between the major groups of eukaryotic single-stranded DNA viruses

“…Regardless, the presence of the RC-Rep gene in the genome of PgV-12T lends additional support to the hypothesis that unicellular algae may host at least some of the CHIVs. More generally, parasitic and symbiotic relationships involving unicellular algae are highly prevalent in aquatic environments 50 and might be central for the emergence of new virus types, such as CHIVs, by providing a unique environment accessible for viruses infecting phylogenetically distant hosts. Such co-localization of various genetic elements of distinct origins and histories could also explain the evolutionary relationships between RC-Reps of prokaryotic plasmids and eukaryotic ssDNA viruses 12,13,15,21,22 .…”

Infection dynamics of Amoebophryidae parasitoids on harmful dinoflagellates in a southern Chilean fjord dominated by diatoms

“…It has recently been postulated that dinoflagellate blooms may also result from the absence of efficient pathogens in newly invaded areas (Salomon et al 2003), a theory known as the 'enemy release hypothesis' in terrestrial ecology (Keane & Crawley 2002). The major eukaryotic pathogens described for dinoflagellates are unicellular parasitoids belonging to the Phylum Alveolata (perkinsoids and Amoebophryidae; Park et al 2004). Both lineages ultimately kill their hosts to accomplish their life cycles (Park et al 2004), endowing these organisms with a typical parasitoid feature (i.e.…”

“…The major eukaryotic pathogens described for dinoflagellates are unicellular parasitoids belonging to the Phylum Alveolata (perkinsoids and Amoebophryidae; Park et al 2004). Both lineages ultimately kill their hosts to accomplish their life cycles (Park et al 2004), endowing these organisms with a typical parasitoid feature (i.e. parasitism is similar to predation by grazers in that a part of the host population will be killed).…”

Cryptic infection of a broad taxonomic and geographic diversity of tadpoles by Perkinsea protists

“…Phylogenetic analysis has shown that Perkinsea are a deeply divergent sister-group of dinoflagellate alveolates (16). Only three representative groups of Perkinsea were previously described morphologically and taxonomically: Perkinsus spp., parasites of marine bivalves (e.g., oysters and clams), Parvilucifera spp., parasites of dinoflagellates, and Rastrimonas subtilis (previously Cryptophagus subtilis), parasites of cryptophyte algae (17)(18)(19)(20). However, environmental sequence Significance Amphibians are among the most threatened animal groups.…”