''Syndinium'' is a cosmopolitan genus of parasitic

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s that infest and kill marine

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic species of

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s and

radiolaria The Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell (biology), cell into the inner and outer portions of endoplasm and Ecto ...

ns.Chatton , E. 1910: The existence of coelom Dinoflagellate parasites. The Syndinium in pelagic copepods. ''Comptes Rendus Hebdomadaires Des Seances De L Academie des Sciences''. 151: 654-656. ''Syndinium'' belongs to order

Syndiniales The Syndiniales are an order of early branching dinoflagellates (also known as Marine Alveolates, "MALVs"), found as parasites of crustaceans, fish, algae, cnidarians, and protists (ciliates, radiolarians, other dinoflagellates). The troph ...

, a candidate for the uncultured group I and II marine alveolates.Guillou, L., et al. 2008: Widespread occurrence and genetic diversity of marine parasitoids belonging to Syndiniales (Alveolata). Environ. Microbiol. 10(12): 3349-3365 The lifecycle of ''Syndinium'' is not well understood beyond the parasitic and

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

stages.Skovgaard, A., Massana, R., Balagué, V., Saiz, E. 2005: Phylogenetic Position of the Copepod-Infesting Parasite ''Syndinium turbo'' (Dinoflagellata, Syndinea). Protist, 156(4): 413-423

History of Research

''Syndinium'' was first described by French biologist

Édouard Chatton Édouard Chatton (; 11 October 1883 – 23 April 1947) was a French biologist who first characterized the distinction between the prokaryotic and eukaryotic cellular types. Chatton coined the terms and published them first in his 1937 paper ' ...

in 1910 as parasites of ''Paracalanus parvus'', a marine

in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

. The first ''Syndinium'' species described was ''Syndinium turbo'', which remains the most studied ''Syndinium'' species today. Due to there being 3 distinct

morphologies for ''Synidium turbo'', Chatton described it as 3 separate ''Syndinium'' species with the same host copepod species. This was corrected in 2005 when Skovgaard et al. discovered that the 3 zoospore morphologies of ''Syndinium turbo'' are genetically identical. Throughout the 20th Century researchers encountered ''Syndinium'' species in a range of

and

n in marine habitats ranging from the Clyde Sea to Port Phillip Bay, Australia. In the 2000s, ''Syndinium'' is given renewed attention from

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

researchers thanks to the maturation of

metagenomics Metagenomics is the study of genetic material recovered directly from environmental or clinical samples by a method called sequencing. The broad field may also be referred to as environmental genomics, ecogenomics, community genomics or microb ...

techniques such as environmental sequencing, bypassing the need to capture and culture. In 2001

rRNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosoma ...

amplification marine plankton samples led to the tentative establishment of group I and group II marine

alveolate The alveolates (meaning "pitted like a honeycomb") are a group of protists, considered a major clade and Biological classification, superphylum within Eukarya. They are currently grouped with the stramenopiles and Rhizaria among the protists with ...

s, two novel lineages that have not yet been cultivated in the laboratory. In 2005 researchers Skovgaard et al. performed phylogenetic analyses using small subunit ribosomal DNA and proposed that Syndiniophyceae, the class in which ''Syndinium'' belongs, is the group II marine alveolates. By 2008 it was confirmed that the group I and II marine alveolates belong to the order

, which includes the genus ''Syndinium''.

Habitat and Ecology

''Syndinium'' species have been recorded in a wide range of marine environments in both the Northern and Southern Hemispheres. The range of ''Syndinium'' species may be increased by human activity, as genetic evidence of ''Syndinium'' along with other protist genera was discovered in the ballast water of oceangoing ships on both sides of the Atlantic Ocean. As parasites, ''Syndinium'' infest planktonic copepods as well as radiolarians. ''Syndinium'' infections are fatal, and many motile zoospores pour out of the exoskeleton after consuming the host from inside out. Parasitism by ''Syndinium'' likely has a regulatory role on host populations, and in some conditions are responsible for sizable portion of host mortality rate.Kimmerer, W. J., McKinnon, A. D. 1990: High mortality in a copepod population caused by a parasitic dinoflagellate. Marine Biology. 107(3): 449-452 As the life cycle of ''Syndinium'' species are not completely known, the ecological role of ''Syndinium'' in non-parasitic life stages are unclear.

Description

Life Cycle

The complete life cycle of ''Syndinium'' species has not been entirely elucidated. The most well studied parts of the ''Syndinium'' life cycle involves the parasitic stage. When infesting a planktonic host such as a

, ''Syndinium'' species develop into a

plasmodial A plasmodium is a living structure of cytoplasm that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from slime molds, but are also found in parasitic Myxosporea, and so ...

stage, successively consuming host organs until the entire volume of the exoskeleton is occupied by the plasmodium, killing the host in the process. From the husk of the host one of three morphologically distinct zoospores emerge:

Macrospores

8-12μm long, 5-8μm wide, resembles an asymmetric

gymnodinium ''Gymnodinium'' is a genus of dinoflagellates, a type of marine and freshwater plankton. It is one of the few naked dinoflagellates, or species lacking armor known as cellulosic plates. Since 2000, the species which had been considered to be par ...

and is biflagellar with the anterior flagellum being longer than that of the posterior. Cells are motile but not only show moderate amounts of locomotion and are able to survive one to two days after exiting the host.

Microspores

8-10μm long, 2-4μm wide, possesses a refractile body at the posterior end, is also biflagellar with a longer anterior flagellum 3 to 4 times the cell length and an anterior flagellum that is approximately the length of the cell. Refractile bodies are used as resource storage for the cell. Microspores are much more active compared macrospores but perishes after only 5 to 8 hours.

Rostrate Spore

resembles an ''

Oxyrrhis ''Oxyrrhis'' is a genus of dinoflagellates. It includes the species '' Oxyrrhis marina''. It is sometimes considered to be a monotypic genus.Lowe, C. D., et al. (2011)Who is ''Oxyrrhis marina''? Morphological and phylogenetic studies on an unus ...

'' cell. Has a teardrop shape overall with a beak like projection at the narrower anterior end. The anterior and posterior flagella are both like the cell in length, and are inserted in the transverse and longitudinal groove, respectively. Rostrate spores can survive for several days out of the host. Only one type of zoospore will emerge from any single host. Once the zoospores exit the host, the life stages of ''Syndinium'' are not well understood. Attempts to infect copepod hosts or to induce sexual reproduction between all combinations of zoospores have so far been unsuccessful.

Mitotic Nuclear Division

Unlike other

s, ''Syndinium'' does not possess the conventional

dinokaryon A dinokaryon is a eukaryotic nucleus present in dinoflagellates in which the chromosomes are fibrillar in appearance (i.e. with unmasked DNA fibrils) and are more or less continuously condensed. The nuclear envelope does not break down during mi ...

or the associated process of dinomitosis. Instead, ''Syndinium'' possess fewer but larger chromosomes than most

s, as few as 4 compared to the typical 20 plus. ''Syndinium'' are notable for their mitotic nuclear division mechanisms involving nuclear membrane attached

kinetochore A kinetochore (, ) is a disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart. The kinetochore assembles on the centromere and ...

s and associated V-shaped chromosomes pushed away from each other by axially aligned

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...

s.Kubai, D. F., Ris, H. 1974: An Unusual Mitotic Mechanism in the Parasitic Protozoan ''Syndinium'' sp. Journal of Cell Biology, 60, Rockefeller University Press. This method of nuclear division, while not altogether rare within

s, were first studied in ''Syndinium''.

List of Species

''Syndinium turbo''

References

{{Taxonbar, from=Q7662330 Dinoflagellate genera Syndiniophyceae