Blastodinium

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Blastodinium
Scientific classification
Domain:
Eukaryota
(unranked):
SAR
(unranked):
Alveolata
Phylum:
Dinoflagellata
Class:
Blastodiniphyceae
Order:
Blastodiniales
Family:
Blastodinidae
Genus:
Blastodinium

Blastodinium (also known as Blastodiniphycaea) is a diverse genus of dinoflagellates and important parasites of planktonic copepods. They exist in either a parasitic stage, a trophont stage, and a dinospore stage. Although morphologically and functionally diverse, as parasites they live exclusively in the intestinal tract of copeods. [1]

Contents

Etymology

Blastodinium is made up of the Greek prefix ‘blasto-’, meaning to germ/bud. This likely refers to its dinospore stage following Blasdotinium reproduction, where sporocytes appear to bud out of a cuticle.

History of knowledge

The Blastodinium taxonomy is entirely based on their morphology at the trophont stage [1] with B. pruvoti being the type species of the group. [2] In 1920, Chatton proposed 3 main groups which are consistent with today's molecular data; Spinoulsum, Contorum, and Mangini. Upon their discovery, it was recognized that Blastodinium organisms had features that distinguished them from the majority of dinoflagellates in the Dinophyceae class. These include their parasitic lifestyle and the lack of histones in their temporary dinokaryon (dinospore) stage. Thus, the genus was placed in a separate class, Blastodiniphyceae, which contained the single order, Blastodiniales. [1] However, the Blastodinium’s dinospore's thecal plate pattern is still noticeably similar to the thecal patterning on dinophyceae dinoflagellates, highlighting the close relationship between the lineages. [1]

Blastodinium exhibit the two features that link all members of the Blastodiniale order; a parasitic life mode and the presence of a temporary dinokaryon at some life cycle stage. [3] However, Blastodinium classification as a monophyletic group is only moderately supported, as small subunit rDNA sequences between some of the genus's species have a relatively large difference. [3]

Habitat and ecology

Blastodinium live most of their life as parasites in the guts of marine planktonic copepods. Although some Blastodinium species are capable of photosynthesis through the copepod's transparent gut, they acquire most of its nutrients from their host. [1]

Blastodinium infection only occurs in juvenile copepods or adult females, since infected male juveniles are unable to molt into an adult stage. When infected, castration of female copepods is commonly observed, along with a general reduction in copepod size and survival. This is likely due to food limitations from the blocked alimentary tract and the added competition against the protist for organic matter. [1]

Morphology

Blastodinium are typically motile and bi-flagellated. These organisms exhibit three life stages; a parasitic stage (also known as trophocyte), a trophont stage, and a sporocyte (dinospore) stage. Most trophonts and dinospores are greenish brown in color, indicating the presence of a plastid. These stages also have thecal plates, which contain trichocyst pores scattered along the surface. [3]

Trophocytes are binucleated and have large Golgi apparati composed of many dictyosomes. Instead of fully functioning chloroplasts, they possess etioplasts and small underdeveloped plastids. Thus, trophocytes perform limited photosynthesis despite being highly metabolically active. Unlike the typical dinoflagellate morphology, trophocytes are multicellular and composed of hundreds of non-flagellated cells. Sometimes, young trophocytes possess an anterior beak, although its function is unknown. [1]

The trophont stage is a multicellular growth stage, composed of many individual cells wrapped by a cellulosic layer. [1]

Dinospores are free-swimming flagellates that exhibit the typical morphology of dinoflagellates. [3] Although initially binucleated, they later divide into four uni-nucleated dinospores. They have clear thecal plates with a dense covering of papillae. They are ellipsoid in shape and have well developed plastids located at the cell's periphery. [1]

Nucleus

Blastodinium have a dinokaryon nucleus, characterized by a lack of histones and permanently condense chromosomes. [1] Blastodinium perform closed mitosis, in which their nuclear envelope remains intact to aid in the orientation and segregation of chromosomes. Mitosis does not involve kinetochores or centrioles, as their chromosomes are attached to the inner membrane. During asexual reproduction, their mitosis stages follow one another in the absence of interphase. [3]

Life cycle

The infection cycle first starts with the ingestion of a free-swimming dinospore by a copepod. Rather than being digested, the dinospore grows and developed into a parasitic trophocyte. At this stage, it takes residence in the copepod's gut lumen, where it competes for nutrients and organic matter.

Following infection, the trophocyte will engage in asexual reproduction by palintomy. [4] During this, the trophocyte divides via binary fission into a secondary trophocyte and a germ cell. The germ cell will then divide into many sporocytes. The secondary trophocyte may divide into a tertiary trophocyte and another germ cell, which may then produce a second layer of sporocytes. These repeated binary fissions continue in the absence of an intermediate growth stage, to get multiple layers of the multicellular growth that is the trophont. All of this occurs within a common cuticle, whose rupture results in the release of sporocytes through the copepod anus and into the environment. Although initially non-motile, sporocytes later develop a flagellum and take on the general morphology of a typical dinoflagellate. [1]

Species list

Related Research Articles

Flagellate Group of protists with at least one whip-like appendage

A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms which are more formally characterized.

Dinoflagellate Unicellular algae with two flagella

The dinoflagellates are a monophyletic group of single-celled Mesokaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations vary with sea surface temperature, salinity, and depth. Many dinoflagellates are photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey.

Dinokaryota Superclass of single-celled organisms

Dinokaryota is a main grouping of dinoflagellates. They include all species where the nucleus remains a dinokaryon throughout the entire cell cycle, which is typically dominated by the haploid stage. All the "typical" dinoflagellates, such as Peridinium and Gymnodinium, belong here. Others are more unusual, including some that are colonial, amoeboid, or parasitic. Symbiodinium contains the symbiotic zooxanthellae.

Copepod Subclass of crustaceans

Copepods are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic, some are benthic, a number of species have parasitic phases, and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as biodiversity indicators.

Biological life cycle Series of stages of an organism

In biology, a biological life cycle is a series of changes in form that an organism undergoes, returning to the starting state. "The concept is closely related to those of the life history, development and ontogeny, but differs from them in stressing renewal." Transitions of form may involve growth, asexual reproduction, or sexual reproduction.

<i>Karenia</i> (dinoflagellate) Genus of single-celled organisms

Karenia is a genus that consists of unicellular, photosynthetic, planktonic organisms found in marine environments. The genus currently consists of 12 described species. They are best known for their dense toxic algal blooms and red tides that cause considerable ecological and economical damage; some Karenia species cause severe animal mortality. One species, Karenia brevis, is known to cause respiratory distress and neurotoxic shellfish poisoning (NSP) in humans.

Syndinium is a cosmopolitan genus of parasitic dinoflagellates that infest and kill marine planktonic species of copepods and radiolarians. Syndinium belongs to order Syndiniales, a candidate for the uncultured group I and II marine alveolates. The lifecycle of Syndinium is not well understood beyond the parasitic and zoospore stages.

Amoebophyra is a genus of dinoflagellates. Amoebophyra is a syndinian parasite that infects free-living dinoflagellates that are attributed to a single species by using several host-specific parasites. It acts as "biological control agents for red tides and in defining species of Amoebophrya." Researchers have found a correlation between a large amount of host specify and the impact host parasites may have on other organisms. Due to the host specificity found in each strain of Amoebophrya's physical makeup, further studies need to be tested to determine whether the Amoebophrya can act as a control against harmful algal blooms.

Polarella is a dinoflagellate, and is the only extant genus of the Suessiaceae family. The genus was described in 1999 by Marina Montresor, Gabriele Procaccini, and Diane K. Stoecker, and contains only one species, Polarella glacialis. Polarella inhabits channels within ice formations in both the Arctic and Antarctic polar regions, where it plays an important role as a primary producer. Polarella is a thecate dinoflagellate, wherein the cell has an outer covering of cellulose plates, which are arranged in nine latitudinal series. The general morphology of Polarella is similar to that of a typical dinoflagellate. and Polarella has a zygotic life history, wherein it alternates between a motile vegetative phase and a non-motile spiny cyst. While it is thought that the cysts of Polarella have lost their ability to form fossils, the cyst life cycle stage has acted as link to extinct members of the Suessiaceae family.

<i>Ornithocercus</i> Genus of single-celled organisms

Ornithocercus is a genus of planktonic dinoflagellate that is known for its complex morphology that features considerable lists growing from its thecal plates, giving an attractive appearance. Discovered in 1883, this genus has a small number of species currently categorized but is widespread in tropical and sub-tropical oceans. The genus is marked by exosymbiotic bacteria gardens under its lists, the inter-organismal dynamics of which are a current field of research. As they reside only in warm water, the genus has been used as a proxy for climate change and has potential to be an indicator species for environmental change if found in novel environments.

<i>Dinophysis</i> Genus of single-celled organisms

Dinophysis is a genus of dinoflagellates common in tropical, temperate, coastal and oceanic waters. It was first described in 1839 by Christian Gottfried Ehrenberg.

Parvilucifera is a genus of marine alveolates that parasitise dinoflagellates. Parvilucifera is a parasitic genus described in 1999 by Norén et al. It is classified perkinsozoa in the supraphylum of Alveolates. This taxon serves as a sister taxon to the dinoflagellates and apicomplexans. Thus far, five species have been described in this taxon, which include: P.infectans, P.sinerae, P.corolla, P.rostrata, and P.prorocentri. The genus Parvilucifera is morphologically characterized by flagellated zoospore. The life cycle of the species in this genus consist of free-living zoospores, an intracellular stage called trophont, and asexual division to form resting sporangium inside host cell. This taxon has gained more interest in research due to its potential significance in terms of negative regulation for dinoflagellates blooms, that have proved harmful for algal species, humans, and the shellfish industry.

Alexandrium is a genus of dinoflagellates. It contains some of the dinoflagellate species most harmful to humans, because it produces toxic harmful algal blooms (HAB) that cause paralytic shellfish poisoning (PSP) in humans. There are about 30 species of Alexandrium that form a clade, defined primarily on morphological characters in their thecal plates.

<i>Oxyrrhis marina</i> Species of single-celled organism

Oxyrrhis marina is a species of dinoflagellates with flagella. A marine heterotroph, it is found in much of the world.

Polykrikaceae Family of single-celled organisms

The Polykrikaceae are a family of athecate dinoflagellates of the order Gymnodiniales. Members of the family are known as polykrikoids. The family contains two genera: Polykrikos and Pheopolykrikos.

<i>Polykrikos</i> Genus of single-celled organisms

Polykrikos is one of the genera of family Polykrikaceae that includes athecate pseudocolony-forming dinoflagellates. Polykrikos are characterized by a sophisticated ballistic apparatus, named the nematocyst-taeniocyst complex, which allows species to prey on a variety of organisms. Polykrikos have been found to regulate algal blooms as they feed on toxic dinoflagellates. However, there is also some data available on Polykrikos being toxic to fish.

Durinskia is a genus of dinoflagellate that can be found in freshwater and marine environments. This genus was created to accommodate its type species, Durinskia baltica, after major classification discrepancies were found. While Durinskia species appear to be typical dinoflagellates that are armored with cellulose plates called theca, the presence of a pennate diatom-derived tertiary endosymbiont is their most defining characteristic. This genus is significant to the study of endosymbiotic events and organelle integration since structures and organelle genomes in the tertiary plastids are not reduced. Like some dinoflagellates, species in Durinskia may cause blooms.

Coccidinium is a genus of parasitic syndinian dinoflagellates that infect the nucleus and cytoplasm of other marine dinoflagellates. Coccidinium, along with two other dinoflagellate genera, Amoebophyra and Duboscquella, contain species that are the primary endoparasites of marine dinoflagellates. While numerous studies have been conducted on the genus Amoebophyra, specifically Amoebophyra ceratii, little is known about Coccidinium. These microscopic organisms have gone relatively unstudied after the initial observations of Édouard Chatton and Berthe Biecheler in 1934 and 1936.

Coolia is a marine dinoflagellate genus in the family Ostreopsidaceae. It was first described by Meunier in 1919. There are currently seven identified species distributed globally in tropical and temperate coastal waters. Coolia is a benthic or epiphytic type dinoflagellate: it can be found adhered to sediment or other organisms but it is not limited to these substrates. It can also be found in a freely motile form in the water column. The life cycle of Coolia involves an asexual stage where the cell divides by binary fission and a sexual stage where cysts are produced. Some of the species, for example, Coolia tropicalis and Coolia malayensis, produce toxins that can potentially cause shellfish poisoning in humans.

<i>Haplozoon</i> Genus of single-celled organisms

Haplozoon (/hæploʊ’zoʊən/) are unicellular endo-parasites, primarily infecting maldanid polychaetes. They belong to Dinoflagellata but differ from typical dinoflagellates. Most dinoflagellates are free-living and possess two flagella. Instead, Haplozoon belong to a 5% minority of parasitic dinoflagellates that are not free-living. Additionally, the Haplozoon trophont stage is particularly unique due to an apparent lack of flagella. The presence of flagella or remnant structures is the subject of ongoing research.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Skovgaard, Alf; Karpov, Sergey A.; Guillou, Laure (2012). "The Parasitic Dinoflagellates Blastodinium spp. Inhabiting the Gut of Marine, Planktonic Copepods: Morphology, Ecology, and Unrecognized Species Diversity". Frontiers in Microbiology. 3: 305. doi: 10.3389/fmicb.2012.00305 . ISSN   1664-302X. PMC   3428600 . PMID   22973263.
  2. ↑ Skovgaard, Alf; M. Salomonsen, Xenia (2009-08-01). "Blastodinium galatheanum sp. nov. (Dinophyceae) a parasite of the planktonic copepod Acartia negligens (Crustacea, Calanoida) in the central Atlantic Ocean". Eur. J. Phycol. 44 (3): 425–438. doi: 10.1080/09670260902878743 .
  3. 1 2 3 4 5 Skovgaard, Alf; Massana, Ramon; Saiz, Enric (2007-06-01). "Parasitic Species of the Genusblastodinium(Blastodiniphyceae) Are Peridinioid Dinoflagellates". Journal of Phycology. 43 (3): 553–560. doi:10.1111/j.1529-8817.2007.00338.x. ISSN   1529-8817. S2CID   83479692.
  4. ↑ Taylor, F.J.R. (1980). "On dinoflagellate evolution". Biosystems. 13 (1–2): 65–108. doi:10.1016/0303-2647(80)90006-4. PMID   7002229.
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