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| A light micrograph of Polykrikos kofoidii showing an extruded nematocyst. Scale bar = 10µm. [1] | |
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| Family: | Polykrikaceae |
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The Polykrikaceae (also known as Polykrikidae) 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 . [2]
The most distinctive feature of polykrikoids is their formation of multinucleate "pseudocolonies" consisting of an even number of subunit zooids. The two genera differ in number of nuclei; possessing two nuclei regardless of the number of zooids is a synapomorphy for Polykrikos, whereas Pheopolykrikos possess equal numbers of nuclei and zooids. [3]
Along with the Warnowiaceae (warnowiids), polykrikoids are known for possessing unusually complex subcellular structures. In particular, an extrusome complex of two organelles called the nematocyst and taeniocyst is considered a synapomorphy for Polykrikos. [1] [3] Molecular phylogenetics studies suggest some inconsistency in the taxonomy of this group, particularly in the assignment of species to one of the two genera. [4] [5]
Most polykrikoids are planktonic, although one species - P. lebourae - is benthic. [3] The family includes photosynthetic, heterotrophic, and mixotrophic species. [6] Some species, such as P. kofoidii , are of scientific interest due to their status as predators of other dinoflagellates, a behavior that is significant in the regulation of algal blooms. [6] [7] [8] Others, such as Ph. hartmanii (which has been reclassified P. hartmanii ) [5] are themselves causes of ichthyotoxic algal blooms. [9] P. hartmanii is capable of both heterothallic (outcrossing) and homothallic (self-fertilizing) sexual reproduction. [10]
The reproductive behaviors of polykrikoids are mostly not well understood, although P. kofoidii has been studied and found to have a complex life cycle of both vegetative (asexual) and sexual reproduction complicated by its pseudocolonial structure. [11]
The family demonstrates a complex evolutionary history indicating multiple instances of loss of photosynthetic plastids in different lineages. [6] The distinctive pseudocolonial structure may have arisen in multiple evolutionary lineages from ancestors capable of forming chains of distinct individual cells. [3]
The dinoflagellates are single-celled eukaryotes constituting the phylum Dinoflagellata. Usually considered algae, dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations are distributed depending on sea surface temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey.
Noctiluca scintillans, commonly known as the sea sparkle, and also published as Noctiluca miliaris, is a free-living, marine-dwelling species of dinoflagellate that exhibits bioluminescence when disturbed. Its bioluminescence is produced throughout the cytoplasm of this single-celled protist, by a luciferin-luciferase reaction in thousands of spherically shaped organelles, called scintillons.
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. Since 2000, the species which had been considered to be part of Gymnodinium have been divided into several genera, based on the nature of the apical groove and partial LSU rDNA sequence data. Amphidinium was redefined later. Gymnodinium belong to red dinoflagellates that, in concentration, can cause red tides.
The Gymnodiniales are an order of dinoflagellates, of the class Dinophyceae. Members of the order are known as gymnodinioid or gymnodinoid. They are athecate, or lacking an armored exterior, and as a result are relatively difficult to study because specimens are easily damaged. Many species are part of the marine plankton and are of interest primarily due to being found in algal blooms. As a group the gymnodinioids have been described as "likely one of the least known groups of the open ocean phytoplankton."
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.
Polykrikos kofoidii is a species of phagotrophic marine pseudocolonial dinoflagellates that can capture and engulf other protist prey, including the toxic dinoflagellate, Alexandrium tamarense. P. kofoidii is of scientific interest due to its status as a predator of other dinoflagellates, a behavior that is significant in the control of algal blooms. It has a complex life cycle of both vegetative (asexual) and sexual reproduction complicated by its pseudocolonial structure.
Luciella masanensis is a species of heterotrophic marine dinoflagellates.
Coolia tropicalis is a species of dinoflagellates, first found in Belize.
An ocelloid is a subcellular structure found in the family Warnowiaceae (warnowiids), which are members of a group of unicellular organisms known as dinoflagellates. The ocelloid is analogous in structure and function to the eyes of multicellular organisms, which focus, process and detect light. The ocelloid is much more complex than the eyespot, a light-sensitive structure also found in unicellular organisms, and is in fact one of the most complex known subcellular structures. It has been described as a striking example of convergent evolution.
The Warnowiaceae are a family of athecate dinoflagellates. Members of the family are known as warnowiids. The family is best known for a light-sensitive subcellular structure known as the ocelloid, a highly complex arrangement of organelles with a structure directly analogous to the eyes of multicellular organisms. The ocelloid has been shown to be composed of multiple types of endosymbionts, namely mitochondria and at least one type of plastid.
A nematocyst is a subcellular structure or organelle containing extrusive filaments found in two families of athecate dinoflagellates, the Warnowiaceae and Polykrikaceae. It is distinct from the similar subcellular structures found in the cnidocyte cells of cnidarians, a group of multicellular organisms including jellyfish and corals; such structures are also often called nematocysts, and cnidocytes are sometimes referred to as nematocytes. It is unclear whether the relationship between dinoflagellate and cnidarian nematocysts is a case of convergent evolution or common descent, although molecular evidence has been interpreted as supporting an endosymbiotic origin for cnidarian nematocysts.
Takayama tuberculata is a species of unarmored dinoflagellates from the genus Takayama, being closely related to T. tasmanica. It was first isolated from the Australian region of the Southern Ocean, just north of the polar front. It is medium-sized and is characterized by its long ovoid cell shape and rather long apical groove. It is considered potentially ichthyotoxic.
Karlodinium antarcticum is a species of unarmored dinoflagellates from the genus Karlodinium. It was first isolated from the Australian region of the Southern Ocean, near the polar front. It is medium-sized and is characterized by its long ovoid cell shape and rather long apical groove. It is considered potentially ichthyotoxic.
Karlodinium ballantinum is a species of unarmored dinoflagellates from the genus Karlodinium. It was first isolated from the Australian region of the Southern Ocean. It is small-sized and is characterized by its very short apical groove. It is considered potentially ichthyotoxic.
Karlodinium corrugatum is a species of unarmored dinoflagellates from the genus Karlodinium. It was first isolated from the Australian region of the Southern Ocean, just south of the polar front. It is small-sized and is characterized by having distinctive striations on the epicone surface which are parallel, and a distinctively shaped and placed ventral pore. It is considered potentially ichthyotoxic.
A piston is a complex contractile organelle found in some dinoflagellates, namely the Erythropsidinium and Greuetodinium genera of the family Warnowiaceae. This group is also well known for possessing other unusually complex subcellular structures such as the ocelloid and nematocyst. Observations of Erythropsidinium samples reveal that the length of the piston is highly variable across specimens. The piston is known to be capable of repetitive and dramatic contractile motion; although its function is unknown, roles in locomotion, prey capture, and defense have been suggested.
Erythropsidinium is a genus of dinoflagellates of the family Warnowiaceae.
Gambierdiscus is a genus of marine dinoflagellates that produce ciguatoxins, a type of toxin that causes the foodborne illness known as ciguatera. They are usually epiphytic on macroalgae growing on coral reefs.
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.
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.