Ostreopsis
| Ostreopsis | |
|---|---|
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| A cell of Ostreopsis cf. ovata | |
| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | Sar |
| (unranked): | Alveolata |
| Phylum: | Dinoflagellata |
| Class: | Dinophyceae |
| Order: | Gonyaulacales |
| Family: | Ostreopsidaceae |
| Genus: |
Ostreopsis J.Schmidt, 1901 |
| Species | |
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Ostreopsis is a genus of free-living dinoflagellates found in marine environments. Some species are benthic; the planktonic species in the genus are known for the toxic algal blooms that they sometimes cause, threatening human and animal health.
The taxonomy of this genus is problematic. When in 1901, Schmidt first created the genus Ostreopsis, he described the type species O. siamensis from the phytoplankton in the waters of the Gulf of Thailand. However, there were anomalies in the original drawing made by Schmidt, and O. siamensis was redescribed by Fukuyo in 1981; at the same time, Fukuyo introduced two new species, O. lenticularis and O. ovata.
Ostreopsis spp. have been found in many marine locations around the world. Despite O. siamensis having been found in the plankton, other species are generally found in benthic habitats. They are most noticeable in temperate seas when they cause algal blooms in summer, an event that has become more frequent in the early part of the twenty-first century. The only species identified in the Mediterranean Sea are O. ovata and O. siamensis. The bloom in 2006 off Sant Andreu de Llavaneres in northeastern Spain, was described as "a conspicuous, thick, brownish mucilage layer covering benthic macroalgae".
Under certain conditions, dinoflagellates can become very numerous and cause algal blooms. These can lower the oxygen concentration of the water and can clog the gills of filter feeding organisms. Some of these dinoflagellates contain toxic chemicals which may be sequestered by animals that eat them, and can threaten public health and cause economic damage to fisheries.
Some species of Ostreopsis contain the vasoconstrictor palytoxin, one of the most toxic, non-protein substances known. Palytoxin was first isolated from the zoanthid Palythoa toxica and proved to be an unusually long chain polyether-type phytotoxin. It is now postulated that the substance is synthesized by the dinoflagellates and is subsequently incorporated into the zoanthid tissues; it may be a symbiotic arrangement, and it is possible that bacteria are involved in the transfer.
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