''Ostreopsis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of free-living dinoflagellates found in marine environments. Some species are

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

; the

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 in the genus are known for the toxic

algal bloom An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompas ...

s that they sometimes cause, threatening human and animal health.

Taxonomy

The taxonomy of this genus is problematic. When in 1901, Schmidt first created the genus ''Ostreopsis'', he described the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

'' O. siamensis'' from the

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

in the waters of the

Gulf of Thailand The Gulf of Thailand, also known as the Gulf of Siam, is a shallow inlet in the southwestern South China Sea, bounded between the southwestern shores of the Indochinese Peninsula and the northern half of the Malay Peninsula. It is around in l ...

. 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''.

Distribution and habitat

''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

habitats. They are most noticeable in temperate seas when they cause

s 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 Sant Andreu de Llavaneres () is a municipality located 36 km north of Barcelona (Catalonia) (Spain), along the Mediterranean coast, between Mataró and Sant Vicenç de Montalt. It belongs to the Maresme comarca and the Barcelona province. The ...

in northeastern Spain, was described as "a conspicuous, thick, brownish mucilage layer covering benthic macroalgae".

Toxicity

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 Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

. Some species of ''Ostreopsis'' contain the

vasoconstrictor Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...

palytoxin Palytoxin, PTX or PLTX is an intense vasoconstrictor, and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice. Palytoxin is a polyhydroxylated and partially unsaturat ...

, one of the most toxic, non-protein substances known. Palytoxin was first isolated from the

zoanthid Zoanthids ( order Zoantharia also called Zoanthidea or Zoanthiniaria) are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different coloniz ...

Palythoa toxica ''Palythoa toxica'', also referred to by its Hawaiian common name, limu-make-o-Hana ('seaweed of death from Hana'), is a species of zoanthid native to Hawaii. It is notable as the species in which palytoxin was discovered and from which it was f ...

'' 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 Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

arrangement, and it is possible that bacteria are involved in the transfer. Species of ''Ostreopsis'' have been implicated in outbreaks of ill health in countries to the immediate north of 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 ...

, particularly Spain, Italy and Greece. Along the

Liguria Liguria (; lij, Ligûria ; french: Ligurie) is a Regions of Italy, region of north-western Italy; its Capital city, capital is Genoa. Its territory is crossed by the Alps and the Apennine Mountains, Apennines Mountain chain, mountain range and is ...

n coast of Italy, large numbers of people were affected after visiting beaches in the summer of 2005, and about 200 people sought medical help; symptoms included

rhinorrhoea Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies (hay fever) or certain viral infections, such as the common cold or COVID-1 ...

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three pha ...

and mild breathing problems, and sometimes

conjunctivitis Conjunctivitis, also known as pink eye, is inflammation of the conjunctiva, outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may ...

. These symptoms have been shown to be the result of

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...

s containing the dinoflagellates, which had been whipped off the surface of the water by winds, and carried ashore to the detriment of public health. In a separate incident, a mass mortality of the sea urchin ''

Evechinus chloroticus Kina (''Evechinus chloroticus'') is a sea urchin endemic to New Zealand. This echinoderm belongs to the family Echinometridae and it can reach a maximum diameter of 16–17 cm. Kina have been a traditional component of Māori diet since pr ...

'' occurred in New Zealand in 2004, associated with a bloom of ''O. siamensis'', although in this instance there were no human casualties.

Species

The

World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms. Content The content of the registry is edited and maintained by scientific specialist ...

includes the following

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the genus : *''

Ostreopsis belizeana ''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 hea ...

'' M. A. Faust *''

Ostreopsis caribbeana ''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 hea ...

'' M. A. Faust *'' Ostreopsis fattorussoi'' Accoroni, Romagnoli & Totti *'' Ostreopsis heptagona'' D. R. Norris, J. W. Bomber & Balech *'' Ostreopsis labens'' M. A. Faust & S. L. Morton *'' Ostreopsis lenticularis'' Y. Fukuyo *'' Ostreopsis marina'' M. A. Faust *'' Ostreopsis mascarenensis'' J. P. Quod *'' Ostreopsis ovata'' Fukuyo *'' Ostreopsis rhodesiae'' Verma, Hoppenrath & S. A. Murray *''

Ostreopsis siamensis ''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 hea ...

'' Johs. Schmidt

References

{{Taxonbar, from=Q19842630 Dinoflagellate genera Gonyaulacales