''Sphaerothecum destruens'' (the rosette agent) is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of fish. It was first discovered in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

in association with

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

including

topmouth gudgeon The stone moroko (''Pseudorasbora parva''), also known as the topmouth gudgeon, is a fish belonging to the Cyprinidae, Cyprinid family, native to Asia, but introduced and now considered an invasive species in Europe and North America. The fish's ...

, but was found to be the causative agent of a disease in the UK affecting

salmonid Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

species such as

Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are ...

and

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

. It is thought to pose more of a risk in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

than in the US, as native species there are more susceptible to the parasite. The disease causes high rates of

morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

and

mortality Mortality is the state of being mortal, or susceptible to death; the opposite of immortality. Mortality may also refer to: * Fish mortality, a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock throug ...

in a number of different salmonid species and can also infect other UK freshwater fish such as

bream Bream ( ) are species of freshwater and marine fish belonging to a variety of genera including ''Abramis'' (e.g., ''A. brama'', the common bream), ''Acanthopagrus'', '' Argyrops'', ''Blicca'', '' Brama'', ''Chilotilapia'', '' Etelis'', ''Lepo ...

carp Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...

, and

roach Roach may refer to: Animals * Cockroach, various insect species of the order Blattodea * Common roach (''Rutilus rutilus''), a fresh and brackish water fish of the family Cyprinidae ** ''Rutilus'' or roaches, a genus of fishes * California roach ...

. The genus ''Sphaerothecum'' is closely related to the genera ''

Dermocystidium ''Dermocystidium'' is a genus of cyst-forming, parasitic eukaryotes of fish, which are the causative agents of dermocystidiosis. Taxonomic History The genus ''Dermocystidium'' was described in 1907. It was previously thought to be a genus of fu ...

'' and '' Rhinosporidium''.

References

Fish diseases Mesomycetozoea {{Holozoa-stub