The Amur bitterling (''Rhodeus sericeus'') is a small

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

of the carp family. It is sometimes just called "bitterling", which dates back to the time when the

European bitterling The European bitterling (''Rhodeus amarus'') is a temperate freshwater fish belonging to the subfamily Acheilognathinae of the family Cyprinidae. It originates in Europe, ranging from the Rhone River basin in France to the Neva River in Russi ...

('' Rhodeus amarus'') was still considered

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organ ...

with ''R. sericeus'', and "bitterling" properly refers to any

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 entire

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 ...

Rhodeus ''Rhodeus'' is a genus of cyprinid fish, consisting of 23 species called bitterlings. The scientific name is derived from the Greek word ', meaning "rose". Most species in the genus are restricted to Asia, but two species are found in Europe ('' ...

''. The Amur bitterling is found in

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...

, while the European bitterling is found from

European Russia European Russia (russian: Европейская Россия, russian: европейская часть России, label=none) is the western and most populated part of Russia. It is geographically situated in Europe, as opposed to the cou ...

westwards.

Mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

s form an essential part of its reproductive system, with bitterling eggs being laid inside them. Long thought to be symbiotic with the mussels (whose larval phase attaches to fish gills during development), recent research has indicated they are in fact parasitic, with co-evolution being seen in Chinese bitterling and mussel species. Bitterlings usually reside in areas with dense plant growth. They are hardy fish, and can survive in water that is not very well oxygenated. They grow to be 3-4 in long at most. The bitterling's diet consists of plant material and small larvae of insects.

Colour variation

Transparent scale variantshttp://www.jstage.jst.go.jp/article/zsj/15/3/425/_pdf of bitterlings occur, though not commonly, and are exploited in the aquarium trade.

References

{{Taxonbar, from=Q855808 Rhodeus Fish described in 1776