The rosy bitterling or Tairiku baratanago (''Rhodeus ocellatus'') is a small freshwater fish belonging to the family

Cyprinidae Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...

(carp), native to

East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea and ...

from the

Amur River The Amur (russian: река́ Аму́р, ), or Heilong Jiang (, "Black Dragon River", ), is the world's List of longest rivers, tenth longest river, forming the border between the Russian Far East and Northeast China, Northeastern China (Inne ...

basin to the

Pearl River The Pearl River, also known by its Chinese name Zhujiang or Zhu Jiang in Mandarin pinyin or Chu Kiang and formerly often known as the , is an extensive river system in southern China. The name "Pearl River" is also often used as a catch-all ...

basin. Females are about long and males are . Their bodies are flat with an argent-colored luster. However, males change to a reddish (sometimes purple) color during the spawning season (March to September) which functions to attract females. This reddish color is similar to the color of a red rose, which is why it is called a rosy bitterling.

Ecology and reproductive system

Rosy bitterlings live in ponds (

reservoirs A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including control ...

) where freshwater

mussels Mussel () is the common name used for members of several families of bivalve mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,0 ...

are abundant. Farm ponds are an important habitat for not only rosy bitterlings, but also mussels and plankton. Freshwater mussels play an important role in rosy bitterling reproduction. The female rosy bitterling has a unique pipe about the same length as its own body, used for laying eggs on a specific spot of mussels. Usually, two or three eggs are laid at once and placed on the gill of the mussel. A male spawns into the gill cavity of the mussels right after a female lays eggs to ensure fertilization. Normally, a female lays eggs repeatedly at 6- to 9-day intervals about 10 times in a season. Eggs grow in the mussels' gills and juveniles stay inside the mussel about 15 to 30 days after fertilization. Eggs hatch after about three days when juveniles are about 2.8 mm long. The body has a unique shape resembling the bud of a

matsutake , ''Tricholoma matsutake'', is a species of choice edible mycorrhizal mushroom that grows in East Asia, Europe, and North America. It is prized in Japanese cuisine for its distinct spicy-aromatic odor. Etymology The common name and specifi ...

mushroom. Juveniles swim out of the mussel from the margin of the excurrent siphon. At this point, juveniles are about 7.5 mm long and about the same shape as adults. Usually, juveniles grow around 40–50 mm within one year, when they become adults. This and ''

Rhodeus smithii ''Rhodeus smithii'', sometimes known as the Japanese rosy bitterling, Japanese bitterling, or Nippon baratanago is a temperate freshwater fish belonging to the Acheilognathinae subfamily of the family Cyprinidae. It originates in stagnant wat ...

'', sometimes called the Japanese rosy bitterling, were formerly considered conspecific. In 1942, rosy bitterling were accidentally introduced with grass ('' Ctenopharyngodon idellus'') and silver carp (''

Hypophthalmichthys molitrix The silver carp (''Hypophthalmichthys molitrix'') is a species of freshwater cyprinid fish, a variety of Asian carp native to China and eastern Siberia, from the Amur River drainage in the north to the Xi Jiang River drainage in the south. Alth ...

'') from mainland

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. Since the rosy bitterling was introduced, their population has been increasing dramatically all over Japan. Hybridization and subsequent gene introgression has been observed within these species in Kashima and Ogori. Because of these interbreeding events, the number of ''R. smithii'' has dramatically declined all over Japan and now is in danger of extinction. In 1994, ''R. smithii'' was on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

as an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

, and now it is critically endangered.

References

External links

Genetic markers distinguishing between the two subspecies of the rosy bitterling, ''Rhodeus ocellatus'' (Cyprinidae)
*
Taxonomy summary for ''R. o. ocellatus''IUCN Red List
{{Taxonbar, from=Q703072 Fish of Asia Rhodeus Fish described in 1866