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Rhodeus ocellatus ocellatus(Hamamatsu,Shizuoka,Japan).jpg
Rosy Bitterling (R. ocellatus)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Subfamily: Acheilognathinae
Genus: Rhodeus
Agassiz, 1832
Type species
Cyprinus amarus
Bloch, 1782
  • Pseudoperilampus Bleeker, 1863

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

Bitterlings are short-lived species, generally surviving only about five years. Their maximum size is 11 cm, but they are usually much shorter. Bitterlings inhabit slow-flowing or still waters, such as ponds, lakes, marshes, muddy and sandy pools, and river backwaters. Because they depend on freshwater mussels to reproduce, their range is restricted. Bitterlings are omnivorous, feeding on both invertebrates and plants.

Bitterlings have a remarkable reproduction strategy where parents transfer responsibility for the care of their young to various species of freshwater mussels (Unionidae and Margaritiferidae). The female extends her long ovipositor into the mantle cavity of the mussel and deposits her eggs between the gill filaments. The male then ejects his sperm into the mussel's inhalent water current and fertilization takes place within the gills of the host. The same female may use a number of mussels, and she deposits only one or two yellow, oval eggs into each. Early developmental stages are protected from predation within the body of the mussel. After 3 to 4 weeks, larvae swim away from the hosts to continue life on their own.

In 1936, the bitterling was thought to respond to hormones in a pregnant woman's urine, but the work was later discredited.[1][2]


This genus and Acheilognathus have a convoluted taxonomic history, one being at times included in the other. They are now considered separate, but some species formerly in Rhodeus are now in Acheilognathus.

There are currently 23 recognized species in this genus:


  1. ^ "Deceptive Bitterling". Time. October 12, 1936. Retrieved 2008-04-16. Not quite two years ago physicians and prospective parents welcomed the news that a small, carp-like fish could tell whether or not a woman was going to have a baby ... The bitterling lost her standing and the doe rabbit and mouse were reinstated as nature's best indicators of human pregnancy. But obstetricians Kanter and Klawans pursued the matter with another research mate, physiologist Broda Otto Barnes, and secured further results which they detailed in Science last week. CS1 maint: discouraged parameter (link)
  2. ^ Barnes, B. O.; Kanter, A. E.; Klawans, A. H. (1936). "Bitterling Ovipositor Lengthening Produced By Adrenal Extracts". Science. 84 (2179): 310. doi:10.1126/science.84.2179.310-a. PMID 17837041.
  3. ^ Li, F.; Arai, R. (2014). "Rhodeus albomarginatus, a new bitterling (Teleostei: Cyprinidae: Acheilognathinae) from China". Zootaxa. 3790 (1): 165–176. doi:10.11646/zootaxa.3790.1.7. PMID 24869865.
  4. ^ a b Li, Fan; Liao, Te-Yu; Arai, Ryoichi (2020-03-03). "Two new species of Rhodeus (Teleostei: Cyprinidae: Acheilognathinae) from the River Yangtze, China". Journal of Vertebrate Biology. 69 (1): 1–17. doi:10.25225/jvb.19055. ISSN 2694-7684.

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