Rosy bitterling

The rosy bitterling or Tairiku baratanago (Rhodeus ocellatus) is a small freshwater fish belonging to the family Cyprinidae (carp), native to East Asia from the Amur River basin to the Pearl River basin.[2]

Rosy bitterling

Data Deficient  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Subfamily: Acheilognathinae
Genus: Rhodeus
Species:
R. ocellatus
Binomial name
Rhodeus ocellatus
(Kner, 1866)
Synonyms
  • Pseudoperilampus ocellatus Kner, 1866
  • Rhodeus ocellatus ocellatus (Kner, 1866)
  • Rhodeus maculatus Fowler, 1910
  • Rhodeus hwanghoensis Mori, 1928
  • Rhodeus notatus Nichols, 1929
  • Rhodeus wangkinfui H. W. Wu, 1930
  • Rhodeus pingi C. P. Miao, 1934

Females are about 4–5 cm (1.6–2.0 in) long and males are 5–8 cm (2.0–3.1 in). 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.[3]

Ecology and reproductive system

Rosy bitterlings live in ponds (reservoirs) where freshwater mussels 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.[4] 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 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.[5] Usually, juveniles grow around 40–50 mm within one year, when they become adults.

This and Rhodeus smithii, 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) from mainland China.[6] 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.[7] 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 as an endangered species, and now it is critically endangered.


R. o. ocellatus
(Tairiku baratanago sex M)
R. o. ocellatus
(Tairiku baratanago sex F)
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References
  1. Huckstorf, V. (2013). "Rhodeus ocellatus". The IUCN Red List of Threatened Species. IUCN. 2013: e.T62207A3109841. doi:10.2305/IUCN.UK.2013-1.RLTS.T62207A3109841.en. Retrieved 15 January 2018.
  2. Froese, Rainer and Pauly, Daniel, eds. (2017). "Rhodeus ocellatus" in FishBase. March 2017 version.
  3. 加納義彦. ニッポンバラタナゴの保護と環境保全.　第５回日本水大賞受賞活動集.　日本水大賞顕彰制度委員会.　42－45. 2003.
  4. Kanoh, Y. 2000. Reproductive success associated with territoriality, sneaking, and grouping in male Rosy Bitterlings, Rhodeus ocellatus (Pisces: Cyprinidae). Env. Biol. Fish. 57: 143-154
  5. Nagata, Y. 1976. Reproductive behavior of a bitterling, Rhodeus ocellatus (Kner). Physiol. Ecol. Japan 17: 85-90 (in Japanese)
  6. Kawamura, K., Nagata, Y., Ohtaka, H., Kanoh, Y., and Kitamura, J. 2001. Genetic diversity in the Japanese rosy bitterling, Rhodeus ocellatus kurumeus (Cyprinidae). Ichthyol Res 48: 369-378
  7. Miyake, K., Tachida, H., Oshima, Y., Arai, R., Kimura, S., Imada, N., and Honjo, T. 2000. Genetic variation of the cytochrome b gene in the rosy bitterling, Rhodeus ocellatus (Cyprinidae) in Japan. Ichthyol Res 48: 105-110
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