Asian arowana

Asian arowana
Super red arowana
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osteoglossiformes
Family: Osteoglossidae
Genus: Scleropages
Species: S. formosus
Additional species disputed (see text)
Binomial name
Scleropages formosus
Sa. Müller & Schlegel, 1840
Synonyms
  • Scleropages macrocephalus Pouyaud et al. 2003
  • Scleropages aureus Pouyaud et al. 2003
  • Scleropages legendrei Pouyaud et al. 2003

The Asian arowana (Scleropages formosus) comprises several phenotypic varieties of freshwater fish distributed geographically across Southeast Asia.[1] While most consider the different varieties to belong to a single species,[2][3][4][1][5] work by Pouyaud et al. (2003)[6] differentiates these varieties into multiple species. They have several other common names, including Asian bonytongue, dragonfish, and a number of names specific to the different color varieties.

Native to Southeast Asia, Asian arowanas inhabit blackwater rivers, slow-moving waters flowing through forested swamps and wetlands. Adults feed on other fish, while juveniles feed on insects.[7]

These popular aquarium fish have special cultural significance in areas influenced by Chinese culture. The name 'dragonfish' stems from their resemblance to the Chinese dragon. This popularity has had both positive and negative effects on their status as endangered species.

Evolution and taxonomy

Like all members of the Osteoglossidae, Asian arowanas are highly adapted to fresh water and are incapable of surviving in the ocean. Therefore, their spread throughout the islands of southeast Asia suggests they diverged from other osteoglossids before the continental breakup was complete. Genetic studies have confirmed this hypothesis, showing the ancestor of the Asian arowanas diverged from the ancestor of the Australian arowanas, S. jardinii and S. leichardti, about 140 million years ago, during the Early Cretaceous period. This divergence took place in the eastern margin of Gondwanaland, with the ancestors of Asian arowanas carried on the Indian subcontinent or smaller landmasses into Asia. The morphological similarity of all Scleropages species shows little evolutionary change has taken place recently for these ancient fish.[8][9]

The first description of this species was published in 1840 by German naturalists Salomon Müller and Hermann Schlegel, under the name Osteoglossum formosum, although later this species was placed in Scleropages with the name S. formosus.[10][11]

Super red arowana in a public aquarium
(video) Asian arowana swimming in a zoo in Japan

Several distinct, naturally occurring colour varieties are recognised as haplotypes, each found in a specific geographic region. They include:

In 2003, a study[6] proposed breaking S. formosus into four separate species. This classification was based on both morphometrics and a phylogenetic analysis using the cytochrome b gene, and includes these species:

The majority of researchers dispute this reclassification, arguing that the published data are insufficient to justify recognizing more than one Southeast Asian species of Scleropages, and that divergent haplotypes used to distinguish the color strains into isolated species were found within a single color strain, contradicting the findings. They are considered monotypic, consisting of closely related haplotypes.[1][2][3][4][5]

Description

Asian arowana scales are large (most over 2 cm in length) and have a delicate net pattern.

Asian arowanas grow up to 90 cm (35 in) total length.[7] Like all Scleropages, Asian arowanas have long bodies; large, elongated pectoral fins, dorsal and anal fins located far back on the body; and a much larger caudal fin than that of their South American relative, the silver arowana, Osteoglossum bicirrhosum. The mouth is oblique with a very wide gape. The prominent lower jaw has two barbels at its tip. The gill rakers are stout. Asian arowanas bear teeth on many bones of the mouth, including the jaws, vomer, palatines, pterygoids, parasphenoid, and tongue.[6][12]

Asian arowana scales are large, cycloid, and, in some varieties, metallic-coloured, with a distinctive mosaic pattern of raised ribs.[6][12] The lateral scales are arranged in horizontal rows numbered from the most ventral (first level) to the most dorsal (fifth level), with dorsal scales designated the sixth level.[13][14]

Asian arowanas are distinguished from Australian congenerics S. jardinii and S. leichardti by having fewer (21-26) lateral line scales (versus 32-36 for the Australian species), longer pectoral and pelvic fins, and a longer anterior snout.[6]

Green arowanas are dark green on the back, silvery or golden green on its sides, and silvery or whitish on the ventral surface, with dark greenish or bluish patches visible through the lateral scales. In mature fish, the top of the eye and the head behind the eye are bright emerald.[6]

Both grey-tailed and yellow-tailed silver Asian arowanas are dark grey on the back and silver on the sides, with dark ring patches on the lateral scales and a silvery or whitish belly. In yellow-tailed specimens, the fin membranes are yellowish with dark-grey rays. In grey-tailed specimens, the fins are uniformly dark grey.[6]

Red-tailed golden arowana: Although the scales are golden, the anal and caudal fins are reddish-brown.

Mature red-tailed golden arowanas have brilliant metallic gold lateral scales, gill covers, bellies, and pectoral and pelvic fin membranes, although the back is dark. In juveniles, the areas destined to develop golden colour start out metallic silver. The anal fin and the bottom portion of the caudal fin are light brown to dark red.[6]

Mature gold crossback arowanas are distinguished from the red-tailed golden arowanas by having metallic gold crossing the back completely. This variety also lacks the reddish fins of the red-tailed golden.[15]

In mature super red arowanas, the gill covers, lateral scales, and fin membranes of these fishes are metallic red, with the exact hue varying from gold-tinged to deep red. The back is dark brown. In juveniles, the darker the dorsal colouration, the deeper the red will be on maturity.[6]

Biology

Reproduction

Unlike most fish, the Asian arowana reaches sexual maturity relatively late, after 3–4 yr. The females produce few eggs, 30-100, which are quite large. After the eggs are fertilized, the Asian arowana exhibits great parental care with paternal mouthbrooding. Both the fertilized eggs and larvae are brooded within the male's mouth.[3][16]

Behavior

They spend the day in the protection of Pandanus roots or other structures, and feed at night.[16]

Relationship with humans

Cultural beliefs

In Prague sea aquarium

Asian arowanas are considered to be symbols of good luck and prosperity, especially by those from Asian cultures. This reputation derives from the species' resemblance to the Chinese dragon, considered an auspicious symbol.[17] The large metallic scales and double barbels are features shared by the Chinese dragon, and the large pectoral fins are said to make the fish resemble "a dragon in full flight."[14]

In addition, positive feng shui associations with water and the colours red and gold make these fishes popular for aquaria. One belief is that while water is a place where chi gathers, it is naturally a source of yin energy and must contain an "auspicious" fish such as an arowana to have balancing yang energy.[15] Another is that a fish can preserve its owner from death by dying itself.[18]

Conservation

Asian arowanas are listed as endangered by the 2006 IUCN Red List, with the most recent evaluation taking place in 1996.[19] International trade in these fishes is controlled under the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES), under which it was placed on Appendix I, the most restrictive category, in 1975.[20] S. formosus is one of only eight fish species listed on Appendix I.[21] A number of registered CITES breeders are in Asia, and the specimens they produce can be imported into several nations. Other nations restrict or prohibit possession of Asian arowanas; for example, the United States has listed this species under the Endangered Species Act, so it cannot be kept in that country without a permit.[22]

Declining habitat is a major threat. For example, Asian arowanas are now uncommon in the Malay Peninsula, where they were once widely distributed, due to environmental destruction.[12] Inclusion in the IUCN Red List was originally based not on biological reasons but on practical ones: though widely distributed throughout southeast Asia, they have been harvested heavily by aquarium collectors. However, habitat loss is likely a greater threat than aquarium collecting.[12]

No recent evaluation of conservation status has been done by the IUCN.[19] Additionally, considering the current confusion as to number of species, as well as the wide distribution, conservation status should be reconsidered. All strains are probably endangered, but some (notably the super red and red-tailed golden) more critically than others.[6] The Asian arowana's high value as aquarium fish has impacted its conservation. Its popularity has soared since the late 1970s, and hobbyists may pay thousands of U.S. dollars for one of these animals.[12][23] Certain color varieties are more endangered than others, since the red and gold varieties are both less common, and in higher demand in the aquarium trade.[5]

In Prague sea aquarium

Beginning in 1989, CITES began allowing Asian arowanas to be traded, provided certain criteria were met, most notably that they were bred in captivity on a fish farm for at least two generations.[24] The first of these farms was in Indonesia.[23] Later, the Singapore government's Agri-food and Veterinary Authority (then called the Primary Production Department) and a local fish exporter collaborated in a captive breeding program. Asian arowanas legally certified by CITES for trade became available from this program in 1994.[21]

Captive-bred arowanas that are legal for trade under CITES are documented in two ways. First, fish farms provide each buyer with a certificate of authenticity and a birth certificate. Second, each specimen receives an implanted microchip, called a passive integrated transponder, which identifies individual animals.[23]

Genetic fingerprinting has been used to assess the genetic diversity of a captive population at a Singapore fish farm to improve the management of this species.[20] DNA markers that distinguish among different strains and between sexes have been identified, allowing aquaculturists to identify these characteristics in immature animals.[25]

In Prague sea aquarium

Care in captivity

Because they can grow up to 90 cm (35 in) long, Asian arowanas require large aquaria. They are territorial and may be kept with other Scleropages only in a very large aquarium, provided all fish are of similar size. Like other arowanas, they need a tight-fitting cover to prevent escape.[21] The water should be well-filtered, soft, and slightly acidic, and maintained at a temperature of 24–30 °C (75–86 °F).[21]

Asian arowanas are carnivorous and should be fed a high-quality diet of meaty food, such as shrimp and crickets. They are surface feeders and prefer to take food in the upper parts of the water column. Aquarists recommend live foods and meaty prepared foods. Examples of appropriate live foods include scorpions, centipedes, mealworms, crickets, shrimps, feeder fish, small frogs, and earthworms. Prepared foods include prawns (shrimp), lean pork, frozen fish food, and pelleted food.[26]

See also

References

Wikimedia Commons has media related to Scleropages formosus.
  1. 1 2 3 Mu, Xi-dong; Hong-mei Song; Xue-jie Wang; Ye-xin Yang; Du Luo; Gand-en Gu; Jian-ren Luo; Yin-chang Hu (2012). "Genetic variability of the Asian arowana, Scleropages formosus, based on mitochondrial DNA genes". Biochemical Systematics and Ecology 44: 141–148. doi:10.1016/j.bse.2012.04.017.
  2. 1 2 Yue, Genhua; Li, Yang; Chen, Fan; Cho, Serena; Lim, Lian Chuan; Orban, Laszlo (2002). "Comparison of three DNA marker systems for assessing genetic diversity in Asian arowana (Scleropages formosus)". Electrophoresis 23 (7-8): 1025–1032. doi:10.1002/1522-2683(200204)23:7/8<1025::AID-ELPS1025>3.0.CO;2-Y.
  3. 1 2 3 Hua Yue, Gen; Li, Yang; Lim, Lian Chuan; Orban, Laszlo (2004). "Monitoring the genetic diversity of three Asian arowana (Scleropages formosus) captive stocks using AFLP and microsatellites". Aquaculture 237 (1-4): 89–102. doi:10.1016/j.aquaculture.2004.04.003.
  4. 1 2 Kottelat, M.; E. Widjanarti (2005). "The fishes of Danau Sentarum National Park and the Kapuas Lakes Area, Kalimantan Barat, Indonesia". The Raffles Bulletin of Zoology: 139–173.
  5. 1 2 3 Mohd-Shamsudin, Maizatul Izzah; Fard, Maryam Zahedi; Mather, Peter B.; Suleiman, Zaini; Hassan, Rosly; Othman, Rofina Yasmin; Bhassu, Subha (2011). "Molecular characterization of relatedness among colour variants of Asian Arowana (Scleropages formosus)". Gene 490 (1-2): 47–53. doi:10.1016/j.gene.2011.08.025.
  6. 1 2 3 4 5 6 7 8 9 10 Pouyaud, L.; Sudarto, Guy G. Teugels (2003). "The different colour varieties of the Asian arowana Scleropages formosus (Osteoglossidae) are distinct species: morphologic and genetic evidences". Cybium 27 (4): 287–305.
  7. 1 2 "Fishbase - Scleropages formosus food items.".
  8. ↑ Kumazawa, Y; M. NISHIDA (December 3–5, 1998). Iwatsuki, K., ed. "Molecular phylogenetic analysis of vertebrate radiations". IIAS International Symposium on Biodiversity (IIAS Reports No. 1999-003) (Kyoto, Japan: International Institute for Advanced Studies): 137–143. Check date values in: |year= / |date= mismatch (help)
  9. ↑ Kumazawa, Yoshinori. "The reason the freshwater fish arowana live across the sea". Biohistory Journal. Retrieved 22 April 2013.
  10. ↑ "Catalog of Fishes". Retrieved 22 April 2013.
  11. ↑ van Oijen, M.J.P; S.E.T. van der Meij (2013). "The types of Osteoglossum formosum Müller & Schlegel, 1840 (Teleostei, Osteoglossidae)". Zootaxa.
  12. 1 2 3 4 5 Ismail, M. (1989). Systematics, Zoogeography, and Conservation of the Freshwater Fishes of Peninsular Malaysia. (Doctoral Dissertation ed.). Colorado State University.
  13. ↑ West & NSK (Arowana Club.com), 2003.
  14. 1 2 West; N.K. "General Parts of an Asian Arowana".
  15. 1 2 Unoaquatic Arowana Group, 1999.
  16. 1 2 Scott, D.B.C.; J.D. Fuller (1976). "The reproductive biology of Scleropages formosus (Muller & Schlegel) (Osteoglossomorpha, Osteoglossidae) In Malaya, and the morphology of its pituitary gland". Journal of Fish Biology 8: 45–53. doi:10.1111/j.1095-8649.1976.tb03906.x.
  17. ↑ "Chinese Belief".
  18. ↑ "Superstitious Bangaloreans eat Arowana fish". Hindustan Times. Archived from the original on May 17, 2006. Retrieved 10 May 2006.
  19. 1 2 Kottelat, M (2011). "Scleropages formosus. In: IUCN 2012.". IUCN Red List of Threatened Species. Version 2012.2. IUCN. Retrieved 22 April 2013.
  20. 1 2 Fernando, A.A.; Lim L.C.; Jeyaseelan K.; Teng S.W.; Liang M.C.; Yeo C.K. (1997). "DNA fingerprinting: application to conservation of the CITES-listed dragon fish, Scleropages formosus (Osteoglossidae)". Aquarium Sciences and Conservation 1 (2): 91–104. doi:10.1023/A:1018387601905.
  21. 1 2 3 4 Dawes, John (2001). Complete Encyclopedia of the Freshwater Aquarium. New York, NY: Firefly Books Ltd. ISBN 1-55297-544-4.
  22. ↑ "United States Fish and Wildlife Service Threatened and Endangered Species System". Retrieved 22 April 2013.
  23. 1 2 3 Lee, Cheng. "The fate of the Asian arowana in the hands of the aquarium industry". Retrieved 25 October 2009.
  24. ↑ Dawes, John (2001). Complete Encyclopedia of the Freshwater Aquarium. New York, NY: Firefly Books Ltd. p. 22. ISBN 1-55297-544-4.
  25. ↑ Yue, G H; Ong, D; Wong, C C; Lim, L C; Orban, L (September 2003). "A strain-specific and a sex-associated STS marker for Asian arowana (Scleropages formosus, Osteoglossidae)". Aquaculture Research 34 (11): 951–957. doi:10.1046/j.1365-2109.2003.00949.x.
  26. ↑ Anglo Aquarium (n.d.); Shin Min Daily News, 2005

External links

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