Molecular diagnosis of the arowanas Osteoglossum ferreirai Kanazawa, 1966 and O. bicirrhossum (Cuvier, 1829) from the Orinoco and Amazon River basins

Abstract

The arowanas, fishes of Gondwanan origin, are represented in South America by the genus Osteoglossum. All species were initially reported as being exclusive to the Amazon region, with O. ferreirai restricted to the Negro River basin and O. bicirrhosum to the Amazon and Essequibo Rivers basin. Starting in the mid 1970's it was reported that O. ferreirai also occurs in the Orinoco River basin. In all regions the arowanas assumed significant socio-economic importance due to their popularity in the international ornamental fish trade, leading to over-exploitation of both species in some areas. The Orinoco populations are particularly heavily exploited, and thus conservation and management measures are needed. Both depend on the clarification of taxonomic status, and phylogenetic distinctness of the Orinoco populations. With the goal of molecularly characterizing the two species of Osteoglossum, and comparing populations of Osteoglossum from the Orinoco and Amazon basins, we characterized individuals sampled from eight localities, one in the Orinoco River basin and seven in the Amazon River basin. We sampled 39 individuals, obtaining 1004 base pairs, of which 79 were synapomorphies. Genetic distance between the two species calculated using the HKY + G model of molecular evolution was 8.94%. Intraspecific distances ranged from 0.42% in O. bicirrhosum to 0.10% in O. ferreirai. The genetic characterization confirmed the taxonomic status of O. ferreirai in the Orinoco basin, and suggested that its distribution in the Orinoco basin is unlikely to be the result of vicariance or natural dispersal, but rather an anthropic introduction.

A review of the systematic biology of fossil and living bony-tongue fishes, Osteoglossomorpha (Actinopterygii: Teleostei)

“…Adults of the two species of Osteoglossum are silver (O. bicirrhosum) or greyish-steel (O. ferreirai) colored, the yolk-sac larvae of O. bicirrhosum are silver whereas those of O. ferreirai, which is restricted to the Rio Negro, are black with a distinct yellow lateral stripe on the body. The species of Osteoglossum are largely allopatric: O. bicirrhosum is found throughout the Amazon and the Branco river basins, and O. ferreirai is found in the Rio Negro basin, including the Branco, and the Orinoco River, which was likely the result of an introduction (Escobar et al, 2013). Using a ~1,000 base-pair fragment of the mitochondrial genome, Escobar et al (2013) calculated a genetic distance of 8.9% between the two species.…”

“…The species of Osteoglossum are largely allopatric: O. bicirrhosum is found throughout the Amazon and the Branco river basins, and O. ferreirai is found in the Rio Negro basin, including the Branco, and the Orinoco River, which was likely the result of an introduction (Escobar et al, 2013). Using a ~1,000 base-pair fragment of the mitochondrial genome, Escobar et al (2013) calculated a genetic distance of 8.9% between the two species. Scleropages comprises four species, two from Southeast Asia (S. formosus from Vietnam, Cambodia, Thailand, the Malay Peninsula, Sumatra, and Borneo, and S. inscriptus from Myanmar) and two from Australia (S. jardinii from the coastal river systems of northern Australia and Papua New Guinea, and S. leichardti from the Fitzroy River basin).…”