An international team of researchers from Malaysia and Australia has successfully sequenced the genome of a famous ornamental fish species called the Asian arowana (Scleropages formosus).
The arowana (Scleropages sp.). Image credit: Marcel Burkhard / CC BY-SA 3.0.
The Asian arowana, sometimes also referred to as dragon fish, is a representative of one of the oldest lineages of ray-finned fish, the Osteoglossomorpha.
“The arowana belongs to a very old group of fish which you could refer to as living fossils,” said team member Christopher Austin, a Professor of Tropical Biology and the Genomics Cluster Leader for Monash University Malaysia’s Tropical Medicine and Biology Multidisciplinary Program.
“One of the things we’re interested in is: where does it fit in the family tree of fishes? Our study indicates that arowana is the most primitive of the modern fishes,” he added.
The study appeared online recently in the journal Genome Biology and Evolution.
“The evolutionary position of the arowana has been disputed in scientific literature – whether it’s the arowana group or the eel group that’s the most primitive form,” Prof. Austin explained.
“Some recent publications suggested eels, but our publication suggests the arowana, which agrees with the more traditional scientific studies.”
“Its appearance has not changed much over a very long period of geological time, and we’re talking millions and millions of years. But just because you’re primitive doesn’t mean you’re obsolete.”
“We can’t entirely say that the arowana is an all-round primitive fish because it’s not,” the scientists said.
“The fact that it produces a small number of big eggs and that the males take care of the eggs is actually sort of more modern, if you like.”
Prof. Austin and his colleagues from the Museum and Art Gallery of the Northern Territory in Darwin, Australia, Monash University Malaysia, and the Malaysian Genomics Resources Center, liken arowanas to sharks, another fish that’s full of primitive characteristics but has survived millions of years.
“When we started, only about 20 fish genomes had been published in the world, which is a small number compared to mammals and birds,” he said.
The team has identified 94 genes in the arowana genome that may influence its color. If studied further, this could be very helpful to fish farmers, who currently breed arowana through traditional breeding, which can be inefficient and lead to inbreeding if not done carefully.
Besides being able to identify and study genes that determine color, a simple genetic test to identify sex – which is very difficult in arowana based on morphology – would be very useful. Finding genes that influence growth and survival would also be of interest to commercial farmers.
Prof. Austin sees that the next step for their research will involve working with arowana breeders and farmers. Together, they could improve the quality of arowana stocks through genetically-enabled breeding programs which would involve genetic testing in the lab and on-farm trials.
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C.M. Austin et al. 2015. Whole genome sequencing of the Asian arowana (Scleropages formosus) provides insights into the evolution of ray-finned fishes. Genome Biology and Evolution 7 (10): 2885-95; doi: 10.1093/gbe/evv186
