A team of scientists from Europe has sequenced and analyzed the nearly complete genome of the wels catfish (Silurus glanis), one of the largest freshwater fish species in the world.
The wels catfish (Silurus glanis). Image credit: Dieter Florian / CC BY-SA 3.0 DE.
The wels catfish, also known as the European catfish or sheatfish, is a species of non-migratory predatory fish that lives mainly in freshwater habitats (large warm lakes and deep, slow-flowing rivers), but also occurs in brackish waters in the Baltic and Black Seas.
This species is native to the North, Baltic, Black, Caspian and Aral Sea basins; its distribution extends from Germany eastwards through Poland and the Baltic States, and from Southern Sweden southwards through Eastern European countries to Turkey, Northern Iran and the Aral Sea basin of Kazakhstan and Uzbekistan.
The wels catfish is the largest fish of the order Siluriformes and the largest among European freshwater teleost fishes.
Its maximum reported size was 5 m and 306 kg, caught in the Dnipro (Dniapro) River, although the typical length and weight vary from 1.3 to 1.6 m and from 15 to 65 kg, respectively.
This top predator plays a key role in ecosystem stability, and represents an iconic trophy-fish for recreational fishermen.
It is also a highly valued for its high-quality boneless flesh, and has been cultivated for over 100 years in Eastern and Central Europe.
The interest in rearing the wels catfish continues to grow; the aquaculture production of this species has almost doubled during the last decade.
However, despite its high ecological, cultural and economic importance, the available genomic resources for the species are very limited.
To fulfill this gap, Estonian University of Life Sciences Professor Riho Gross, Dr. Mikhail Ozerov from the Swedish University of Agricultural Sciences and their colleagues sequenced and assembled the whole genome sequence of a female wels catfish.
“Assembled wels catfish genome allows us to find genomic regions and gene variants that impact growth rate, age at sexual maturity, disease resistance and other relevant traits for aquaculture,” Professor Gross said.
“The genome assembly will serve as a springboard for future research aimed at addressing the bottlenecks in catfish aquaculture and challenges linked to conservation of wild populations,” added Professor Anti Vasemägi, a researcher at the Estonian University of Life Sciences and the Swedish University of Agricultural Sciences.
The size of the wels catfish genome is around 800 million base pairs, comparable to that of the most closely related bony fishes.
The researchers identified 21,316 protein-coding genes and annotated 19,627 genes with known homology.
“Given the ecological, cultural and economic importance of the wels catfish, as well as its increasing aquaculture production, the generated genome assembly will serve as a backbone for future genomics, genetics, conservation, and breeding research of the wels catfish and other fish species of the family Siluridae,” they said.
The results were published in the journal G3: Genes, Genomes, Genetics.
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Mikhail Yu. Ozerov et al. Draft Genome Assembly of the Freshwater Apex Predator Wels Catfish (Silurus glanis) Using Linked-Read Sequencing. G3: Genes, Genomes, Genetics, published online September 11, 2020; doi: 10.1534/g3.120.401711
