Atlantic cod are actually five separate species of fish, not one, researchers have claimed after conducting a genetic analysis 鈥� though not everyone agrees with their findings.
鈥淲hat we thought was a single species is actually more species,鈥� says at the University of Iceland. 鈥淚t鈥檚 important in terms of biodiversity.鈥�
Arnason and his colleagues have sequenced the genomes of nearly 1700 Atlantic cod, currently regarded as a single species called Gadus morhua, from across the Atlantic Ocean. For comparison, they also sequenced the genomes of several related species, including Pacific cod and Greenland cod.
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They found the Atlantic cod genomes could all be separated into one of five distinct groups. 鈥淭hey are not interbreeding,鈥� says Arnason.
There is a lot of overlap in the geographic areas where the five cod groups are found, with all located in various places around Iceland, for instance. But the team thinks each group lives in distinct habitats at different depths.
鈥淭hey are habitat specialists, and they are breeding in the habitat that they choose to live in,鈥� says Arnason. 鈥淭he sea is three dimensional. They can be separated out even though they reside at the same coordinates.鈥�
For instance, the team calls one of the groups SS, because it lives on shell sands. Another, known as S, is found mostly around the Baltic Sea and appears adapted to brackish water.
The team has yet to give the five groups scientific names. The researchers are now investigating the many questions raised by their discovery, Arnason says, such as whether there are previously unnoticed physical differences, and whether any of the five are threatened.
But other researchers are yet to be convinced. 鈥淚 am a bit surprised about the conclusion that there exist five cryptic [hidden] species,鈥� says at the University of Oslo, Norway, whose team was the first to sequence .
bioRxiv
