Traces of DNA in seawater can provide new insight into populations of the elusive whale shark.
DNA found in the environment (eDNA) can come from the dead skin cells and faeces of animals. Philip Francis Thomsen at the University of Copenhagen and his colleagues compared eDNA sequences from seawater off the coast of Qatar with mitochondrial DNA sampled from a group of whale sharks (Rhincodon typus; pictured) in the same location. The two sets of DNA showed similar genetic patterns, but the eDNA included extra sequences — suggesting that eDNA may reveal greater genetic diversity. Comparing the eDNA data with those from whale-shark groups worldwide showed that the Qatari animals are similar to other Indo-Pacific groups, which are genetically distinct from Atlantic populations.
Using eDNA is a powerful way to study population dynamics in marine animals, the authors say.