So long suckers (Image: Tsunemi Kubodera of the National Science Museum of Japan/AP)

IT’S a small world after all for giant squid. The first genetic study of global squid populations shows that the mysterious animals are very similar to each other, even though they live so far apart. The finding suggests that their young are dispersed thousands of kilometres by powerful global currents.

M. Thomas Gilbert of the University of Copenhagen in Denmark and colleagues sequenced the mitochondrial genomes of 43 giant squid (Architeuthis dux) samples from all over the world. The genomes were unusually similar, with only 181 genetic base pairs out of 20,331 varying between the individual squid. Other widely distributed animals show much more variation.

The genetic evidence suggests there is a single, global population of giant squid. But studies of adult squid suggest that individuals confine themselves to small pockets of the deep ocean, whether this be in Japan or Florida. So how come they seem to be so closely related?


Gilbert thinks squid larvae are the explanation. They could travel thousands of kilometres from their place of birth, carried on global ocean currents. He says the larvae, brought to the surface by upwellings, may feed on plankton and other small animals. When they have grown, they dive into the depths and find a nutrient-rich area that has plenty of large prey, where they can settle down.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2013.0273