The Global Kraken - National Geographic

Now, a team of scientists from eight countries, led by Inger Winkelmann from the University of Copenhagen, has tried to settle the debate by looking at the kraken’s genes. Together, they amassed tissue samples from 43 giant squids caught all over the animal’s range, from Florida to South Africa to New Zealand. They sequenced each sample to piece together its mitochondrial genome—a small secondary set of DNA, which sits outside the main genome in tiny bean-shaped batteries.

The team found that the giant squid’s genetic diversity is incredibly low. Even though the individuals hailed from opposite corners of the world, they differed at less than 1 in every 100 DNA letters. For comparison, that’s 44 times less diverse than the Humboldt squid, which only lives in the eastern Pacific. In fact, the giant squid seems to be genetically narrower than any other sea-going species that scientists have tested, with the sole exception of the basking shark.

This strongly suggests that the 21 proposed species of giant squid can indeed be collapsed into one. There’s just the one global kraken—Architeuthis dux, the one-and-only original. What’s more, the population seems to have very little structure—in other words, squids that hail from nearby waters aren’t going to be genetically closer than distant individuals. The mitochondrial DNA of a Japanese squid is basically the same as that of a Floridian squid.

Why? It’s possible that the adults are wandering nomads that swim over large areas, but that seems unlikely. Chemical analyses of their beaks suggest that they stick within a relatively contained patch of ocean.  The alternative is that they go a-wanderin’ as larvae and youngsters. Young marine animals are certainly capable of passively drifting over tens of thousands of kilometres on ocean currents, so it’s entirely possible that the squids do the same. These young nomads would feed on plankton and other small creatures until they became big, whereupon they’d settle down and sink to the nutrient-rich waters of the deep ocean.

“I am not in the least surprised by their findings,” says giant squid expert Steve O’Shea. “They support what has been said many times earlier by some, contradicted by others and debated by a few, to what end I will never know.” O’Shea himself has suggested that larval giants drift over considerable distances and, on another Discovery Channel-sponsored research trip, he has captured 17 of these larvae at the surface of the ocean.