DNA Study Reveals Enigmatic Giant Squid All One Species

A new research on the elusive giant squid Architeuthis, published in the Proceedings of the Royal Society B, has revealed there is just one species.

Architeuthis dux, and Homo sapiens for comparison of size (© Tsunemi Kubodera / National Museum of Nature and Science, Japan)

Architeuthis dux, and Homo sapiens for comparison of size (© Tsunemi Kubodera / National Museum of Nature and Science, Japan)

Little was previously known about the giant squid, believed to grow up to 43 feet (13 m) long and weigh over 900 kg.

The creature is extremely rarely seen except when its remains are washed ashore. In 1857, Japetus Steenstrup realized that it was this beast that had given rise to centuries of sailors’ tales, and become immortalized by writers such as Jules Verne.

Less than a year ago the researchers captured the first ever film of a giant squid in the wild. After 100 missions and 400 hours of filming, the footage was taken from a small submarine off the Japanese island of Chichi Jima, at a depth of 2,070 feet (600 m).

An international team of scientists led by Prof Tom Gilbert from the University of Copenhagen carried out molecular analysis on 43 giant squid samples.

From these samples the researchers analyzed the mitochondrial DNA, which are the energy structures in every cell that contain their own DNA and that are inherited through the mother.

The findings indicate that the giant squid has very low genetic diversity. Individuals tested from the furthest regions of the world are virtually the same genetically. This suggests that there is just one species of giant squid, Architeuthis dux, worldwide. They also found no difference in the structure of populations living far apart, so for example individuals in Japan are no more closely related to each other than they are to those in Florida.

“We have analyzed DNA from the remains of 43 giant squid collected from all over the world. The results show, that the animal is nearly genetically identical all over the planet, and shows no evidence of living in geographically structured populations,” explained first author Inger Winkelmann, also from the University of Copenhagen.

“One possible explanation for this is that although evidence suggests the adults remain in relatively restricted geographic regions, the young that live on the oceans’ surfaces must drift in the currents globally. Once they reach a large enough size to survive the depths, we believe they dive to the nearest suitable deep waters, and begin the cycle again.”

“Nevertheless, we still lack a huge amount of knowledge about these creatures. How big a range do they really inhabit as adults? Have they been threatened by things such as climate change, and the populations of their natural enemies, such as the sperm whale? And at an even more basic level… how long do they live and how quickly do they grow?”

“It’s been a fantastic experience to work with the giant squid because of its legendary status as a sea monster. But despite our findings I have no doubt that the myths and legends will continue,” Prof Gilbert added.

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Bibliographic information: Inger Winkelmann et al. 2013. Mitochondrial genome diversity and population structure of the giant squid Architeuthis: genetics sheds new light on one of the most enigmatic marine species. Proc. R. Soc. B, vol. 280, no. 1759; doi: 10.1098/rspb.2013.0273