All Giant Squids Belong to One Species: Study

There is just one species of giant squid in the world, even though the creatures may look different, according to a new study.

The giant squid was first described by Danish naturalist Japetus Steenstrup in 1857. Despite its enormous size, precious little is known about these deep-sea creatures. For many years, researchers relied on carcasses found by fishermen to understand the creature. It was in 2004 that a team of Japanese researchers photographed a giant squid. And in 2012, Discovery team filmed a giant squid in its natural habitat.

The present study was conducted by a team of researchers led by professor Tom Gilbert, from the Basic Research Centre in GeoGenetics at the Natural History Museum of Denmark, Copenhagen University.

Researchers found surprisingly little genetic variation among giant squids, which raises questions about the creatures' recent history.

The study included 43 samples of giant squid tissues from many countries including Spain, South Africa and Japan. Few of the samples were obtained from dead giant squids that were found floating in the ocean or stranded on the shore, others were found in the stomach of a sperm whale, reports Science. Researchers then analyzed mitochondrial DNA obtained from the cells of the samples. Study analysis showed surprisingly little genetic variation, despite the samples coming from around the world.

"Your general [giant] squid is a long, scrawny beast: it's got a long thin body and long thin arms," said professor M. Thomas P. Gilbert, from the Natural History Museum of Denmark, BBC reports."But off [the coast of] Japan for example, they're much shorter and stubbier. Their arms are fatter and much shorter."

Professor Gilbert told BBC that the findings were "very weird", as animals do have genetic variation. He suggested that the giant squids' genetic similarity may arise from migration.

"We speculate the larval stage must drift globally in the currents then dive to the nearest dark, deep spot when they are large enough, thus stopping any [population] structure appearing," Gilbert explained, reports BBC.

The study is published in the journal Proceedings of the Royal Society B.