Release the Kraken! Scientists Finally Sequence Giant Squid Genome

Thursday, 16 January 2020 - 9:59AM
Weird Science
Thursday, 16 January 2020 - 9:59AM
Release the Kraken! Scientists Finally Sequence Giant Squid Genome
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Alfred Frédol/Public Domain
There's something remarkable about cephalopods and it's not just that they're likely smarter than your four-year-old, to say nothing of your dog. Their symmetry, ability to change color to camouflage themselves, and, in the case of the giant squid, reputation as fearless hunters, are enough to raise insecurity in any biped who has ever ventured towards the horizon across the ocean's vast abyss. Indeed, the seldom-seen giant squid is one of nature's most perfect designs. That design has now been revealed by an international team of scientists who've successfully sequenced the giant squid's genome.

The researchers were led by the University of Copenhagen's Rute da Fonseca and included Caroline Albertin of the University of Chicago's Marine Biological Laboratory, who sequenced the first genome of a cephalopod in 2015. They discovered that the genome was composed of an estimated 2.7 billion DNA base pairs – roughly 90% the size of a human's genome – revealing a complex, intelligent creature that, at first glance, seems to have changed very little over the millennia. A press release covering the highlights of the research published in the journal GigaScience noted that Albertin "found that important developmental genes in almost all animals (Hox and Wnt) were present in single copies only in the giant squid genome. That means this gigantic, invertebrate creature - long a source of sea-monster lore - did NOT get so big through whole-genome duplication, a strategy that evolution took long ago to increase the size of vertebrates."

That means scientists still aren't sure how these giant squids attained their colossal size. In an interview with Gizmodo, Albertin discussed the finding. "Whole genome duplication has been described in a number of different groups of organisms," she told the website. "Some plants are famous for this, but vertebrates-animals with a backbone-also had a whole genome duplication that has been hypothesized to be important in their evolution. We don't see evidence for whole genome duplication in any of the cephalopods examined thus far, including the giant squid."


Nevertheless, giant squid aren't completely out of this world. Despite the strangeness of the creatures, Albertin did discover some interesting similarities between the giant squid and its vertebrate planet-sharers: over a hundred genes in the protocadherin subgroup that suggest a complex nervous system also found in its smaller cousins.

"Protocadherins are thought to be important in wiring up a complicated brain correctly," Albertin explains. "They were thought they were a vertebrate innovation, so we were really surprised when we found more than 100 of them in the octopus genome (in 2015). That seemed like a smoking gun to how you make a complicated brain. And we have found a similar expansion of protocadherins in the giant squid, as well."

Smithsonian Institute

Further research into the genome and gene expression in the giant squid will potentially explain how it came to have the largest brain of all invertebrates and shed some light on its overall size, intelligence, and skill at hunting and hiding. "While cephalopods have many complex and elaborate features," Albertin said, "they are thought to have evolved independently of the vertebrates. By comparing their genomes we can ask, 'Are cephalopods and vertebrates built the same way or are they built differently?'"

We're one step closer to finding out exactly that. 

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International Team of Scientists Sequence Giant Squid Genome