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The legendary giant squid has been feared by mariners for centuries, but now the first full sequencing of its genome has been published.
Fabled to have eyes the size of dinner plates and the strength to crush a ship, the giant squid (Architeuthis dux) is one of the most mysterious marine creatures on the planet, having rarely been seen or captured alive.
As a result, we have known little about its biology. However, a University of Copenhagen-led team has published the results of its first full genome sequencing to the journal GigaScience.
Led by Rute da Fonseca, the team discovered that the giant squid genome is massive. With an estimated 2.7bn DNA base pairs, the genome is approximately 90pc the size of the human genome. Scientists also discovered that important developmental genes found in almost all animals were present in single copies only in the giant squid genome.
This means that the gigantic, mysterious creature did not get to the size it is through whole-genome duplication. This is a strategy that evolution took long ago to increase the size of vertebrates, which means further probing of the giant squid genome is needed to find an answer about its size.
A ‘smoking gun’ for a complicated brain
Caroline Albertin, a scientist at the US Marine Biological Laboratory who took part in the research, said that this is the first step to answering a lot of the questions about the biology of these “very weird animals”.
For example, how did it acquire such a large brain and how did it develop its incredible skills of instantaneous camouflage?
“While cephalopods have many complex and elaborate features, 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?’” Albertin said.
The sequencing also revealed more than 100 genes in the protocadherin family, not typically found in invertebrates.
“Protocadherins are thought to be important in wiring up a complicated brain correctly,” Albertin said.
“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 a previous study]. 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.”
