An article published in the magazine “GigaScience” reports a DNA sequencing of Architeuthis dux, commonly known as giant squid. A team of researchers led by Rute da Fonseca of the Danish University of Copenhagen employed a number of genetic techniques to obtain the complete genome of this cephalopod, one of the largest in the history of this group of invertebrates. Its DNA is very large with its 2.7 billion base pairs of DNA, approximately 90% of the size of the human genome. Among the interesting results there’s the discovery of over 100 genes that encode proteins of the protocadherin family, important in the correct connectivity of a complex brain.
The legend of the Kraken, a sea monster that could destroy whole ships, may have been inspired by the giant squid. This animal is one of the most sensational examples of deep-sea gigantism, the tendency of animals living in the depths of the seas to be much larger than their cousins living in shallow waters. The amount of species that actually make up the genus Architeuthis is the subject of discussion: after the description of Architeuthis dux in 1857, several others were described in the following decades. In some cases, those descriptions were considered synonyms, which means subsequent descriptions of the same species with another name that after being recognized is no longer considered valid. Genetic research is an excellent method to resolve the issue and is one of the possible consequences of the study led by the University of Copenhagen.
In recent years, the genomes of some other cephalopods were sequenced, but finding quality DNA from a giant squid was more difficult. The available samples were taken from corpses preserved using various substances that make DNA isolation more difficult. In the end, the researchers managed to extract the DNA of a single Architeuthis dux individual, an important result because other types of study of these cephalopods are rare due to the few sightings and difficulties in looking for animals that live in deep seas.
The genome of Architeuthis dux is of considerable size, about 90% of the human one with its approximately 2.7 billion base pairs of DNA. The researchers were able to compare that DNA with those of the other cephalopods of which it was sequenced and with the human one, to try to understand where there can be similarities and differences between such different species.
An interesting result is the discovery of over 100 genes that encode proteins from the protocadherin family. It’s not news regarding cephalopods since even in the octopus (Octopus vulgaris) those genes are present in that amount, double that of mammals. Those genes are important in neural development and confirm that the giant squid has a complex brain as well.
Other interesting genetic characteristics in the giant squid are the ones related to the color changes used for camouflage. They’re part of the general studies on cephalopods, animals that developed unique characteristics and for this reason many scientists are intrigued by studies on their evolution.
