The giant squid (Architeuthis dux, affectionately known as Archie ) is an animal so mysterious and mighty that it has inspired the tale of the mythical kraken that has been told since the height of the sea fairing days. This signifies its gargantuan size but also its absence in our eyes. Not much is known about the animal but now, thanks to the research done by Marine Biological Laboratory and its various partner institutions, we now have a complete functioning genome for the oceanic legend.

This discovery can answer long standing questions about Architeuthis dux and other deep-sea creatures. We can finally take crucial steps to understand large size growth in animals and the conservation of the giant squid.

The genome was formed by taking 116GB of raw data and processing that into a complete 2.7GB model. To complete this, high-molecular-weight DNA was extracted from a single giant squid individual. Since it was practically impossible to get live samples of genetic information, the researchers created a library of genetic information from other cephalopod species. This was used to create DNA libraries that proved compatible to the raw data from the sample.

The DNA libraries were used to form proteins that were dissolved in squid tissue fluid and submerged in liquid nitrogen. Analyzing these proteins led to the coding of genes. These genes were then compared to genes from the four other cephalopod species to test their viability. In some cases, predictions were made using the genes from other cephalopods as a blueprint to cover up empty spaces in the genome of the giant squid. After a total of 18,054 predictions, a completed genome was formed.

A figure showing the genetic makeup of various cepholopods including the giant squid that has 50% repeated genome From GigaScience, via academic.oup.com

The results show that the giant squid’s genome has a single copy of developmental genes that are present and used in most species to grow larger. This stands to reject the theory that whole-genome duplication, a process where there are multiple copies of all genes in a species, is what leads to the giant squid’s humungous size. What was also found was that the squid’s genes were repeats, however, they did not contain the developmental genes, further rejecting the viability of the whole-genome duplication process.

In recent years, processes such as oceanic warming and acidification, pollution, heightened bodily oxygen deprivation, and fishing have been shown to affect cephalopod populations. High concentrations of Mercury and flame-retardant chemicals have been found in the giant squid’s tissues. Therefore, it is crucial to have a greater biological understanding of these important, but rarely encountered animals, in order to aid conservation efforts and ensure their continued existence. The genome is an important resource for future population genomic studies aiming at characterizing the diversity of the legendary squid.

The giant squid is a rarely sighted species which has never been caught and kept alive, meaning their biology was largely a mystery. The enigmatic giant has a worldwide distribution in the deep ocean, except in the high Arctic and Antarctic waters. Which is why, having a genome assembled for this deep-sea–dwelling species will allow several pending evolutionary questions to be unlocked.

References:

Foncesca, R. da., et al. 2020. A Draft Genome Sequence of the Elusive Giant Squid, Architeuthis dux. GigaScience, 9(1).

Link: https://academic.oup.com/gigascience/article/9/1/giz152/5697198