The giant squid has long been a subject of horror lore. In this original illustration from Jules Verne’s “20,000 Leagues Under the Sea,” a giant squid grasps a helpless sailor.

University of Chicago / Alphonse de Neuville 

Everything about the mysterious giant squid Architeuthis dux is massive. It grows as big as a school bus, has eyes the size of dinner plates, and tentacles that can snatch prey from 30 feet away. The legendary source of sea-lore has frightened humans for ages, but how did they get so enormous in the first place? New research may soon offer answers, as the mighty cephalopod’s genome was finally revealed Thursday. 

“A genome is a first step for answering a lot of questions about the biology of these very weird animals,” scientist Caroline Albertin said in a release from the University of Chicago. Those questions include how giant squids acquired the largest brain among the invertebrates, and how they became so agile and skillful. 

“While cephalopods have many complex and elaborate features, they are thought to have evolved independently of the vertebrates,” Albertin said in the release. “By comparing their genomes we can ask, ‘Are cephalopods and vertebrates built the same way or are they built differently?'”

While the genome’s revelation may offer answers to some questions, it raises more in the immediate term. A key finding from the research shows how how giant squids’ size-driving genes break with the patterns found among the important developmental genes in almost all other animals. This means that giant squids’ enormity didn’t come through whole-genome duplication, a strategy that evolution took long ago to increase the size of vertebrates. 

It also means scientists have more work to do to get to the bottom of the giant squid’s mysterious size. 

Even so, having the giant squid genome is an important node in helping scientists understand what makes a cephalopod a cephalopod, Albertin said. It can also help scientists understand how new and novel genes arise in evolution and development. 

Read more: Eerie giant squid shows off tentacles in rare video