Scientists finally sequence the vampire squid's huge genome, revealing secrets of the 'living fossil'

The genetic link between squids and octopuses may just be found in the vampire squid genome. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Cephalopod evolution has long had a missing chapter in its story: how did squid-like ancestors give rise to today's octopuses? The answer, it turns out, was floating in the deep sea all along.With its glowing ghostly eyes, eight arms like its octopus cousins and a dark ruby coloring to match, the elusive vampire squid (Vampyroteuthis infernalis) has finally revealed its genetic secrets.In a study published Nov. 27 in the journal iScience, researchers sequenced the genome of Vampyrotheuthis and discovered its chromosomes still resemble those of squids and cuttlefish — despite belonging to the octopus order. This discovery hints at what the common ancestor of modern squids and octopuses may have looked like at the genetic level 300 million years ago when octopus and squid evolutionarily diverged. The researchers described the vampire squid as a "living fossil."On the cephalopod evolutionary tree, the vampire squid belongs to the group that includes octopuses, but underwent a "very ancient split" from the rest of the clade, study lead author Oleg Simakov, a researcher at the Department of Neuroscience and Developmental Biology in the University of Vienna, Austria, told Live Science in an email.After acquiring a tissue sample from a vampire squid collected as bycatch in the West Pacific Ocean from a research cruise, the researchers used a genetic analysis platform called PacBio to sequence the DNA of the sample. Unfortunately, there were no other vampire squid samples to compare it to, due to their rarity. Using PacBio, the researchers compared the vampire squid's genome to that of other cephalopods like the Argonaut (Argonauta hians), the common octopus (Octopus vulgaris) and the curled octopus (Eledone cirrhosa).The findings revealed the vampire squid has an 11 billion-base-pair-long genome, almost four times the size of the human genome — and the largest cephalopod genome sequenced to date.While modern octopuses have DNA that consistently gets reshuffled, resulting in some chromosomal mixing, the researchers found that the vampire squid's genome kept much of its ancestral, squid-like chromosomal arrangement. Essentially, it's an octopod that genetically looks like an ancient squid.Get the world’s most fascinating discoveries delivered straight to your inbox.The vampire squid has had a long history of being misunderstood. When it was initially discovered in 1903, it was thought to be a cirrate octopus due to its unique webbing between its arms. In the 1950s however, scientists reclassified it as its own group, belonging to neither octopus nor squid but in the order Vampyromorphida, so named because it looks like it's wearing a vampire-like cloak.—Never-before-seen vampire squid species discovered in twilight zone of South China Sea—Ancient 10-armed vampire squid relative named for Joe Biden—Vampire squid fossil 'lost' during the Hungarian Revolution rediscoveredThe finding is welcome news for cephalopod scientists as it is "nice to have resolved" why vampire squids retain much of their ancestral, squid-like traits, said Bruce Robison, senior scientist at the Monterey Bay Aquarium Research Institute (MBARI) who was not involved in the research.Part of what makes the fully sequenced genome so valuable is how hard it is to study vampire squids, mainly "because they live in a habitat that is difficult to access, they are solitary, rare, and do not survive well in captivity," Robison said. "Some people think that we can just dive into deep water, and find one whenever we like, which is definitely not the case."He added that the findings "reinforce the notion held by some of us that vamps would be the key to the puzzle. They are interesting to study because they are such cool animals, and because they just look like they are hiding secrets."Kenna Hughes-Castleberry is the Content Manager at Space.com. Formerly, she was the Science Communicator at JILA, a physics research institute. Kenna is also a freelance science journalist. Her beats include quantum technology, AI, animal intelligence, corvids, and cephalopods.You must confirm your public display name before commentingPlease logout and then login again, you will then be prompted to enter your display name. Live Science is part of Future US Inc, an international media group and leading digital publisher. Visit our corporate site. © Future US, Inc. Full 7th Floor, 130 West 42nd Street, New York, NY 10036. Please login or signup to comment Please wait...