Genome vampire squid (Vampiroteuthis sp.) – one of the largest animal genomes, exceeding 10 billion base pairs.
Vampire squid (Vampiroteuthis sp.) is one of the most mysterious animals of the deep sea. Image credit: Stephen Haddock/MBRI.
“Living Fossil” – Vampire Squid lives deep waters of all basins of the world's oceans at depths from 500 to 3000 m.
This species is a soft-bodied, passive creature the size, shape and color of a football.
It has a dark red body, huge blue eyes, and a cape-like web running between its eight arms.
When threatened, the squid turns inside out, revealing rows of sinister-looking “antennae.”
While other squids reproduce simultaneously at the end of their lives, vampire squids show signs of multiple reproductive cycles.
“Modern cephalopods (coleoids), including squid, octopuses and cuttlefish, split into two main lineages more than 300 million years ago: ten-armed decapods (squid and cuttlefish) and eight-armed eight-legged ones (octopuses and vampire squids),” said Shimane University biologist Masaaki Yoshida and his colleagues.
“Despite its name, the vampire squid has eight arms, like the octopus, but shares key genomic features with squid and cuttlefish.”
“This takes the intermediate position between these two lineages is a relationship that its genome reveals for the first time at the chromosomal level.”
“Although it belongs to the octopus lineage, it retains elements of an older, squid-like chromosomal organization, providing new insight into the early evolution of cephalopods.”
In the new study, the authors sequenced the genome of a vampire squid caught in the western Pacific Ocean.
“At more than 11 billion base pairs, the vampire squid genome is approximately four times larger than the human genome, making it the largest cephalopod genome ever analyzed,” they said.
“Despite this size, its chromosomes exhibit a remarkably conserved structure.”
“Because of this, Vampiroteuthis considered a “genomic living fossil”—a modern representative of an ancient lineage that has retained key features of its evolutionary past.”
The researchers found that it retained parts of its decapodiform karyotype, whereas modern octopuses have undergone extensive chromosomal fusions and rearrangements during evolution.
This conserved genomic architecture provides new clues about how cephalopod lineages diverged.
“The vampire squid is right on the border between octopuses and squids,” said Dr. Oleg Simakov, a researcher at the University of Vienna.
“Its genome reveals deep evolutionary mysteries about how two strikingly different lineages could have evolved from a common ancestor.”
Comparing the vampire squid with other sequenced species, including the pelagic octopus. Argonaut hiansScientists were able to trace the direction of chromosomal changes over evolutionary time.
“Genome sequence Argonaut hians (paper nautilus), a “strange” pelagic octopus whose females secondarily acquired a crustacean, calcified structure, was also represented for the first time in our study,” they said.
“The analysis shows that early coleoids had a squid-like chromosomal organization that later fused and condensed into the genome of the modern octopus, a process known as admixture fusion.”
“These irreversible rearrangements likely led to key morphological innovations such as hand specialization and loss of outer membranes.”
“Although it is classified as an octopus, the vampire squid retains genetic heritage that predates both lineages,” added Dr Emese Toth, a researcher at the University of Vienna.
“This gives us a direct look at the earliest stages of cephalopod evolution.”
“Our study provides the clearest genetic evidence yet that the common ancestor of octopuses and squid was more squid-like than previously thought.”
“This highlights that large-scale chromosomal reorganization, rather than the emergence of new genes, was the main driver of the remarkable diversity of modern cephalopods.”
results were published on November 21, 2025 in the magazine iScience.
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Masa-aki Yoshida etc.. 2025. The giant vampire squid genome reveals the derived state of modern octopus karyotypes. iScience 28 (11): 113832; two: 10.1016/j.isci.2025.113832
