The genome of the vampire squid (Vampirotutis sp.) is among the largest of any animal, containing over 10 billion base pairs.

The vampire squid, often referred to as a “living fossil,” inhabits ocean basins worldwide at depths ranging from 500 to 3,000 meters.

This creature is soft-bodied and has a size, shape, and color reminiscent of a football.

It features a dark red body, large blue eyes, and cloak-like webbing connecting its eight arms.

When threatened, the squid can turn itself inside out, displaying rows of menacing “siri.”

In contrast to other squid species that reproduce in a single event later in life, vampire squids exhibit signs of multiple reproductive cycles.

“Modern cephalopods, including squids, octopuses, and cuttlefish, diverged into two main lineages over 300 million years ago: the 10-armed Decapoda (cuttlefish and cuttlefish) and the eight-armed Octopoda (octopuses and vampire squids),” explained biologist Masaaki Yoshida from Shimane University and his team.

“Despite its name, the vampire squid has eight arms similar to those of an octopus, yet it shares significant genomic characteristics with cuttlefish and cuttlefish.”

“It occupies a unique position between these two lineages, and for the first time, its relationship has been revealed at the chromosomal level through genome analysis.”

“Although classified within the octopus lineage, it retains features of a more ancestral squid-like chromosomal structure, shedding light on the evolutionary history of early cephalopods.”

A recent study sequenced the genome of a vampire squid from specimens gathered in the Western Pacific Ocean.

“With over 11 billion base pairs, the vampire squid’s genome is nearly four times larger than the human genome and represents the largest cephalopod genome analyzed to date,” the researchers noted.

“Despite its vast size, the chromosomes share a surprisingly conserved structure.”

“Thus, Vampirotutis is termed a ‘living fossil of the genome,’ embodying modern-day descendants of ancient lineages that retain essential features from their evolutionary background.”

The study revealed that while modern octopuses have undergone significant chromosome fusions and alterations during evolution, octopuses have managed to preserve some decapod-like karyotypes.

This conserved genome structure provides fresh insights into how cephalopod lineages branched apart.

“Vampire squids exist right on the boundary between octopuses and squids,” commented Dr. Oleg Simakov, a researcher at the University of Vienna.

“The genome unfolds deep evolutionary narratives about how these distinctly different lineages emerged from a shared ancestor.”

By comparing the vampire squid with other sequenced species, including the pelagic octopus Argonauta hians, scientists could trace the trajectory of chromosomal changes throughout evolution.

“The genome sequence of Argonauta hians reveals, for the first time, a ‘bizarre’ pelagic octopus (paper nautilus) where females have secondarily acquired shell-like calcified structures,” the researchers stated.

“The analysis suggests that early coleoids had a squid-like chromosomal organization that subsequently fused and compacted into the modern octopus genome, a process termed mixed fusion.”

“These irreversible rearrangements may have instigated significant morphological innovations, including weapon specialization and the loss of the outer shell.”

“Although the vampire squid is classified among octopuses, it preserves an older genetic lineage than both groups,” added Dr. Emese Todt, a researcher at the University of Vienna.

“This enables us to study the early phases of cephalopod evolution directly.”

“Our research provides the clearest genetic evidence to date indicating that the common ancestor of octopuses and squids was more squid-like than previously recognized.”

“This study underscores that large-scale chromosomal rearrangements, rather than the emergence of new genes, have primarily driven the extraordinary diversity of modern cephalopods.”

The findings are detailed in a study published in the Journal on November 21, 2025 iscience.

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Masaaki Yoshida et al. 2025. The extensive genome of a vampire squid unveils the derived state of modern octopod karyotypes. iscience 28 (11): 113832; doi: 10.1016/j.isci.2025.113832