Evolution of octopuses explained with DNA analysis of 'vampire squid from hell'

For the first time, researchers have successfully sequenced the genome of the enigmatic deep-sea creature known as the "vampire squid from hell," shedding light on the evolutionary origins of cephalopods, including octopuses. With over 11 billion DNA bases, this is the largest cephalopod genome ever decodedtwice the size of the largest known squid genome and four times larger than the human genome.

Analysis revealed that the vampire squid retains genetic traits from ancient species, implying that modern octopuses evolved from squid-like ancestors. The species, scientifically named Vampyroteuthis infernalis, is characterized by its dark body, large eyes that can appear red or blue, and webbing between its arms that resembles a cloak. Despite its fearsome name, the vampire squid does not consume blood, instead feeding peacefully on organic detritus.

Although classified as an octopus, the vampire squid exhibits traits common to both squids and cuttlefish. To trace the evolutionary history of the species, scientists at the National Institute of Technology, Wakayama College, Japan, sequenced its genome and compared it with other cephalopods, including pelagic octopuses. This comparison allowed them to track genetic changes over time and reconstruct an important chapter in cephalopod evolution.

Modern cephalopods diverged over 300 million years ago into two main groups: the eight-armed Octopodiformes, which include octopuses and the vampire squid, and the ten-armed Decapodiformes, including squids and cuttlefish. Despite having eight arms, the vampire squid shares crucial genomic features with squids and cuttlefish, placing it in an intermediate evolutionary position.

"The vampire squid sits right at the interface between octopuses and squids," explained Oleg Simakov, senior author of the study published in iScience. "Its genome reveals deep evolutionary secrets about how two very different lineages could emerge from a shared ancestor."

Emese Tth, a co-author from the University of Vienna, added, "Although classified as an octopus, the vampire squid retains genetic elements that predate both lineages. It offers a direct glimpse into the earliest stages of cephalopod evolution."

Genomic analysis suggests that the common ancestor of octopuses and squids was more squid-like than previously thought. At some point, this ancestor underwent major genome reorganisation, driving the extraordinary diversity observed in modern cephalopods, researchers concluded.

Analysis: Unveiling the Genetic Blueprint of the Vampire Squid

The recent successful sequencing of the vampire squid genome represents a major milestone in cephalopod research. This breakthrough provides a deeper understanding of the evolutionary origins of cephalopods, including octopuses and squids. With over 11 billion DNA bases, the genome of Vampyroteuthis infernalis is not only the largest ever decoded for a cephalopod but also serves as a key to understanding the genetic evolution of these fascinating creatures.

While often referred to as the "vampire squid from hell" due to its eerie appearance, this species does not live up to its menacing moniker. Instead of consuming blood, it feeds on organic detritus, making it an intriguing contrast to its ominous reputation. However, its classification as an octopus is misleading, as it shares significant genetic traits with both squids and cuttlefish. This hybrid nature of the vampire squid has now been confirmed at the genomic level, revealing its position as a unique link between the octopodiform and decapodiform groups.

As researchers at the National Institute of Technology, Wakayama College, Japan, compare the vampire squid's genome with that of other cephalopods, a clearer picture of the evolutionary divergence over 300 million years ago begins to emerge. The genomic analysis not only sheds light on the ancient traits preserved by the vampire squid but also suggests that the common ancestor of modern octopuses and squids was more squid-like than previously thought. This finding challenges earlier assumptions and opens up new avenues for understanding the major genomic reorganizations that led to the extraordinary diversity seen in cephalopods today.

In conclusion, the sequencing of the vampire squid genome provides invaluable insight into the evolutionary history of cephalopods. By unlocking the genetic secrets of this enigmatic species, scientists have gained a clearer view of how two very different lineages—octopuses and squids—could have evolved from a shared ancestor. This research not only reshapes our understanding of cephalopod evolution but also highlights the importance of genomic studies in tracing the deep history of life on Earth.

Sources:

• DNA of ‘vampire squid from hell’ helps explain how octopuses evolved