The Vampire Squid Genome Has Helped Explain the Early Evolution of the Cephalopods — Here’s How
According to a new study in iScienceresearchers have now sequenced the largest cephalopod genome in history. Generate the vampire squid genome (Vampyroteuthis sp.) and comparing it to the genomes of other cephalopods, the team revealed that the species – which has a combination of octopus, squid and cuttlefish characteristics – has ancient architecture in its genome, and specifically in its chromosomes, indicating that the common ancestor of modern cephalopods was strikingly similar to a squid.
“The vampire squid sits right at the interface between octopuses and squid,” said Oleg Simakov, study author and biologist at the University of Vienna, according to a press release. “Its genome reveals deep evolutionary secrets about how two strikingly different lineages could emerge from a common ancestor.”
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The origins of cephalopods
About 300 million years ago, the ancestors of modern cephalopods split into two lineages, including the modern Octopodiformes (octopuses) and the modern Decapodiforms (squid and cuttlefish). But the exact nature of these ancient ancestors, and whether they were more like octopuses or squid and cuttlefish, have long perplexed scientists.
To help solve the mystery, the authors of the new study turned to the genome of the vampire squid, which is actually classified as an octopus, to explain the evolution of early cephalopods. By closely examining the structure of the vampire squid’s chromosomes, researchers discovered that the species, which exhibits a mixture of characteristics from octopuses and squid and cuttlefish, represents a link between the two lineages, retaining some of the chromosomal traits of their common ancestors.
“Despite being classified as an octopus, the vampire squid retains a genetic heritage that predates both lineages,” Emese Tóth, another study author and biologist at the University of Vienna, said in the press release. “This gives us direct insight into the early stages of cephalopod evolution.”
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The ancient architecture of the vampire squid
About four times the size of the human genome, the vampire squid genome contains an abundance of genetic material. Sifting through this material during their analysis, the team was surprised to find that certain sections of the species’ chromosome structure were highly conserved, or saved over time, making the species a “living genomic fossil” or a modern species that preserves the genetics of its ancestors.
By comparing the vampire squid’s genome to that of other cephalopod species, the researchers then concluded that the species has an ancient, squid-like architecture in its chromosomes. While the majority of modern octopuses do not possess this structure, thanks to significant chromosomal reorganizations that occurred during their evolution, the vampire squid has retained this structure over time, providing important insights into the emergence of cephalopods.
In fact, the researchers added, the study strongly supports the theory that today’s octopuses, squid and cuttlefish evolved from a creature that looked less like an octopus and more like a squid or cuttlefish, around 300 million years ago. They also said their research highlights that the reorganization and restructuring of chromosomes may have contributed to the incredible variety seen today in modern cephalopods, which come in all shapes and sizes, from the largest octopus to the smallest cuttlefish, today.
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