doi.org/10.1038/s41559-026-03009-1
Credibility: 989
#Lulas
Scientists have finally solved an old enigma about the evolution of squid and cuttlefish
These fascinating animals, known for their ability to change color rapidly and move like rockets through the water, had a longer and more complicated evolutionary path than previously thought.
A new genomic study shows that they emerged in the deep ocean, survived a major extinction in isolated refuges, and only then diversified explosively.
The work, published in the journal “Nature Ecology & Evolution,” was led by researchers from the Okinawa Institute of Science and Technology (OIST) in Japan.
They analyzed complete genomes of several species, including three recently sequenced ones, and combined this data with fossil evidence.
The result reveals a pattern called a “slow thread”: a long period of discrete changes followed by a rapid explosion of diversity.
Squid and cuttlefish, known as decapodiform cephalopods (those with ten arms), live from the dark depths of the sea to shallow coastal waters.
Most possess an internal shell, which can be rounded as in cuttlefish, thin and blade-shaped in many squid, or spiral, as in the rare ram’s horn squid.
Some shallow-water species have lost this structure completely.
For decades, scientists struggled to understand their evolutionary relationships.
Fossils are rare, and previous genetic data was incomplete, leading to confusing conclusions.
Now, with whole genome sequencing-which can be up to twice the size of the human genome-the picture has become much clearer.
According to lead researcher Dr. Gustavo Sanchez, these animals originated in the deep ocean about 100 million years ago, during the Cretaceous period.
When the great mass extinction occurred 66 million years ago-the same one that wiped out the dinosaurs-the surface waters became hostile: acidic, oxygen-poor, and devastated.
Ancestral squid and cuttlefish survived by taking refuge in small, deep zones with more oxygen, which helped preserve their internal shells.
Only later, when the oceans recovered and coral reefs reformed near the coast, did these cephalopods migrate to shallower environments.
It was then that the great diversification occurred: many new species emerged rapidly, adapting to new habitats and developing incredible abilities such as dynamic camouflage and a sophisticated nervous system.
The study also corrected old misconceptions.
For example, the ram’s horn squid (“Spirula spirula”), with its spiral shell, is not as closely related to cuttlefish as previously thought.
Its position in the deep ocean confirms the group’s deep-sea origin.
This research opens doors to a better understanding of how the unique characteristics of these animals, which have inspired science for centuries, arose.
With the “family tree” now well defined, scientists will be able to compare genomes and discover the genes responsible for special organs, impressive intelligence, and the ability to camouflage themselves in seconds.
In short, squid and cuttlefish were not always the agile and colorful animals we know today.
Their story is one of evolutionary patience: a long period of discreet survival at the bottom of the sea, followed by an explosion of life when the world recovered.
A beautiful example of how life finds surprising ways to thrive.
Published in 04/13/2026 01h50
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
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