University of Tokyo researchers found that cephalopod suckers develop using Ets1, a gene normally active in early mollusk embryos, rather than the genes that pattern the arms they sit on.
The suckers lining an octopus’s arms are among the most remarkable structures in the animal kingdom. Each one can grip, release and even taste, and an octopus can control them individually. Cuttlefish and squid have suckers too. Yet no other group of animals has anything quite like them, raising a basic evolutionary question: where did they come from?
A study from the University of Tokyo offers part of the answer. Writing in iScience, researchers report that cephalopod suckers appear to have evolved not by inventing new genes but by redeploying an existing gene in a new place. The gene, called Ets1, is normally associated with early embryonic development in mollusks.
Arms versus suckers
Cephalopods, the group that includes octopuses, squid and cuttlefish, are mollusks, related to snails and clams. Their arms are thought to have evolved from part of the ancestral mollusk foot, and the suckers developed later on those arms.
Octopus suckers are far more than passive suction cups. Each contains thousands of sensory receptors, including chemical sensors that let the animal taste what it touches, and a dense supply of nerves that allows it to move and grip independently. Researchers have even drawn on their design for robotic grippers and medical adhesives.
The team, led by postdoctoral fellow Ryosuke Kimbara and professor Toru Miura, compared gene activity during embryonic development in cuttlefish, octopuses and snails. They first looked at genes known to help pattern appendages, the genetic toolkit that helps shape limbs in animals as different as insects and mammals.
Several of those genes were active along developing cephalopod arms. Kimbara said the findings suggest that “cephalopod arm development involves conserved patterning genes” also used to build appendages in other animals.
The suckers were a different story. The team had initially expected the same appendage genes to shape both arms and suckers. When they could not find those genes active in developing suckers, they broadened their search and found Ets1 instead. The gene was active where suckers form in both cuttlefish and octopuses.
An embryonic program reused
The researchers also examined how cells behave as suckers form. They observed changes in cell shape and movement that resemble a process called epithelial-mesenchymal transition, or EMT, in which tightly connected sheet-like cells loosen their attachments, change shape and become able to move.
EMT is a fundamental process in early embryos, where it helps cells migrate to form new tissues and organs. It also plays a role in wound healing and, less helpfully, in the spread of cancer. Kimbara noted that because the processes seen in developing suckers resemble those in early embryonic development, the same mechanism may be reused at a later developmental stage.
The researchers suggest that changes in cell shape, cell movement and cell division together build the suckers’ adhesive structure.
Ets1 belongs to a family of transcription factors, proteins that switch other genes on and off. Members of the family are found throughout the animal kingdom, where they influence processes including cell migration, the formation of blood vessels and the development of the immune system. That versatility may help explain how the gene could be recruited for a new role.
Evolution as a tinkerer
The findings fit a broad theme in evolutionary biology. New structures rarely arise from entirely new genes. Instead, evolution tends to work like a tinkerer, taking genes that already exist and switching them on in new places or at new times. This process, known as co-option, has been linked to the origin of features such as butterfly wing eyespots, the shells of turtles and the feathers of birds.
The authors propose that cephalopods evolved suckers in the same way, borrowing an early embryonic gene and the cell behaviors it helps control. They suggest that similar gene reuse may help explain other distinctive cephalopod traits, including chromatophores, the pigment cells that allow rapid color change, the ink sac and the beak, although they stress that more research is needed.
What remains to be tested
The study documents patterns of gene activity rather than testing what the genes do. Showing that Ets1 is active where suckers form does not prove that it is required to build them. The authors say experiments that switch individual genes on or off will be needed to confirm Ets1’s role and to establish how extensively EMT is involved.
Such experiments are challenging in cephalopods, which are difficult to breed in the laboratory and have long been less accessible to genetic tools than animals such as fruit flies, zebrafish or mice. That is changing, as researchers have developed methods for editing genes in squid and are working to establish cephalopods as laboratory models.
Comparisons across more mollusk species will also be needed. The researchers note that different cephalopod lineages may have evolved some of these mechanisms independently. Studying a wider range of species could help show when Ets1 took on its new role and whether the same genetic recipe is used in all cephalopods with suckers.
The work was supported by the Japan Society for the Promotion of Science and Japan’s Ministry of Education, Culture, Sports, Science and Technology. Its authors include Hisanori Kohtsuka, Kohei Oguchi and Daisuke Kurokawa as well as Kimbara and Miura.
The results suggest that one of the animal kingdom’s most versatile tools was built from parts already in the cephalopod genome, assembled in a new way.
Notes
- Kimbara, R., Kohtsuka, H., Oguchi, K., Kurokawa, D., and Miura, T. “Developmental Mechanism and Evolutionary Process of Cephalopod Suckers.” iScience, 2026.
- University of Tokyo. “Why are cephalopods such suckers?” EurekAlert!, 20 October 2026. https://www.eurekalert.org/news-releases/1148205.
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