This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Cephalopods, like the octopus, have specialized arms and suckers, but how these structures evolved from the simple bodies of their mollusk ancestors remains a mystery. Researchers from the University of Tokyo compared gene activity during embryonic development of cuttlefish, octopus and snail body parts.
They found that several genes associated with appendage patterning showed expression along developing cephalopod arms, but no comparable patterns in developing suckers. Developing suckers instead expressed Ets1, a gene associated with early embryonic development in mollusks. The findings suggest cephalopods evolved suckers by reusing existing genes in new ways.
Squids, octopuses, cuttlefish and enigmatic nautiluses are creatures that intrigue anyone with an affinity for sea life. They have many distinctive features, including long prehensile arms with suckers for gripping prey. That they share a common ancestor with gastropods such as slugs and snails can be surprising to some, given how the former are famed for their intelligence and complex behavior, while the latter are not.
But this raises the question: How did cephalopods' complex arms with functional suckers evolve from the simple foot of a mollusk ancestor? The work is published in the journal iScience. "Our findings suggest that cephalopod arm development involves conserved patterning genes also used in appendage development in other animals like insects and mammals.
But suckers on their arms have a unique developmental mechanism in which a gene used in early embryogenesis, Ets1, is reused," said postdoctoral fellow Ryosuke Kimbara. "At first, we hypothesized that appendage patterning genes would be involved both in arm and sucker patterning. But we ran into a challenge in identifying the genes expressed in suckers.
Therefore, we switched to a more comprehensive method and continued screening until we found a gene with a distinctive expression pattern in developing suckers, and it wasn't where we expected to find it." While looking at potential genetic explanations for sucker development, one gene, Ets1, which is normally involved in early developmental processes in mollusks, stood out. The researchers found Ets1 activity in the region where suckers form in cuttlefish and octopus. They also noticed changes in cell shapes and the way cells moved as suckers developed, processes that resemble those during a developmental process called epithelial-mesenchymal transition, or EMT.
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