A new paper in Biology and evolution of the genome indicates that a type of octopus appears to have evolved independently to develop something resembling a shell, although it has lost the genetic code that produced true shells in its ancestors and relatives.
Argonauta argo is a species of octopus that lives in tropical and subtropical high seas. Female argonauts have a protective, spiral-shaped shell-like egg case, which protects the eggs inside. Researchers have long wondered about the origin of this egg crate. It looks a lot like the shell of the commonly known pearly nautilus (the very distant relative of the argonaut), which has a real hard shell and lives on the ocean floor, but that may just be a coincidence.
While the argonaut egg shell and the nautilus shell are formed by the secretion of proteins, they would have formed differently and would look different at the microscopic level. Did the egg shell evolve from the shell or did it develop independently?
By sequencing the species’ draft genome, a team of Japanese researchers, led by Masa-aki Yoshida and Davin Setiamarga, attempted to reveal the genomic background of the argonauts and show how the species adapted to the open ocean and acquired its shell-like shape. egg cases. Scientists had previously avoided targeting argonauts because it was difficult to keep the animals in aquariums for research purposes. The authors here, however, had access to a location in the Sea of Japan that was ideal for acquiring fresh samples.
The new genome data discovered here provides insight into several features related to shell evolution and egg case formation. The researchers found the genes coding for eggshell proteins in argonauts and found that most of these genes were not used to form shells in distant species, including the nautilus. This suggests that while the distant ancestors of the Argonaut octopuses probably had shells, the shells did not evolve into egg cases.
“The argonaut genome is particularly intriguing because it shows that the syntenic breakdown reported in the known octopus genome is not a general trait of this group,” Yoshida and Setiamarga said. “We have demonstrated that contrary to popular belief, cephalopods do not necessarily exhibit distinct genome evolution. We anticipate that our findings will advance research on the genome evolution of metazoans, molluscs, and cephalopods, which has remained largely unexplored until now.”
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Masa-aki Yoshida et al, gene recruitments and releases in the argonaut genome provide insight into pelagic lifestyle adaptation and reacquisition of shell-like eggs, Biology and evolution of the genome (2022). DOI: 10.1093/evac/evac140
Provided by Oxford University Press
Quote: New research shows how octopuses may have evolved (2022, October 26) Retrieved October 27, 2022 from https://phys.org/news/2022-10-octopuses-evolved.html
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