A seafaring octopus, long after its ancestors had deleted their genetic code to make a hard shell, has rediscovered a recipe for making one.
Recent genetic analysis of the papernautilus (or greater argonaut) has been done.Argonauta argo() has discovered a surprising origin of the protective casing that it uses, and it doesn’t even resemble its closest relatives.
Cephalopods have gotten rid of their outer shells and are now able to wear them on the outside, just like sensible snails. Many shells, including those of squid and octopus, have been lost completely or are only left with vestigial fragments.
Other species include cuttlefish, ram’s-horn squid and the cuttlefishSpirula spirula), wear their shells on the inside. The ram’shorn squid was an Spiral shell with internal chambers It acts as a skeleton. It’s buoyant and surprisingly strong.Many times, they are washed up at beaches.
The nautilus is a rare exception in cephalopods.Nautilus belauensis), which still has an external shell – complete with air chambers that it uses to regulate its buoyancy as it floats through the open oceans. Its shell and the shells of its extinct cephalopod ancestors are made of proteins that contain minerals like aragonite or calcite in complex microscopic structures.
These protective structures are believed to have been present in all modern cephalopods, which originated during the Ordovician Period, approximately 440 million years ago.
Although it is commonly called paper nautili argonautsActually, they are a genus octopus. This unusual group is made up of only females, who produce a protective spiral case by secreting calciumifying proteins from the arms. The shells of the Argonauts look almost identical to a nautilus shell, but they have a completely distinct microscopic structure.
Argonauts don’t attach to their mantle; instead, they grip onto their shell homes using several of their arms.
Researchers have been attempting to figure out how or why one group of octopuses was able to reclaim a shell, since most lost their outer casings many years ago.
Masaaki Yoshida, a Shimane University marine biologist, sequenced DNA of the Japanese species with a team made up of researchers from Japan. Argonauta argo. They compared the genomes of the argonauts to those of other mollusks such as the California two-spot Octopus (Octopus bimaculoides) and the nautilus.
“Consistently with previous results, most proteins don’t appear to be shared with the shell matrix protein of [cephalopods and relatives]”The team, including Nautilus’s,” They write in their paper.
However, some of the genes and proteins that they produce have been found in shelled mollusks such as the limpet.Lottia gigantea) and Japanese pearl oyster (Pinctada fucata). Other sequences were found in shell-less octopuses – suggesting the argonaut cobbled together their protective casing using proteins unrelated to ancestral shell formation.
Unlike other octopuses, argonauts aren’t benthic – they don’t live near the sea floor or other structures. They have taken up the lifestyle of drifters, living in the open tropical and subtropical seas all their lives. The nautilus shares this same lifestyle.
Yoshida, Yoshida, and their team explain that argonauts had to use techniques to enable floating. Their shells lack the more complex internal structure of air chambers that make up the nautilus, It can still trap air..
The shell is also believed to be the argonaut’s egg case. This would explain why only females can develop them. The shell protects the females from the elements, so they can brood eggs.
Argonauts seem to have completely redesigned the shell to help it transition from substrate dweller into water drifter. This is a remarkable example. convergent evolution.
This research was published in Genome Biology & Evolution.
