Endowed with great intelligence, octopuses prove to be fascinating creatures in many ways. Recent research has shed light on their “dark side”, involving the tragic dieback of females after mating.

A tragic end

Octopuses are doomed to be orphans from an early age. After laying her eggs, the Female stops feeding and begins to self-harm, ripping off her skin and frantically twisting the tips of her tentacles. When a young octopus hatches from its egg, its mother is already dead. A few months later, his father will also disappear.

The short and sinister life of these cephalopods has long fascinated scientists. In 1944, researchers hypothesized that mating triggered some sort of molecular mechanism ” of self-destruction in these sea creatures. It took almost 80 years, but this vague assumption could finally be confirmed. Researchers recently found that mating alters several critical biochemical pathways involving cholesterol in female octopuses.

” We knew that cholesterol was important from a dietary point of view, but also within different signaling systems in the body “, Explain Z.Yan Wanga molecular biologist at the University of Washington and lead author of the study, published in the journal Current Biology. “ Although it is involved in a wide range of processes, from the flexibility of cell membranes to the production of stress hormones, finding that it also plays a key role in the life cycle of octopuses came as a surprise.. »

In humans, some cholesterol precursors are toxic at high levels. Genetic disorders that increase the metabolism of this lipid can lead to serious developmental and behavioral problems, including repeated self-harm and eating disorders, which can be fatal. If these symptoms are strangely reminiscent of those of female octopuses at the end of their lives, it took years to confirm that similar mechanisms were at the origin.

decades of research

In 1977, researchers discovered that the optic gland played a role in the programmed death of the octopus. Comparable to the pituitary gland in humans, this organ located between the eyes of the cephalopod is linked to sexual development and aging. Experiments carried out on female octopuses at the time showed that its removal allowed these creatures to live for several months after laying their eggs.

Four years ago, the sequencing of theRNA the optic glands of two female octopuses at different stages of decline had made it possible to deepen this research. As one of them approached death, the authors noted increased levels of activity in several genes controlling sex hormones, blood sugar and cholesterol metabolism.

The new study involved the direct analysis of molecules secreted by this organ in fertilized and unfertilized females, suggesting that the optic gland actually produces more sex hormones, such as insulin and cholesterol precursors. While it is probable that the simple accumulation of these molecules in the octopus’ body proves fatal, as is the case in humans, they could also feed the signaling systems triggering the programmed death of cephalopods.

“We have at least three seemingly independent pathways to steroid hormones”

If the optic gland had previously been linked to the production of sex hormones in cephalopods, the other two pathways have only recently been identified in their “ self-destruct sequence “. In the future, Wang and his colleagues hope to look further downstream, to see what other molecules are participating in this ” planned suicide “.

” The fact that females go through this progression of changes where they seem to go crazy just before they die is striking. “, valued Clifton Ragsdaleneurobiologist at theuniversity of chicago and co-author of the study. ” Now we have at least three seemingly independent pathways to steroid hormones that could account for the multiplicity of effects seen in these creatures.. »

” Thanks to this work, we now have evidence that two pathways previously identified in rodents are also present in octopuses. », adds Wang.
” The existence of such similarities between such different animals is truly surprising.. »