Octopuses kill themselves after mating. Maybe we finally know why

(ORDO NEWS) — Octopuses are doomed to orphanhood from a very young age. After the female octopus lays her eggs, she stops eating and begins to self-mutilate, tearing off the skin and biting off the tips of the tentacles.

By the time the young octopus crawls out of the egg, its mother is already dead. A few months later, his father also dies.

The short and dark life of the octopus has long attracted scientists. In 1944, researchers hypothesized that mating somehow pushed a molecular self-destruct button in marine animals.

Almost 80 years have passed, but this vague hypothesis has finally taken shape. Researchers have recently found that mating appears to alter several critical biochemical pathways based on the conversion of cholesterol to various hormones in female octopuses.

“We know that cholesterol is important in terms of diet as well as in various body signaling systems,” explains molecular biologist Z. Yang Wang, who led the study at the University of Chicago.

“It’s involved in everything from the flexibility of cell membranes to the production of stress hormones, but it was a big surprise to me to see it play a role in this life cycle process as well.”

Among humans, some cholesterol precursors are toxic at high levels. Therefore, genetic disorders that increase cholesterol metabolism can lead to serious developmental and behavioral problems, including repetitive self-harm and feeding disorders. Severe cases can even be life-threatening.

These symptoms are oddly reminiscent of a female octopus in its final days, leading the researchers to speculate that the researchers may be up to something.

It took years, and a lot of it has to do with the small and underappreciated organ that octopuses and squid have.

In 1977, researchers figured out that the optic gland somehow plays a role in the programmed death of the octopus.

This organ is similar to the pituitary gland in humans. It is located between the eyes of the octopus and is associated with sexual development and aging in cephalopods. When it is removed from a female octopus, the creature lives for several months after laying its eggs.

In 2018, scientists took advantage of this knowledge and sequenced the RNA of two optic glands from two female octopuses in different stages of extinction.

As the octopus approached death, the authors noticed higher levels of activity in several genes that control sex hormones, insulin-like hormones, and cholesterol metabolism.

Now, a few years later, the same researchers have directly analyzed the molecules secreted by this organ in mating and non-mating females.

It turned out that after mating, the optic gland actually releases more sex hormones, insulin-like hormones, and cholesterol precursors.

All three of these molecules may ultimately contribute to the signaling systems that cause death. Or perhaps just the accumulation of these molecules in the body of an octopus is fatal, as it happens in humans.

If the optic gland was previously associated with the production of sex hormones in cephalopods, then two other ways of “self-destruction” have only recently been identified.

In the future, Wang and her colleagues hope to look further “downstream” to find out what other molecules are involved in this strangely timed death.

“It’s amazing that [octopuses] go through such a progression of change where they seem to go crazy right before they die,” says neuroscientist Clifton Ragsdale of the University of Chicago.

“Maybe it’s two processes, maybe three or four. We now have at least three apparently independent pathways to steroid hormones that could explain the multiplicity of effects that these animals exhibit.”

Wang says she is particularly excited that two of the pathways her team has identified are known from other rodent studies.

“Now our research shows that these pathways are likely present in octopuses as well,” says Wang.

“It was really interesting to see the similarities between such different animals.”

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