Scientists astounded after finding out why female octopuses self-destruct after laying eggs

Nature is full of strange and fascinating adaptations, many of which humans still struggle to understand. Take octopuses, for example: these marine creatures have a unique and almost dramatic way of surviving. They can throw ink or debris to ward off threats, and each of their arms can operate independently. But one of the most puzzling behaviors is how female octopuses self-destruct after reproducing. In June 2022, scientists finally uncovered the reason for this gruesome process, with their findings published in Current Biology.

Female octopuses are destined to leave their young as orphans soon after birth. Once they lay their eggs, they enter a phase of self-neglect—refusing to eat and even mutilating themselves, sometimes tearing at their own skin or biting off the tips of their tentacles. Tragically, by the time their offspring hatch, the mother is gone. A few months later, the father suffers a similar fate. This grim and mysterious lifecycle has intrigued scientists for years. Back in 1944, researchers hypothesized that mating triggers a molecular "self-destruct" mechanism, but solid evidence of this wasn't found until recently.

A research team led by Z. Yan Wang, a professor of psychology and biology at the University of Washington, finally found a plausible reason. Their study detected changes in various biochemical pathways related to cholesterol metabolism and hormone production in female octopuses after mating, per Science Alert. "We know cholesterol is important from a dietary perspective, and within different signaling systems in the body too. It's involved in everything from the flexibility of cell membranes to the production of stress hormones, but it was a big surprise to see it play a part in this life cycle process as well," Dr. Wang told EurekAlert. They found that higher levels of cholesterol precursors might lead to behavioral impacts like self-injury and ceasing to eat, even in humans. 

The same has happened with these cephalopods. In 1977, one study attributed these predestined octopus deaths to the presence of an optic gland that functions similarly to the human pituitary gland, reported Science. Located between the eyes, the optic gland is involved in sexual maturation and aging. In a remarkable discovery, when it is removed from a female octopus, she can live several months longer after laying her eggs. Now, years later, Wang and her team analyzed the direct investigations of the molecules secreted by the optic gland in both mated and unmated females. Their findings revealed that after mating, the optic gland indeed releases elevated levels of sex hormones, insulin-like hormones and cholesterol precursors that lead to self-mutilation in female octopuses after laying eggs.

Looking forward, Wang and her colleagues plan to delve deeper into the biochemical processes involved so that additional molecules responsible for the cephalopods' programmed death can be found. "What's striking is that [octopuses] go through this progression of changes where they seem to go crazy right before they die," Clifton Ragsdale, a neurobiologist from the University of Chicago and a part of the research team, told the media channel. "The important parallel here is that what we see in humans, as well as in octopuses, is that high levels of 7-DHC are associated with lethality and toxicity. And that, to me, is really interesting, just because of how evolutionarily divergent these two animals are," Dr. Wang told New Scientist.