Exactly why octopus mothers engage in a form of self-harm that leads to death soon after breeding remains a mystery. However A study published Thursday in the journal Current Biology He uses the California two-spot octopus as a model to help explain the physiology of this strange behavior.
Z. Yan Wang, assistant professor of psychology and biology at the University of Washington and author of the study, explained that the female of the species goes through three reproductive stages.
After mating, the mother produces and carefully handles her eggs. She takes each egg one by one and carefully arranges them in long tufts. He then sticks them to the wall of his lair and stays there, blowing water over the eggs to oxygenate them and fiercely protect them from predators.
But then he stops eating. He begins to spend a lot of time away from the eggs. Loses color and muscle tone; eyes are damaged. Many mothers begin to injure themselves. Some injure their skin by rubbing against the pebbles of the seafloor; others use their suckers to create lesions throughout their bodies. In some cases, they even eat their own arms.
Scientists have known for some time that reproductive behavior in octopus, including death, is controlled by the animal’s two optic glands, which function like the pituitary in vertebrates, secreting hormones and other products that control various bodily processes. (The glands are called “optics” because of their location between the animal’s eyes. It has nothing to do with vision.) If both glands are surgically removed, the female will abandon her young, begin to eat again, grow, and extend her lifespan. .
The new study explains the specific chemical pathways produced by the optic glands that govern this reproductive behavior.
One route they found produces pregnenolone and progesterone, unsurprisingly because these substances are produced by many other animals to support reproduction.
Another produces precursors of bile acids that promote the absorption of dietary fats, and a third makes 7-dehydrocholesterol or 7-DHC. 7-DHC is also produced in many vertebrates. In humans, it has several functions, including essential roles in the production of cholesterol and vitamin D. But high levels of 7-DHC are toxic and have been linked to disorders such as Smith-Lemli-Opitz syndrome, a rare inherited disease. severe intellectual, developmental, and behavioral problems. In octopuses, Dr. Wang and colleagues suspect that 7-DHC may be the key factor in triggering the self-harming behavior that leads to death.
“This is an elegant and original study that addresses a longstanding question in reproduction and programmed death,” said Roger T. Hanlon, a senior scientist at the Marine Biology Laboratory in Woods Hole, Massachusetts, who was not involved in the study. most octopuses.”
Dr. “What was most exciting for us was seeing this parallel between octopuses, other invertebrates, and even humans,” Wang said. He added that it is remarkable to see this common use of the same molecules in animals far apart.
The molecules may be the same, he said, but death is very different. We often view human death as a failure of organ systems or function.
“But in an octopus that’s not true,” said Dr. wang. “The system needs to do that.”