Many animals die after they reproduce. But in octopus mothers, this decline is particularly alarming: In most species, when an octopus mother’s egg nears hatching, it stops eating. Then she left the crowd to protect her mother and become self-destructive. She can smash herself into rocks, rip her own skin, even eat pieces of her arm.
Now, researchers have discovered chemicals that can control this deadly frenzy. After an octopus lays eggs, she undergoes changes in the production and use of cholesterol in her body, thereby increasing the production of steroid hormones – a biochemical change that will destroy her. Z. Yan Wang, associate professor of psychology and bibliography at the University of Washington.
“Now that we have these pathways, we really want to link them to individual behaviors or even individual differences in the way animals exhibit these behaviors,” Wang told Live Science. this vi.
Programming to die
Even as a university student majoring in English, Wang was intrigued by female fertility, she said. When she transferred to graduate school of science, she kept that interest and was moved by the tragic deaths of octopus mothers after they laid eggs. No one knows the purpose of the behavior. Theories include the idea that the dramatic death screen pulls predators away from the eggs, or that the mother’s body secretes nutrients into the water to nourish the eggs. Most likely, Wang said, death protects children from the old generation. Octopuses are carnivores, she said, and if old octopuses get stuck around, they could end up eating each other’s young.
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A 1977 study by psychologist Jerome Wodinsky of Brandeis University found the mechanism behind this self-destruction lies in the visual glands, a set of glands near the octopus’s eyes roughly equivalent to the glands. peace in humans. Wodinsky found that if the nerves to the optic gland were cut, the mother octopus would give up her eggs, start eating again, and live another four to six months. That’s an impressive lifespan extension for creatures that live only about a year.
But no one knows what the visual glands do to control this cascade of self-injury.
“From the very beginning, I really wanted to do the experiments that we outlined in the paper that we just published, which basically squeeze the optic gland and then identify the components of the optic gland,” says Wang. that juice.
Wang and her colleagues analyzed chemotaxis produced in the visual glands of the California two-spotted octopus (Octopus bimaculoides) after they lay eggs. In 2018, a genetic analysis of the same species showed that after laying eggs, the genes in the visual glands that produce steroid hormones (in part built with cholesterol components) begin to overgrow. level. With that study as a guide, the scientists focused on steroids and related chemicals produced by the visual glands in two-spotted octopuses.
They found three distinct chemical changes that occur around the time the mother octopus lays her eggs. The first is an increase in pregnenolone and progesterone, two hormones involved in reproduction in many organisms (in humans, progesterone is increased in Ovulation and while early pregnancy). The second case is more surprising. The mother octopuses began to make higher levels of a cholesterol block called 7-dehydrocholesterol, or 7-DHC. Man-made 7-DHC in the manufacturing process cholesterol same, but they don’t keep anything in their system for long; compounds are toxic. In fact, babies born with the genetic disorder Smith-Lemli-Opitz cannot get rid of 7-DHC. The result is intellectual disability, behavioral problems including self-harm and physical abnormalities such as extra fingers and toes, and cleft palate.
Eventually, the visual glands also begin to produce more components for bile acids, which are acids made by the liver in humans and other animals. Octopuses don’t have the same bile acids as mammals, but they do seem to make the building blocks for those bile acids.
“It shows that it is a whole new class of signaling molecules in octopuses,” said Wang.
The bile acid composition is intriguing, says Wang, because a similar set of acids has been shown to control the lifespan of worms. Caenorhabditis elegans, is commonly used in scientific research because of its simplicity. It is possible that bile acid compositions are important for controlling the lifespan of invertebrates, says Wang.
Octopuses are difficult to study in captivity because they require a lot of space and perfect conditions for them to mature and reproduce. Wang and other octopus researchers have now found a way to keep the striped octopus species less likely in the Pacific (Chierchiae octopus) live and reproduce in the laboratory. Unlike most other species of octopus, the Pacific striped octopus can mate multiple times and incubate many eggs. They do not self-destruct as their eggs prepare to hatch, making them perfect specimens for studying the origins of disease behavior.
“I was really excited to study the dynamics of the visual gland in that species,” says Wang.
The researchers published their findings on May 12 in the journal Current Biology.
Originally published on Live Science.
https://www.livescience.com/why-octopus-moms-self-destruct Octopuses torture and eat themselves after mating. Science finally knows why.