Many animal species die after breeding. But in octopus mothers, this decline is particularly alarming: in most species, as the octopus’s mother eggs approach their final stage, she stops eating.
She then leaves her protective covering over her offspring and leads to self-destruction. He can hit a rock, tear his skin, or even eat pieces of his own tentacles.
Now, researchers have discovered the chemicals that seem to control this fatal rage. After the octopus lays eggs, it undergoes changes in the production and use of cholesterol in its body, which in turn increases its production of steroid hormones – a biochemical change that will doom it to ruin. “Some of the changes may indicate processes that explain the longevity of invertebrates in general.” Ian Wang, assistant professor of psychology and biology at the University of Washington.
“Now that we have these pathways, we are really interested in relating them to individual behaviors, and even to individual differences in how animals express these behaviors,” Wang said.
Programmed to die
Even as an undergraduate student in English, Wang was intrigued by female reproduction, she said. When she switched to a postgraduate degree in science, she retained that interest and was impressed by the dramatic death of octopus mothers after laying eggs. No one knows the purpose of the behavior. Theories include the idea that dramatic depictions of death distract predators from the eggs or that the mother’s body releases nutrients into the water nourished by the eggs. Most likely, says Wang, dying protects babies of the older generation. Octopuses are cannibals, she says, and if older octopuses turn around, they can eat all the cubs.
Wang and her colleagues analyzed the chemicals produced in the optic glands of California colon octopuses (Octopus bimaculoides) after they laid eggs. In 2018, genetic analysis of the same species showed that after laying eggs, genes in the optic glands that produce steroid hormones (which are partly made up of cholesterol components) began to exceed normal amounts. With that study as a guide, the scientists focused on steroids and related chemicals produced by the optic glands in colon octopuses.