Tobias Schwarz via Reuters
BIODIVERSITY – After laying her eggs, the female octopus stops feeding and begins to self-harm, ripping off her skin and biting off the tips of her tentacles. The male will kill himself a few months later. This behavior of octopuses has until now been enigmatic to science. Researchers have just found the explanation and publish their results this Thursday, May 12 in the journal Current Biology.
In the animal kingdom, the bigger your brain, the longer you live. “Yet, unlike other large-brained animals, cephalopods have exceptionally short lifespans,” the study authors write. Octopuses generally do not live for more than a year. To understand this paradox, scientists looked closely at the octopus’ optic glands, the organ that controls lifespan and reproduction.
It was in 1977 that researchers understood that the optic gland was at the origin of the “programmed” death of the octopus, explains the media sciencealert. This organ is similar to the pituitary gland in humans. When removed from a female octopus, the creature lives for several months after laying its eggs.
Today, researchers know much more about this organ. They find that at least three pathways of the optic gland are mobilized after mating. One secretes hormones known to stimulate reproduction. The other two produce active ingredients, “dehydrocholesterol and bile acid intermediates”, whose involvement in the reproductive strategy was unknown before this study.
Thanks to this breakthrough, researchers can now name the reproductive behavior of the octopus: the “semelparity”. In short, this means that the animal can reproduce and give birth only once in its life.
A slow decomposition
“Semelparity” is more often attributed to plants, such as cereals and vegetables, which have a limited lifespan. Some also call this reproductive strategy “Big Bang” because it is prolific (octopuses lay more than 50,000 eggs on average) and fatal.
This death “programmed” by nature is a slow decomposition. The purple dress of the octopus mom takes on dull colors to become white. Over the months, the female shrivels and decomposes. A spectacular transformation due to the fact that she feeds her eggs with her own reserves.
Researchers now hope to study the other molecules involved in this slow agony and explain other sexual attitudes of the animal. “What is striking is that octopuses (…) seem to go crazy just before they die,” says neurobiologist Clifton Ragsdale from the University of Chicago. The extremely complex reproductive behavior of the octopus still harbors many mysteries.
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