An the list of intelligence, cephalopods hold a unique place, almost equal to the great apes, marine mammals and other crows or parrots. We know the ability of octopuses to use their suction cups to open jars from the inside. But, more broadly, the researchers who work on a daily basis on these creatures with small brains but with intelligence distributed in their tentacles describe beings who are clever, skilful, facetious, endowed with a memory and a rare capacity for learning.
This, however, is not their only scientific interest. For nearly forty years, the death of females has confronted researchers with a thick mystery. Around the age of one year, they mate, lay eggs, place their eggs on a cord that they fix to the wall of their stony refuge. Then their ordeal begins. They stop eating, lose their colors, their muscles, their sight. They injure themselves, permanently entangle their arms when they are not self-harming. Finally, they die before the birth of their young.
Threat to the species
The seat of this sad behavior was known: the two so-called “optic” glands, more or less the equivalent of our pituitary gland. Experiments had shown that their removal interrupted this fatal drift. The mothers abandoned their eggs, resumed the hunt, fed and even offered a new reproduction. So why this planned suicide? And by what intermediary?
To the first question, scientists are still guessing. The main hypothesis is that the survivors would cannibalize the eggs of their congeners. This threatens the survival of the species. Coherent, but still to be demonstrated.
As for the second, a study published on May 12 in Current Biology points to a culprit: cholesterol and its synthesis. The team of Z. Yan Wang, assistant professor of biology and psychology at the University of Washington, in Seattle (USA), used mass spectrography to analyze the production of the famous optical glands (which have nothing to do with vision but are located near the eyes) in California two-spotted octopuses. By comparing specimens that had just laid eggs with non-breeding females, she unsurprisingly found in the former an increase in maternal hormones – pregnenolone and progesterone. But she also discovered an intermediate product of bile, and especially 7-dehydrocholesterol (7-DHC), a precursor steroid of cholesterol.
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