The source of this bizarre maternal behavior seems to be the optic gland, an organ similar to the pituitary gland in mammals. For years, just how this gland triggered the gruesome death spiral was unclear, but a new study by researchers from the University of Chicago, the University of Washington, and the University of Illinois Chicago (UIC) shows that the optic gland in maternal octopuses undergoes a massive shift in cholesterol metabolism, resulting in dramatic changes in the steroid hormones produced. Alterations in cholesterol metabolism in other animals, including humans, can have serious consequences on longevity and behavior, and the study's authors believe this reveals important similarities in the functions of these steroids across the animal kingdom, in soft-bodied cephalopods and vertebrates alike.

"We know cholesterol is important from a dietary perspective, and within different signaling systems in the body too," said Z. Yan Wang, Ph.D., Assistant Professor of Psychology and Biology at the University of Washington and lead author of the study. "It's involved in everything from the flexibility of cell membranes to production of stress hormones, but it was a big surprise to see it play a part in this life cycle process as well."

Self-destruct hormones

In 1977, Brandeis University psychologist Jerome Wodinsky showed that if he removed the optic gland from Caribbean two-spot octopus (Octopus hummelincki) mothers, they abandoned their clutch of eggs, resumed feeding, and lived for months longer. At the time, cephalopod biologists concluded that the optic gland must secrete some kind of "self-destruct" hormone, but just what it was and how it worked was unclear.