Octopuses are the undisputed darlings of the science internet world, and for good reason. They’re incredibly intelligent problem-solvers and devious escape artists with large, complex nervous systems. They have near-magical abilities to change colors, skin textures and shapes instantaneously, and they can regenerate missing arms at will.
But the final days of a female octopus after it reproduces are quite grim, at least to human eyes. Octopuses are semelparous animals, which means they reproduce once and then they die. After a female octopus lays a clutch of eggs, she quits eating and wastes away; by the time the eggs hatch, she dies. In the later stages, some females in captivity even seem to intentionally speed along the death spiral, banging into the sides of the tank, tearing off pieces of skin or eating the tips of their own tentacles. (If you’re wondering, the males don’t get off any easier. Females often kill and eat their mates; if not, they die a few months later, too).
In 1977, Brandeis University psychologist Jerome Wodinsky showed that if he removed the optic gland from female Caribbean two-spot octopuses (Octopus hummelincki), something interesting happened. The optic gland is similar to the pituitary gland of most land animals, so-called because it sits between the eyes. Without them, the female octopuses abandoned their eggs, resumed feeding and some even mated again. At the time, Wodinsky and other cephalopod biologists concluded that the optic gland must secrete some kind of “self-destruct” hormone, but just what it was or how it worked was unclear.
A new study by neurobiologists at the University of Chicago uses modern genetic sequencing tools to describe several distinct molecular signals produced by the optic gland after a female octopus reproduces. The study, published in the Journal of Experimental Biology, also details four separate phases of maternal behavior and links them to these signals, suggesting how the optic gland controls a mother octopus’ demise.
“We're bringing cephalopod research into the 21st century, and what better way to do that than have this unveiling of an organ that has historically fascinated cephalopod biologists for a long, long time,” said Z. Yan Wang, a graduate student in neurobiology at UChicago who led the research study.
“These behaviors are so distinct and so stereotyped when you actually see them. It’s really exciting because it’s the first time we can pinpoint any molecular mechanism to such dramatic behaviors, which to me is the entire purpose of studying neuroscience,” she said.