It’s a matter of hormones
After giving birth, some female octopuses enter a self-destructive spiral that culminates in their death and the disappearance of their offspring before they hatch. From birth, their young are effectively destined to be orphans. Pregnancy triggers a hormonal shift that affects the eyes, driving dramatic changes in steroids, altering appetite and behavior, and sometimes leading to death.
Scientists have studied these cephalopods for years, puzzled by how an intelligent animal could erase itself in such a way. In captivity, that self-destruction can be seen more clearly, with females banging against tank walls and twisting their long tentacles to bring about their own demise long before their offspring reach safety.
This sequence appears to originate in the optic glands of these animals. A recent study confirmed that this gland, akin to a pituitary in humans but located in the eye region, undergoes a sudden hormonal shift during reproduction. The result is a cascade that includes changes in progesterone, cholestanoids, and 7-dehydrocholesterol, a cholesterol precursor, all linked to the animal’s lifecycle.
Biologists describe the glands as remarkable for their influence on behavior. The research highlights the importance of cholesterol in dietary and signaling systems and notes the surprising role it plays in vertebrate-like hormonal processes as well as in cephalopod biology. This finding underscores how a simple gland near the eyes can drive a complex and fatal reproductive program.
Early observations suggested that removing the optic gland extended the female octopus’s lifespan after giving birth. This spurred researchers to investigate the chemical milieu within the eyes of octopuses. The investigations used modern analytical techniques to examine the biochemical changes in Octopus bimaculoides, a two-spotted species in California, particularly after reproduction. Mass spectrometry helped reveal the composition of these biological samples and their relationship to the observed behaviors.
What happens to the hormones
Researchers identified three distinct hormonal pathways that rise during reproduction. The first pathway produces pregnenolone and progesterone, hormones commonly linked with pregnancy. The second pathway generates maternal cholestanoids, intermediate components of bile acids. The third pathway elevates levels of 7-dehydrocholesterol, a cholesterol precursor. When the cycle progresses, the octopus appears to move toward the end of life with striking behavioral changes and eventual death. Experts note that this pattern is part of a programmed sequence rather than a random occurrence.
The optic glands responsible for this behavior hold a key to understanding cephalopod reproduction, offering insight into how different species evolve strategies for survival and reproduction. Future studies will compare this process in species such as the lesser Pacific striped octopus, which does not self-destruct after spawning, to uncover clues that might prevent such tragic outcomes in other animals.
As researchers point out, the optic gland is present across soft-bodied cephalopods, suggesting a shared mechanism underlying diverse reproductive strategies. The gland’s influence on both female and male behaviors highlights an intricate endocrine system that can steer life history in surprising directions.
These findings contribute to a broader picture of how hormones shape life cycles in cephalopods and beyond, inviting continued exploration into the links between eye-associated glands and reproductive timing.
Reference work: Science (doi: 10.1126/science.198.4320.948).
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