We know that octopuses have awesome visual systems and super-sensitive suckers. We have even learned that they can hear. But little scientific attention has been paid to their sense of smell. And new research suggests that the octopus's olfactory system could play a strong role in the octopus's life cycle—especially when it comes to mating.
"They possess a well developed olfactory organ, but to date almost nothing is known" about how it works, write the authors of a new review paper on the topic, published online earlier this month in General and Comparative Endocrinology.
Like us on land, octopuses detect "smell" via floating molecules—only theirs happen to be in a saltwater solution. Aquatic mollusks, including the octopus, have similar olfactory structures and pathways to their land-dwelling cousins, which suggests the system has important evolutionary roots.
Octopuses, however, don't exactly have noses—at least as you and I do. So how do they pick up on smells? Scientists have found chemical receptors in small "dimples" on the mantel that can detect scents from distant sources. (Their suckers, on the other hand, are equipped with chemical sensors that can "taste" compounds from objects they come into contact with. And these flexible tasters come in handy: "Octopods use the arms to explore and detect tactile and chemosensory information functioning as 'natural biosensors,'" write the authors of the paper.)
For most of its short life, an octopus focuses on getting food—and turning that food into body mass. Only in the last months (or in some cases possibly weeks or years), does an octopus's interest turn to love—or reproduction, at least. Recent research suggests that somehow the olfactory organs are partly responsible in this switch from growing to reproduction. As it happens, the olfactory lobe in the octopus's central nervous system is located near the optic gland, which as been implicated in sexual maturation—as well as the strange but inevitable phenomenon of post-reproduction rapid senescence. Cutting the optic nerves, for example, can spur a female into sexual maturation, which the researchers note, makes sense given that "in the wild, this kind of effect could be related to the life history of O. vulgaris [common octopus] females, which leave shallow and brighter waters for deeper and darker waters for spawning." The researchers found three telling peptides linked to the balance of metabolism and reproduction in this area of the nervous system.
It is also possible, the researchers suggest, that as a female transitions from growth to a reproductive phase of life, this center of the brain could tune her sense of smell away from food (which she will not eat much or any of after laying her eggs) to that of sexual partners.
But just what an eligible octopus smells like is still a mystery of science.
Learn more about the strange world of the octopus at two upcoming events: Books & Brews on October 25, and Nerd Nite on October 30. And if you can't make it, check out Octopus! The Most Mysterious Creature In the Sea.
Illustration courtesy of Ivan Phillipsen