Octopuses have marveled humans for as long as they’ve co-existed. From the Scandinavian Kraken legends to less-threatening shows like Netflix’s My Octopus Teacher, these mysterious, odd-looking creatures are vastly unexplored. A team of Harvard scientists decided to delve deeper and try to understand how the tentacles, and the suction cups on them, in particular, do their work. How do they recognize what is food and what is not? After a series of biomechanics experiments, they finally have some answers.
How Do Octopuses’ Tentacles Work on a Molecular Level?
That was the question that Nicholas Bellono, an assistant professor of cellular and molecular biology, wanted to find out together with his fellow scientists. What their research found was that the suction cups on the octopus’ tentacles have adapted to respond to and detect molecules that are insoluble in water. Bellono and his colleagues discovered a novel family of sensors, called chemotactile receptors, located in the first layer of cells inside the suction cups.
To identify these sensors and test their responsiveness, researchers isolated and cloned the detection cells in the suction cups. Then, they inserted the cloned cells into frog eggs as well as in human cell lines to study how these detection cells would function in isolation. Since these receptors don’t exist in frog or human cells, they acted like closed vessels and allowed biologists to study them.
The researchers exposed the detection cells to molecules that octopuses are known to react to. Some of these were water-soluble, and others weren’t. Surprisingly, the receptors were only activated when exposed to the items with poorly soluble molecules. To conclude the experiment, Bellono and his team went back to the octopuses in their lab and tested them for the same extracts that caused the cloned cells to respond. The only odorants the octopuses’ receptors responded to were identical to those of the cloned cells.
While the study does answer how tentacles and their suction cups “sift through” prey and non-prey items on a molecular level, scientists believe that more research is necessary to uncover the other natural compounds that stimulate octopuses’ receptors and their behaviors.