Nicholas Bellono, one a professor of molecular and cellular biology at Harvard University, worried about his first octopus. “It’s not trivial to have an octopus in the lab,” he said. They are cunning creatures, require specific water conditions and diet, and are prone to complicated escapes. But those worries did not match Bellono’s curiosity. “We just thought, ‘This animal is pretty crazy, so we should study it,’ he said.
The result of that curiosity was an article published at Thursday UMBRELLA in which Bellono’s lab revealed something very interesting about these invertebrates: a unique receptor in the tissues of their suction senses that can taste surfaces by touching them. “Octopus arms are like large tongues probing and touching each other,” says Bellono. As they pass their hands over the surfaces, molecules on that surface bind to the receptors in the aspirator, which send signals to a long axial nerve that runs along the length of the octopus limb.
The new paper also shows that the signal doesn̵7;t need to be transmitted to an animal’s brain to be decoded. Instead, it is processed and operated by nerves located in the arm, independent of the central nervous system of the octopus. The finding further explains how cephalopods perceive and explore their environment and how their limbs function independently of stimuli.
“This is a really interesting finding,” said Charles Derby, professor of neurology and biology at Georgia State University who was not involved in the study. Whenever scientists find a new kind of receptor, that’s a big problem, he says. “Animals are interesting in that they are really plastic, in an evolutionary sense,” he said. This study adds to the big picture of how animals have evolved and adapted to their surroundings over time.
Bellono specializes in studying how animals adapt their sensory systems to exist in specific environments. In just two short years, he brought about 30 species into his lab, including sharks, squid, jellyfish, photosynthetic sea slugs and anemones. He loves entering the animal room and is amazed at each creature’s unique adaptation. And when it comes to octopus, Bellono is particularly concerned with its limbs. This creature will explore surfaces by gliding through objects, and sometimes, when there are specific chemicals, an octopus will change the type of touch it is using, quickly touching the surface. . Previous studies have described this “tactile taste” behavior, but there are no studies of stimuli, cells, receptors or nerve processing involved in this process. So Bellono began to explore what sensory mechanisms could explain this unique behavior and which molecules might be interesting with octopus.
Just defining what taste is and how it works against aquatic organisms can be counterintuitive for terrestrial dwellers. For those of us who are above water, taste occurs when dissolved molecules – chemicals that are dissolved in liquids or fats – come into contact with receptors on the tongue. Insoluble molecules, insoluble and air-permeable, are perceived through olfactory nerve cells in the nose. But in the country it is the opposite. Soluble molecules float easily in a water environment, while insoluble molecules – which will not dissolve – stick to the surface and must be physically touched to be perceived. So for the octopus, Bellono asked, “Is it just based on a detected molecule? Is it agency based? Is it based on distance? “
“In the case of an octopus, it really depends on contact,” he concluded. To find these taste receptors, the researchers started by looking at cells where the octopus was most exposed to objects: its aspirations. The Harvard team was able to identify mechanical receptors that react to induction, but the team was unable to find any chemical receptors that react to chemical signals.