The world's oceans cover a vast majority of the surface of our planet and are home to the most peculiar creatures. Some of them appear quite extraterrestrial and continue to astonish scientists. For instance, our own hands are approximately as flexible as the tentacles of an octopus, akin to the old branches of a tree, as noted by Science Alert.
In total, an octopus has eight tentacles, or arms, and researchers believe that their anatomy is at least as unique as the animals themselves. In a new study, a team from San Francisco State University focused on uncovering their mysteries and, for the first time in history, aimed to thoroughly map the intricate network of muscles and nerves in octopus arms.
Until now, this task has seemed exceptionally challenging, and our knowledge has been limited to collecting two-dimensional slices and conjecturing about their functions. Now, two studies from the laboratory of evolutionary biologist Robin Crook at San Francisco State University have revealed an unprecedented level of detail regarding the tissues of a creature that many consider to be the closest thing to an alien on Earth.
Previous research has already provided a broad understanding of the interactions between oblique and longitudinal muscles, as well as how hundreds of millions of neurons cluster into groups known as ganglia, granting each arm its own level of control. Essentially, each of an octopus's tentacles can move independently from the others and perform various tasks individually.
Just as the human brain consists of a network of different classes of neurons operating under the influence of a wide array of neurotransmitters, the nervous system of octopus arms must possess a certain level of neurochemical organization, enabling them to move, sense, and think with a degree of autonomy.
In the new study, Crook and his team conducted two separate investigations, which helped them reconstruct the location and classification of nerves in the arms of the dwarf octopus Bock (Octopus bocki).
In the first study, the team performed an experiment using a form of DNA technology to label and identify various types of nerve cells. As a result, they were able to obtain high-resolution images of the cephalopod's arms—utilizing a new state-of-the-art microscope. They successfully reproduced how each class of nerve cells is distributed in three dimensions.
In the second study, the researchers employed electron microscopy to reconstruct the architecture of neurons, muscles, and skin—they were able to recreate how different tissues connect and disconnect.
As a result, the team created an alternative 3D map and discovered astonishing patterns in the octopus's brain cortex, including oblique connections of intramuscular nerve bundles, recurring structures containing nerve ganglia and blood vessels corresponding to the positions of suckers, as well as the location of rare, enlarged nerve cells within cellular layers.
Thus, for the first time in history, scientists have created a complete atlas of octopus anatomy, which will further enable the tracing of the evolutionary path of this cephalopod.