The octopus: alternative evolution toward learning and intellect?

Common octopus by Albert Kok

The evolutionary drive toward complexity and specific organizational neuronal complexity is highly evident during evolution. Octopuses, which have independently evolved camera-type eyes (with a lens, iris, and retina), a highly derived early embryogenesis, closed circulatory systems, and large brains, are an excellent example of parallel evolution. The recently sequenced octopus genome shows a spectacular example of the evolutionary drive toward greater complexity. The octopus probably achieved the limit of intellectual, organizational complexity that is possible in a non-vertebrate animal. They are among the very few animals that are known to master tool use. Octopuses display extraordinarily sophisticated behaviors, including complex problem solving, task-dependent conditional discrimination, observational learning, and spectacular camouflage displays. Its dexterous arms are lined with hundreds of suckers that function as specialized tactile and chemosensory organs. They have elaborate special pigments containing a cell system that enables rapid changes in appearance. Vastly modified in size and organization relative to other mollusks, the octopus nervous system is diffuse, with only one-third of it is located inside the actual brain. Axial nerve cords in each arm function with some functional autonomy. Altogether in these structures, nearly half a billion neurons, more than six times the number of a mouse brain, are contained.

In early 2012 dozens of researchers uncovered the octopus sequence, the largest-known genome in the invertebrate world. Since the octopus has more genes (33 000) than humans (20,000 to 25,000), the work has been challenging. The collaboration of scientists has paid off, as the octopus genome was recently published in the journal Nature. The octopus's radically different evolutionary path to intelligence from vertebrates is an amazing puzzle and has huge evolutionary importance. In octopuses, a sophisticated neuronal wiring system forms throughout their entire bodies, allowing fast and intricate camouflage by expanding and contracting pigment-filled sacks within milliseconds. This regulation can change overall color and even pattern in a blink of an eye. This complex neuronal network also empowers the octopus complex sensing with its suckers. Genes, known to be involved in developing complex neural networks in mammals, are shared with the octopus. RNA editing is a molecular process through which some cells can make discrete changes to specific nucleotide sequences within an RNA. Shared with humans and other animals, octopuses' mastery of this molecular process might help them regulate highly organized, concerted nerve firings. The new genetic analysis also shows the genes' ability to move around on the genome, which might boost learning and memory. Gene duplication, a well-known evolutionary step invertebrate, seems to be missing in octopuses, making their intellectual and organizational complexity all the more remarkable. The neuronal organization of the octopus might provide a blueprint for new designs in robotics. 

The octopus arms can avoid the light even when the octopus could not see it with its eyes. Even when the octopuses reached an arm out of a small opening on an opaque, covered aquarium for food, the arm would quickly retract when the light was shined on it. However, it is still a mystery how an octopus’s arms can detect light, let alone respond to it.

The octopus genome demonstrates the power of evolution to enhance complexity in the living world. Although they display impressive learning ability and some purposeful behavior, octopuses do not form emotions, which is the basis of the intellectual abilities of mammals and birds. However, this does not mean that they are not engaged in some of the funniest purposeful behavior: Judge for yourself!

Copyright © 2017 by Eva Deli