Coming off some recent books about neuroscience and animal cognition, I found The Soul of an Octopus by nature writer Sy Montgomery in the local library. I thought it fit my reading theme nicely, so I decided to give it a try.Overall, the book is interesting and easy to read. Unlike the books I normally read, the organization is not centered around the scientific themes, but rather towards the author's experience of the wonders of the octopus. The book focuses on the author's visits to the New England Aquarium here in Boston as well as to a few other aquariums around the country (notably the Seattle aquarium, which hosts an octopus blind date on Valentine's Day). She also visits the cephalopod laboratory at Middlebury College, where researchers study octopus cognition using an array of mazes and puzzles.
Octopuses (one thing I learned is that this is the correct form of octopus as it is a Greek derivative, like hippopotamus) are incredibly developed in their cognition. Their nervous system is on par with mammals like dogs in terms of the numbers of neurons. This complexity makes them expert problem solvers – they can use tools to help them catch prey and they can figure out how to remove food from puzzle boxes. They are natural escape artists, which makes it difficult for aquarium staff to keep them caged. YouTube has lots of examples of daring octopus escapes.
Perhaps the most amazing thing I learned was about octopus ink, which is a complex mixture of molecules. Of course, the list includes melanin, which gives ink its characteristic color; it also contains molecules like tyrosinase, which can irritate the eyes and gills of the surrounding sea life. More surprisingly, tyrosinase has been reported to have effects on oxytocin and vasopressin levels, suggesting that octopus ink could calm the squirted prey. Ink also includes dopamine, a neurotransmitter often called the reward hormone. These features of ink suggest that ink isn't just for defensive purposes, but it may also be used to help them capture prey. This has been observed in some species of squid, but not in octopus.
The book spurred me to look into recent publications on cephalopod neural complexity. One notable paper in Cell shows that cephalopods like the octopus have an unusually high rate of RNA editing. The process is unique to the branch of cephalopods called the coleoids, which are behaviorally complex (some might label them as "smart"). In addition, the sites of genome editing occur most frequently in genes associated with the nervous system. These correlations suggest that the ability to edit their genome is what gives them their complexity. Surprisingly, these changes at the RNA level can be inherited. Of course, this ability has its price. While these cephalopods have greater plasticity of the proteins made by RNA, they have a decreased mutation rate in the protein coding regions of DNA, which is the more traditional fodder for evolutionary variation. For more information on this surprising ability, check out the coverage in The Atlantic and New Scientist.
These stories left me wondering what other sorts of mysteries can be found in the octopus, an organism that is often compared to an alien due to its ability to camouflage rapidly, its knack for squeezing into tight spaces, its unusual defense mechanisms, and its uncanny problem solving. I will be heading soon to the New England aquarium to catch a glimpse of one of the octopuses that the author describes and will keep an eye out for more primary research that explains the mysteries of this amazing creature.
