More Octo-fun

 kw: book reviews, nonfiction, zoology, cephalopods, octopus, octopuses

Almost a year ago I reviewed Soul of an Octopus by Sy Montgomery. She has followed up with a delightful, small book Secrets of the Octopus. Even more than the prior book, this one is replete with amazing pictures of these astounding creatures. The core of Soul is the relationship Dr. Montgomery had with four Giant Pacific Octopus individuals, during the short time (just a few years) that each resided in the aquarium at Monterey Bay. In Secrets we find a number of newer discoveries about octopuses.

At present we know of about 300 species of octopus. The largest is the Giant Pacific Octopus, Enteroctopus dofleini, which can reach twice the size of a man and weigh between 100-250 pounds. The first octopus I saw was one of these, at Marineland of the Pacific, when it was still open. I was about ten years old. The large female was plastered to the glass, and I had to look in from the side to see her mantle (which many people mistake for the head; it is behind the head).

I remember at the time being told that red color for an octopus meant anger, but that is wrong. It means interest or excitement. An angry octopus will instead blacken, particularly when it rises up to intimidate an opponent. The animal in this photo is excited from interacting with the diver. Many species of octopus quickly learn to enjoy human company.

Octopuses are cephalopods, the "brainy" order of mollusks, which also includes squids, cuttlefish, argonauts (which produce lovely, featherweight shells), nautiluses (with coiled, heavier shells), and sepiolids (often called "dumbo octopuses"). All cephalopods have arms, which most people call "tentacles", but to a biologist, the tentacles are the two long, extensible members that shoot out to capture prey, and only have suckers at their ends, the part often called a club. Arms typically have suckers all long their length. Also, all cephalopods have color-shifting skin, and many have skin that can dramatically change shape. Almost any octopus can mimic a rock or patch of seaweed in both color and shape.

The smallest octopus is the Hairy Octopus, which was discovered only a couple of years ago. It is so new a scientific binomial name hasn't been chosen yet. These lovely little critters, only 5 cm long (2 inches, or the size of a large paper clip), exhibit the shape-shifting skill almost all the time, looking mostly like drifting bits of seaweed. Depending on the screen you are using, this picture is probably twice as large as the actual animal.

It was once thought that octopuses are strictly solitary, only meeting to mate or fight or eat one another. This is also out of date. A lot depends on the density or scarcity of food. In abundant circumstances, some (perhaps many) species can be quite social, as seen with a few "octo-cities" such as Octopolis near Australia. While no large settlements of Giant Pacific Octopuses are known, their apparent enjoyment of human association indicates that they also can be quite sociable.

Some octopuses use tools. The Coconut Octopus, Amphioctopus marginatus, is just the right size to fit into a coconut shell. When an individual finds either a coconut shell portion (or two), or a similarly-sized shell of a clam or scallop, it will typically begin to carry it around to use as an impromptu shelter. This is a good strategy for an orange-sized, tasty morsel in an ocean full of predators.

This species is also one that "walks". Holding a shell with up to six arms, it uses two to stride along the ocean floor like a bellhop with a heavy suitcase. This image is two clips from a video of an octopus that wraps six arms around its body while walking on the other two. Starting about 10 seconds into this video, we see another species "stand up and walk away" from the photographer.

This is the video link, in case the one above doesn't work right: https://www.youtube.com/watch?v=kHwUW1inDCs.

These are just a few of the recent learnings about various species of octopus. The last part of the book, "Octoprofiles" by Warren K. Carlyle IV, presents brief descriptions of sixteen cephalopod species to give us a taste of their variety. Reading this book and gazing at the terrific pictures is pure enjoyment.