It starts with the egg, where "octopuses lay either tens of thousands of tiny eggs or approximately 100 larger eggs, depending on the species" and the females guard their eggs and then die. The offspring from larger eggs commence life immediately on the shallow areas of ocean floor, but most species have tiny paralarvae that are planktonic, drifting with currents and eating (and mostly being eaten) until they become large enough and find a suitable place to settle.
Octopuses are eclectic eaters, as evidenced by observation, gut contents and middens, but really like crustaceans: "A bite or drill through the joint or skeleton and the injection of venom from the salivary gland result in a quick death for prey. The pygmy octopus can subdue a crab its own size very quickly."
Dens are very important to octopuses. These have "a maximum volume two to three times that of the octopus", with a small opening, and can be found — in crevices, clamshells, shipwrecks, ancient amphorae, and beer bottles — or made by excavating and moving sand and rocks.
When it comes to getting around, octopuses are constrained by their anatomical heritage as well as a trade-off between speed, endurance, maneuverability, and energetics: they "normally move slowly along the bottom by both pulling with the arms and jetting through the funnel", but though not nearly as fast as squid can also use pure jet propulsion. Octopuses are also notable for their decentralized limb coordination and limb regeneration.
Octopuses are "far better camouflage artists than chameleons" in their ability to rapidly change color and texture; as well as background matching, they use disruptive coloration and disguise their eyes as a "bar". This is some use in displays to one another (for mating), but octopuses are color-blind themselves and "fish rather than other octopuses were the designers of the cephalopod skin; octopuses that failed in ability to be invisible got eaten". Other octopus defences include deimatic display (pretending to be bigger, or mimicking something else), jetting water, blowing ink, biting (sometimes with venom), and tentacle detachment.
The evidence for personalities and intelligence in octopuses is mixed and Mather et al. don't overhype things here, instead providing a summary of the experimental results, including the negative ones: "we know a lot of what an octopus can't do". Research into octopus learning has revealed some fascinating details about anatomy and information processing: "When an octopus learns about a situation by getting information with one eye, it stores the data in one side of the brain, and by the next day, has transferred the information to both sides of its brain."
Sex for octopuses is a once-off at the end of their lives: males begin to senesce immediately after mating and females after guarding their eggs. "Even the largest octopus species has a life span of three to four years at most, and for the smallest species it's six months or less."
Octopus concludes with a brief look at "the rest of the group", at the nautilus, squid, cuttlefish, and (deep-ocean) vampire squid. Supplementing the text are thirty-two pages of attractive colour photographs. And a twenty-page appendix offers a guide to keeping octopuses in an aquarium.
There is only a little in The Ocean's Intelligent Invertebrate on anatomy, evolution, and ecology, and some questions are barely touched on: How did molluscs evolve into organisms as active as octopuses? What is unusual about their genomes? How important are they to broader ecosystems? The material that is covered, however, is fascinating, and for anyone curious about animal behavior this is an accessible introduction to a strikingly unusual organism.
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