The Amazing Octopus

Living close to the ocean, we coastal Georgians have an array of neighbors the rest of the state does not. Arguably one of our most fascinating neighbors is the octopus. Octopuses (no, it’s not octopi) are found in all the world’s oceans and are especially abundant in warm, tropical waters. They are solitary animals that live alone in dens that they build of rocks. Octopuses, along with squid and cuttlefish, are a class of marine mollusks called cephalopods which means “head foot” in Greek.

There are roughly 300 species of octopuses that are currently known to science, but new species are still being discovered. Some species are deep sea dwellers while others live around coral reefs. Octopus sizes range from less than an inch to 20 feet measured arm tip to arm tip. Octopuses can weigh up to 100lbs and live 1-3 years. Octopus bodies are around 90% muscle and have eight equally long arms that are used to “walk.” Their arms are covered with suction cups which they use to both touch and taste. These interesting critters can lose an arm and regrow it with no permanent damage (even more interesting when you understand the intelligence of their arms, but more on that in a minute). An octopus’ body is on top of their head with their mouth on the underside in the center of their arms. They have three hearts – two to pump blood through their gills (to receive oxygen) and one to move oxygenated blood throughout the body. Octopuses have blue blood that is copper based unlike our iron based red blood. Copper based blood is more efficient at transporting oxygen at low temperatures and in low oxygen conditions. Interestingly, when the octopus dies and the blood becomes deoxygenated, it becomes clear.

Octopuses have a beaklike jaw and venomous saliva. They can get their bodies through any hole that their beak will fit through. This bird-like beak is used to inject venom, but also to penetrate hard-shelled prey. Their prey includes crabs, shrimps, lobsters, and occasionally larger items like sharks. Octopuses are ambush predators usually dropping down on their prey from above, using the suction on their arms to pull prey into their mouth. They may also use their ink to disorient prey before attacking. My favorite prey strategy they use is the old tap the wrong shoulder trick. They’ll sneak up on prey, reach an arm around and tap the far side of the animal causing it to jet away from the perceived threat – right into the octopus’ mouth. Common blanket octopuses have been documented carrying tentacles of the Portuguese man o’ war to use as weapon to subdue prey and ward off predators – that’s not too shabby either.

Octopuses are masters of disguise and defense. Eels, seals, fish, sea otters, sperm whales and birds are on the list of octopus predators. Octopuses evade predators using jet propulsion – sucking water into their mantle cavity and forcing it out through their siphon by quickly contracting muscles. They often do this in combination with ejecting ink which can be used to confuse or startle predators. The ink even contains a substance that dulls a predator’s sense of smell. The most fascinating of their predator evasion (and prey ambush) techniques is their camouflage skills. Octopuses can quickly change both the color and the texture of their skin to match their surroundings instantly using cells in their skin called chromatophores. They can also use these abilities to perfectly mimic other creatures such as starfish.

Much like other facets of octopus biology, mating is odd and interesting. Males have a modified arm that they use to pass sperm to a female through her siphon (which is in a location similar to a human’s ear). In some species the male will detach that special leg and leave it in the female or leave it with her for future use. He won’t need it anyway, as males die shortly after mating. After mating, females find a suitable den site and lay chains of eggs attached to rocks, coral, or the den itself. Eggs can number in the hundreds of thousands. The female guards, cleans, and aerates her eggs until they hatch. Brooding commonly lasts up to three months, but in some species has been documented to last up to 4.5 years. During this time the female does not leave her eggs and does not eat. Not surprisingly, the female dies after her brood has hatched. The young can swim, eat, and produce ink as soon as they hatch.

The most fascinating and mystifying thing about octopuses is their intelligence. Octopus and vertebrate brains have no shared anatomy but have several similar features such as short and long-term memory, sleep, and abilities to recognize individuals and explore objects through play. Octopuses have a doughnut-shaped central brain that is wrapped around the esophagus, large optic lobes, and highly developed eyes. Most of an octopus’ neurons are actually in the arms – almost twice as many as are in the central brain. Their arms have the capacity to touch, taste, sense chemicals, and smell. Research is showing that the arms may have a simple type of short-term memory. Even when an arm has been surgically removed, it can still perform basic functions like reaching and grasping. Octopuses are capable of learning, using tools, remembering locations, “playing” with toys or objects, and recognizing individual humans – even when they wear identical uniforms or scuba gear. Octopuses behave differently towards different humans and octopuses in captivity will shoot water at humans they don’t like. Some octopuses collect coconut hulls or large seashells, clean them, and fashion them into a mobile shelter. They are great problem solvers and can navigate simple mazes. They can learn to unscrew jars to access food inside – even from the inside out. Octopuses in aquariums have even learned to turn off lights that annoy them by squirting water at the bulbs causing them to short-circuit. They’re great escape artists. They will watch their human keepers and wait until the keepers are distracted to make their escape. Captive octopuses have been caught on video leaving their tank at night, opening a neighboring fish tank, eating the fish, closing the lid to the fish tank, and returning to their own tank. Keep in mind that all these tanks have seemingly secure lids. Other mischievous deeds include intentionally plugging their outflow valves with an arm to raise the water level in their tank and flood the facility.

Octopuses are just one of the millions of strange and amazing organisms that we share this planet with. I find the more we learn about other creatures, the more understanding we gain of ourselves and our own species. Afterall, we’re more alike than we are different.