Octopuses, squids and their cephalopod cousins have haunted the human imagination for centuries. Their long, unfurling arms and temperamental behavior have inspired legends, from the Kraken of Norse mythology to the giant Japanese Akkorokamui that supposedly lurks at the bottom of the ocean, waiting to swallow ships and whales whole.

Cephalopods sit apart from other invertebrates because they have evolved with highly complex nervous systems that give their arms a mind of their own, making the creatures star attractions at many aquariums. They are brilliant at camouflage despite being colorblind, have a talent for opening jars and shape-shifting, and can communicate in their own Morse code.

Ecstasy makes octopuses more cuddly

Scientists have a hard time studying octopuses. The animals often have to be kept in separate tanks so they don’t kill each other. But when a group of researchers gave octopuses a dose of the party drug ecstasy last year, the creatures suddenly became more social. They slid up to the edge of their tanks and even reached out to interact with neighboring octopuses.

The drug had triggered the release of serotonin, the same brain chemical that produces happy feelings in humans — which suggests that our brain chemistry may be more similar to that of cephalopods than previously thought.

Cuttlefish are surprisingly confrontational

A cuttlefish conflict escalated from a visual display of aggression into actual aggression in the first recording of a physical battle between male cuttlefish.

When not on an experimental high, most cephalopods are extremely aggressive. Cuttlefish are no exception. Males will attack other males that intrude on their territory. And they will battle over females, conveying their agitation through body movements, flashing colors and spurts of dark brown ink.

Their arms aren’t so different from ours

Cephalopods, flies and even humans share genes that help the respective embryos sprout limbs. These genes tell each cell how much to grow and in which direction to elongate. The difference is that octopuses end up with eight arms, whereas we grow two.

Squid and cuttlefish also develop two specialized limbs, called tentacles, in addition to their eight arms. These are equipped with powerful suckers that they use to grab prey. One of their arms also has adapted to deposit sperm packets in females during mating.

Once upon a time, all cephalopods had shells

Hundreds of millions of years ago, all cephalopods had heavily armored shells. But when cuttlefish, squids and octopuses began to evolve separately — 160 million to 100 million years ago, during the so-called Mesozoic Marine Revolution — life was undergoing a rapid change. There was a burst in fish diversity, and predators had to become strong enough to crush shellfish or fast enough to catch their prey.

“It became a much more successful strategy to be a really high-metabolism, very rapid-moving animal,” Alastair Tanner, a biologist at the University of Bristol, in England, told The Times in 2017.

Cephalopods are scary smart

Today, there are some 800 living species of cephalopods, all of them whip smart. They have relatively big brains and millions of neurons in their arms. They also evolved a unique genetic mechanism, called RNA editing, that lets them diversify the number of proteins in their neurons. Over the course of evolution, this may have helped make their cognitive abilities more complex than those of other invertebrate relatives like snails.

Pigment makes them masters of disguise

Cephalopods can change the color of their skin as they cross sand, coral and grass. These color transformations are made possible by sacs of pigment embedded in their skin. In a recent study, scientists found that some cephalopods, such as squid, had additional proteins in their skin that produced metallic hues and reflected ambient light, aiding in their camouflage.

“We were always continuously surprised by these animals,” Leila Deravi, a professor of chemistry at Northeastern University, told The Times earlier this year. “As soon as you think you kind of understand how they work, you find something else.”

They flee with jet propulsion

The chambered nautilus is one of the lesser-known relatives of octopuses and squids, and the only cephalopod that still has an external shell. But it is a much more efficient swimmer than squid because it sucks in water through a tube, called a siphuncle, and forces it out in jets that thrust the nautilus backward and help it turn.

Squid sex is aggressive and ends badly

Squids and octopuses don’t live long lives — typically, just long enough to reproduce in one spectacularly gruesome affair. Male squids inject their sperm at high pressure into the female and then die. Once the eggs have hatched, females also begin to starve themselves; in some species, they sink to the bottom of the ocean after they die, becoming food for crustaceans and sea stars. Their fate may hold some poetic justice — the carcasses help sequester carbon, and scientists believe they may play an important role in forestalling climate change.

By Knvul Sheikh – NYT