Why do we love cephalopods so much at Science Friday? Partly it’s because they’re cute (or at least some of them are). Partly it’s because they’re so smart. But it’s also because they’re…well…kinda weird.

You don’t need to turn to the world of fiction to find fascinating examples of animals with traits that make us scratch our heads in wonder. Some cephalopods are able to mimic their environment so well that they take on the color and texture of their surroundings. Cephalopod eyes developed independently of vertebrate eyes, but they managed to evolve many of the same structures, a classic example of convergent evolution. And cephalopods solve problems remarkably well. One octopus in New Zealand was able to unscrew a jar containing his crab lunch in less than a minute.

This year for Cephalopod Week we illustrated a few of our favorite species in the cephalopoda class. Here’s some fun facts about the ones we chose that keep us (ahem) tentacled pink.

Adorabilis

The only way you could describe this big-eyed, deep-water dumbo octopus species is adorable. In fact, researcher Stephanie Bush spoke to Science Friday in 2015 about why she thinks “Adorabilis” should be its formal name.

• Adorabilis, like many other deep-sea creatures, is pink because seawater at that depth absorbs red light, camouflaging this small species in the darkness.
• Like other deep-sea cephalopods, the adorabilis thrives in cold, oxygen poor environments. When Monterey Bay Aquarium aquarist Bret Grasse created a tank to display them, he had to install special coolers to keep the water chilly and filters to remove oxygen from the water.
• Like their relatives the flapjack octopus, adorabilis octopi move by flapping the webbing between their legs to hover over the ground.

Blanket Octopus

If Bob Mackie were to design an octopus, this is probably the species he’d come up with. The females of the species grow up to six-and-a-half feet in length and sport a thin “blanket” of flesh between their legs that they unfurl when threatened.

• The blanket octopus is an extreme example of sexual dimorphism. Females of the species are 10,000 times larger than the males.
• Males and young females have been known to rip the stinging tentacles right off Portuguese man-o-war and use them as weapons to defend themselves.

Chambered Nautilus

Unlike other cephalopods, the chambered nautilus has a hard shell that surrounds its body. It also has a more primitive brain than its squid, octopus, and cuttlefish cousins—though as we learned in this video, it’s possible to teach an old cephalopod new tricks.

• A nautilus will grow new chambers as it matures. A newly hatched nautilus will start life with around four chambers, but on average they grow thirty chambers in adulthood.
• Because they exert such little energy while swimming, a nautilus only needs to eat about once a month.
• Their beautiful shells are prized by some collectors, which is leading to population decline in the wild.

Common Cuttlefish

Over 120 species of cuttlefish have been described, but the common cuttlefish (which is who inspired this illustration) is the most well known. These cuttlefish, like other cephalopod species, have a special organ—called chromatophores—that allow them to rapidly change their color. Cuttlefish skin is covered in chromatophores. They have up to 200 for each .001 square inch of skin.

• Cuttlefish belong to the order Sepiida, and the color known as sepia was originally made from cuttlefish ink.
• Cuttlefish change their own color, but they are actually colorblind themselves.
• Although most cuttlefish are small, the giant cuttlefish grow to a foot-and-a-half in length.

Long Armed Squid

Even when compared to other cephalopods, the long armed (also known as “big fin” or “elbowed”) squid is unusual. Very little is known about this creature since only juveniles have been studied in the lab. But some remote operated vehicles have captured videos of adults, showing behavior that seemingly has more in common with a jellyfish than a typical squid.

• A long-armed squid’s body is likely only a couple of feet in length. But its arms and tentacles can extend out to 20 feet in length.
• The length isn’t the only unusual part of this squid’s appendages. Unlike most other cephalopods, the arms have a pronounced bend or “elbow.”

Blue-Ringed Octopus

Of the nearly 300 described species of octopus, the blue-ringed (or blue-lined) octopus is likely the most deadly. But that’s because of the power of its venom—the octopus itself is mostly content to stay hidden. We profiled the blue ringed octopus in a Sci-Candy article in 2014.

• The dramatic coloring of the blue ringed octopus only shows up when it is angered or frightened. It spends the rest of the time camouflaged with its surroundings.
• Males of this species cannot discern females from other males. This leads to a “crapshoot” mating strategy with the males grabbing the closest octopus of either gender to mate.
• This highly venomous octopus lives in the waters of Australia. Because of course it does.

Vampire Squid

As we explored in this video, the scientific name of the vampire squid is Vampyroteuthis infernalis, which means “vampire squid from hell.” This species, though, is anything but. The vampire squid is neither a vampire nor a true squid—rather it is the last remnant of an ancient lineage.

• Vampire squids are the only cephalopods that feed on non-living matter. Their diet is made up of “marine snow,” the detritus of sea life from higher up in the ocean.
• These creatures live in the deepest parts of the sea, where very little life, or indeed very little oxygen, manages to penetrate.
• When faced with a predator, vampire squid curl up their bodies and turn themselves “inside out,” showing an impressive array of scary-looking cirri.