Curious Cuttles – Dwarf Cuttlefish (and friends)

    There appears to be some unspoken rule that tiny versions of things are exponentially more adorable. Take for instance hummingbirds, pygmy marmosets, dwarf elephants, pygmy hippos, or Brookesia micra (the chameleon that fits comfortably on the head of a match). The dwarf cuttlefish (Sepia bandensis), with a mantle length of under three inches, is no exception. Dwarf cuttlefish are at home in the warm waters of the Indo-Pacific including, but not limited to, the Philippines, New Guinea, and Sulawesi. Living mostly in shallow coastal waters, these tiny cephalopods are most active at night, feeding on small crustaceans or fish found over sand and reef. Like almost all members of their group, dwarf cuttlefish are exclusively shallow water inhabitants. This is because of the vestigial cuttlebone that’s contained within the mantle. The cuttlebone is a remnant from the ancient history of cephalopods. Like the ancestral shell, it still retains tiny chambers filled with gas that assist with buoyancy. As a consequence, the cuttlebone will implode if the poor creature swims too deep. Being relatively restricted to shallow water does have its perks, though. Since there is so much light, cuttlefish get to fully utilize their incredible skin to create a wide variety of colors, patterns, and textures to communicate with each other and other animals.

     One of the most spectacular displays used by these tiny cuttles is known as the “passing cloud”. It consists of dark bands of color moving down the animal’s mantle via the pulsing of chromatophores in the skin. While this occurs, the cuttlefish keeps the rest of its body’s color and pattern static (unchanging).

Here you can see the passing cloud display in action on this dwarf cuttlefish that I filmed at the Seattle Aquarium. It does it at the beginning and the end of the video.

S. bandensis is not the only cuttlefish species to display these strange, psychedelic waves. Many other cuttlefish do this as well, and also some octopuses. Not surprisingly, the display differs in each species and there are many variations of it. These bands can occur on almost any part of the body and go in different directions depending on the species. The delightfully named Wunderpus photogenicus, an octopus, pulses dark bands over its eyestalks. Perhaps the most interesting thing about pulsing displays like the passing cloud is that no one knows for sure what the purpose is.

Did you notice the pulses on Wunderpus’s eyestalks?

     There is a myriad of possibilities of what the displays could be used for. Some cephalopods, such as the broadclub cuttlefish (Sepia latimanus), almost certainly use these displays for hunting. These cuttlefish can sometimes be seen rapidly pulsing the chromatophores on their arms before pouncing on prey. It’s possible that the chromatic pulses mesmerize prey, holding them in place while the cuttlefish positions itself for a deadly strike. The Australian giant cuttlefish (Sepia apama) has been observed using pulse displays in spawning aggression and while drifting in and out of seaweed. These are both notable examples of how pulse displays can be used. Male cuttlefish are well known for displaying aggression to rivals with one half of the body, while showing receptivity to females with the other half. Communication is extremely important among cephalopods and pulse displays seem to serve this purpose well. Camouflage is also a famous attribute of cuttlefish and octopuses alike. Creating rhythmic waves that mimic the rippling light coming from the surface while drifting with the weeds is an excellent way to hide. It definitely puts those chromatophores to good use by helping protect the animal from predators.

This broadclub cuttlefish is using its chromatic pulses to hypnotize a crab. It has its two outer arms positioned in what is called a “branched coral” pose.

     The functions of chromatic pulse displays like the passing cloud are not as obvious in other contexts. The extraordinarily cute and adorably named flamboyant cuttlefish (Metasepia pfefferi) will pass waves over its body in as simple a situation as sauntering over an open mudflat. There is a possibility that, along with its bright colors, this could serve as a warning to potential predators. Cephalopod expert Mark Norman has found that the flesh of this little cuttlefish is incredibly toxic. However, this is only anecdotally recorded in the NOVA special Kings of Camouflage and there has been no scientific study published yet that analyzes the toxins. Toxic or not, the flamboyant cuttlefish uses it’s chromatophores to send a message, supporting the potential communication function of pulse displays.

This tiny flamboyant cuttlefish is too cute as it walks around strutting its stuff. Could it be saying “Don’t eat me, I’m toxic!”?

     It’s pretty clear that passing clouds and other pulses have specific uses depending upon the environmental or behavioral context of the animal creating them. That is, it’s pretty clear for most of the cuttlefish I’ve mentioned. Alas, the star of this article – the diminutive dwarf cuttlefish – still hides its secrets. Although I am privileged to have seen and video recorded the passing cloud behavior at the Seattle Aquarium many times, I still can’t figure out what these little cuttles are using it for. One minute, an individual may be hovering in place with wave after wave passing over its mantle and the next it will be almost completely black and fighting with a tank mate. From my pathetically inferior human perspective, it seems random. There is the possibility that these captive bred cuttlefish are behaving a little differently than they would in the wild, or that they are influenced by the presence of people. With so many variables, it’s difficult to tell what the dwarf cuttlefish are using it for without a full blown scientific study. Even with the most skilled researchers giving it their all, we will probably never know just what goes on in the minds of these tiny cuttlefish (or any of the other species).


This is a photo I took at the Seattle Aquarium. You can see the tiny suckers on this dwarf cuttlefish’s adorable little arms as it watches me through the glass.

     Cephalopod nervous systems are so different from our own that we can only make feeble guesses at how they think and feel about the world. Can you imagine having your brain directly connected to your skin so you could change color and texture in fractions of a second just by thinking? Me neither, but wouldn’t it be cool? That’s an everyday reality for almost all modern cephalopods and something we can’t even begin to relate to. As our understanding of these fascinating creatures improves and science gives us new ways of studying them, we may come closer to discovering what it all means. Until then, let’s just admire their beautiful and complex alien language for what it is – one of the many wonderful mysteries of the natural world.

1. Mustain, Andrea. “World’s Tiniest Chameleon Discovered.” LiveScience. Purch, 14 Feb. 2012. Web. 12 July 2017

2.“Stumpy-spined Cuttlefishes, Sepia bandensis.” MarineBio Conservation Society, n.d. Web. 2 March 2017.

3. How, Martin J., et al. “Dynamic Skin Patterns in Cephalopods.” Frontiers in Physiology, vol. 8, 2017, Accessed 31 July 2017.

4. Cuthill, Innes C. “Animal Behaviour: Strategic Signalling by Cephalopods.” Current Biology, vol. 17, no. 24, 2007, pp. 1059–1060. ScienceDirect, Accessed 31 July 2017.

5. Hanlon, Roger. “Cephalopod Dynamic Camouflage.” Current Biology, vol. 17, no. 11, 2007, pp. 400–404. ScienceDirect, Accessed 31 July 2017.

6. Osorio, Daniel. “Cephalopod Behavior: Skin Flicks.” Current Biology, vol. 24, no. 15, 2014, pp. 684–685. ScienceDirect, Accessed 31 July 2017.

7. Laan, Andres, et al. “Behavioral Analysis of Cuttlefish Traveling Waves and Its Implications for Neural Control.” Current Biology, vol. 24, no. 15, 2014, pp. 1737–1742. ScienceDirect, Accessed 31 July 2017.

8. Kaufmann, Gisela, director. Kings of Camouflage. NOVA, 2011.

9. Staaf, Danna. “Sheathing the Shell.” Squid Empire: the Rise and Fall of the Cephalopods, ForeEdge, an Imprint of University Press of New England, 2017, p. 112.

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Soft-bodied Brainiacs – Giant Pacific Octopus

Most people have heard that octopuses are smart. But how smart are we talking about, and how did they get that way independent of vertebrates? Cephalopoda, which includes octopuses, squid, cuttlefish, and nautiluses, is highly a specialized and advanced class of invertebrates dating back to the late Cambrian. These animals share the same phylum, Mollusca, with slugs and snails, clams, and other “lower” organisms. So what made them so different? All but the nautilus have completely lost their shells, and in cuttlefish, it is reduced to a small internal structure called the cuttlebone – you know, that thing people give parrots and rodents to chew on as a supplement. This has given the group a ridiculous amount of flexibility (both literally and figuratively) to hunt, explore, manipulate, and perform complex behaviors not seen in other mollusks.


We will explore the reasons behind the development of intelligence and the extent to which we understand it in these amazing animals by looking at the giant Pacific octopus (Enteroctopus dofleini). This cephalopod, also called the North Pacific giant octopus, is the largest of its kind in the world that has been discovered so far. Only the female seven-armed octopus (Haliphron atlanticus) and the giant (Architeuthis sp.) and colossal (Mesonychoteuthis hamiltoni) squids can contend with it in a battle of size. The largest specimens can reach up to 30 feet from arm tip to arm tip and weigh several hundred pounds. Despite its large size, this octopus is generally considered to be a curious, gentle giant. That is, unless you’re a tasty crab. Unfortunately, a long lived octopus will only get to be 5 years old. If an animal has such a short life, why and how is it so intelligent?


Photo by Drew Collins.

There are several hypotheses as to the rapid evolution of intelligence in cephalopods. One idea is that coleoids, the taxon that includes all shell-less cephalopods, evolved side by side with teleosts, or bony fish, during the Jurassic. Teleost fish during this period, all of which possessed complex vertebrate behavior, were undergoing rapid diversification and occupying countless environmental niches. In response, the coleoids developed intelligence of their own in order to survive in a quickly changing environment filled with new pressures from these vertebrate predators and prey. These cephalopods had to be able to learn, remember, interpret and predict the behaviors and actions of the bony fish to survive. Their positions within the trophic web (food chain) and their life habits created a demanding existence, making higher cognition a necessity.

Giant Pacific octopuses typically use one den for several weeks at a time in the wild. After a foraging outing, they are able to remember where they are in the environment in relationship to their home, and travel back quickly, often jetting over the sea floor. This shows that they have a sense of self as separate from their surroundings and can understand where they are positioned in space. Cognition like this is typical of vertebrates, but cephalopods are the only group of invertebrates that display this advanced form of spatial navigation and problem solving. Not only are they able to return to a den site with ease after hunting, giant Pacific octopuses will not visit the same foraging area consecutively. Behavior such as this demonstrates that these animals have an awareness of how they themselves have impacted the environment in which they live (removed prey from it) in the past, and modify their hunting strategies accordingly. Thus, the octopuses are able to remember where they were and what took place. The navigational abilities of octopuses are still not well understood, but they do use many tactile cues, such as following the contours of the sea floor to relocate a den. Their excellent vision helps them navigate in clear, shallow waters and allows them to use jet propulsion as a movement option.


It is not surprising that the giant Pacific octopus is able to navigate and live successfully in such a complicated environment when you consider that cephalopods have the largest brain to body ratio of any invertebrate. This ratio is comparable to that of mammals and birds. Octopuses are strange in that their arms are radially symmetrical, yet they have bilateral brains. Half of the arms are controlled by one half of the brain and half are controlled by the other. Because of this, octopuses often display “handedness” like humans do. The front pair of tentacles is the pair mainly used for manipulation of objects and the environment, and octopuses can show favoritism towards the left or right tentacle, depending on the individual. Three fifths of the octopus nervous system is concentrated in these arms. The arm and sucker control is highly complex and very precise, allowing possibly the widest range of motion seen in any animal. Such freedom of motion allows these cephalopods to explore their environment in ways that other species would not be capable of. With this exploration comes lots of learning.

Exploration through sight and touch is everything to an octopus. When something novel is presented, such as a new environment, it will proceed to gather as much information as it can through these senses, building a mental map and gaining an understanding of how things work. As familiarity is established, the octopus’ exploratory behavior will decline, and more time will be spent resting and hiding, suggesting that the animal remembers what it learned and has no need for continued exploration. This is seen often in tanks when an octopus is brought in from the wild or a different aquarium. After the territory and sense of safety is established, the octopus has a tendency to display very play-like behavior when given a novel object. One such study, performed at Washington’s very own Seattle Aquarium, presented eight giant Pacific octopuses with a toy (an empty pill bottle with a float in it) and observed their behavior over ten trials. Two of the octopuses took the bottle with a stretched out arm and held it in place before jetting water to make it float to the other side of the tank. They waited until the slow current returned the bottle to them and then repeated the process over 20 times. Other studies with the common octopus (Octopus vulgaris) also described play behavior. When given a choice of clam prey, empty shells, and plastic blocks, the octopuses ignored the shells, ate the clams, and often manipulated the blocks for quite some time. They were seen passing a single block from arm to arm, pulling it around with them when they moved, and bringing it back and forth from the center of their bodies. Octopuses are solitary and do not need to play to learn about their place in a social group, and the play-behavior displayed is not restricted to a specific environment as it would be in a vertebrate (like the safety of a family group). Also unlike vertebrates, play occurs equally throughout the lifespan, though it is infrequent.


Ramsey the octopus from Plymouth’s National Marine Aquarium with a soccer ball.

Wild and captive giant Pacific octopuses are also capable of human recognition, among their many other astounding abilities. Another study done at the Seattle Aquarium collected eight octopuses from Neah Bay in Washington and Seaside, Oregon. The animals were transported to the Seattle Aquarium and placed in separate tanks. Three researchers, dressed identically, interacted with the octopuses over ten days with a two day break in the middle. The interactions were done in a non-predictable order. One tester fed the octopus while the other “mildly irritated” it by gently touching it with a bristly stick for 30 seconds. A range of behaviors from these interactions was catalogued. At the end of the experimentation period, each researcher looked into the octopuses’ tanks and recorded their reactions. The order of researchers was reversed for each octopus and presentations were ten minutes apart. When the irritator appeared, octopuses overwhelmingly reacted with responses consistent with their irritation trials, such as displaying a dark Eyebar or jetting water at the observer. Likewise, the octopuses’ behavior toward feeders reflected that of the feeding trials. This just adds to the already impressive array of cognitive abilities in these amazing animals.


Eyebar on Octopus vulgaris. Photo Credit: Lawrence Tulissi

If I haven’t already convinced you that giant Pacific octopuses and other cephalopods are fascinating creatures, then you have no sense of wonder and should reevaluate your life. To top everything off, here is one more thing to impress you. I could list more, but then I would be writing this article forever!

Octopuses have personalities too! Yet another study conducted at the Seattle Aquarium demonstrated that giant Pacific octopuses vary across three dimensions: Activity, Reactivity, and Avoidance. For comparison, the standard temperament dimensions established for humans are Activity, Emotionality, and Sociability. As mentioned before, octopuses are solitary animals, so it is not realistic to measure variance in the Sociability or Emotionality dimensions. Because of this, the researchers designated Reactivity and Avoidance as the analogues. The results from the study showed that variance in octopus behavior accounted for by these three dimensions was 45%. To give you an idea of how amazing this is, compare that to 43% of the individual variance explained by Sanson et al.’s nine factors for human babies. In addition, much of this variance was across the Approach and Activity dimensions. It is not known why octopuses display so much difference between individuals, but it may again be due to their ever changing and demanding environments and evolutionary competition with teleost fish. There are many adaptive reasons for this variance and octopuses are highly intelligent, learning animals that are shaped by life experiences. It is no wonder that each octopus has its own way of behaving and thinking about the world.

Cephalopods like the giant Pacific octopus can teach us so much about the minds of invertebrate animals and the heights to which intelligence can rise. We really know very little about how other animals perceive the world and solve the problems that they are faced with throughout their lives. Learning about cephalopods opens a door to other mollusks and in turn other invertebrates. Intelligence is something that fascinates us because we consider it to be a key factor of what makes us “different” from other animals. Animals such as the giant Pacific octopus may make us question what really sets us apart as we discover more about them.

1. “The Elusive Giant Pacific Octopus.” NOAA Fisheries. United States Department of Commerce, n.d. Web. 22 Sept. 2015. <;.

2. Anderson, Roland C., et al. “Octopuses (Enteroctopus dofleini) recognize individual humans.” Journal of Applied Animal Welfare Science 13.3 (2010): 261-272.

3. Tzar, Jennifer, and Eric Scigliano. “Through the Eye of an Octopus.” Discover. Kalmbach Publishing Co., 1 Oct. 2003. Web. 22 Sept. 2015. <;.

4. Mather, Jennifer A., and Michael J. Kuba. “The cephalopod specialties: complex nervous system, learning, and cognition 1.” Canadian Journal of Zoology 91.6 (2013): 431-449.

5. Scheel, D., and L. Bisson. “Movement patterns of giant Pacific octopuses, Enteroctopus dofleini (Wülker, 1910).” Journal of Experimental Marine Biology and Ecology 416 (2012): 21-31.

6. Mather, Jennifer A., and Roland C. Anderson. “Personalities of octopuses (Octopus rubescens).” Journal of Comparative Psychology 107.3 (1993): 336.

7. Mather, Jennifer A. “To boldly go where no mollusc has gone before: Personality, play, thinking, and consciousness in cephalopods*.” American Malacological Bulletin 24.1 (2008): 51-58.

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Beautiful, but Dangerous – Blue-Ringed Octopus

Today I will talk about a fantastic little creature called the blue-ringed octopus (Hapalochlaena lunulata). This is yet another venomous animal that haunts the waters of Australia as well as the Pacific and Indian Oceans. There are several species within the Hapalachlaena genus and I will be writing about that, as all species share the same general characteristics.
Though it is very small and vulnerable, the blue-ringed octopus is fairly docile unless provoked. It likes to hunt in tide pools and shallow reef waters where it scrounges out small crabs and shrimp that are killed quickly with its powerful venom. It is diurnal, so it mainly only comes out to hunt during the daytime. When it catches a prey item such as a small crab, it uses its sharp beak to break open the shell and eat out the insides.

When disturbed, the blue-ringed octopus will show the elaborate coloration that it is named for. Chromatophores in cephalopods such as octopuses, squid, and cuttlefish, are units of neuron controlled glial, muscle, and sheath cells. These are contained in an elastic sac that can expand and contract to change the opacity and translucency of the pigment within. The blue-ringed octopus is unusual in that it does not have chromatophores over its rings, but only surrounding them and underneath them. The iridescent, electric blue pigments in its skin are always present, yet only visible when it wishes them to be. Certain muscles above the iridophores, specialized light reflecting organelles within the cells, hide the blue-green light reflectors until they are contracted and expose the bright color. This is a very quick and highly controlled method of display that is not seen in other species of octopus.

Rings concealed.

Threat display.

A blue-ringed octopus may only be from five to eight inches in length, but it packs potent enough toxins to kill an adult human in a matter of minutes. It has special salivary glands behind its beak containing bacteria that produce the deadly cocktail it delivers. An envenomation from one of these octopuses starts out with nausea and quickly progresses to numbness, difficulty swallowing, visual abnormalities, and eventually motor and respiratory arrest. Because there is little to no effect on cardiac muscles, a victim’s heart may continue to beat until asphyxia sets in and the central nervous system is deprived of oxygen completely. The bite itself may be painless and show only vague evidence of wound infliction. What makes the venom so deadly is the tetrodotoxin (TTX). This is the same toxin found in pufferfish and is designed to block sodium channels on neuron cell membranes, which in turn causes total paralysis throughout most vital areas of the body (minus the circulatory system). There is currently no quick fix in existence for blue-ringed octopus envenomation, so treatment is limited to life support measures, such as artificial respiration, until the effects of the venom wear off. Sometimes victims may be fully conscious and aware of their surroundings, but unable to move or speak due to the paralysis. Those who survive the first twenty four hours will typically make a full recovery.

DO NOT DO THIS! (unless you are a properly trained biologist)

Blue-ringed octopuses might be scary, but they are tender love-makers just like we imagine ourselves to be. A male blue-ring will court the female of his choice by approaching her and gently caressing her with his modified arm used for delivering sperm. He will then pull her close to him by grasping her mantle and use this arm to deposit packets of sperm inside her mantle cavity again and again until she is decides she is done. Sometimes the male has to be removed by force because he wants to keep going. Male blue-rings aren’t picky about who they court and will often attempt to mount other males of their own species. However, these interactions are usually much shorter lived and result in both males withdrawing, possibly in embarrassment, without a struggle or exchange of sperm. A little while after a female has been fertilized, she lays a single clutch of about fifty eggs and incubates them with her arms for up to six months. As with all octopuses, she does not eat during this time and dies shortly after her babies emerge from their eggs.

Baby blue-ring:

Unfortunately for such a pretty and intelligent animal, the maximum lifespan for a blue-ringed octopus is only two years. But hopefully it is two years well spent hunting, fascinating curious humans, and making sweet, sweet octopus love.

1. Mäthger, Lydia M., et al. “How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?.” The Journal of experimental biology 215.21 (2012): 3752-3757.

2. Yotsu-Yamashita, Mari, Dietrich Mebs, and Wolfgang Flachsenberger. “Distribution of tetrodotoxin in the body of the blue-ringed octopus (Hapalochlaena maculosa).” Toxicon 49.3 (2007): 410-412.

3. “Australian Marine Envenomations.” Marine Envenomation. University of Sydney, n.d. Web. 23 June 2015. <;.

4. Cheng, Mary W., and Roy L. Caldwell. “Sex identification and mating in the blue-ringed octopus, Hapalochlaena lunulata.” Animal behaviour 60.1 (2000): 27-33.

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