Recently, the EU passed a directive that will require all of its member states to follow certain guidelines when using any animals for research. This piece of legislation, passed in 2010, replaced an older law from 1986 on the same topic. Besides updating the ethical and technical aspects of the law, it expanded the scope of the law to include more species than the 1986 law:
3. This Directive shall apply to the following animals:
(a) live non-human vertebrate animals, including:
(i) independently feeding larval forms; and
(ii) foetal forms of mammals as from the last third of their normal development; (b) live cephalopods.
The first question that comes to mind is: why cephalopods? The answer, it turns out, lies in a document published by the Animal Health and Animal Welfare Panel of the European Food Safety Authority – their scientific report revealed that they had initially considered “all invertebrate animals” for inclusion under the law, but ended up recommending that cyclostomes (a group including lampreys and hagfish,) decapod crustaceans (like lobsters and crabs), and cephalopods should be included in the law. They also noted that other invertebrates, like spiders, tunicates, social insects and amphioxus are on the “borderline” of inclusion – that is, they seem to be complex enough (in their behavior and their nervous systems) that it is reasonable to think that they could experience pain or suffering, but there’s not enough evidence to suggest that they do to justify including them in the law. In any case, the only group of animals from this recommendation that ended up making it into the law was cephalopods, with crustaceans being excluded despite the Panel’s recommendation.
The reasons that the Panel cited for recommending cephalopods seem pretty straightforward; cephalopods exhibit what might be called complex cognitive abilities, being able to learn and remember rather flexibly, have large complex brains, and have strong behavioral responses to a variety of stimuli that we’d call noxious. These points, and their relationship to the possibilities of pain and suffering in cephalopods, are far from settled issues, and there’s a lot of arguments that can be made about why they may or may not be adequate justification for including cephalopods in the directive. In a sense, though, it is too late for these arguments; the directive has already passed, and will be in force as early as 2013.
As one might expect, this whole shebang was big news to cephalopod researchers. As I mentioned a few posts ago, a conference (dubbed Euroceph) was called so that cephalopod researchers could get together and talk about what the new law means to them and their work, and what needs to be done next. And there is a lot to be done.
The directive requires that certain criteria be met when using any vertebrate or cephalopod in research: for example, steps must be taken to minimize the animal’s pain and suffering, the animals used should be (if possible) bred for the purpose of research by regulated suppliers and not taken from the wild, and kept in enclosures that “are appropriate to their health and well-being.” One might run into some problems in applying these standards, which have been used in one form or another for regulating the use of vertebrate lab animals for many years, to cephalopods; for example, there is very little known about to biology of how cephalopods might feel pain, and what the consequences of that pain might be to a cephalopod’s health and behavior. There are only a few anesthetics that are used for cephalopods, and since we know almost nothing about the (presumably existent) pain system of cephalopods, we have no drugs to give them as pain-killers – indeed, it’s hard to even know where to start looking to identify drugs that would work as analgesics in cephalopods.
Another problem that came up repeatedly at Euroceph was the requirement for captive-bred animals. So far, there have only been a few limited successes at breeding cephalopods in captivity – among these, the only real successes have been with cuttlefish. Even in this case, though, captive-bred animals appear to behave differently than their wild-caught brethren (which isn’t really a surprise, if you think about how different the two lifestyles are;) perhaps more troubling, captive-bred cuttlefish seem to lose their ability to produce healthy offspring over several generations, limiting the extent of captive breeding programs. For researchers who want to study the behavior of cephalopods as it might be relevant to their lives in the wild, there is “a fundamental scientific problem” with requiring the use of captive bred cephalopods, said Rogen Hanlon, a cephalopod researcher at the Marine Biological Laboratory at Wood’s Hole. ) “If you want the best model [of cephalopod behavior], you use nature’s fittest, and that’s what you get from wild-caught animals.” Having to use captive-bred cephalopods for behavioral research could require research conducted using wild-caught animals that has been relied upon for decades to be re-done with captive-bred animals; even after this, it would still be difficult to predict what this research would mean in terms of how wild cephalopods actually behave.
While the EU directive contains very specific guidelines for the care of common lab animals like rats and rabbits, it contains almost no specific guidelines about caring for or handling cephalopods. This is because, while there is a long history of requiring that lab mammals be dealt with in a certain way (ie. they must have so much space, be given such-and-such a drug before each procedure to reduce pain, be fed every so often, be kept at such-and-such a temperature,) this is the first time that the research community has been required to come up with a standardized set of guidelines for using cephalopods. This might actually be an advantage to cephalopod researchers – they’re in the position now to shape these guidelines themselves, since there are virtually no other sources of information about how it is best to keep cephalopods in captivity. Hopefully, with the help of forthcoming regulations that are tailored to suit cephalopod research in particular, and more research into the health and husbandry of cephalopods, cephalopod research will continue without too much trouble.
Cephalopods have a lot to offer – tentacles, beaks, and big scary (and perhaps cute) eyeballs. Today, though, let’s look at a part of the cephalopod body that doesn’t get paid so much attention to, especially by us neurobiologist types: the ink.
Fossil squid with preserved ink sac. Ink sacs are often easily visable in coleoid cephalopod fossils. (via Maitri on Flickr - click through for original.)
Most coleoid cephalopods (that is, all the living cephalopods excluding nautiluses and a few deep-water octopuses) produce ink. This ink is composed chiefly of melanin, which is a dark brown pigment that is found throughout the animal kingdom. Humans have used cephalopod ink for a variety of purposes, including writing, drawing, dying, and cooking (the fact that both a dark brown color of ink and a genus of cuttlefish are both named Sepia is not coincidence.) In fact, you can buy tubs of cephalopod ink online.
Cephalopods use their ink for a different purpose, though; it helps them get away from sticky situations. When severely startled, cephalopods will release ink from their ink sac, which is pushed out of their funnel with a jet of water (which usually also jets the cephalopod in the opposite direction away from the perceved danger.) The resulting cloud of ink could serve many functions; it could conceal the escaping cephalopod’s location from the predator, serve as a false target for the predator (who would attack the dark ink instead of pursuing its prey,) frighten the predator, or even trick the predator’s sensory systems into thinking it had already caught something (I’ll explain this last one at the end of the post.)
One neat property of cephalopod ink, though, has nothing to do with how predators perceive it, but rather how cephalopods perceive it.
When one squid in a shoal inks (“inking” being the action of expelling ink into the water) the rest of the shoal can certainly see what has happened and be alerted to the immanent danger that way. In addition to this, though, it has been hypothesized that squid can chemically sense the ink in the water, which would give them another way to keep abreast of squid-predator interactions going on around them.
One study that found evidence for this hypothesis (which is actually a part of a series of studies in this line of research) was done by Gilly and Lucero (1991) at Hopkins Marine Station in California. These investigators restrained squid (loligo opalescens) by attaching their dorsal mantle to a platform with cyanoacrylate glue (the same stuff that Super Glue is made of,) and then used a pipette to place small amounts of various substances onto a chemoreceptive organ located behind the squid’s eye.
Photograph and photomicrograph of squid olfactory organ - from Gilly and Lucero (1992)
They recorded the activity of the squid with a video camera, and everything was done remotely, so that the movement of the experimenter’s would not upset the squid and cause extra escape-like behavior. Escape-like behavior was measured in terms of the pressure inside the squid’s mantle, which was recorded via a tiny pressure transducer inserted inside the squid’s mantle. One of their records is shown here – the spikes in pressure reflect jets of water being expelled from the squid’s mantle, as it presumably attempts to escape from the chemical stimuli that signal some sort of danger in the environment.
They found that pipetting ink from an animal of the same species of the test animal onto the olfactory organ caused jetting. Furthermore, they found that a specific component of squid ink, L-DOPA (which is a precursor of melanin, the main pigment in squid ink) caused jetting just as much as did whole ink. On this basis, the authors concluded that L-DOPA is used as a sort of chemical alarm signal between L. opalescens individuals. (I should note that some of the authors cited in this post write that squid ink is actually a cue, not a signal, as a signal results in an action on the part of the receiver that benefits both the receiver and the sender of the signal. Escape responses by squid in response to the ink of conspecifics do not fit this definition.)
A more recent study by Wood, Pennoyer, and Derby (2008) looked at the responses of Caribbean reef squid (Sepioteuthis sepioidea) to squid ink preparations. This species of squid has ink that hangs together in a mucous-ey glob in the water, forming what the authors call a “psuedomorph”, or false animal shape that confuses predators.
Each squid was tested by placing a small amount of an ink preparation into its aquarium and videotaping its behavior during and after this event. The authors used a scoring system to determine how defensively each squid behaved during each test, with points on a scale of defensiveness being awarded for behaviors like jetting, specific postures that are used to hide from predators, and certain color changes that are known to signal alarm. A higher score on this measure of defensiveness indicated that the squid was “alarmed” (or something like that) during the test. Below is a video showing on of their tests, produced by New Scientist:
The authors found that S. sepioidea responsed with alarm to fresh squid ink placed in their aquarium. The ink worked to cause alarm responses even after it had been frozen, albeit not as well – the authors noted that it changed in consistency, and dispersed much more quickly. Ink that was placed into an adjacent aquarium (meaning the squid could see it, but could definitely not chemically sense it) worked very well to stimulate escape behavior. This argues that one of the stimuli that this species of squid uses to respond to ink is its appearance. What about chemoreception, though?
The authors produced “melanin-free ink” by centrifuging fresh ink to remove all of the melanin-containing granules in it. They reasoned that this ink was just link the whole ink chemically, except that it did not contain the specific chemical that made it opaque (melanin). They found that the squids did not respond to this ink that they could not see. These results point to the use of vision exclusively in S. sepioidea in responding to other squid’s ink, apparently conclusively.
Frustratingly, they don’t, really. It would be easy enough to chalk this result up to species differences – one species can chemically sense ink, and the other species cannot. These results, however, don’t say enough to make this claim (although there may exist other research that answers this question.)
In a paper by Lucero, Farrington, and Gilly (1994), squid (L. opalescens) ink was analyzed for the presence of L-DOPA and dopamine (they found it, but that’s not the reason I mention it.) They found that, in seawater, L-DOPA and dopamine are rapidly degraded via oxidation reactions, which would certainly dampen any effects they would have on the behavior of squid swimming in that water. They also found that the L-DOPA and dopamine in squid ink did not degrade this rapidly – these preparations behaved as if they were being protected by some sort of antioxidant contained within squid ink. While the authors used ascorbic acid (a small, soluble molecule) to replicate this effect, it’s possible that any anti-oxidant activity in the squid ink is provided by a protein (or another large, centrifuge-seperable molecule.) When Wood et al. prepared their “melanin-free ink”, they may also have removed some component of the ink that is essential for its activity as a chemical signal (for a hypothetical example, a protein that prevents that oxidation of L-DOPA and dopamine in the vicinity of the ink blob.) They may even have done something that eliminated the L-DOPA and dopamine altogether – they provide not chemical analysis of their ink preparations, and so it’s hard to know. The authors acknowledge that this is a shortcoming of their work in their paper, so there’s been no oversight on their part – it just would have been nice if they’d done a bit more in the way of quantifying the chemistry of the preparations they were using. Oh well – it’s something for the next round of studies, I guess.
I mentioned that squid ink might trick predators into “thinking” they had already caught the squid and were eating it, a trick called phagomimicry. This is because squid ink (and the exudates that other molluscs exude under stress) contains, among other things, a full complement of free amino acids – these are chemicals that predators taste when they eat flesh. If a predator gets a mouthful of ink, if they can sense the amino acids that normally tell them that they’re eating flesh, they may behave as if they have already caught and/or eaten their prey, and give up pursuit.
Thanks for reading!
W. F. Gilly and Mary T. Lucero (1992). Behavioral Responses to Chemical Stimulation of the Olfactory Organ of the Squid, Loligo opalescens Journal of Experimental Biology
WOOD, J., PENNOYER, K., & DERBY, C. (2008). Ink is a conspecific alarm cue in the Caribbean reef squid, Sepioteuthis sepioidea Journal of Experimental Marine Biology and Ecology, 367 (1), 11-16 DOI: 10.1016/j.jembe.2008.08.004
Lucero, M., Farrington, H., & Gilly, W. (1994). Quantification of l-Dopa and Dopamine in Squid Ink: Implications for Chemoreception Biological Bulletin, 187 (1) DOI: 10.2307/1542165
To get things started, here’s a video of an octopus with a Mr. Potato Head Toy (and other things):
You’ll see why this is relevant in a minute. Now on to the post!
“Enrichment” is a psychological term that’s been thrown around a lot. It’s become a buzzword in publications about education, perhaps rightly so given its huge impact on the field of developmental psychology. It has been the subject of intense study in psychology, and continues to be the subject of study. But what exactly is it that we are referring to when we use the term “enrichment”?
Before I get to that, let’s take a step back and consider how brains work. Brains, in the sense that I am talking about, are simply big networks of neurons (there are other types of cells, but we can ignore them for now.) These neurons get sensory input from the body, talk amongst themselves, and send out signals that cause the organism to behave in a certain way. This is, in a nutshell, what brains do – they generate behavior. Importantly, though, they don’t just generate any behavior at a given time; they generate the appropriate behavioral response to the immediate situation. Even more impressively, in some animals, they generate the response that will lead to a positive outcome in some hypothetical future situation (for example, when birds hide food to recover later.) Thus, brains work because they can process incoming sensory information into relevant and adaptive behaviors. Neurons can do this because they are connected to each other in complex but well-controlled and highly-specific ways. Much in the way that an electrical device will only operate if all of its components are connected correctly, brains will only work if all of their neurons (or at least most of them) are “wired” together into functional circuits.
It may come as no surprise, then, that brains only wired the way they are because of the sensory input they receive. During brain development (and, to a lesser extent, throughout life,) neurons require sensory input and behavioral output to form proper connections as well as get rid of improper connections. At the cellular level, this phenomenon is called activity-dependent or experience-dependent plasticity. One can think of it this way: connections between neurons (called synapses) that are used a lot and produce functional behaviors get stronger; that is, they become more efficient and transmit larger signals from neuron to neuron. Synapses that are not used, or that don’t contribute or contribute negatively to the function of a certain circuit become weaker; that is, they become smaller and less efficient, and may even disappear altogether.
This can be demonstrated directly by looking at neurons that process incoming visual information from the eyes. Suppose we were to raise one group of animals (lets say, ferrets) completely in the dark, and another, otherwise identical group of animals normally. Then, we kill both groups of animals and look at the neurons in their visual system (for example, in visual cortex.) The group that was raised under normal light will have, by definition, normal connections between the neurons in the visual system – specifically, these neurons will form functional circuits that allow animals to sense and respond to their environment. In the animals that were reared in the dark (called, sensibly, “dark-reared” animals,) we’ll see a host of abnormalities – cells will have the wrong shapes, end up in the wrong places, and have the wrong connections. Besides this, we could demonstrate some deficiencies in visual perception in the dark-reared animals. Taken together, these results, which have been replicated in a variety of vertebrates, strongly support the idea that sensory systems need input during development in order to develop properly.
It’s a small logical step to tentatively extend the principal of experience-dependent plasticity to brain functions that are more complex than immediate sensory analysis. In the mammalian cortex (which is involved in such complex behaviors as navigation, auditory and visual perception, social behavior, speech, thought, and so forth,) normal development is dependent on the experience of the animal in question during development. The input that these brain areas deal with is almost unthinkably complex. Their function often involves the monitoring the interaction of large parts of the organism with the environment over an extended period of time. For example, cortical areas involved in directing complex hand movements (say, playing a musical instrument) receive their input in the context of a feedback loop that involves planning a movement, executing it, and then determining whether the movement was successful and, if it was not, how it needs to be changed in order to be successful the next time. More abstract cognitive processes become even more complicated, as the brain areas responsible for these have to take into account such complex “stimuli” as the animals current and previous emotional states, inferred emotional states in other animals, the value of various hypothetical outcomes to the organism, prior cognitive states the animal has had, and so forth.
Here’s where the idea of environmental enrichment comes into the picture. The logic goes like this: because neural development is facilitated by the nervous system’s interaction with the environment, and because the more integrative areas of the brain (like the cortex) interact with the environment in very complex ways, normal brain development requires interaction with a very complex environment. If this theory is true, animals raised in very restricted environments (we might call them “environmentally impoverished”) should show maladaptive or sub-normal behavior as adults. In fact, this prediction has been borne out in many studies, which find that (among other things) environmentally impoverished animals (and, although it has been less directly demonstrated, people) have altered learning abilities, exploratory behavior, cognition, stress reactivity, and social behavior.
A corollary of this theory is the idea that nervous systems which have evolved to deal with the environment in very complex ways function abnormally when they do not have complex environments to deal with, much like the way that muscles atrophy if they are not used. Part of successfully engaging a complex environment is continually interacting with and exploring it – indeed, many animals have evolved a propensity to explore and manipulate their environment. Thus, animals with complex behavioral repertoires require complex environments to interact with in order to maintain normal brain function. This theory predicts that a lack of complexity in some animals’ (or people’s) environments should lead to aberrant behavior, and that such behavior can be corrected by providing an appropriately complex environment to those animals (or people.) This prediction is borne out in a variety of studies that show that, in captive adult animals, providing more complex environments leads to lower stress levels, less aggression, and fewer pathological and stereotyped behaviors.
Dr. James Wood’s article, “Environmental Enrichment in the Giant Pacific Octopus; Happy as a clam?” makes the case that aquariums should provide environmental enrichment for captive octopuses. I won’t follow his arguments exactly, but I will examine some of the same questions that he covers, and make reference to and critiques of his work as I find it relevant.
The big question is this: Should we provide environmental enrichment to captive cephalopods? Let me rephrase this: do the benefits of providing environmental enrichment to cephalopods justify the costs incurred by doing so?
First, let’s consider the possible benefits. Anderson and Wood point out several:
1. Captive animals should be kept healthy and allowed to behave normally. Behavioral health is as important to the longevity and quality of animal’s lives as is physiologic health. The real question here is whether cephalopods have complex enough behavior that they might show pathological behavior in response to captive conditions. Put in a more cognitive frame: are cephalopods smart enough to be hurt by captivity and, consequently, to benefit from enrichment?
Indeed, it is hard to tell whether cephalopods could benefit from enrichment. To the question of how we can tell if giant pacific octopuses could benefit from enrichment, Anderson and Wood succinctly conclude: “Simply put, we cannot.” Because cephalopods have evolved under predation from fishes, they reason, they spend most of the time during which they are not hunting hiding in their dens. It’s hard to tell if this is “good” for the octopus (after all, it seems like it would be nice not to have the daily stress of fleeing from predators and risking death during hunting) or bad (because, if cephalopods can become bored, this behavior certainly seems like it would be really boring.) In addition, little is know about how behavioral pathology might look in cephalopods, because we know so little about their behavior in general.
In sum, cephalopods may or may not benefit from enrichment. Given how complex their behavior appears to be, and the likelihood that at least some cephalopods possess cognitive capacities to rival at least some vertebrates, it seems like there’s a reasonably good chance that they could. This isn’t a convincing case in itself – it really depends on the costs of providing enrichment to cephalopods. If the costs are low, this might be enough of a reason to do it; with increasing costs, it becomes an increasingly bad bet.
2. Animal enclosures should meet the expectations of the public. Showing the public what they want to see – which is, it seems, natural-looking enclosures that animals can interact with) will lead to financial success and public support for zoos and aquariums. Researchers, institutions, and the enterprise of biological science in general stand to benefit from the increased public support that comes with presenting a public-pleasing image of animal husbandry in research. Also, if the public sees naturally-behaving animals instead of pathologically-behaving animals, they learn more about the animal’s behavior. A primary function of zoos and aquariums is to educate the public about animals, and so the potential to improve on this education is an important possible result of providing enrichment to cephalopods.
This is an interesting idea to me. Octopuses are popular aquarium animals, but not very popular research animals. The public face of animal research is usually mammalian, including rats, mice, rabbits, and primates. It’s doubtful to me that researchers would benefit from an improved public image if all octopuses used in research were given lots of enrichment. In zoos and aquariums, though, this seems like a valid concern. Indeed, it could offset the monetary costs of providing enrichment for these institutions, which allows less tangible benefits (like the possibility of relieving the suffering of bored octopodes) to be given more weight in deciding whether or not to provide enrichment for captive cephalopods.
3. Finally, zoos and aquariums often care for animals with the goal of eventually releasing them into the wild. Animals whose behavior is dependent on learning need to practice skills that will allow them to succeed, such as hunting, defending from predators and rivals, and maintaining good relationships with other individuals of their species. The Seattle aquarium, for example, does this with their giant pacific octopuses. They catch individuals, hold and display them for a few years, and then release them into the wild so that they have a chance to breed.
It’s doubtful to me that enrichment benefits cephalopods in this way. I can’t say that it’s impossible, but it seems unlikely. While cephalopods are able learners, the basics of cephalopod behavior – feeding, escape, and mating – appear to be largely innate. For example, octopuses learn things in order to adapt to the specific micro-environments they end up in. The characteristics of these environments are impossible for aquariums to predict, and so they cannot be simulated. Feeding a cephalopod common local prey species so that it learns how to eat those species efficiently might help it succeed if it is released, but besides this one example there seems to be relatively little to do in the way of “preparing” a cephalopod for release.
Before I hash out some of the costs of providing enrichment to captive cephalopods, let’s consider what providing such enrichment entail. Anderson and Wood suggest several ideas for giant pacific octopuses, most of which could work with other species of cephalopods. The one that sticks out to me is feeding the animals a variety of live prey. This would provide them with a good deal of activity, a variety of problems to solve (how to catch and eat different species of prey,) and is very entertaining for the public to watch. Some cephalopods (cuttlefish come to mind – I’ve read cuttlefish keepers complaints about this) will only reliably eat live food, anyways.
The authors also suggest that the octopuses be given objects to explore, which can be smeared with fish drippings or have food hidden in them to attract the octopus and encourage exploration. In my favorite quote of the paper, they recount a particular use of this technique:
Wood and Wood… hid food in a play ship – the octopus had to “sink” the ship to get the proffered food. Such a demonstration with a large octopus… would interest the paying customers of a public aquarium by invoking a “sea monster” image.”
The future of cephalopod husbandry.
They also suggest the use of “training” to provide enrichment to octopuses (I put “training” in scare quotes, because some of their specific suggestions, such as smearing fish-smelling fluid on parts of the tank, don’t necessarily involve learning.) This seems like a moot point to me. There are two ways in which you can train a cephalopod – by rewarding it with food, or by punishing it with electric shocks (or some other unpleasant stimulus.) In the first case, you might as well simply give the animal the food, the capture of which seems like it would provide most of the activity inherent in training. In the latter case, well, who’s going to argue that training an animal by electric shock improves its quality of life or reduces its suffering (assuming that the training isn’t absolutely necessary, such as teaching it not to attack people or run into traffic, etc.)?
What would be the costs of providing this sort of enrichment to cephalopods? In my estimation, they would be small. Here’s my reasoning:
It should be relatively easy for aquariums, especially those near coasts, to obtain live prey to feed to cephalopods. By advertising the feeding times (as is done with the animals like sharks, dolphins, and sea lions) aquariums could turn this into a way to entertain visitors and draw more business. The increased popularity of octopus exhibits would likely make up for the extra cost of providing more live food. One of the complaints I hear about the giant pacific octopus exhibit at the Niagara Falls Aquarium is that it just sits there all the time. In the interest of furthering public interest in cephalopods, I make sure to write “Please publicize octopus feeding times!” in their guestbook each time I visit. I’m sure that if they did this, their visitors would be more interested in the octopus and happier with the aquarium overall.
Similar reasoning applies to constructing interesting enclosures that encourage cephalopods to explore. The public likes to see animals doing things, and the increased public interest will more than make up for the expenses of outfitting an octopus tank (which can be as cheap as a few plastic toys) These forms of enrichment are probably very cost effective, at least for public aquariums, even if they have only a small chance of benefit the captive animals.
When we consider animals used for research, the costs become larger. Giving animals a less monotonous environment may exaggerate inter-individual variation. It is usually argued that enrichment produces consistently healthy experimental animals, and so reduces variation in experimental results. The research that is used to make this argument in the case of mammals, however, has not been replicated in cephalopods. Without such evidence, it’s hard to say what effect different kinds of enrichment would have on behavioral experiments with octopuses. Such evidence would be rather expensive and time-consuming to obtain, and providing enriched environments to experimental cephalopods on the assumption that it would improve results could be, if that assumption were wrong, very costly as well. If behavioral research on cephalopods becomes more popular, this will become a more urgent question, and somebody will have to take on the task and expense of answering it.
Generally, providing enrichment for captive cephalopods seems worth it. Given the (even relatively slight) chance that they could benefit from basic environmental enrichment and the small cost of such enrichment, there’s no reason not to do it. The deal only becomes sweeter when you take into account the benefits to aquarium popularity and public education. Even if the cephalopods don’t benefit from it, it can hardly hurt.
Thanks for reading!
Anderson, R., & Wood, J. (2001). Enrichment for Giant Pacific Octopuses: Happy as a Clam? Journal of Applied Animal Welfare Science, 4 (2), 157-168 DOI: 10.1207/S15327604JAWS0402_10
After a moray eel attack (the octopus footage starts about 5 minutes into the video):
I wonder how that octopus coped afterwards. It seems to be swimming just fine, but it’s likely that, even if it could still function, it would get an infection or fall prey to another predator it was no longer strong enough to get away from. Thanks to Glenn Patton for that great video!
Next on this week’s cephalopod video revue, Let’s take a look at some cuttlefish. I never get tired of watching these guys change color.
Both of the users who posted these videos (ScandanavianDiveTeam and Tmukouhara) have a bunch of other dive videos, so click through and check them out.
Finally, the Shedd Aquarium in Chicago just posted a neat video starring one member of the cephalopod family that never gets enough attention: the nautilus.
An article came out this week in the US News and World Report covering research being done on Humboldt Squid populations off of the Pacific coast of the US (including some quotes by newly-named MacArthur fellow and oceanographer Kelly Benoit-Bird.) They mostly avoided the “vicious man-eater” stereotyping of the squid that I so deplore, but managed to squeeze in a toned-down version of it that I found quite funny:
Mexican fishermen call them diablos rojos, or “red devils,’’ because they are extremely aggressive. “I don’t think I would choose to get in the water with them when they are actively feeding,’’ Benoit-Bird said, noting, however, that they lose their propulsion when captured. Even so, “you don’t want to stick your fingers in their mouths,’’ she added.
Pretty much any animal is dangerous when you stick your fingers in its mouth. I have 2 pet rabbits – cute little fluffy bunnies – and I wouldn’t recommend sticking your fingers in their mouths, especially while they are eating. Somehow, this testimony doesn’t quite convince me.
Finally, I’m still looking for submissions for Encephalon , the psychology/neuroscience blog carnival. Drop me a line on twitter ( @Cephalover ) or via email ( mike.lisieski (at) gmail (dot) com ) to submit a post!
Cephalopods are great subjects for studies on vision, because they are so dependent on their vision that you can get robust behavioral effects by manipulating the visual environment of a test animal. In some new research in the October edition of the Journal of Experimental Biology, CM Talbot and J Marshall (from Queensland) investigate the visual system of the pyjama squid (S. lineolata) and two species of cuttlefish (S. plangon and S. mestrus) – specifically, to find out whether they can respond to polarized light, and in the case of S. lineolata, how photoreceptors are distributed on its retina. I’ve blogged about a study on visual perception in Nautilus before, as well as a study on the retinal topography of squid, so if you would like to see more of the same sort of research, check out those posts.
In these two papers, the authors assessed the ability of their experimental specimens to respond to polarized light by monitoring their optokinetic and optomotor responses to a rotating drum. The optokinetic response is the movement of an animals eyeballs to follow a moving object in the visual environment, while the optomotor response is the movement of the animal’s body to follow movement in the visual environment. The experimenters monitored the optokinetic response in S. lineolata, because it tends to stay motionless on the substrate, partially buried – as such, it will not exhibit an optomotor response under most circumstances. On the other hand, S. plangon and S. mestus both tend to hover in the water, and so show optomotor responses more readily.
A basic scheme of the apparatus used is shown in this figure from the S. lineolata paper:
The animal is in the tank (in this case, prevented from burying itself by being enclosing in a transparent cylinder,) while a drum is rotated around the tank. By varying the pattern on the drum, it is possible to determine the sensory abilities of the animal – assuming that animals generally don’t inhibit optokinetic or optomotor responses, the animal will respond to any pattern it can perceive. If the animal can’t perceive the pattern on the drum (for example, if the drum is visually continuous, as is the case with an all white drum,) it will not perceive any motion and the response will be absent.
The authors used a drum that consisted of alternating stripes of orthogonally oriented polarization filters – that is, the drums were striped, but the difference between adjacent stripes was only in the direction of polarized light that they transmitted. All the stripes transmitted the same total amount of light, and had the same appearance. Thus, the animals would only show an optomotor or optokinetic response to these drums if they could perceive the direction of polarization of the light.
In fact, this is what happened, in all three species. Two control drums were used, one of alternating black and white stripes (to make sure the animals had otherwise normal optokinetic and optomotor responses) and one of a uniform-direction polarization filter (to make sure that the animals weren’t responding to some other part of the drum – the tape used to hold it together, seams resulting from the drum’s construction, etc.,) making it pretty clear that the animals were responding to the alternating directions of polarization and not anything else.
This result is pretty unambiguous, but I’d like to point out a problem that this type of experiment presents in its interpretation: specifically, it’s very difficult to interpret negative results. In this case, it’s very easy to know what it means in terms of the animal’s sensory ability when it responds to a stimulus: it means the animal can detect that stimulus. But what if the cuttlefish didn’t respond (for example, as was found in a very similar study by Darmaillacq and Shashar (2008) in a different species of cuttlefish, Sepia elongata)? It’s hard to know what that means – did the animal fail to perceive the stimulus, or did the stimulus just not mean enough to generate a behavioral response? This is a general problem that crops up in studies on sensation and perception in animals, or any study that relies on an animal perceiving something and emitting a behavioral response. Many things need to happen to get any behavioral response to a stimulus, even one as apparently simple as eye movements. The animal must have a functional sensory apparatus appropriate to perceive the stimulus, it must have the energy and intact musculature to perform whatever behavior it is you’re looking for, it must be expressing no other behaviors that might mask or supress the behavior of interest, it must be motivated to perform the behavior of interest, etc. A negative result in such an experiment means that one of these many things is not the case, but because it’s so difficult to tell the difference between all of these steps between “stimulus” and “behavior”, it’s hard to say what exactly it is that the animal isn’t doing. Is it failing to sense the stimulus, is it failing to respond because the stimulus isn’t relevant, or is it failing to behave because it’s afraid, or stressed, or tired? Darmaillacq and Shashar note that S. elongata has retinal anatomy that looks like it would allow the animal to sense polarized light, and so they are (wisely) wary of claiming that their subjects could not perceive polarized light – but there’s no way to make any claim about S. elongata‘s vision at all from these results (except, of course, the most conservative assertion that S. elongata failed to show an optomotor response to a certain type of polarized-light stimulus under the experimental conditions used in that specific study.)
Fortunately, though, Talbot and Marshall found positive results, and so avoided that quagmire all together. It turns out that all three species they studied can respond to polarized-light stimuli with optokinetic or optomotor responses. They went on to examine the distribution of photoreceptor cells (also called “retinal topography”) in the S. lineolata retina. If you’ll remember from my post on squid visual ecology, it turns out that you can relate the retinal topography of cephalopods to their lifestyle – squids that live near coasts have retinas that are specialized to allow the animal to see below it clearly, whereas oceanic squids have retinas that are specialized for monitoring the water column above them. What might we expect from S. lineolata, an animal who spends much of its time buried in sand? The sensible answer is that is eyes would be specified to look up, since that’s where its predators and prey would be in most cases. Let’s take a look at what Talbot and Marshall found:
The darker the blue is, the higher photoreceptor density is in that area. It turns out that the striped pyjama squid does indeed have a high photoreceptor density in the ventral part of its retina, which probably gives it good visual acuity in the upper part of its visual field (if you don’t know why this is, check out this explanation of image formation in the eye for a primer.) This fits in neatly with what we know about the lifestyle of this squid.
I hope these studies represent the start of a trend towards the study of less “classical” cephalopod species (the “classical” ones being Loligo pealai, Octopus vulgaris, Sepia officinalis.) There’s a lot to learn from the less common species of cephalopods, due in part to the fact they we know very little about most of them.
Thanks for reading!
Talbot CM, & Marshall J (2010). Polarization sensitivity and retinal topography of the striped pyjama squid (Sepioloidea lineolata – Quoy/Gaimard 1832). The Journal of experimental biology, 213 (Pt 19), 3371-7 PMID: 20833931
Talbot CM, & Marshall J (2010). Polarization sensitivity in two species of cuttlefish – Sepia plangon (Gray 1849) and Sepia mestus (Gray 1849) – demonstrated with polarized optomotor stimuli. The Journal of experimental biology, 213 (Pt 19), 3364-70 PMID: 20833930
I have three exams next week, so I won’t have another substantive post up until Thursday-ish, at least. In the mean time, enjoy this (under-viewed – only 600 views in 2 years!) video of some captive-bred baby cuttlefish munching on some copepods:
Everybody likes cuttlefish, it seems. They’re neat-looking, sociable, and display lots of entertaining behavior. I think it’s about time, then, to start talking about what cuttlefish do best: change color! I’ll start at what is, as far as I can tell, the beginning.
In 1988, Roger Hanlon and John Messenger published a paper called “Adaptive Coloration in Young Cuttlefish (Sepia Officinalis L.): The Morphology and Development of Body Patterns and Their Relation to Behaviour.” This paper lays out a description of the body-patterning behavior of young cuttlefish (S. officinalis), paving the way for many future studies on this behavior and the environmental features mediating it. The authors hatched and raised “more than 50″ cuttlefish, recording their behavior while they were in the laboratory, and then releasing them into the sea and videotaping them. From this (very large) set of data, they developed a systematic description of the various components of cuttlefish body patterns, as well as some ideas about what adaptive function they serve to the cuttlefish to use them. In addition, they did some microscopic analyses of the animal’s brains and skins, which I will spend less time on here.
The authors decided, based on precident as well as their own ingenuity, to describe the body patterns of cuttlefish (that is, the patterns of postures and colors that cuttlefish display) using a hierarchical scheme. In this scheme, each body pattern corresponds to one or a few behaviors, during which it is expressed. The body pattern is itself composed of multiple components – it has chromatic components (specific patterns of coloration,) textural components (specific patterns of skin texture,) postural components ( specific ways the cuttlefish holds its body,) and locomotor components (the ways the cuttlefish moves its body during the display.) Each of these components is made up of several units. The term “unit” as used here refers to a group of muscles that acts together to produce a local effect, many of which add up to become a body pattern component. For example, the group of muscles in each arm that hold that arm in a certain position make up a postural unit, and all of the postural units (that is, all of the arm and mantle muscle groups) together make up a postural body pattern component. Each unit is in turn made up of a number of elements, which are the smallest possible pieces that can display a particular tiny piece of a body pattern – for example, a single arm or skin muscle, or a single chromatophore. If that confused you, just take a look at their first figure, diagramming this concept:
Click through for a larger version.
The authors identify 54 components in all: 34 chromatic components, 6 textural components, 8 postural components, and 6 locomotor components. They also identify 13 distinct body patterns that are made out of these components: 6 chronic patterns (those expressed stably for a long time) and 7 acute patterns (those expressed transiently, usually in reaction to some significant or disturbing event.)
As an aside, I’d like take a moment to throw around a few counter-arguments to a common abuse of this line of research – namely, the claim that people like to throw around that cuttlefish and squid have a “language” that they express with their skin.
Firstly, cuttlefish displays are not symbolic – a cuttlefish who displays (for example) a pattern associated with mating is symoblizing sex, or the desire to have sex – the fact is that cuttlefish that want to have sex behave in a particular way. Calling this language is like saying that your dog is speaking to you when he humps your leg. He’s not telling you that he wants to have sex – he’s just doing what amorous dogs do.
Secondly, cuttlefish displays do not seem to have syntax. One of the things that makes language useful, and indeed defines language, is the ability to use various components of that language in novel ways, to communicate novel ideas. Related to this is the fact that the meanings of symbols are arbitrary – they can change, and do not neccessarily resemble or otherwise relate to whatever is being symbolized. There is simply no evidence that cuttlefish body patterns are this flexible, or ever mean anything besides making the behaviors they are part of more distinctive or effective. They may serve as an avenue of communication between conspecifics in some instances (in fact, they almost certainly do) but it is woefully inaccurate to describe them as language, especially without any further qualification.
Even if cuttlefish body patterning were a language, it would be a poor one. In most languages, a small number of symbols are used in various combinations to make a variety of units of meaning. For example, letters combine to form words, which combine to form short phrases. In english, there are 26 letters and many thousands of words and short phrases. Combining letters generates new information, not contained in the individual letters. The transition from components to body patterns in cuttlefish, on the other hand, causes information to be lost. Out of many components, cuttlefish put together only a few units of meaning.
So dear internet: I know how much you love cuttlefish, and I know that you want everybody else to love them, too. Exaggerating the evidence to make them seem more “intelligent” is not a valid way to do this, and makes you look unintelligent, dishonest, or both. Please, for your own good and the good of cephalopods everywhere, stop.
Anyways, back to the paper:
What do cuttlefish use these body patterns for? Most of the chronic body patterns are used for crypsis, or camoflage. A cuttlefish will use these patterns to blend into whatever is around them, so that they don’t get eaten. The plate below shows three cuttlefish in different developmental stages blending into the same substrate. The youngest one (towards the bottom of the photograph) is showing (as well as I can tell) a “strong disruptive” pattern, made up of highly contrasting dark and light components. The next oldest one (towards the top of the photograph) is showing a “weak disruptive” pattern, with the same basic scheme but with less contrast. The oldest one (right in the middle) is showing a “dark mottle” pattern, which is just what it sounds like:
When hiding fails, cuttlefish will show a variety of acute patterns in defense. Included among these are “uniform blanching” and “uniform darkening”, both of which are used to confuse would predators. A posture called “flamboyant”, where the cuttlefish waves its arms in the water, is used to startle predators. Adult cuttlefish use a pattern called the “deimatic” pattern, where the cuttlefish flattens and turns completely white except for a few dark markings on the mantle is theorized to be a sort of bluff: it makes the cuttlefish look bigger, and (hopefully) frightenes whatever predator is pursuing the cuttlefish enough to drive it off.
Patterns called “zebra” and “intense zebra” are used in social behavior, which primarily consists of sexual behavior and agonistic behavior (fighting or aggressive displays.) Variations on these patterns are used to distinguish between males and females. The picture below shows a male displaying the “intense zebra” pattern to a female. The authors note the critical inclusion of the extended and densely patterned fourth arm (the one most towards the bottom of the photograph,) the absence of which is one of the things that distinguishes the female “zebra” display from the male “zebra” display.
Click through for a larger version.
Finally, (and this is what I like best about this paper,) the authors close with a call for work “towards a comparative cephalopod ethology.” I can’t say it any better than they did:
It is clear from our work and [others] that cephalopod body patterns are inextricably linked with cephalopod behaviour so that study of body patterns becomes central to cephalopod ethology…
Recently there has been increased interest in ecological studies of cephalopods and we hope field researchers will begin to record systematically ethological data such as adaptive coloration, with the long-term goal of providing a more comprehensive view of their behaviour and life style.
Thanks for reading! I only covered this paper in the roughest way, so I urge those who want to know more to check it out – it’s available from Royal Society Publishing.
Hanlon, R., & Messenger, J. (1988). Adaptive Coloration in Young Cuttlefish (Sepia Officinalis L.): The Morphology and Development of Body Patterns and Their Relation to Behaviour Philosophical Transactions of the Royal Society B: Biological Sciences, 320 (1200), 437-487 DOI: 10.1098/rstb.1988.0087
To hold over all of you cephalophiles until I can finish the upcoming post on the study of cuttlefish body patterns (it will be good, I promise) here’s a selection of some of the best recent cephalopod-related videos posted to Youtube:
First, the Flapjack Octopus, O. californiana. This is benthic (ocean-bottom dwelling) species of octopus found off of Japan and California (and I suspect, other places in the Pacific, even though it’s only been found off of those coasts.) It’s also probably the most awkward-looking cephalopod in existence.
Let’s take a look at some cuttlefish! This first one shows some great slow-motion footage of a cuttlefish feeding on crustaceans (well, he misses one, but gets the other.)
Here’s a very young cuttlefish (probably S. bandensis) taking a walk around its tank. In case you’re wondering, yes, it is as cute as it sounds.
Here’s the same cuttlefish (I think), a bit older, and hanging out with some coral polyps. It looks like it’s mimicking the movement of the polyps with its tentacles.
Finally, we see the cute little guy (I think it’s the same one, but I could be wrong) “begging”, a behavior that is (anecdotally) reported in many cuttlefish kept in tanks, and is folk-theorized to be related to the cuttlefish learning that people bring them food.
Here it is, finally: the post you’ve been waiting for. Having already convinced you that you should care about the possibility of consciousness in cephalopods in Part 1 and having briefly outlined the state of research on consciousness in non-human animals in Part 2, I’ll get right down to it and discuss the possibility of consciousness in cephalopods in this post. If you’re unfamiliar with the topic, I suggest reading Parts 1 and 2 of the series – in this article, I’ll be very brief with explaining some concepts that are explained in more detail there.
In this post, I’ll reference Jennifer Mather’s 2008 article (which I can’t recommend highly enough) “Cephalopod consciousness: behavioural evidence” and Edelman and Seth’s article (which is also an excellent read) “Animal consciousness: A synthetic approach”. These are both review articles, so I’ll be citing their descriptions of other people’s experiments a lot – I know this is bad practice, but hey, this is a blog – I can get away with it. I’ll cite a research study itself if I discuss it detail, but I’ll mostly be sticking to the arguments outlined in these two papers.
If you’ll remember from the last post in the series (and I’m sure you do, but I’ll summarize here anyways,) there are several methods that researchers use to get at the question of consciousness. Most directly, there is accurate self-report, whose use is limited to animals with whom we can communicate through language. This is not a useful approach with cephalopods, who (thus far) are not known to use language.
In the absence of language, animals can be trained to report on their experience (such as by performing a task for a reward when they detect a certain stimulus.) This approach is not well developed in cephalopods. Octopuses have been trained through reward and punishment to attack certain stimuli and not others in many studies; despite this, there is no protocol (that I know of) that to train octopuses with a task that would allow hypotheses about the animal’s awareness of its own experience to be tested directly in the ways that has been done for primates (for example.) Nevertheless, there is some evidence suggesting that cephalopods may be consciously aware from studies that use specific trained tasks.
Mather makes the point that the ability of cephalopods to learn a variety of tasks reliably and quickly, and then to forget them afterwards, makes them good candidates for at least primary consciousness because it implies the sort of behavioral and cognitive complexity that appears to be associated with consicousness in vertebrates. As an example of this, when experiments on visual discrimination in the octopus were done (mostly by M. J. Wells in the 1970′s and earlier,) experimenters attempted to discover the basis by which octopuses discriminated between two visual stimuli. In a sense, they were looking at how the octopus categorized stimuli. A number of hypotheses were generated to explain this within a simple, computational framework, but it was eventually concluded that octopuses (that is, individuals of the species O. vulgaris, the common octopus) don’t use a set of simple rules to categorize objects. Rather, Mather argues, they “[evaluate] a figure on several dimensions and [generate] a simple concept, where [a] concept is an abstract or general idea inferred or derived from specific instances.” Other evidence for the ability of cephalopods to exhibit learning like that taken to indicate cognitive ability (and thus the potential for consciousness) in vertebrate species comes from more complex learning tasks. The spatial learning abilities of cephalopods have been studied and it has been found, in general, that they might be capable of spatial learning to rival that of commonly used vertebrate laboratory species (such as rodents,) as long as the apparatus used is adapted to their capabilities (obviously, we cannot expect a rat and a cuttlefish to learn the same things in the same circumstance, but both can show impressive spatial learning given the right circumstances.)
Consciousness can also be suggested by non-trained behavior of an animal. As I’ll address at more length in a little bit, such evidence in cephalopods is found in accounts of their foraging behavior, their responses to novel objects in their environment, and the presence of sleep-like (and possibly REM-like) states. Most convincingly, in my mind, is the evidence suggesting the superior behavioral flexibility of cephalopods.
One of the more straight-forward tasks that is used to suggest conscious awareness in human and non-human alike is the mirror self-recognition task (MSR). What happens when you show a cephalopod a mirror – does it recognize itself, or does it treat its reflection as if it were another animal? Mather cites a personal communication suggesting that cuttlefish fail the MSR. You can see for yourself, in this great video of a cuttlefish at Epcot being shown its own image on an electronic screen. It turns very dark and pursues its image as if it were confronting another cuttlefish. The mechanics are a bit different, but it’s essentially similar to the MSR:
Mather makes a case for the cognitive abilities of cephalopods using the results of a study that looked at the strategies that octopuses use to open bivalves (which she discusses in this interview on Scientific American.) Not only do octopuses use different techniques for opening clams of different species (that is, they pry open the shells of the weaker ones, and drilling holes through the shells of the stronger ones, but they could switch strategies if one wasn’t working properly. When the experimenters took the clams that the octopus normally ate by prying open and wired them together so that they couldn’t be opened, the octopus figured this out and started drilling. This sort of behavioral flexibility, particularly the selection of one possible behavior among many on the basis of its effectiveness in a specific situation, could be attributed to some sort of centralized “executive processor” that might associated with consciousness.
Although definitions of “play” are often disagreed-upon, Mather argues that some octopuses have been observed playing with objects. While the existence of play behavior in a species is not indicative of consciousness, it suggests the possibility of consciousness; object play is, as Mather says, “something that intelligent animals do” to allow them to learn about things in their environment. (You can read my discussion of one study of octopus play at this link.)
It has also been (rather famously) argued that some octopuses have evolved the ability to use tools – specifically, one species of octopus (Amphioctopus marginatus) has been seen carrying empty coconut shells across the sea floor, which they use as mobile shelters. It can be argued that tool use is only possible when the animal using the tool has developed some rather sophisticated cognitive awareness of their surroundings that allows them to appreciate how an object can be used for a certain function. Here’s a video of this behavior, taken by one of the authors of the 2009 paper on the subject:
The comparative neuroanatomical argument for consciousness (epitomized by Panksepp’s “triangulation” approach to the problem, which recommends using affective, behavioral, and neural approaches together to infer consciousness in non-humans) is much more difficult to make for cephalopods than it is for vertebrates. The reason for this is simple: humans are vertebrates, and share many features of the anatomical and functional organization of our brains with other vertebrates. If you dissect a rat brain and a human brain side-by-side, most of the parts in one of them will show up in the other one in some form. Thus, it is rather easy to make an argument from analogy claiming that, because the brain activity and behavior of the two species in some situation are similar, it is likely that their experiences are likely to also be similar. It is harder to make this argument between people and cephalopods, because there is no direct equivalence between any of the parts of a cephalopod brain and the parts of a human brain, with the possible exceptions of the retina and primary visual processing areas of the two species and some parts of memory systems (eg. the vertical lobe system in cephalopods and the hippocampus in humans.) Even these are examples of convergent evolution (meaning they started from different places and got the same functional result,) and so the equivalences between these two brain areas in cephalopods and humans are only approximate, and based on a very limited knowledge of the functions of the cephalopod brain. Despite this difficulty, there are some overall features of the cephalopod brain that suggest consciousness, including its apparent organization as a complex integrator for sensory information, its lateralization, and its patterns of activity during sleep and wakefulness.
Edelman and Seth argue that we have a good reason to suspect that birds have some sort of consciousness, based on apparent anatomical and functional correspondence between the brains of mammals (including humans) and birds. They show this figure, which illustrates this correspondence – it shows diagrams of a human brain and a finch brain, with homologous structures colored similarly in each diagram:
As you can see, human and zebra finch brains (and indeed, mammalian and avian brains in general) have somewhat similar layouts, which allows one to make an argument for the inference of similar subjective states that correspond to certain types of neural activity in multiple vertebrate species. The basic logic is simple: if the brains are similar, and most of the output of the brain (that is, behavior) is similar in a certain situation, the rest of the output of the brain (that is, affective and/or conceptual awareness, eg. consciousness) is reasonably likely to be similar.
At the bottom of the figure, though, they show the octopus brain. Notice that it’s done in a completely different color scheme. This is because the functional or anatomical subunits of the octopus brain are not clearly equivalent to those found in vertebrate brains. A few localized functions of the octopus brain can be compared to those of vertebrate brains – for one, the vertebrate retina and the octopus optic lobe have apparently analogous structures and functions (that being the initial processing of visual information,) and the vertical lobe/medial superior frontal lobe system of the octopus is known to be involved in memory consolidation, and may have a microscopic structure that resembles that found in the mammalian hippocampus (for more info on this, check out Young, 1991, who makes the argument that the cellular structure and computational properties of the mammalian hippocampus might resemble those of the octopus memory system.)
Functionally, however, it is possible to find similarities between cephalopod brains and vertebrate brains, even if it is difficult to do so anatomically. Mather discusses the evidence for lateralized specialization of function in the cephalopod brain at length (that is, the general feature of the brain that two mirror-image halves can work somewhat independently, and may have different functions.) Lateralization is seen in humans and other primates, and seems to be one evolutionary result of the need for cortical tissue to be both locally differentiated and highly interconnected; it allows for more specialized cortical areas, because the right and left sides of the brain need not be functionally equivalent. Thus, the apparent laterality of the octopus brain (as this is already getting on in length, I’ll let you check out Mather’s article for a more complete discussion) might suggest that it has also evolved the sort of complex cognitive capacities that lateralization is associated with in mammals.
Finally, EEG-like recordings have been done in both octopus and cuttlefish, leading to the general (but very preliminary) finding that cephalopods have complex, low-frequency “background” electrical activity in some parts of their brains that seems to vary with their states of consciousness. In addition, they show sensory-evoked changes in this activity, in the same way that human EEGs do. This suggests that some of the gross functional properties of the cephalopod brain might resemble those of mammals on a system-wide level.
All of the arguments by analogy should be taken with a grain of salt, because while it is interesting to consider the possible theoretical importance of the apparent similarities between octopus and vertebrate brains, it seems premature at this point, given how little we know about them. While laterality, distributed low-amplitude electrical activity, and a certain kind of memory system architecture are found in the brains of animals who are almost definitely conscious (eg. mammals and birds,) it’s hard to say that their presence in such highly divergent nervous systems (eg. those of vertebrates and cephalopods) has the same set of functional consequences in all cases.
So there it is – these are the arguments for consciousness in cephalopods. It’s an astoundingly complicated and difficult question, and one that I’m sure I haven’t done justice to. Look for the last planned article of the series later this week, where I’ll reflect upon these arguments and figure out where I stand (and also hopefully invite discussion) on the science of cephalopod consciousness.
Thanks for reading!
P.S. Today is my first day of classes for the Fall semester. Wish me luck!
MATHER, J. (2008). Cephalopod consciousness: Behavioural evidence Consciousness and Cognition, 17 (1), 37-48 DOI: 10.1016/j.concog.2006.11.006
Edelman, D., & Seth, A. (2009). Animal consciousness: a synthetic approach Trends in Neurosciences, 32 (9), 476-484 DOI: 10.1016/j.tins.2009.05.008
Young, J. (1991). Computation in the Learning System of Cephalopods Biological Bulletin, 180 (2) DOI: 10.2307/1542389
Finn, J., Tregenza, T., & Norman, M. (2009). Defensive tool use in a coconut-carrying octopus Current Biology, 19 (23) DOI: 10.1016/j.cub.2009.10.052
I periodically (read: every 2-3 days) search Youtube for new videos of cephalopods, and my most recent search turned up three good ones that I want to share.
First is this little guy, whom the video poster says is a cuttlefish. I think it’s a bobtail squid of some sort. They are known to bury themselves and have specialized skin on their dorsal body surface that holds grains of sand on the skin, providing camouflage. This video shows both of these behaviors:
This next one is some stock footage of the flamboyant cuttlefish, Metasepia pfefferi. If you’ve ever wondered why it’s called “flamboyant”, watch this:
Finally, Terry Lilley (who is apparently a marine biologist who gives eco-tours) narrates this great clip of an octopus (I’d guess O. cyanea) jetting about and changing colors. Who else is wondering about the affective/conscious state of the animal as the videographer chases it about? This is the sort of ethical quandary I was talking about in my last post!
Thanks for reading, and I hope you’ve enjoyed these!