Notes on the Argonaut

(Photo by Bernd Hofman.)

One of my favorite parts about reading the research on any topic is reading very old research on that topic.  Today, I came across this paper on the argonaut, Notes on the Argonaut (1869), by W. H. Dall, published in The American Naturalist, volume 3.  The argonauts are a neat genus of pelagic octopods (Argonauta,) the females of which secrete a thin shell from specialized areas on their arms (pictured above in ecological conditions, inside the shell, and drawn below without the shell.)

 (Lithograph by Arthur Bartholomew, ~1870)

Almost 150 years ago, this guy put together a pretty good description of argonaut behavior, although it was brief.  Reading his work renews my faith in the power of good old observation, as well as flowery phrasing in otherwise dry writing.  For example, Dall comments on the argonaut's sexual dimorphism, with a healthy dose of Victorian sexism:

                    The Argonant shell is formed, curiously enough, by the females only; 

                    as among more highly organized beings sometimes, the gentler sex 

                    outshine their brothers in the splendor of their apparel, and the 

                    extent it occupies. Unlike many, however, the Argonaut toils not, 

                    neither does she spin.

The last sentence of that quote is genuinely confusing to me.  What exactly does he mean?  What evidence is there that argonauts do not "toil"?  What does it even mean for an octopod to toil?  Without being accustomed to the zoological vernacular that Dall is writing in, it's hard to get what he means by this.  

Another gem is his description of argonaut mating habits.  Unlike today's biological authors (fortunately or unfortunately, it's your call,) Dall doesn't shy away from anthropomorphism:

                    When the tender passion seizes him, as he rocks on some sunny wavelet, 

                    far from female society, he does not go in search of a wife, but with 

                    Spartan courage, detaches one of his eight hands (or arms) and consigns 

                    it to the deep, in the hope that some tender hearted individual of the other 

                    sex will fall in with it and take it under her protection. Thus for a long time 

                    the male Argonaut was unknown, the arm (which does not die when 

                    detached, but lives an independent worm-like life) was, when found in 

                    the gill-chamber of the female, supposed to be a parasite, and was called 

                    Hecto-cotylus.

Interestingly enough, although this name was given to the organ because it was thought to be a parasite, the modified arm that octopus and squid use to mate is still called a heteroctylus.

In closing, Dall acknowledges the unique contributions of one Madame Jeannette Power (a pioneer of the use of aquaria) to the study of the argonaut with a quaint tone of amazement:

                    It is pleasant to add that our first detailed account of the Argonaut and its 

                    development, was published by a lady, Madame Power, who made her 

                    observations in the Mediterranean, having a sort of marine enclosure 

                    made, where she kept these animals and observed their habits from life.

I know this was a short one.  I couldn't help it - I can't resist dusting off a few of the old chestnuts in the scientific literature and reveling in my own fantasies of some lost scientific world, where it's considered adequately professional to use the term "tender passions" when describing the behavior of a mollusc in a leading biology journal.

Thanks for reading!

Detour Experiments in Octopus

Today I’ll review the earliest Octopus behavioral research study I could find (that is, except for a few very old papers in French, that I shamefully do not have the skill to read, although I am working on translating a few of them, bit by bit.) This is a study by Paul Schiller published in the Journal of Comparative Psychology in 1949, titled “Delayed Detour Response in the Octopus”. It’s a very early experiment on the ability of octopus to apply detours to a learned task (that is, you teach the animal to go somewhere for a reward, usually food, and then you put a barrier in its way. Depending on the character of the animal’s “intelligence”, it may or may not be able to successfully pass the barrier to get the reward.) If you have access to scholarly databases, you can probably get ahold of it (I got mine for Scirius, and I think Ovid has it as well) – unfortunately, I can’t link to a free .pdf of the article here.


Interestingly, Schiller begins his description of his methods by describing a procedure that does not work with octopus:

                    The conventional technique of using two inverted cans, one covering a baited, the other
                    an unbaited container, both of them previously exposed to the vision of the octopus, was
                    tried on 4 animals with rather discouraging results. Both cans were attacked and lifted indiscriminately
                    or, if not far enough from each other, simultaneously. This happened often
                    even in the preliminary stage when the covering cups were transparent. The tendency to
                    crawl in or lift up the containers was so powerful that the animal did not regard the bait at
                   all unless specifically trained to do so.

This makes a lot of sense – it turns out, as shown in this and later experiments on octopus, that their top performance in response-selection tasks is somewhere around 70-80% correct responses. They are “curious” enough that they will choose to investigate the “wrong” stimulus regularly. This makes sense for a foraging, active predator, who is more successful if they inspect many new areas of their environment than if they are entirely predictable.

Shown in this figure is the apparatus he settled on. The octopus is confined in the starting compartment and allowed to investigate a crab in a beaker through a screen. Then, the entrance door is opened, and the octopus learned to move through the opaque corridor to receive the crab. It was found that, after learning this, Schiller’s octopuses made 75% correct responses – well above chance (which is 50%, in this set-up.) Furthermore, Schiller found that the longer it takes the octopus to get through the corridor, the worst its chance of being correct. He also finds that, using a female whose reward is returning to her nest instead of a crab, that disorientation of her body posture by making her crawl through a small hole destroyed her ability to make the correct choice in the delayed detour task:

              It seems, with this one animal now under the more powerful motivation of her
              nest instead of food, that a delay of at least one minute does not interfere with
              the correct choice. The same amount of delay, however, if it involves disorganization
              of the bodily posture while in locomotion, prevents a successful delayed
              choice. There is no need to assume central representative factors for the delayed
              detour performance which, in the octopus, may be mediated by locomotional
              cues.

Basically, although we can explain detour performance in (for example) rats by showing that they probably have some flexible internal representation of the test space (see Tolman's discussion of cognitive maps for more information,) it appears that this same ability in octopus can be explained by intervening postural and sensory cues, without recourse to more complicated cognitive processes.

Thanks for reading!

The "Devil-Fish"

While working on a bigger post about the timeline of Octopus behavioral research, I came upon this book - "The Octopus; the 'Devil-Fish' of Fiction and of Fact". Read it here on the Internet Archive – it’s available in several formats.

This piece is a colorful account by one Henry Lee of his experience with Octopuses (more properly, about some specific octopuses “with whom [he has] been on friendly terms”.) He has great, livid descriptions of octopus behavior in here, such as his account of feeding an octopus a crab against a pane of glass, so that the process could be observed:

                    Not a movement, not a struggle was visible or possible : each leg, each 
                    claw, was grasped all over by suckers — enfolded in them — stretched 

                    out to its full extent by them. The back of the carapace was 

                    covered all over with the tenacious vacuum-discs, brought together 

                    by the adaptable contraction of the limb, and ranged in close 

                    order, shoulder to shoulder, touching each other ; whilst, between 

                    those which dragged the abdominal plates towards the mouth, the 

                    black tip of the hard, horny beak was seen for a single instant 

                    protruding from the circular orifice in the centre of the radiation 

                    of the arms, and, the next, had crunched through the shell, and 

                    was buried deep in the flesh of the victim.
All in all, it’s an entertaining and informative (although scientifically questionable) read, and is one of the earliest description of octopus behavior that I have yet found free full text for - Aristotle’s descriptions in “The History of Animals” notwithstanding, a translation of which is available at the link, if you’re interested.

The Squid Giant Axon

This post is dedicated to the squid giant axon (not the giant squid axon, although there is presumably a giant squid giant axon – and it’s really big!)  These axons carry information to the muscles of a squid’s mantle when it is startled, causing them to contract and jet to safety.  These axons are notable because they are so large – up to 1mm in diameter.  If this doesn’t seem large to you, consider that typical axons in humans are only a few micrometers in diameter.  The squid giant axon is several hundred times larger than the typical human axon.  You can see the axon in question in this diagram, labeled “III” (It turns out that the axons commonly studied are the third step in the chain of large axons that carry this specific information; hence they are often referred to as “tertiary giant axons.”)

If you haven’t heard of the squid giant fiber system before, you are probably thinking “So what?”  Well, I’ll tell you what.  Nowadays, we have technologies that let us interact with various neurons in various ways.  For example, we can use tiny glass pipettes to inject current or voltage into a neuron or record its activity.  We can use arrays of electrodes to do the same thing with a large population of neurons.  These procedures are rather routine in neuroscience, and are done with many different types of neurons in a great variety of animals and specific preparations.

When J. Z. Young was dissecting squid in the 1930’s, however, the techniques available to him were not so refined.  He devised a way to isolate a single neuro-muscular unit from the rest of the squids anatomy and manipulate it (see The Function of the Giant Nerve Fibres of the Squid for his description of the procedure – I highly recommend this article, as he’s a great writer and it really is a classic in the history of neuroscience.)  Although there were already theories of action potential conduction (notably, Bernstein’s theory that action potentials propagated due to changes in ions flowing across the cell membrane, which turned out to be correct,) Young’s preparation allowed him to directly demonstrate basic properties of single nerve cells.  This allowed theories about neuronal function to be empirically tested at a whole new resolution.  For example, in the paper cited above, he clearly demonstrates the all-or-none nature of action potentials (that is, when neurons are stimulated, they have a binary response: they either send an action potential down their or they don’t.  There are no graded, partial responses.)

Young’s technique opened up the squid giant axon as a model system for many investigators who were trying to understand the behavior of neurons.  Notably, Hodkin and Huxley developed a quantitative model of the propagation of action potentials using this preparation, in a famous series of papers that are summarized in A Quantitative Description of the Membrane Curent and its Application to Conduction and Excitation in Nerve.  Essentially, the squid giant axon preparation gave researchers an incredible tool, with which they developed the basic models and techniques (for example, the development of voltage clamp by Kenneth Cole in the 1940’s, which allowed the ionic basis of action potentials to be investigated.)

In short, the basic electrophysiological techniques that are in use today almost all stem from Young’s work with the squid giant axon.

On a tangentially related note, Young spent much of the rest of his career trying to convince the scientific community that invertebrates, especially cephalopods, were good model animals with which to study neuroscience.  At length, he’s convinced me, as well as (at least some) contemporary scientists, as evidenced by this recent review of the octopus as a model organism for studying memory systems (The Octopus: A Model for a Comparative Analysis of the Evolution of Learning and Memory Mechanisms ).

I have my own ideas about why it’s particularly good to study octopus; but alas, that’s for another post.