Cephalopod Photography: Klaus Stiefel

Next on my (long and growing) list of cephalopod photographers to feature here is Klaus M. Stiefel, a neurobiologist who currently works in Okinawa.  All of the photos in this post were taken by him.  He was cool enough to release them under a creative commons license, so feel free to use them, just don't use them for anything commercial and make sure to give him credit (lots and lots of it.)  You can click through on all of the photos to access them on Flickr, including larger versions (which I always recommend - they make great desktop wallpapers.)  Let's dive right in, shall we?

To start off, a portrait of an adorable cuttlefish of unknown species (if anybody can tell, please post it in the comments - I'm embarrassed to admit it, but I'm very bad at identifying species):



Moving right along, we have these two lovely photos of the flamboyant cuttlefish, Metasepia pfefferi.  Klaus calls this posture a "threat display", although I'm pretty sure it is used both as a defensive behavior and during hunting, especially for shrimp and prawns.  My favorite thing about pictures of M. pfefferi is that they always look so relaxed, just because of the shape of their pupils.





Last in our illustrious lineup of cuttlefish is an unidentified individual who is expressing its papillae beautifully and showing off its ability to use binocular vision by looking at the camera with (count 'em) two eyes.



You want squid?  We've got squid!  Well, a squid.  This is a juvenile squid (species unknown, though one of the commenters on Flickr suggests that it's a bigfin reef squid, Sepioteuthis lessoniana) floating among the fronds of a sea lily.



Here is an octopus (again, species unknown) expressing a very striking white ring around its eye.  This looks to me like it might be related to the eye-bar body pattern component, which is used during defensive behavior by adult octopuses to obscure the shape of the eye or make it appear larger than it really is.



Here's a great shot of some octopus arm suckers, showing various degrees of flexion of the suckers themselves.  I wish I knew the species of octopus that these belonged to.



I just love pictures of octopuses peeking out of things!  Here is the obligatory inquisitive-octopus-eyes shot:



In this series of photos, Klaus captured a dramatic color change in an octopus.  It looks to me like the octopus tried to camouflage itself, then decided that wasn't going to work and began to hide under the rocks.









 Finally, we'll close with a gorgeous photo of a cephalopod that is too often ignored: the Nautilus.

 

 Thanks for reading!

Cephalopod Photography: Lawrence Tulissi

I stumbled upon the Flickr group: Cephalopods , and decided that it was about time to put up some more eye candy on the site.  I've gotten in touch with some of the photographers whose cephalopod photos are in the group, and I'll be doing a series of posts with each post featuring the work of a single photographer. 

First on the list is Lawrence Tulissi. All of the photos in this post are click-through-able if you want a larger image - which I highly recommend - and are his property (so don't steal them.)

First is an octopus (looks like it could be O. cyanea to me, but I'm not the best at species identification) in a neat posture, with a very striking pattern of coloration.  This was taken at Truk Lagoon, which sounds like an incredible place to dive.



This next one shows the suckers of a giant Pacific octopus.  I like that you can see suckers in various states of contraction, showing the great flexibility that having multiple sets of muscles in each sucker affords the octopus.



This next one is of O. briareus, the Caribbean reef octopus, showing off its long arms and exhibiting some great body patterning.  This posture is probably defensive, judging by how conspicuous its coloration is and the fact that the interbrachial web is spread.

This picture shows the eye of a giant Pacific octopus.  The description of the photo says that the octopus was in its den, and the closed pupil slit indicates that it was likely resting.  In a neat case of functional homology, octopuses, like many vertebrates, tend to close their eyes when they rest - it's just that, since they have no eyelids, they do this by closing their pupils.  If you don't believe me check out Brain and behavioural evidence for rest-activity cycles in Octopus vulgaris by Brown et al. (2006).



Moving on from octopuses (as much as it pains me), we'll finish up with two wonderful shots of Carribean reef squid, Sepioteuthis sepioidea:





Thanks for the photos, Lawrence!

Everybody else, thanks for reading.  I'll be writing on some brand-spanking-new research on the role of serotonin in the octopus learning system next week, so I'll see you then!

Links: 3rd Edition

It's time for some links!  I'm working on some posts about cephalopod statocysts (to continue my coverage of sensory systems,) but in the mean time, here's what's going on (cephalopod-wise, mostly) on the web.  There are some really funny news items this week.

An article at Deep Sea News makes the argument that Paul the octopus is actually psychic; at least as far as we can tell by current statistical standards.

Speaking of our friend Paul, he has officially reached internet stardom:  Parry Gripp has written a song about him.

Another brand-spanking-new article from the same site addresses the possibility that pharmaceutical waste can alter marine ecosystems.

I recently lam-blasted the way popular media talks about the Humboldt squid.  Over at Thoughtomics, this article exposes another sciency media frenzy for what it is: crap.

A burglar in Reno, Nevada decided to mess with his victims in a very creative way:  by microwaving a squid.  Seriously.

A new Syfy channel original movie, Sharktopus, gives us a vivid picture of what life would be like if half-shark, half-octopod monsters roamed the sea.  And I though Lifetime movies were bad...

Apparently, email spammers are trying to sell people squid now.  Does this mean that Viagra and pornography are no longer profitable?  Let's hope that this ushers in a new, more creative era of spam marketing.

North Korea has started leasing squid fishing rights to China.  The arrangement brings income to North Korea and supplies the strapped squid market in China.  I find fishery management interesting, if only because it's so critical to ocean ecology.

Finally, this UK man is charged for possessing squid pornography (and child pornography, but that's not interesting enough for a tabloid headline.)  It's apparently a criminal offense in the UK to have photos of somebody having sex with a dead squid.  My favorite line of this story: "Prosecuters amended the charge when it was admitted it could have been an octopus in the picture."  Oh, it was an octopus?  That's a different story.

I wish I could make this stuff up.

The Myth of the Humboldt Squid

I recently got a request (thanks to arvindpillai at Fins to Feet) to do a post on the shoaling and predatory behavior of Humboldt squid, Dosidicus gigas (also known as the Jumbo squid, and by those who don't know any better, the giant squid.)  I decided that this would be a good thing to do, because I hadn't read much about the predatory behavior of D. gigas.  So I spent a week searching the literature for scientific studies on Humboldt squid predatory behavior, and guess what?  I still haven't read much about it!

It turns out that there is very little known about the behavior of these squid.  The paucity of our ethological knowledge of them is shocking to me, given the disproportionate attention to this species in popular media.  I've seen at least one budding cephalopod enthusiast become intrigued by stories about this species to the extent of obsession, and it's not hard to see why.  Somehow, these squid have gained a reputation as fierce predators that are so bloodthirsty as to be regularly deadly to humans.  As such, popular TV shows and news magazines have run numerous stories about them, usually finding one or two divers who have (presumably) had experience with these squids (or at least heard stories about them) to expound on just how ferocious and aggressive they are.  Invariably, some sensational quip (that is almost always unsupported by scientific literature because, well, that literature does not exist) is used to drive home just how scary these squid are:

"It has probing arms and tooth-lined tentacles, a raptor-like beak and an insatiable craving for flesh -- any kind of flesh, even that of humans," says Pete Thomas in "Warning lights of the sea". 

Mike Bear, an otherwise anonymous diver from San Diego is quoted in this article as saying "I wouldn't go into the water with them for the same reason I wouldn't walk into a pride of lions on the Serengeti." 

“The Humboldt squid is a voracious predator that will eat anything it can get its tentacles on,” says Kelly Benoit-Bird, an oceanographer, quoted by Mark Floyd in this piece.

With all the hubbub, these guys must be pretty dangerous, right?  The stuff of nightmares, even!  I mean, just look at this bloodthirsty monster!

Oh wait, it's kind of cute, isn't it?

This is the myth of the Humboldt squid: that they are first and foremost dangerous, indiscriminate killing machines.  This is, frustratingly, the first (and often only) piece of information that is repeated about them in any given article.  But what's the real story?

Let's put this in perspective by considering the case of sharks, another predatory ocean-dweller that has been sensationalized as being imminently dangerous to humans (remember "Jaws"?  It was pretty silly, but a lot of people took that era's shark scares seriously.)  Fatal shark attacks on humans are documented somewhat regularly, and are discussed (albeit infrequently) in the scientific and medical literature (ie. this study on fatal shark attacks.)  I cannot find a single verifiable record of a fatal squid attack on a human in the medical literature (admittedly, I have only searched 3 online databases and Google scholar - I might be missing something.)  The closest thing I can find are fisherman's accounts in popular media of other fisherman's stories about hearing about people being killed by Humboldt squid.  Keeping in mind the D. gigas is a rather common animal, is fished for sport by casual fishermen, and is usually encountered in large groups (the commonly cited size is 1000-1200 animals per shoal, but I can't find anything peer reviewed to support this,) it looks like these squid are all but harmless, given how often it is encountered by lay-people and how few (if any) fatal encounters there have been.

This is not to say that I don't think it's possible that a Humboldt might kill a human someday; they are clearly aggressive, as several documented, non-fatal "attacks" on humans show.  I have to say, though, that the media attention that is payed to them (which is probably the reason why so many people are "interested" in them) is really a nuisance.  By making inflated claims about a species that we have little behavioral research about, media outlets encourage people to accept hearsay and horror stories as if they were biological fact.  These stories also draw attention away from other squid species whose behavior is very well characterized (ie. L. Pelalei) which might be better used to teach the public basic information about cephalopods.  Finally, by attempting to catch people's eye using gorey stories, such articles serve to blind people to really learning about these animals by focusing on how "bloodthirsty" and "horrifying" they are - an effect that can't be any good for conservation effforts.  I recognize that most people want an entertaining story rather than a dissertation out of their media, but this obvious bias in popular media coverage on this particular variety of cephalopods just bugs me because it is so pervasive and one-sided.

Now that I'm done ranting and raving, and have hopefully convinced you that D. gigas might not be the single-minded killers that they are often portrayed to be, I'll try to get at the facts (that is, our very limited scientific knowledge) of this species.  Most of the research that has been done on them has been about their interactions with predator and prey species and their movement through their habitat, rather than their ethology.  This is because they are an important species in the study of ocean ecology.  They can be caught regularly in relatively large numbers throughout their range with little risk of damaging populations - this is uncommon among large predators, which tend to be much more rare than those lower on the food chain.  They are also suitable to be tracked using remotely monitored tags (as per Markaida et al. 2005) which are difficult to attach to less robust cephalopod species.  As such, they are convenient and informative to study when trying to learn about how oceanic food chains work.

So, what do we know about their feeding habits?  For one, we know that, as Dr. Benoit-Bird was trying to point out, that Humboldts are active, generalist predators, eating (according to Nigmatullin et al.) all manner of prey including "cepepods, hyperiid amphipods, euphausiids, pelagic shrimps and red crabs... heteropod molluscs, squid, pelagic octopods and various fishes."  The authors also note that D. gigas is commonly cannibalistic, a facet of their predation that has probably contributed to their mythological status.  They are especially cannibalistic during squid jigging sessions, when they are excited by bright lights and surrounded by their injured conspecifics.  They feed near the surface mostly during the night, especially at dusk and dawn, and spend their days deeper in the water column (200-400m deep), as was shown by a radio tracking study by Gilly et al. in 2006.  They can vary their diet depending on changes in their environment, showing an adaptability that no doubt contributes to their great abundance (Markaid and Sosa-Nishizaki, 2002).  Interestingly, recent ecological research has shown that their range has recently expanded from its historical locus in the equatorial Pacific ocean off of Central and South America to extend to the Pacific Northwest (as described by Cosgrove and Sendal, 2005, Zeidberg and Robison, 2007, and Field et al., 2007), possibly due to their unique ability to deal with hypoxic conditions that other predatory species cannot.   The squid can retreat into deep water with very little oxygen in between daily trips to feed at the surface, and thus avoid predation by other species such as Mako sharks (Vetter et al, 2008)..  On an unrelated note, if I were a squid researcher named Zeidberg, I'd just go ahead and change it to "Zoidberg".  It's too perfect.

There is dissappointingly little to say about the shoaling and predatory behavior of D. gigas.  If there are any glaring omissions in my coverage of the topic, please let me know; however, I think I found most of what's in the scientific literature.  Basically, we know that they form large shoals, and that they are generalist predators.  More detailed information than that on the behavior of this species will have to wait for a new generation of adventurous ethologists.  Until then, I'll be turning back to those species of cephalopod about which we have enough information to draw useful conclusions about behavior.  Perhaps someday the sort of experiments that have been done in smaller, more easily handled species will be done in D. gigas, but until that happens, I will probably stay mostly silent about them in favor of covering studies on less glamorous species in detail.

Please excuse me if it seems like I've rained on the proverbial parade.  Excuse me also for not getting into the methods of the studies that I've cited.  I encourage you to peruse them, but I opted to cover a greater area of research superficially rather than getting in depth about any specific finding in this post, so that I could adequately sum up the state of scientific knowledge of the Humboldt squid.  To lighten the mood, I'll leave you with one more quote about the Humboldtl, by the realtively famous undersea cameraman, Scott Cassell, who has spent much of his professional career filming these squid (including a documentary titled "Humboldt: the Man-Eating Squid") and is quoted in this piece by Tim Zimmermann:  "They are one of the most beautiful creatures, and they just happen to be lethal... There is no life form on this planet more alien than a Humboldt squid."  I guess I didn't realize that any life form on this planet was "alien", given that they all evolved here.  Oh well - what do I know?

Thanks for reading!

Gilly, W., Markaida, U., Baxter, C., Block, B., Boustany, A., Zeidberg, L., Reisenbichler, K., Robison, B., Bazzino, G., & Salinas, C. (2006). Vertical and horizontal migrations by the jumbo squid Dosidicus gigas revealed by electronic tagging Marine Ecology Progress Series, 324, 1-17 DOI: 10.3354/meps324001

JOHN C. FIELD, KEN BALTZ, A. JASON PHILLIPS, & WILLIAM A. WALKER (2007). RANGE EXPANSION AND TROPHIC INTERACTIONS OF THE JUMBO SQUID,
DOSIDICUS GIGAS, IN THE CALIFORNIA CURRENT CalCOFI Rep., 48 : http://swfsc.noaa.gov/publications/FED/00859.pdf

James A. Cosgrove, & Kelly A. Sendall (2005). First Records of Dosidicus gigas, the Humboldt Squid
in the Temperate North-eastern Pacific Archives of the British Columbia Royal Museum

Unai Markaida, Joshua J. C. Rosenthal, & William F. Gilly (2005). Tagging studies on the jumbo squid
(Dosidicus gigas) in the Gulf of California, Mexico Fisheriy Bulletin, 103, 219-226

Markaida, U., & Sosa-Nishizaki, O. (2003). Food and feeding habits of jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) from the Gulf of California, Mexico Journal of the Marine Biological Association of the UK, 83 (3), 507-522 DOI: 10.1017/S0025315403007434h

Nigmatullin, C. (2001). A review of the biology of the jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) Fisheries Research, 54 (1), 9-19 DOI: 10.1016/S0165-7836(01)00371-X

RUSS VETTER, SUZANNE KOHIN, ANTONELLA PRETI, SAM MCCLATCHIE AND HEIDI DEWAR (2008). PREDATORY INTERACTIONS AND NICHE OVERLAP BETWEEN MAKO SHARK,
ISURUS OXYRINCHUS, AND JUMBO SQUID, DOSIDICUS GIGAS, IN THE CALIFORNIA CURRENT CalCOFI Rep., 49

Zeidberg LD, & Robison BH (2007). Invasive range expansion by the Humboldt squid, Dosidicus gigas, in the eastern North Pacific. Proceedings of the National Academy of Sciences of the United States of America, 104 (31), 12948-50 PMID: 17646649

Byard RW, Gilbert JD, & Brown K (2000). Pathologic features of fatal shark attacks. The American journal of forensic medicine and pathology : official publication of the National Association of Medical Examiners, 21 (3), 225-9 PMID: 10990281

I know these citations are sloppy - for some reason, I'm having some trouble working with the ResearchBlogging citation generator.  I promise I'll fix it before next time.

Getting to know some squids

Time for a treat!  The last post was about the ecological significance of retinal organization in coastal and oceanic squids.  The study I reviewed used 5 species of squid, and I thought it would be nice to take a moment to get to know the research subjects.

Euprymna morsei



This little guy is commonly known as a Mimika bobtail squid.  E. morsei is benthic (meaning bottom-dwelling,) and forages for crustaceans in sandy and muddy seafloors all around western Asia and Indonesia.

Sepioteuthis lessoniana



Also known as the bigfin reef squid, S. lessoniana is a coastal squid that is found throughout the South Asian and Australian coastlines.  In this video, we see a group performing courtship rituals and laying eggs.

Todarodes pacificus



Also known as the Japanese flying squid, this oceanic squid is an important fishery in the pacific.  I'm not sure where this video clip is from, but they sure are cute!

Eucleoteuthis luminosa

I could not find a video of this guy, but here's an image (by Michael Vecchione, originally uploaded on www.TOLweb.org.)  The distinctive feature of this squid is the photophores (which look white in this image,) especially the two long ones that run the length of the mantle.

Thysanoteuthis rhombus



T. rhombus (also called the diamondback squid) is a large squid that is found throughout the world.  This (slightly depressing) video shows two specimens in a tank.  Note the large, muscular fins on either side of the mantle.

Thanks, Youtube, for bringing squids to us all.

Squid Visual Ecology

Keeping with the theme of sensory systems, I thought I'd review some newer research on squids.

While searching for recent cephalopod neurobehavioral research (which is pretty scant) to blog about, I came upon Makino and Miyazaki's study on the distribution of retinal cells in the retina of squids.  I have a soft spot for visual neuroscience that I picked up from working with my first research advisor, who works on the visual system of frogs.  In any case, this is a good paper (although it was a bit hard to get my hand on,) and I'll review it here.

The study aims to look at the distribution of retinal cells in the retinas of a variety of squid species.  This has been done in several vertebrates, with the general finding that animals have retinas that perform well for their lifestyle.  Seems pretty simple, right?  For example, fish who live in "closed" environments have dense retinal ganglion cells (RGCs) in the area of the retina that sees light from directly ahead, while oceanic fish have a strip of high-density RGCs that stretch laterally across the whole visual field.  Thus (to make a horribly crude generalization,) cave and reef dwelling fish have focused binocular vision, while oceanic fish largely lack this but have a greater ability to monitor their whole visual field, ie. for predators or food items.

In vertebrates, retinal ganglion cells are often mapped in this sort of study.  By the time RGCs exit the retina, they are carrying visual information that is already processed into the very basic components of visual perception (namely, hue and tone contrast.)  As vertebrates have complex retinas, it is also possible to map photoreceptors in vertebrate retina, or a variety of other types of cells (which might be more or less informative.)  Cephalopods, however, only have one type of visual cell in their retina - the retinal cell (or rhabdomere.)  So, the authors chose to map this.  It is useful to keep in mind that this is not directly comparable to the mapping of retinal ganglion cells in vertebrates - it could be the case that the density of visual cells in an animal's retina is not always correlated with the importance of that piece of the visual field in further levels of visual processing.  This problem is partially solved in studies on vertebrates by the use of RGCs, in which the processing of information from photoreceptors is already underway.  With cephalopods, however, there is currently no way to probe this any deeper, and so for now it remains an assumption - albeit a pretty noncontroversial one - that rhabdomere density is correlated well with the relative importance (behaviorally and neurophysiologically) of portions of the visual field.  (For more on cephalopod visual anatomy, check out my earlier post on cephalopod eyes.)

The image to the left shows cell counts (in retinal cells per mm) across the retinas of the 5 species of squid.  I added color to this image to make it easier to see the distribution of cells.  It's important to not that the colors are relative within each figure, and do not represent absolute cell density, which is shown as (difficult to read) numbers on the boundaries of regions.  Also note the scale bars, which are 10mm in every image. 

In terms of orientation, keeping things straight gets a little tricky (as it does with all cephalopods.)  Dorsal-ventral orientation is pretty easy - remember that the lens of the eye inverts the light coming through it, so that the ventral part of the retina forms the top part of the visual field and the dorsal part of the retina forms the bottom part of the visual field.  Anterior is the direction the squids' arms point in, so the anterior retina forms the posterior part of the visual field.  The posterior retina is the part that forms the anterior part of the visual field.  This is the part that is used when squids look forward to form a binocular image.

Using this data, the authors estimated the visual axes of the squids, based on the location of the highest density of photoreceptors.  The visual axis is the general point of focus, which is known to be of utmost behavioral importance in vertebrates.  When you follow a moving object with your eyes, you are keeping it in your visual axis.  The location of an animal's visual axis is key to its visual ecology - many predators have forward facing visual axes so that they can see their prey accurately, while prey species often have very laterally oriented visual axes (think of rabbits and deer) so that they can monitor more of their environment at any given time.  Thus, we'd expect that squids with different lifestyles have different visual axes, because they will be looking for food and predators in different places.

In coastal squid (E. morsei and S. lessoniana), the visual axis is directed downwards, presumably reflecting the importance of monitoring activity on the substrate that these species live on.  In oceanic squid (T. pacificus, E. luminosa, and T. rhombus,) the visual axis is directed upwards, and the eyes have a much greater density of photoreceptors overall.  I think the retinal cell density map of E. luminosa is especially interesting, because the concentration of cells on the extreme posterior edge of the retina suggests that binocular vision is disproportionately important to this species.  The authors conjecture that this eye may be specialized to detect and track bioluminescence in the open ocean, but this is purely speculation.

These findings are important because they expand our knowledge of cephalopod eyes, which are a model evolutionary system.  If we can begin understand the impact of ecology on the organization of visual systems (which is part of the emerging field of visual ecology,) we can generate a wealth of testable hypotheses about the ecological conditions that occurred during the evolution of differnt species eyes, as well as the other sorts of adaptations we might see in sensory systems as they diverge (or converge) during evolution.  It's also a nice piece of evidence that our rather basic theories about visual ecology and the structure-function relationship of the visual system are largely correct.  This is good to know, as we base an incredible amount of more complicated neuroscience research on these theories.

Thanks for reading!


Akihiko Makino, & Taeko Miyazaki (2010). Topographical distribution of visual cell nuclei in the retina in relation to the habitat of five species of decapodiformes (Cephalopoda) Journal of Mulluscan Studies, 76, 180-185 : 10.1093/mollus/eyp055

Cephalopod eyes

I just wrote a big post about cephalopod eyes, and then realized that I had neglect to show any real-life pictures of cephalopod eyes.  This blog seems to be getting a bit dry, so let's take some time off and just gaze at some of our beautiful, squishy friends.  All images are from the wikimedia commons and have been under a creative commons license.

(Photo by Parent Géry)  This guy is Octopus vulgaris, also known as the common octopus.  It the most-studied octopod.  You can see the slit-shaped pupil clearly.

(Photo by Theasereje)  Here's a body shot of another O. vulgaris.  Notice how they can look at you with both eyes at the same time - they have the capability for binocular vision.  Octopuses, however, prefer monocular vision, and will always use just one eye to sight their prey during an attack (for more info, see this "Lateral asymmetry of eye use in Octopus vulgaris" by Byrne et al.)

(Photo by Elapied)  Here we have another gorgeous shot of O. Vulgaris peering out of a hideout with one eye.

(Photo from www.opencage.info)  This is an ocellated octopus, O. ocellatus.  Besides being very cute, as he peeks out from the shell, he is probably using his mostly monocular vision to monitor his whole environment for danger.

(Photo by Jens Petersen)  Here is Amphioctopus marginatus, the coconut octopus, showing us how it can focus both eyes on the same area of space, even if it usually doesn't like to.

By now, you're probably tired of octopuses.  Let me give you a break then, and venture into the world of cuttlefish and squid!

(Photo by Bernd)  This is Sepia prashadi, the hooded cuttlefish.  Cuttlefish hunt by visually stalking their prey and then shooting out their tentacles to grab it.  Thus, they need to have a binocular field of vision so that they can accurately catch prey.  This little guy's eyes are apparent on either side of his head (look for the curved, black pupil slits.)  As you can see, cuttlefish can look in front of themselves with both eyes.

(Photo by Nick Hobgood)  This is Sepia latimanus, the reef cuttlefish.  Here you have a better view of the eye.  The eyes are not closed - the pupil of cuttlefish is always a horizontal slit.

(Photo by Nick Hobgood)  This is another S. latimanus, showing a different coloration.

(Photo by Nick Hobgood)  This is Sepioteuthis lessoniana, the bigfin reef squid.  Most squid normally have mostly monocular vision, but can move their eyes towards the front of their head to have temporary binocular vision.

Euprymna scolopes (Bobtail squid in orange form).(Photo by Nick Hobgood)  This is Euprymna scolopes, the Hawaiin bobtail squid.  In this photo, you can see the cuttlefish-like pupil shape and the existence of binocular overlap.

(Photo by Michael Vecchione)  I'll leave you with the bizarre-looking eye of Helico pfefferi, the piglet squid.  I don't know anything about them, but they sure look cool.

Thanks for reading!

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.

First Post

I like cephalopods, especially octoposes, for a lot of reasons; so much so that I've decided to author a blog about them.

First, though, a bit of background about myself: I'm a student at the University at Buffalo in the Psychology and Pharmacology departments. I came to my interest in cephalopods through a passing interest in comparative behavioral neuroscience (that is, the study of how the nervous system control behavior across a variety of species.) That passing interest turned into a burning interest, and now I'm hooked on cephalopods (I'll post more about why I love them so much). That brings us pretty much up to speed.

This blog is my attempt to systematize and clarify my own learning about cephalopods. I hope I can entertain and inform other people at the same time, and share all the wonderful knowledge that has been gathered about these creatures. That said, my interest in cephalopods is primarily scientific – I'll try to stay close to the primary literature wherever I can, and I might get jargon-ey at some points, although I'll try to explain myself as much as possible.

Thanks for reading, and I look forward to learning more and more and more with you! I'm working on two posts right now, one about cephalopod systematics (that is, their classification as organisms) and the other about the importance of the cephalopods, especially octopods (that is, cephalopods with eight appendages,) in comparative neuroscience and comparative psychology.