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Archive for March, 2012

Here now is the promised blog post, which uses the rhino foot mystery pic as a springboard to address a phenomenon that is a bit better known, partly because it is an even worse situation and involving (arguably) even more charismatic critters: elephants.

A rotating movie of a CT scan reconstruction is a good way to kick this off:

This shows the right hind foot of an Asian elephant that had mild pathology; mostly a roughening of some of the bone surfaces that is called osteitis (proliferative bone growth possibly due to infection or other irritation) and perhaps a mild case of degenerative joint disease such as osteoarthritis. But this is nothing compared to the severe cases we’ve observed in other elephant feet, and indeed may not have anything to do with why this elephant died (I’m not sure; I was given very little medical history for this one).

If you want more elephant anatomy lessons, see the videos from the posting on six-toed elephants. I will proceed assuming some basic familiarity with bones of the feet in animals, although you may be just fine even without that.

About 50% of elephants in captivity die from foot disorders of one kind or another. Elephant keepers spend a huge amount of time and energy taking the best care of elephant feet that they can, but a variety of factors including anatomy, biomechanics, exercise, obesity, ground surface, hygiene, “hoof” care including trimming, nutrition, and much more are part of the very complex causal nexus underlying these disorders. Wild elephants get similar problems, too, but less frequently (e.g. in drought periods, I’m told); there are few solid data on this, however.

Onwards, then! I shall present a cavalcade of horrific examples of the kinds of elephant foot pathology that we have observed in specimens that have come through my freezers at the RVC.

Let’s start with what one of our vets might see on examination of a live elephant at a zoo:

This is an x-ray image of the third (on the left) and fourth (on the right) toes of an elephant’s front foot. The RVC (Dr. Renate Weller and myself) have developed protocols to take such x-rays on live elephants.  The anatomy shown here is pretty normal and non-pathological. So with that in mind, check this out; toes four (on the left) and five (on the right), different animal:

Ouch! Digit 4 (“ring finger”) has a proliferation of bone that is characteristic of an animal with osteomyelitis: a flowering of bone in response to infection and painful swelling, probably caused by an abscess on the toe’s sole/nail. This animal was put down because of its unresolvable misery from this disorder. Oddly, we see toe 4 as well as 3 and 5 as the most commonly pathological; toes 1 and 2 seldom are. We’ll be discussing this in a new paper coming out soon; I’ll get back to that another day.

Assuming such conditions don’t resolve, the next place the foot may end up is in The Freezer at the RVC, and then into our CT scanner before we do postmortem dissections and a report on the pathologies so the zoo knows what went wrong. Here’s an example of what we cut off the end of the fourth toe of such an animal:

Just looks like a glob of tissue, right? The joint between two segments of the toe is visible as a pinkish white structure on the right side, with some bleeding on the cartilage where it wore down to the bone surface. But it gets worse. Here is how that same toe bone looked when we cleaned it up (boiling and bleaching away soft tissues):

Here, that same roughened joint surface is visible at the top of the specimen. Two toe bones have become fused together (the bottom one is not visible), encased in a cocoon of lacy, spiny bone. Again, ouch. The next specimen had a different kind of “ouch”- its fifth toe basically shattered:

That toe is almost unrecognizable, having disintegrated rather than proliferated its bony scaffolding. Other specimens may be in less extreme states of pathology but still likely to have been in pain:

The label here says it all; third toe with a cyst where an infection entered the bone.

This one, the end of a third metatarsal, shows degenerative joint disease with a loss of articular cartilage, and holes where abrasion has worn down into the bone and caused bleeding. In contrast, and to give you a breather from the horrors, here is a healthy, younger elephant’s similar joint surface:

Nice white, fresh, shiny cartilage! Ahhh…

But then we dive back into Grand Guignol-level aberrations:

Here we’re looking at the back side of a right hind foot of an elephant, at the level of the ankle joint. The joint capsule surrounding the ankle joint has been cut open in my dissection to expose the terribly pathological, but still somewhat white and shiny, cartilages (middle of the image) which have been abraded (in some regions) but also extended by new bone formation (in other regions) to creep around the back of the ankle. Here, the bone growth was fulfulling a role to limit joint mobility and thereby restrict painful joint motions- the joint was fusing into an ankylosis (no, not an ankylosaur,  but same Greek root). Here is a closer look, removing the tibia and fibula that were at the top of the screen in the above image, and looking down onto the ankle joint surface:

You should be able to more clearly see how the cartilage and underlying bone are not forming a smooth edge, as they should on the talus (ankle bone), but rather an irregular, jagged contour (area to the right of the label). This animal would have been visibly lame, to say the least; elephant ankles can’t move much even in normal animals but this one was even less mobile. We’ve had some specimens where the ankle was so fused it was totally immobile and took a saw to separate the two sides of the joint. Oddly, I haven’t seen an ankylosis like that in the wrist, which in normal elephants is as flexible a joint as the ankle is inflexible.

Pathologies like these sadly aren’t uncommon in elephant feet but zoo/park keepers are doing their best to turn the trend around. Zoo conditions generally were a lot worse 50 years ago. The pictures below document this, from museum specimens we’ve studied (among many others) at the University Museum of Zoology at Cambridge and the Natural History Museum in London. See what pathologies you can spot! Some are from wild-shot animals, reinforcing that foot pathologies are not just a zoo thing. (click to embiggen)

      

Zoo/park conditions are improving now– in the UK for example, elephants are being moved into more safari park-like environs and given more varied surfaces to walk on or even dig (e.g. sand at Chester Zoo). But because elephants live long lives, and foot pathologies sometimes cannot be reversible (or even detectable, sometimes), any pathologies existing now may well still be evident, or even worsen despite the best care, for decades to come. The lag time for fixing the global problem of elephant foot pathologies is not a short one. I won’t get into the controversy over whether elephants should be in zoos/parks or not, but at least for the short to medium term they are, and we need to make the best of that. The images in this post help show why, and perhaps point a way toward how.

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I will go into more detail soon on the broader subject that this involves, but am posting this image as a teaser– what’s up with this foot from my freezer?

Other than the obvious dead-ness and non-attached-to-body-ness…

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Utterly puerile post ahead. I was just in one of those silly moods… Six-year-old daughter, lately with a strong potty-humour tendency, will do that to you. So with that forewarning in mind…

I was rummaging around in the back of Freezersaurus yesterday and was quite surprised to encounter this:

I am deeply, deeply disturbed. And shocked. And a bit violated. Cover your shame, Freezersaurus! Now, I’ll freely admit, penises are great. Hilarious floppy bits to the common person, and fascinating adaptations to the scientist; e.g., duck penises, alligator penises… I’ll never forget the time my invertebrate zoology teacher showed a video of barnacle penises (immobile animals that need to reproduce by copulation– you do the math). But I digress. I was conveying my disturbed feelings about this blatant ICE PENIS in my freezer. Clearly Freezersaurus was either very happy to see me; perhaps titillated by all my rummaging around; or I need to get out more and get my mind out of the anatomical gutter. C’mon, look closer:

In any other place, it might just be an icicle. But here, under the baleful Eye-of-Sauron-like gaze of Freezersaurus’s fan unit, it can be only one thing. Penisicle. I’m not sure what to do with it now. It was such an awkward moment, I had to back off and leave The Freezer to its privacy. Not sure if I can go back there, especially not alone.

My therapy sessions start Monday. I’ll keep you posted on my progress. In the meantime: My gift to you: another emanation from The Freezer; because the last Mystery Dissection pic was too hard and then too easy after a not-so-subtle nudge…

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OK, I had an inspiration for another short image-based blog post. People seemed to enjoy the wallaby mystery photo, so I’ll start a tradition here of mystery images from dissections of “my” specimens. That could even be an easy quasi-weekly thing to do.

What’s this animal? Binomial required. One guess per person please, unless you all get stumped. Bonus myology-nerd points to those who can name all the labelled muscles without checking literature (I’ve used these abbreviations a lot in my papers!).

Too hard I think! Extra hint sneak peek as per comments; same specimen — hmm what’s this, a jaw or something else? Bad image (these things aren’t easy to come by for photo ops), but quite distinctive…

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I’m gearing up for a major post with lots of striking pictures from The Freezers, but to tide you over, here’s a simple movie from one of my CT scans of a Hellbender salamander (Cryptobranchus alleganiensis; with a supportive rod down its GI tract; this was a museum specimen that apparently needed the rod to keep its body straight). We’ve scanned loads of salamanders and other cool critters for our NERC-funded project on the evolution of terrestrial locomotion in the earliest tetrapods (more about that coming up in a future post, as we have some Big News from that study!); this is just one of them.

The huge gaps between limb joints indicate extensive articular cartilage (typical of many aquatic animals, especially some amphibians) and would make a sauropod jealous. The relatively homogenous vertebral column, without much differentiation from head to tail, is also striking, contrasting even with that observed in animals with vaguely similar locomotor styles such as lizards; not to mention mammals, which take that regionalization to an extreme. Also, like most (all?) salamanders, this one has almost no ribs — this is a secondary reduction during their evolution; early fossil tetrapods had nice big ribs. But those ribs aren’t useless (they play a role in moving and breathing), and at least one caudate (member of the broader salamander group) has evolved a very cool use for them!

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Well, it’s time for the Grand Reveal of what the picture in the previous post is (reproduced below). The guesses ranged from bird to wallaby/kangaroo to the stuff of nightmares. And indeed Nick Gardner got it right first, it is a wallaby. Specifically, it is a Bennett’s Wallaby (Macropus rufogriseus rufogriseus), which is the Tasmanian island form related to the Red-necked Wallaby, and an animal that has gone feral (along with mara and other cool critters) in Whipsnade Zoo near the RVC. You can tell it is a wallaby and not a bird, because there is an “Achilles tendon” attaching to a calcaneal tuber (“heel bone”) on the back side of the limb (shown with asterisk below) that birds lack, and if you look closely the toes are hairy, lack bird-like claws, and a few other details like the profile of the musculature are very different; more mammalian than avian. The stump of the muscular tail (cut off) is also a clue. Although the avian similarity in the case of wallabies is still striking, which is one reason I chose this image. Well done, Nick!

I found this picture in my archives and remembered when it was taken back in ~2005- some lab members received some frozen wallaby legs and thawed them out to use in experiments. They tried to compress the legs in an Instron machine (mechanical testing system; partly visible at the top of the pic) to see what the passive, springlike properties of the legs are like in a wallaby, vs. the properties they could measure in a living animal. (The shiny white reflective areas in the pic are for tracking joint motions) And I thought it was a freaky cool pic, so I shared it.

I also posted that pic because my team has done some in vivo analysis of the leg properties in such animals (previous news story here; paper in preparation), and because we use this technique of loading cadaveric legs in such machines quite routinely. We did this for elephant feet to study how the “sixth toe” of elephants works, and we’re analyzing data (as I write) for how elephant feet and rhino feet deform or move when loaded similarly. This method has a long history; we didn’t invent it; perhaps most famously used for studying horse limb mechanics [pdf example], which have a lot of passive properties (almost everything below the elbow/knee is non-muscular). Many animals’ limbs are tendinous/elastic toward their distal end (toes), so the limbs tend to become less actively controlled by the nervous system and become more of a mechanical control system (sometimes involving a non-neural “preflex“) in that region; although it’s all a matter of relative degree of passive:active control in different situations, species, and limbs.

The picture below shows an x-ray of an elephant’s whole hind foot, in which you should be able to see the bones (brighter white) of the foot surrounded by a lot of soft tissue, mostly more passive kinds like fat, skin, fascial sheets, ligaments and tendon.

Here (further below) is a preliminary image from our elephant foot studies in progress, intended to reveal the passive properties/motions of the feet so we can figure out how those properties are combined with more active control, and how actively elephants control their feet vs. other, possibly more ‘passive-footed’ animals like horses. This is interesting from anatomical and evolutionary perspectives, and for helping with foot health problems that are serious concerns for such animals– more about that later. The arrow in the picture below shows where a lot of the motion is: at the knuckle (metatarsophalangeal) joints of the toes; the rest of the foot tends to rotate around these mobile joints. We can’t peer inside living elephant feet to see if they actually do this, but we can compare the external motions, pressure patterns, and other data from living and dead elephant feet to see how they match up, which is what we’re doing now — and we’re doing the same thing with rhinos, which have cool 3-toed, more “hoof-like” feet, as opposed to the 5-toed, fatter feet of elephants. To get this image, we’ve had to put the foot inside a custom-made device using a car jack to apply a constant load, and a wooden framework to hold the specimen still, and then run it through a CT machine in unloaded and then loaded states to see how the bones move. Here is what the crazy apparatus looks like, with enthusiastic undergrad for scale:

This, below, is a right hind foot (pes) of an Asian elephant, shown from the inside of the foot (toes are numbered 1-4 from the big toe/hallux toward the outside of the foot; 5th toe is not visible). The yellow image is the relaxed, unloaded foot; the green is after applying a large load equivalent to the animal standing on one foot (or running quickly). Notice how the third metatarsal (the long bone that the arrowhead is touching) for the unloaded state is in front of that for the loaded state, whereas yellow and green images of the bones toward the tip of the toes are overlapping more, indicating they did not move much/at all. That tells us that the motion is occuring at the joint indicated (“knuckle”), which makes sense anatomically, because that joint looks like it has a lot of mobility.

Image

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On a serious note, in case you aren’t aware of it, there is a huge crisis afoot with the world’s rhino populations, because of demonstrably false claims about the health benefits of rhino horn (e.g. curing cancer) leading to a surge in its value worldwide, and thereby a massive upswing in poaching- as well as theft of museum specimens(!?). It may just be a matter of time before zoos’ and safari parks’ rhinos outside of Africa/Asia get hit, too. If sustained, this poaching could wipe out multiple rhino species in a matter of years; it is that severe and seems to already be worse this year than it was last year- and that was a Very Bad Year for rhinos.

However, a lot of people are uniting against the cruel greed and gross ignorance that has fueled the decline of rhinos, and public support seems to be growing. You can contribute, too; one example is this cause, or this one, to name but two. I’ve tried to make this my #1 cause, both on personal/ethical and scientific grounds (e.g. our work on rhino foot mechanics, health and care, to be detailed here later), and have been educating myself about it.

Anatomist extraordinaire Professor Larry Witmer of Ohio University has been contributing scientifically to helping rhinos, in an unexpected (but very sensible) way. This is a perfect example of how important basic science is; if we didn’t know rhino horn/nose anatomy we’d be less able to treat problems when they arise, and such problems can come from unexpected directions. His team’s contributions in the understanding of rhino anatomy are helping in one horrible case (see video below), in which three rhinos had their horns slashed off (along with part of the top of their skulls!) and two have survived so far. The vets in South Africa are trying to treat these two mutilated animals, and Larry’s group has been providing anatomical advice along with superb pictures on their Facebook page, which I want to publicize here because it is such GREAT freezer-based anatomical science and stunning imagery, and a seriously urgent cause. Please take a look. And while you’re at it, check out the Kariega Game Reserve’s Facebook page with more info on the plight of poor Themba and Thandi.

Edit: also check out this great story on our research, by Ann and Steve Toon, rhino conservationists/photographers/journalists.

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