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Posts Tagged ‘pathology’

Less words, more pictures in this post, and I’ll get the one lame cake joke out of the way early. I’ve nearly finished my research blitz through the postcranial material of the NHM-Tring’s osteological collection and have made some pit-stops for cake skulls now and then when I see one that pleases me. Now I shall present a survey of some of the species I’ve examined. I’ll proceed up from the base of the crown clade of living birds (Neornithes/Aves; the most recent common ancestor of living birds and all its descendants) and first take a tour of Palaeognathae; the ratites and kin; then move another step up into the Neognathae, first featuring the lineage featuring the ground fowl (Galliformes) and then the waterfowl (Anseriformes). If all this taxonomy and phylogeny is a bit much, check out this page for a brush-up on the bushy branches of bird biodiversity.

First, lots of bones of our cast of currasows, chachalacas, cassowaries and other kooky characters. And then, perhaps, a stop to the excessive alliteration. Finally, I will finish with some examples of species oddity (hat tip to Chris Hadfield).

Stomach-Churning Rating: 2/10- some bony pathologies but still just dry bones. Minimal cake jokes, and no filthy swearing this time.


BRING ON THE BONES:

My photographs are shown with kind permission from the Natural History Museum, London.

Exploded skull of an ostrich/ This takes skill.

Exploded skull of an ostrich, Struthio camelus. This kind of careful preparation takes crazy skill, and creates a thing of rare beauty.

Neat skull of a cassowary, Casuarius casuarius.

Imposing skull of a cassowary, Casuarius casuarius, with a rather worn head casque.

Mummified Owen's Little Spotted kiwi, Apteryx owenii.

Mummified Owen’s Little Spotted Kiwi, Apteryx owenii. The feathers were still soft and fluffy, but I would not call this specimen cuddly.

Dorsal view of the back/hips of the Great Spotted kiwi, Apteryx haasti.

Dorsal view of the back/hips of the Great Spotted Kiwi, Apteryx haasti. I like this photo and am not sure why. The symmetry and shading pleases me, I guess.

Front view of the back/hips of the Great Spotted kiwi, Apteryx haasti.

Front view of the back/hips of the Great Spotted Kiwi, Apteryx haasti, watching over my laptop and watching me while I write this blog on my laptop… so meta(ornithine)!

Wing of a kiwi, showing the fragile bones and feather attachments.

Wing of a kiwi, showing the fragile bones and feather attachments. “Apteryx” = “no wings”… well not quite. Click to emkiwi(?) so you can identify the individual bones, from the humerus right down to the fingers! I love this specimen.

The left leg (in front view) of the elephant-bird, Aepyornis maximus, from Madagascar, with a small moa nearby in left side view.

The titanic left leg (in front view) of the Elephant Bird, Aepyornis maximus, from Madagascar, with a small moa nearby in left side view. There’s so much awesomeness about elephant birds I don’t know where to start, but this is one good place to do so.

Mummified Unulated tinamou, Crypturellus undulatus.

The smaller end of the palaeognath scale: a mummified Undulated Tinamou, Crypturellus undulatus. Somehow the head got stuck into the abdominal cavity underneath the sternum, so this tinamou almost had its head up its arse. A tinamou with head in its proper position looks and sounds like this (video).

And now we take a left turn into the Galloanseres, most basal branch of the neognath birds, to see some of the neglected, strange early branches off from the “main line” that led to the modern diversity of ducks, geeses and swans (Anatinae, Anserinae).

Screamers (Anhimidae) are to Anseriformes as megapodes (see below; brush turkeys) are to Galliformes. By that I mean that both screamers and megapodes are very early branches off the main line of their respective lineages’ evolution, and both are quite strange when seen in that context… an unfair one, frankly; over-focused on the most familiar, “modern” or most speciose group. More about this issue further below.

This was my first hands-on experience with screamer anatomy; I was familiar from reading Tetrapod Zoology and other material about them. Check out the sound that gives them their name here! I’m now a big fan- they have so many strange features: oddly chunky but often very light bones, big feet with long toes, and then these switchblade-wrists, which would make Batman jealous:

Crested screamer, Chauna torquata, showing the wicked spur on the carpometacarpus.

Crested Screamer, Chauna torquata, showing the wicked spur (and smaller one) on the carpometacarpus.

Horned screamer, Anhima cornuta; similar carpometacarpal spur as in Chauna.

Horned Screamer, Anhima cornuta; similar carpometacarpal spurs as in Chauna.

Torso of a screamer seen in top view. Nice narrow body.

Torso of a screamer seen in top view. Nice narrow body, and no uncinate processes (spur-like bony struts that cross the ribs and act as levers for the muscles that move the ribcage during breathing)

The long, gracile, clawed toes of a screamer.

The long, gracile, clawed toes of a screamer. Those toes, especially as they belong to an animal called a screamer, are spooky for me. Note also: very little toe-webbing for a “waterfowl.”

Not to be outdone, on the Galliformes side of Galloanserae, we have some funky headgear in the Maleo (a megapode bird/Megapodiidae; a very basal branch of “brush turkeys” and kin) and curassows (part of the Cracidae; odd South American birds whose males make booming sounds, presumably using their head-casques as resonating chambers?):

Skull of a male maleo, Macrocephalon maleo.

Skull of a male Maleo, Macrocephalon maleo. AR Wallace famously pursued it, and here is its funky call.

Australian brush-turkeys, Alectura lathami i, at the Alma Park Zoo near Brisbane, Australia; they run wild there. Here they are doing what they are best known for: making a mound-like nest.

Australian brush-turkeys, Alectura lathami, at the Alma Park Zoo near Brisbane, Australia; they run wild there. Here they are doing what they are best known for: making a mound-like nest. We were doing kangaroo biomechanics experiments and they were everywhere. I was in awe to see such exotic (to me) birds; locals seemed not so enthused (the birds are loud and make a lot of mess).

Skull of Helmeted curassow, Crax/Pauxi pauxi.

Skull of Helmeted Curassow, Crax/Pauxi pauxi,  showing that resonating chamber. Along with this boom-boom-room, the male uses a piece of food that he holds to draw in the female; if she takes it, then it’s sexy time.

Foot of a Russian Black Grouse, Tetrao tetrix (nothing to do with a certain videogame), with and without flesh.

Foot of a Siberian Black Grouse, Tetrao tetrix (nothing to do with a certain videogame), with and without flesh. Regard the broad, feathered feet, well insulated and with plenty of surface area for prancing around in the snow or moorlands. Tetrao engage in a cool display pattern called lekking, in which the males group together and show off to watching females.

A theme in the section above that is not to be missed is that there is some amazing disparity of anatomical forms in these basal lineages of poultry-relatives. Don’t dismiss the Galloanserae as just boring food-birds! Heaps of not-so-well-studied species exist here, surely with a treasure trove of cool neontological and evolutionary questions waiting for the right person to ask! Darwin’s chickens may get their share of neglect, but that pales in comparison to how little we understand about many basal Galloanserae.

What a lot of people think of as a “ground fowl” or galliform way of life is more of a way of life somewhat typical of the Phasanidae- chickens, pheasants and their familiar kin. Megapodes, curassows, guans, grouse and other Galliformes do not necessarily do things in the “typical” ground fowl way, much as the earlier branches of the Anseriformes don’t always look/act like “proper water fowl” (i.e. Anatidae). The phenomenon at play here is one of the great bugaboos in biology: essentialism— the often implicit misconception that variation away from some abstract ideal is negligible, uninteresting or just not conceivable due to mental blinders. When we say something like “the chicken is a fascinating species” we are sliding down the essentialistic slope. There is no “the chicken.” Not really. Oh dear, speaking of slippery slopes, I’d best stop here before I start talking about species concepts. And no one wants that to happen! Anyway, essentialism still pervades a lot of modern scientific thinking, and has its place as a conceptual crutch sometimes. But in biology, essentialism can be very insidious and misleading. It burrows in deep into the scientific mind and can be hard to root out. Unfortunately, it is entrenched in a lot of science education, as it makes things easier to teach if you sweep aside the exceptions to the essentialist “rules” in biology. I catch myself thinking in static, essentialist ways sometimes. The punishment is no cake for a week; so awful. 🙂

And speaking of “normal” or “typical,” morphology is of course often not that way even within a species, age class or gender. Pathology is a great example; by definition it is abnormal. It is a shattering of the “essence” of animals, brought on by some malady.

Next I’ve highlighted some of the amazing pathologies I’ve seen in the Tring skeletons. There have been so many I’ve been unable to keep track of them– some of these birds had the stuffing beaten out of them, and I’m not talking about Thanksgiving turkeys. Some were captive animals, in which the pathology might be blamed on living an inappropriate environment, but some were wild-caught — given the extreme pathologies, it’s a wonder those even survived to be found, but perhaps less a surprise that they were caught.


BONES GONE BONKERS:

View of left knee of a specimen of the Highland guan, Penelopina nigra, showing some nasty osteoarthritis around the whole joint.

View of left knee of a specimen of the Highland Guan, Penelopina nigra, showing some nasty osteoarthritis around the whole joint. Eew.  A happier Guan sounds like this.

Femora and tibiae of the Blue-throated Piping Guan, Aburria cumanensis. Amazing pathology involving the left femur (broken, rehealed) and tibiotarsus (secondary infection?).

Femora and tibiotarsi of the Blue-throated Piping Guan, Aburria cumanensis. Amazing pathology involving the left femur (broken, rehealed) and tibiotarsus (secondary infection?). Interestingly, the non-fractured limb also showed some pathology, perhaps indicating general infection and/or arthritis in reaction to the severe damage to the other leg, or just increased load-bearing on that leg.

Little Chachalaca, Ortalis motmot, showing a broken and rehealed right femur and the tibiotarsus.

Little Chachalaca, Ortalis motmot, showing a broken and rehealed right femur and the tibiotarsus. As in the guan above, this animal was not walking for many weeks; its femur had snapped in two, but somehow melted back together. The tibiotarsus didn’t look too great, either; lumpy and bendy. In better times, the Chachalaca does the cha-cha like this.

These two specimens blew my mind. On the right is a normal Tetrao tetrix (Black grouse); on the left is one hybridized with another (unknown) species.

These two specimens blew my mind. On the left is a normal Tetrao tetrix (Black Grouse); on the right is one hybridized with another (unknown) species.

In the picture above, what amazed me first was the very unusual flattened pelvis/synsacrum of Tetrao, which characteristically is light and wide. But in the hybrid this morphology was completely gone; the pelvis had a more standard “galliform” (read: Phasianid)-like shape, deeper and narrower and more solid in build. I am guessing that the hybrid was a cross with a pheasant like Phasianus itself, whose anatomy would be more like this. Somewhere in here there is a fantastic evo-devo/morphometrics project waiting to happen.

That’s my quick specimen-based tour of “basal birds”. Beyond these two clades of Palaeognathae and Galloanseres, there lies the forebidding territory of Neoaves: much of living avian diversity, and extremely contentious in its phylogenetic relationships. I’m tackling them next for my research on the evolution of the patella/kneecap. But first, I’ll be at the NHM-Tring today for a whirlwind tour through the respectably speciose “normal” Galloanseres clades of Phasianidae and Anserinae+Anatidae, so off I go! (It’s my wife’s birthday celebration, so cake may have to wait for later this time)

So what do you think? What’s your favourite neglected “primitive” bird group (more apropos: early branching avian lineage that may still be very specialized, rare and poorly understood), or cool factoid about palaeognaths and basal neognaths?

No quaggas were harmed during the writing of this post.

No quaggas were harmed during the writing of this post. Polly wanna quagga?

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I’m not sure if this is a new tradition at this blog or not (probably not), but hey let’s give it a name: an Anatomy Vignette. Just something curious I notice during my research that deserves more than just a tweet. I borrowed some bones from the University of Cambridge Museum of Zoology (whom I love, because they have great exhibits and are very research-friendly) to CT scan for some projects. I noticed this:

femur-path

And I thought “Ouch! That’s nasty, dude.” (the holes in the bone just above the knee joint– these should just be a roughened area where the adductor muscles and other leg muscles attach)

So I was interested to see the CT scan images to find out how these possibly osteomyelitic lesions continued into the bone. They’re really pervasive, continuing into the marrow cavity quite far up the femur, as this shows (good CT-viewing practice to match up what you are seeing in the photo above with this movie):

I would be surprised if this was not the reason this animal died (presumably being euthanased at a UK zoo). There would have been extensive infection and pain resulting from this bony disease. How did it originate? Who knows. Maybe the animal strained a muscle and bacteria got inside, or maybe there was a fall or other injury. Hard to tell.

Oh, and also note the lack of a true marrow cavity in hippos, which is true for all the long bones. The “cavity” is filled in with cancellous bone. Same with rhinos, elephants, and many other species… science doesn’t entirely know why but this feature surely does help support the body on land, and grants at least some extra negative buoyancy in water; at a cost of some extra weight to lug around, of course.

And so ends this Anatomy Vignette.

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Here is a little vignette for you; a taster of the BBSRC-funded chicken biomechanics project my team has underway in collaboration with Jonathan Codd’s team at Uni Manchester. I did not know about the following situation until a couple of years ago during my former PhD student (now postdoc) Heather Paxton‘s research on chicken mechanics.

Regard this chicken, slit open along the midline to show the viscera. The huge pectoralis muscles (breast meat) have been pushed aside; the right side’s are clumsily outlined (I blame caffeine?) in blue.

Then consider the heart, within the jagged, shamefully and ineptly drawn green circle. I’ll come back to that.

So this broiler chicken took 6 weeks to reach this size, of about 3 kilograms (6.6 lbs). Fifty years ago, before artificial selection was imposed on a MASSIVE scale (many billions of chickens per year worldwide, bred in a complex pyramid scheme of crossed strains), that same chicken strain would have taken 15 weeks to reach a normal slaughter mass of roughly 2 kg (4.4 lbs). The major selection, of course, has been for edible meat, especially that lovely breast muscle’s white meat.

If we look at red junglefowl, to a large degree the “wild type” ancestors of domestic chickens that are native to southeast Asia, the leg muscles take up about 7.7% body mass per leg vs. about 6.3% in the broiler. Just a small decrease, but probably an important one, and something our research focuses a lot on (walking ability, lameness, activity levels etc). But that’s a subject for a future post. In stark contrast, the breast muscles (back to the blue ellipse above)  have gone from 7% to up to 11.6% body mass per wing; a huge change!

Now let’s return to another large muscle, the one within the green circle above; the heart. Not only must the heart, which has become relatively larger by perhaps 25%, pump blood to a body that has enlarged by >50%, but it also must perfuse the giant pectoral muscles, which have enlarged by >65%.

Herein lies the problem… You probably can predict what happens.

Several syndromes may develop, but the one I want to cover here is called deep pectoral myopathy (AKA “Oregon disease” or better yet “green muscle disease”, a very appropriate term as you’ll see below). Basically, the giant pectoralis muscles receive inadequate blood flow from the smallish heart, because the muscles are so big and under so much pressure, creating resistance to flow, and so the muscles begin dying from within. A picture tells the story:

While surely uncomfortable for the birds and hence a welfare problem, it is usually not found until the animals are slaughtered, and then of course the meat is destroyed rather than delivered for human consumption. Because of the welfare problems and loss of meat (i.e. financial loss), the poultry industry is trying to remedy this problem. W’e’re working on aspects of this as well, as part of our study of how the locomotor and ventilatory systems of chickens develop and have evolved.

I am blogging this as a great example of how anatomy can go haywire and become imbalanced when evolutionary selection pressures are intense and highly specific (e.g. almost single-minded human selection for large breast muscle). It is also a conundrum that human society faces: while chicken meat seems more efficient and more ecologically sound than some other meats, and there is growing demand for meat as the human population grows, how do we balance welfare concerns with food security, economics and other factors? And how do we judge when artificial selection has gone too far? I do not present an answer because the answer is not easy, and because my team is still learning about how to answer it.

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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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