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Nice GIF of the human biceps in action- By Niwadare - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=38718790

GIF of the human biceps (above) and its antagonist triceps (below) in action- By “Niwadare” – own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=38718790

Last year on Darwin Day I debuted “Better Know A Muscle” (BKAM), which was intended to be a series of posts focusing on one cool muscle at a time, and its anatomical, functional and evolutionary diversity and history. A year later, it’s another post on another muscle! Several dozen more muscles to go, so I’ve got my work cut out for me… But today: get ready to FLEX your myology knowledge! Our subject is Musculus biceps brachii; the “biceps” (“two-headed muscle of the arm”). Beloved of Arnie and anatomists alike, the biceps brachii is. Let’s get pumped up!

Stomach-Churning Rating: 7/10. Lots of meaty elbow flexion!

While the previous BKAM’s topic was a hindlimb muscle with a somewhat complex history (and some uncertainties), the biceps brachii is a forelimb muscle with a simpler, clearer history. Fish lack a biceps, just having simple fin ab/adductor muscles with little differentiation. Between fish and tetrapods (limb-bearing vertebrates), there was an explosion in the number of muscles; part of transforming fins into limbs; and the biceps is thenceforth evident in all known tetrapods in a readily identifiable anatomical form. In salamanders and their amphibian kin, there is a muscle usually called “humeroantebrachialis” that seems to be an undivided mass corresponding to the biceps brachii plus the brachialis (shorter humerus-to-elbow) muscle:

Most of the humerobrachialis muscle (purplish colour), in dorsal (top) view of the right forelimb of the fire salamander Salamandra salamandra (draft from unpublished work by my team).

Most of the humerobrachialis muscle (purplish colour), in dorsal (top) view of the right forelimb of the fire salamander Salamandra salamandra (draft from unpublished work by my team).

In all other tetrapods; the amniote group (reptiles, mammals, etc.); there is a separate biceps and brachialis, so these muscles split up from the ancestrally single “humeroantebrachialis” muscle sometime after the amphibian lineage diverged from the amniotes. And not much changed after then– the biceps is a relatively conservative muscle, in an evolutionary (not political!) sense. In amniote tetrapods that have a biceps, it develops as part of the ventral mass of the embryonic forelimb along with other muscles such as the shorter, humerus-originating brachialis, from which it diverges late in development (reinforcing that these two muscles are more recent evolutionary divergences, too).

Biceps brachialis or humerobrachialis, the “biceps group” tends to originate just in front of the shoulder (from the scapula/coracoid/pectoral girdle), running in front of (parallel to) the humerus. It usually forms of two closely linked heads (hence the “two heads” name), most obviously in mammals; one head is longer and comes from higher/deeper on the pectoral girdle, whereas the other is closer to the shoulder joint and thus is shorter. The two heads fuse as they cross the shoulder joint and we can then refer to them collectively as “the biceps”. It can be harder to see the longer vs. shorter heads of the biceps in non-mammals such as crocodiles, or they may be more or less fused/undifferentiated, but that’s just details of relatively minor evolutionary variation.

The biceps muscle then crosses in front of the elbow to insert mainly onto the radius (bone that connects your elbow to your wrist/thumb region) and somewhat to the ulna (“funny bone”) via various extra tendons, fascia and/or aponeuroses. The origin from the shoulder region tends to have a strong mark or bony process that identifies it, such as the coracoid process in most mammals (I know this well as I had my coracoid process surgically moved!). The insertion onto the radius tends to have a marked muscle scar (the radial tuberosity or a similar name), shared with the brachialis to some degree. A nice thing about the biceps is that, because it may leave clear tendinous marks on the skeleton, we sometimes can reconstruct how its attachments and path evolved (and any obvious specializations; even perhaps changes of functions if/when they happened).

Here are some biceps examples from the world of crocodiles:

Crocodile's right forelimb showing the huge pectoralis, and the biceps underlying it on the bottom right.

Crocodile’s right forelimb showing the huge pectoralis, and the biceps underlying it; on the bottom right (“BB”- click to embiceps it).

Crocodile left forelimb with biceps visible (

Crocodile left forelimb with biceps visible (“BB”) on the left.

Crocodile biceps muscle cut off, showing the proximal and distal tendons (and long parallel muscle fibres) for a typical amniote vertebrate.

Crocodile biceps muscle cut off, showing the proximal (to right) and distal (to left) tendons (and long parallel muscle fibres) for a typical amniote vertebrate.

What does the biceps muscle do? It flexes (draws forward) the shoulder joint/humerus, and does the same for the elbow/forearm while supinating it (i.e. rotating the radius around the ulna so that the palm faces upwards, in animals like us who can rotate those two bones around each other). In humans, which have had their biceps muscles studied by far the most extensively, we know for example that the biceps is most effective at flexing the elbow (e.g. lifting a dumbbell weight) when the elbow is moderately straight. These same general functions (shoulder and elbow flexion; with some supination) prevail across the biceps muscle of [almost; I am sure there are exceptions] all tetrapods, because the attachments and path of the biceps brachii are so conservative.

And this flexor function of the biceps brachii stands in contrast to our first BKAM muscle, the caudofemoralis (longus): that muscle acts mainly during weight support (stance phase) as an antigravity/extensor muscle, whereas the flexor action of biceps makes it more useful as a limb protractor or “swing phase” muscle used to collapse the limb and draw it forwards during weight support. However, mammals add some complexity to that non-supportive function of the biceps…

Hey mammals! Show us your biceps!

Jaguar forelimb with biceps peeking out from the other superficial muscles, and its cousin brachialis nicely visible.

Jaguar forelimb with biceps peeking out from the other superficial muscles, and its cousin brachialis nicely visible, running along the front of the forearm for a bit.

Elephant's left forelimb with the biceps labelled.

Elephant’s left forelimb with the biceps labelled.

Longitudinal slice thru the biceps of an elephant, showing the internal tendon.

Longitudinal slice thru the biceps of an elephant, showing the internal tendon that helps identify where the two bellies of the biceps fuse.

In certain mammals; the phylogenetic distribution of which is still not clear; the biceps brachii forms a key part of a passive “stay apparatus” that helps keep the forelimb upright against gravity while standing (even sleeping). The classic example is in horses but plenty of other quadrupedal mammals, especially ungulate herbivores, show evidence of similar traits:

Giraffe biceps cut away proximally to show the

Giraffe biceps cut away proximally to show the “stay apparatus” around the shoulder joint (upper right).

Zooming in on the

Zooming in on the “stay apparatus”; now in proximal view, with the biceps tendon on the left and the humeral head (showing some arthritic damage) on the right, with the groove for the biceps in between.

Hippo's humerus (upper left) and biceps muscle cut away proximally, displaying the same sort of

Hippo’s humerus (upper left) and biceps muscle cut away proximally, displaying the same sort of “stay apparatus” as in the giraffe. Again, note the stout proximal and distal tendons of the biceps. The proximal tendon fits into the groove of the humerus on the far left side of the image; becoming constrained into a narrow circular “tunnel” there. It’s neat to dissect that region because of its fascinating relationships between bone and soft tissues.

The biceps brachii, in those mammals with a stay apparatus, seems to me to have a larger tendon overall, especially around the shoulder, and that helps brace the shoulder joint from extending (retracting) too far backward, whilst also transmitting passive tension down the arm to the forearm, and bracing the elbow (as well as distal joints via other muscles and ligaments). It’s a neat adaptation whose evolution still needs to be further inspected.

Otherwise, I shouldn’t say this but the biceps is sort of boring, anatomically. Whether you’re a lizard, croc, bird or mammal, a biceps is a biceps is a biceps; more or less-ceps. But the biceps still has a clear evolutionary history and Darwin would gladly flex his biceps to raise a pint in toast to it.

So now we know a muscle better. That’s two muscles now. And that is good; be you predator or prey. Let’s shake on it!

I was greatly inspired by scenes from the global Women’s March this weekend. It was one of the more beautiful things I’ve seen lately in times that otherwise feel very dark. I write this post with some trepidation but fuelled by that inspiration. While it is nominally about women (in science and the world) it applies just about as well to many other parts of American/British, Western and global society; especially to issues of social equality. I am definitely not an expert on this topic; experts probably will see nothing new here. Some would say that means I should be silent. I feel compelled to say something, for many reasons that I feel are valid. However, I have made dumb mistakes or just been ignorant of the issues throughout my life, so I do not claim to be on a pedestal of model behaviour. But this post is not about me or anyone I personally know per se. It is about humanity and what inspires (e.g. yesterday’s marchers) and worries (e.g. a person whose surname begins with a “T”) many people, and what I have gradually learned about human nature. If it helps one person inspect and maybe change their attitudes that would be wonderful, but I may never know if that is the case, which is fine. That, anyway, is my motivation; to support what I feel is important, and to address what the post’s title refers to. Not in a smug, let’s-show-how-politically-correct-we-are way, but in a positive way, endorsing that by opening our minds and hearts we can surprise ourselves with change that improves others’ lives and our own.

Stomach-Churning Rating: reactions will vary. No pictures.

If we abstract (Western) history into a direction over time, the status quo of white (non-poor, heterosexual, religious, etc.) males has changed over recent centuries, but it remains undeniably strong. The 1950s-1960s saw considerable changes and this trend continues. As a very brief generalization, that is cause for hope for humanity. But what worries many people today is that this trend, like any in history, could reverse, and thereby do great harm to many people. This concern is not based simply on idle speculation or propaganda but on clear actions, policies and statements of some world leaders (not just the “T” guy but he is prominent). No one knows what the future holds but people can choose to act or not act; and act in person (most effective) vs. act vocally (better than silence). Yesterday’s protests were peaceful, probably even more so than the inauguration was, and society should breathe a sigh of relief for that. But it doesn’t end there.

I want to get to one of the core issues that has helped me understand – and understanding here is so vital for society to heal the frightening rifts that have developed – why people are upset. This unsettled feeling many of us experience cuts both ways: those on the right-ward side of politics also may feel that their values are threatened. Some of those values are indeed common values, such as economic inequality and concerns about terrorism or war, much as we may differ on how we react to or prioritize them. These common values give me hope. There are few values that apply to 100% of us and that means there will always be people that are unhappy; I’m not an idealist who expects utopia anytime soon. Some values will not endure the “arrow of history”, either permanently or temporarily, and that frightens people for various reasons across the political spectrum. Neo-Nazis, and those that share some beliefs with them even if they consider themselves to be very distinct from fascists, might be emboldened lately, but they have a lot of history and social momentum to contend with.

For those that are unsettled by yesterday’s marches and other recent events, for whatever reason, I ask them to think about this: try putting yourself in the shoes of one of the marchers. Step outside yourself, be curious about what their background is, and practice empathy – what is it like to be, for example, a woman at this point in history? I’m a male so I can’t wholly experience that, but I am curious and I have cultivated some skill in empathy. I want to know what it’s like being different from me. Growing up in a moderately liberal Midwestern family with three females helped me do that (plus now having my own family), and now that I am a senior(ish) leader in my field I have to think about these things on a daily basis. But I’m not perfect, either. I keep learning. I try to listen.

One way that I continually remind myself to practice is to think of “death by a thousand cuts” (good STEM example linked there) – what does it feel like to, throughout one’s life, experience what a member of the non-status quo does? In the case of a woman, what does it feel like to continually be judged based on appearance, to be treated like property, to be told you’re inferior, to be expected to obey men, to statistically have worse pay and career advancement chances, to be dismissed as inexperienced no matter what your qualifications are, and much more; all in ways that qualitatively or quantitatively are not experienced by most men. It would wear me down, and that’s what women and other disadvantaged members of society experience. The situation has improved in some areas but still is far from fair or pleasant or, simply put, far from moral and ethical. Personally, the “thousand cuts” metaphor has helped me to empathize with many people. I reflect on it regularly.

The status quo have it easier (by definition), so hearing such people tell “social justice warriors” to be silent; to endure discrimination or assault; is deeply unsettling to those that have lived their lives suffering the thousand cuts, and to those that care about them. Free speech cuts both ways, too; it may feel hard to be criticized if you get shamed for speaking out against social equality. But do centuries of history of male dominance validate that men, too, have suffered the thousand cuts? No way, man. That’s where major fracture lines in society lie – women and other people don’t get to choose that they are on those lines, and may validly feel that their power to affect what society chooses to do is weaker.

Maybe the marches yesterday inspired, you, too. Maybe this post gets you to examine your own biases? Maybe we all have inclinations that are unconsciously a bit sexist, racist, homophobic and intolerant. And yes, we need to listen to those across the political spectrum, too, and try to find common ground that can improve life for as many people as possible. To bring things back to science and this blog, that common ground needs to have a foundation of facts. Those facts are out there, and in this “post-truth” time we need to work harder to share them and establish them, which does seem to make finding a common ground harder. Nonetheless, I hold on to hopes that we can do that, much as these times often feel very grim, as if we are at a critical juncture in history (e.g. climate change!) and yet society is so fractured it cannot do the right thing.

The world is complex. I’ve over-simplified things here; an “arrow of history” is debatable and probably not inevitable in most cases (maybe better put: there are sustained directions AND repeated cycles in history; most traversing generations). Simple statements often don’t hold true across reality; science shows us that the more we learn, the more complex and nuanced the world looks, and that can be baffling or even scary. Much as we should be suspicious of simple answers like “do not question authority” or “authority is wrong”, we should consider some simple answers as useful points of departure for deeper discussions. One such simple answer is that the women’s marchers did the right thing, showing peaceful but strong solidarity against oppressive stances that threaten them. If you oppose that simple answer, can you view it from their side, though, and understand their argument through curiosity about it and empathy for their lives? Inspect your own answer. Self-doubt is something scientists learn to practice and it is a healthy life-skill too.

Can you dream another person’s dreams? Can you help people wake up from their living nightmare? It needn’t take bravery to do this. It takes honest curiosity and empathy about the world outside your own. This applies to humanity and across nature, too. I’m not brave in posting this; I have it relatively easy. I can embrace that and I can make what might seem like sacrifices, and I can enjoy the outcome; I would love to see others live a better life. Many things have to happen for humanity to draw closer together, but these are among them. Not only could more curiosity and empathy make life better for humanity, but on a personal level those traits are good for mentoring, for teamwork, for being a good colleague, and should be good for anyone you care about.

As attentive readers may know, Freezersaurus died over a month ago. We’ve been thankful for the winter’s chill that slowed the thawing process of our treasure trove of specimens while we complete the move to a temporary freezer. The gelid torch was thus being passed to the next walk-in freezer at a glacial pace– but with the glacier-scale force of Team Hutch’s collective muscles.

Stomach-Churning Rating: Hmm tough call; 6/10 if you know what it’s like to clean out a nasty freezer, 4/10 if not.

Aww. The freezer-moving team is not thrilled by the task ahead.

Aww. The freezer-moving team is not thrilled by the task ahead, and is exerting their frowning-muscles. (photo: Sophie Regnault)

Santa (Jim Usherwoodclaus) brings a bag-- of elephant feet!

Santa (Jim Usherwoodclaus) brings a bag– of elephant feet! (photo: Sophie Regnault)

Yet this week it all ends. With Crimbo’s long break ahead and an uncouth urinal smell pervading the dripping carcass of Freezersaurus, we have to clear out our little frozen ark. Some specimens have had to meet the incinerator early; others have returned to frozen limbo pending our future attention; and some are now just clean bones.

One of our many young emus that needed cleaning after thawing; here, just the right leg bones.

One of our many young emus that needed cleaning after thawing; here, just the left leg bones.

Quite a puzzle: one young emu's skeleton to reassemble in the future. Thanks to Sandy Kawano et al. for cleaning help!

Quite a puzzle: one young emu’s skeleton to reassemble in the future. Thanks to Sandy Kawano et al. for cleaning help!

Horse forelimb from an old joint range-of-motion study we did; now reduced to bones (why did I keep this frozen anyway? who knows).

Horse forelimb from an old joint range-of-motion study we did; now reduced to bones (why did I keep this frozen anyway? who knows).

So our temporary new freezer could use a name; Freezersaurus II just won’t do. In the spirit of democracy (and Yuletide), I’ll open the floor to nominations. Nothing could go wrong with populism, right 2016? Hello? Oh crap.

Last cartful of elephant feet!

Last cartful of elephant feet! (also: keen eyes may spot some gory graffiti)

Last look at Freezersaurus: Inside looking out.

Last look at Freezersaurus: Inside looking out.

Last look at Freezersaurus: outside looking in. Ice still lingering on the cow and horse legs from old XROMM studies.

Last look at Freezersaurus: outside looking in. Ice still lingering on the cow and horse legs from old XROMM studies, at the back, past the slurry of blood.

Enjoy some photos of the move, and please make freezer name suggestions in the Comments.

Our new digs, for the time being.

Our new digs, for the time being.

And, if I don’t post again in time, Happy Holidays! May the dark times not Krampus your style.

-John, Dean of the Demochilling Polarpublic of Freezevania

Let’s let Mike Ness sing us out…

UPDATE:

OK we have, via various forms of social media, these nominations for our temporary freezer’s name (I took one from each person suggesting a name;  I hope I caught them all); so let’s open it to a poll!

link:

https://polldaddy.com/poll/9610500/

[Wordpress is not showing the poll on all browsers so you may have to click the link]

(The nominations: Freezersuchus, Freezertherius, Freezopolis, Eofrigidum, Narnia and Pleistoscene)

While you’re at it, check out Anatomy To You’s new blog post: do turtles wiggle their hips and if so how much? Now we know!

Open Tuatara

A quick heads-up that we just posted on our sister blog Anatomy To You, about a new open-access paper we’ve published on the skeletal anatomy of the tuatara Sphenodon. Lots of cool images you can’t see anywhere else are there!

In focus: The big picture of little bones in tuatara

I give it a Stomach-Churning Rating of 3/10- some picked specimens of tuatara but they’re still cute, not nasty, I’d say.

AND, like the Cool-Whip or vanilla ice cream atop your leftover pumpkin pie, there’s an added delicious bonus: a huge dataset of microCT scans from 19 tuatara specimens, free to access here:

https://osf.io/bds35/

We are VERY pumped up about getting this paper and dataset released, so we are spreading the word as wide as we can!

Sayonara.

Thanksversity

First, a moment of silence for Freezersaurus (2009-2016); Rest In Recycling. This week we close the door on our years of arctic antics together. A new, uncertain relationship is beginning, with our diversity of icy inhabitants hanging in the balance. A future post will provide an update.freezer

Stomach-Churning Rating: 2/10; no photos, but some politics; take it or leave it.

Speaking of diversity, it’s Thanksgiving in my home of the USA and thus a time for reflection. Such reflections this year inevitably turn to current global events, in which “diversity” has come up in many ways, and then back to my own life, and back again. It certainly has been a year for reflection, and – like many others – my current taste for dystopian tales mirrors that reflection.

In (the United States of) America, Thanksgiving is a tradition of (at least implicitly) commemorating the meeting of two cultures (Native and newly-immigrated American/Puritan) and the eventual fusion/phagocytosis of those two diverse cultures into something new; leading to the USA of today and its diverse inhabitants and cultures. We spend time with family and have awkward conversations or cheer on sports teams or take engorgement-induced naps. We eat diverse foods of the harvest time and thank the spirits/divinity/cooks for their bounty. Many Americans, across our cultural diversity, take time to ponder what they are grateful for. I’ve always loved this holiday because of that, and my fond memories of past Thanksgivings.

And so I am drawn to reflection on the giving of thanks, and the significance of diversity, and I choose today to type some words that echo my thoughts.

I am grateful for what diversity we have. My life is enmeshed with that diversity: I study biodiversity and marvel at the diversity of nature, which both bring great joy to my life. I worry about the state of funding for, and reciprocally the appreciation of, the scientific study of nature and the human value placed on biodiversity, and the implications of those for the future of diverse life on Earth, both human and non-human. It is well known that they are all under threat, in diverse ways, from sociopolitical and other factors.

To me, human diversity (cultural, ethnic, other) is part of this natural diversity; it has evolved and will continue to, for as long as it exists. It is not going away. I am grateful for that human diversity. Some parts of it bring me terrible revulsion, and those are the source of much worry, and our own nature is their source, too. But it brings my life great meaning to interact with different people, to learn new things from them, and to share experiences in more positive ways. I am curious about all of these things, and because of that curiosity in 2016 I have learned more about that human diversity than I ever have before. Some of that learning has been about the dark side of humanity, from political and social trends (or glaring exposure of longstanding biases) in the UK and USA and more globally. Yet also some of that learning has been about the virtues of human diversity and realizing how much solidarity I feel (and have long felt) for those who are trapped in disadvantageous positions along the fault lines of confrontations between different components of that diversity. It has brought out some of my best and worst feelings.

Like a snail, this year I feel that I have periodically been moving forward to inspect the greater world, enjoying it for a time, then recoiling once I encounter the xenophobia, anti-intellectualism, and selfishness, which make me want to stay inside my shell. Long have I inhabited that shell in 2016. I’m not proud of those feelings and that tenancy in my little partition of this world, but they are what I’ve been able to manage. Today, I am trying to appreciate the broader picture and remind myself of where there is still goodness in the world, and how cycles of diversity can stabilize. We have choices to make about how we control those cycles; we humans are unique in our control of them; and those choices are best poised on the understanding that comes from curiosity. It is there in that diversity that Darwin celebrated; “There is grandeur in this view of life,” and today I am thankful for the grandeur that does still remain around us. I am curious to view what grandeur that diversity presents next. We could all use more of that grandeur.

And thanks for reading this post.

(Marcela with some furry friends; photo by Oliver Siddon)

(Marcela with some felid friends; photo by Oliver Siddon)

A guest post by Marcela Randau (m.randau@ucl.ac.uk)

Stomach-Churning Rating: 1/10; just bones and data plots!

It is often said that all cats are very similar in terms of their skeletal morphology (“a cat is a cat is a cat”). But is this really the case? It may be if only gross, qualitative anatomy is taken into consideration, i.e., if you just eyeball the skeletons of tigers and lions you might find yourself not knowing which one is which. But with huge advances in technology that allows for extracting detailed shape information off a structure (e.g., a skull) and for analysing this information (‘Geometric Morphometrics’), it has become more and more possible to distinguish between relatively similar forms – which may be from distinct species, separate sexes, or even just different populations of the same taxon.

And it is reasonable to think that cat skeletons might be a lot more different than what meets the eye, as for a lineage of apparently similarly built animals, with not that much variation in diet  (all cats are hypercarnivores) there is substantial variation in body mass (over 300-fold just in living species!) and in ecology across cat species. From the cursorial cheetah to the arboreal clouded leopard, felids present a wide range of locomotory adaptations. Yes, all cats can climb, but some do it better than others: think lion versus margay (yes, they do descend trees head-first). As hypercarnivores, all cats are meat specialists, but they also change with regards to how big their prey is, with a general and sometimes-not-so-black-and-white three-tier classification into small, mixed and large prey specialists. The rule of thumb is ‘if you are lighter than ~20-25 kg, hunt small stuff. If you are heavier than that, hunt BIG BIG things; bigger than yourself. And if you are in the middle ground, hunt some small-ish things, some big-ish things, and things about your size. Well, -ish’ – their prey size preference has a lot to do with energetic constraints (have a look at Carbone et al. 1999; and Carbone et al. 2007, if you’re interested in this). But the fun bit here is that form sometimes correlates quite strongly with function, so we should be able to find differences in some of their bones that carry this ecological signal.

Indeed, for a while now, we have known that the shape of the skull and limbs of felids can tell us a lot about how they move and how big their prey is (Meachen-Samuels and Van Valkenburgh 2009, 2009), but a large proportion of their skeleton has been largely ignored: we don’t know half as much about ecomorphology and evolution of the vertebral column. Well, it was time we changed this a bit! As the PhD student in the Leverhulme-funded ‘Walking the cat back’ (or more informally, “Team Cat”) project, I’ve spend a big chunk of my first two years travelling around the world (well, ok, mainly to several locations in the USA) carrying a heavy pellet case containing my working tool, a Microscribe, to collect 3-D landmarks (Fig. 1) across the presacral vertebral column of several cat species. And some of first results are just out! Check them out by reading our latest paper, “Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories” in the Organisms Diversity and Evolution journal (Randau, Cuff, et al. 2016).

cheetah-verts

Fig. 1: Different vertebral morphologies and their respective three-dimensional landmarks. Vertebral images are from CT scans of Acinonyx jubatus (Cheetah, USNM 520539)

Building from results based on our linear vertebral data from the beginning of the year (Randau, Goswami, et al. 2016), the 3-D vertebral coordinates carry a lot more information and we were able to describe how this complex shape-function relationship takes place throughout the axial skeleton (in cats at least) in much better detail than our prior study did. One of the difficulties in studying serial structures such as the vertebral column is that some clades present variation in vertebral count which makes it less straightforward to compare individual vertebrae or regions across species. However, mammals are relatively strongly constrained in vertebral count, and Felidae (cats; living and known fossils) show no variation at all, having 27 presacral vertebrae. So adaptation of the axial skeleton in mammals has been suggested to happen by modification of shape rather than changes in vertebral number.

Using a variety of geometric morphometric analyses, under a phylogenetically informative methodology, we have shown that there is clear shape and functional regionalisation across the vertebral column, with vertebrae forming clusters that share similar signal. Most interestingly, the big picture of these results is a neck region which is either very conservative in shape, or is under much stronger constraints preventing it from responding to direct evolutionary pressures, contrasting with the ‘posteriormost’ post-diaphragmatic tenth thoracic (T10) to last lumbar (L7) vertebral region, which show the strongest ecological correlations.

We were able to analyse shape change through functional vertebral regions, rather than individual vertebrae alone, by making a novel application of a technique called the ‘Phenotypic Trajectory Analysis’, and demonstrated that the direction of vertebral shape trajectories in the morphospace changes considerably between both prey size and locomotory ecomorphs in cats, but that the amount of change in each group was the same. It was again in this T10-L7 region that ecological groups differed the most in vertebral shape trajectories (Fig. 2).

pta-cats

Figure 2: Phenotypic trajectory analysis (PTA) of vertebrae in the T10 – L7 region grouped by prey size (A) and locomotory (B) categories.

So in the postcranial morphology of cats can be distinguished, changing its anatomy in order to accommodate the different lifestyles we see across species. But the distinct parts of this structure respond to selection differently. The next step is figuring out how that might happen and we are working on it.

While Team Cat continues to investigate other biomechanical and evolutionary aspects of postcranial morphology in this interesting family, we’ve been able to discuss some of these and other results in a recent outreach event organised by the University College of London Grant Museum of Zoology and The Royal Veterinary College. We called it “Wild Cats Uncovered: movement evolves”. Check how it went here: (https://blogs.ucl.ac.uk/museums/2016/11/17/cheetah-post-mortem/) and here (http://www.rvc.ac.uk/research/research-centres-and-facilities/structure-and-motion/news/wild-cats-uncovered), with even more pics here (https://www.flickr.com/photos/144824896@N07/sets/72157676695634065/).

References used here:

Carbone, C., Mace, G. M., Roberts, S. C., and Macdonald, D. W. 1999. Energetic constaints on the diet of terrestrial carnivores. Nature 402:286-288.

Carbone, C., Teacher, A., and Rowcliffe, J. M. 2007. The costs of carnivory. PLoS biology 5 (2):e22.

Meachen-Samuels, J. and Van Valkenburgh, B. 2009. Craniodental indicators of prey size preference in the Felidae. Biol J Linn Soc 96 (4):784-799.

———. 2009. Forelimb indicators of prey-size preference in the Felidae. Journal of morphology 270 (6):729-744.

Randau, M., Cuff, A. R., Hutchinson, J. R., Pierce, S. E., and Goswami, A. 2016. Regional differentiation of felid vertebral column evolution: a study of 3D shape trajectories. Organisms Diversity and Evolution Online First.

Randau, M., Goswami, A., Hutchinson, J. R., Cuff, A. R., and Pierce, S. E. 2016. Cryptic complexity in felid vertebral evolution: shape differentiation and allometry of the axial skeleton. Zoological Journal of the Linnean Society 178 (1):183-202.

Time

It has been almost three months since my last post here, and things have fallen quiet on our sister blog Anatomy to You, too. I thought it was time for an update, which is mostly a summary of stuff we’ve been doing on my team, but also featuring some interesting images if you stick around. The relative silence here has partly been due to me giving myself some nice holiday time w/family in L.A., then having surgery to fix my right shoulder, then recovering from that and some complications (still underway, but the fact that I am doing this post is itself evidence of recovery).

Stomach-Churning Rating: 4/10; semi-gruesome x-rays of me and hippo bits at the end, but just bones really.

X-ray of my right shoulder from frontal view, unlabelled

X-ray of my right shoulder from frontal view, unlabelled

Labelled x-ray

Labelled x-ray

So my priorities shifted to those things and to what work priorities most badly needed my limited energy and time. I’ve also felt that, especially since my health has had its two-year rough patch, this blog has been quieter and less interactive than it used to be, but that is the nature of things and maybe part of a broader trend in blogs, too. My creative juices in terms of social media just haven’t been at their ~2011-2014 levels but much is out of my control, and I am hopeful that time will reverse that trend. Enough about all this. I want to talk about science for the rest of this post.

My team, and collaborators as well, have published six recent studies that are very relevant to this blog’s theme- how about we run through them quickly? OK then.

  1. Panagiotopoulou, O., Pataky, T.C., Day, M., Hensman, M.C., Hensman, S., Hutchinson, J.R., Clemente, C.J. 2016. Foot pressure distributions during walking in African elephants (Loxodonta africana). Royal Society Open Science 3: 160203.

Our Australian collaborators got five African elephants together in Limpopo, South Africa and walked them over pressure-measuring mats, mimicking our 2012 study of Asian elephants. While sample sizes were too limited to say much statistically, in qualitatively descriptive terms we didn’t find striking differences between the two species’ foot pressure patterns. I particularly like how the centre of pressure of each foot (i.e. abstracting all regional pressures down to one mean point over time) followed essentially the same pattern in our African and Asian elephants, with a variable heelstrike concentration that then moved forward throughout the step, and finally moved toward the outer (3rd-5th; especially 3rd) toes as the foot pushed off the ground, as below.

African elephant foot COP traces vs. time in red; Asian elephant in orange. Left and right forefeet above; hindfeet below.

African elephant foot COP traces vs. time in red; Asian elephant in orange-yellow. Left and right forefeet above; hindfeet below.

Gradually, this work is moving the field toward better ability to use similar techniques to compare elephant foot mechanics among species, individuals, or over time– especially with the potential of using this method (popular in human clinical gait labs) to monitor foot (and broader musculoskeletal) health in elephants. I am hopeful that a difference can be made, and the basic science we’ve done to date will be a foundation for that.

  1. Panagiotopoulou, O., Rankin, J.W., Gatesy, S.M., Hutchinson, J.R. 2016. A preliminary case study of the effect of shoe-wearing on the biomechanics of a horse’s foot. PeerJ 4: e2164.

Finally, about six years after we collected some very challenging experimental data in our lab, we’ve published our first study on them. It’s a methodological study of one horse, not something one can hang any hats on statistically, but we threw the “kitchen sink” of biomechanics at that horse (harmlessly!) by combining standard in vivo forceplate analysis with “XROMM” (scientific rotoscopy with biplanar fluoroscopy or “x-ray video”) to conduct dynamic analysis of forefoot joint motions and forces (with and without horseshoes on the horse), and then to use these data as input values for finite element analysis (FEA) of estimated skeletal stresses and strains. This method sets the stage for some even more ambitious comparative studies that we’re finishing up now. And it is not in short supply of cool biomechanical, anatomical images so here ya go:

fig5-vonmises

Above: The toe bones (phalanges) of our horse’s forefoot in dorsal (cranial/front) view, from our FEA results, with hot colours showing higher relative stresses- in this case, hinting (but not demonstrating statistically) that wearing horseshoes might increase stresses in some regions on the feet. But more convincingly, showing that we have a scientific workflow set up to do these kinds of biomechanical calculations from experiments to computer models and simulations, which was not trivial.

And a cool XROMM video of our horse’s foot motions:

  1. Bates, K.T., Mannion, P.D., Falkingham, P.L., Brusatte, S.L., Hutchinson, J.R., Otero, A., Sellers, W.I., Sullivan, C., Stevens, K.A., Allen, V. 2016. Temporal and phylogenetic evolution of the sauropod dinosaur body plan. Royal Society Open Science 3: 150636.

I had the good fortune of joining a big international team of sauropod experts to look at how the shapes and sizes of body segments in sauropods evolved and how those influenced the position of the body’s centre of mass, similar to what we did earlier with theropod dinosaurs. My role was minor but I enjoyed the study (despite a rough ride with some early reviews) and the final product is one cool paper in my opinion. Here’s an example:

fig6a-bates-sauropod-com-evol

The (embiggenable-by-clicking) plot shows that early dinosaurs shifted their centre of mass (COM) backwards (maybe related to becoming bipedal?) and then sauropods shifted the COM forwards again (i.e. toward their forelimbs and heads) throughout much of their evolution. This was related to quadrupedalism and giant size as well as to evolving a longer neck; which makes sense (and I’m glad the data broadly supported it). But it is also a reminder that not all sauropods moved in the same ways- the change of COM would have required changes in how they moved. There was also plenty of methodological nuance here to cover all the uncertainties but for that, see the 17 page paper and 86 pages of supplementary material…

  1. Randau, M., Goswami, A., Hutchinson, J.R., Cuff, A.R., Pierce, S.E. 2016. Cryptic complexity in felid vertebral evolution: shape differentiation and allometry of the axial skeleton. Zoological Journal of the Linnean Society 178:183-202.

Back in 2011, Stephanie Pierce, Jenny Clack and I tried some simple linear morphometrics (shape analysis) to see how pinniped (seal, walrus, etc) mammals changed their vertebral morphology with size and regionally across their backbones. Now in this new study, with “Team Cat” assembled, PhD student Marcela Randau collected her own big dataset for felid (cat) backbones and applied some even fancier techniques to see how cat spines change their shape and size. We found that overall the vertebrae tended to get relatively more robust in larger cats, helping to resist gravity and other forces, and that cats with different ecologies across the arboreal-to-terrestrial spectrum also changed their (lumbar) vertebral shape differently. Now Marcela’s work is diving even deeper into these issues; stay tuned…

fig2-randau-measurements

Example measurements taken on felid vertebrae, from the neck (A-F) to the lumbar region (G-J), using a cheetah skeleton.

  1. Charles, J.P., Cappellari, O., Spence, A.J., Hutchinson, J.R., Wells, D.J. 2016. Musculoskeletal geometry, muscle architecture and functional specialisations of the mouse hindlimb. PLOS One 11(4): e0147669.

RVC PhD student James Charles measured the heck out of some normal mice, dissecting their hindlimb muscle anatomy, and using microCT scans produced some gorgeous images of that anatomy too. In the process, he also quantified how each muscle is differently specialized for the ability to produce large forces, rapid contractions or fine control. Those data were essential for the next study, where we got more computational!

mouse-mimics

  1. Charles, J.P., Cappellari, O., Spence, A.J., Wells, D.J., Hutchinson, J.R. 2016. Muscle moment arms and sensitivity analysis of a mouse hindlimb musculoskeletal model. Journal of Anatomy 229:514–535.

James wrangled together a lovely musculoskeletal model of our representative mouse subject’s hindlimb in the SIMM software that my team uses for these kinds of biomechanical analyses. As we normally do as a first step, we used the model to estimate things that are hard to measure directly, such as the leverages (moment arms) of each individual muscle and how those change with limb posture (which can produce variable gearing of muscles around joints). James has his PhD viva (defense) next week so good luck James!

mouse-simm

The horse and mouse papers are exemplars of what my team now does routinely. For about 15 years now, I’ve been building my team toward doing these kinds of fusion of data from anatomy, experimental biomechanics, musculoskeletal and other models, and simulation (i.e. estimating unmeasurable parameters by telling a model to execute a behaviour with a given set of criteria to try to perform well). Big thanks go to collaborator Jeff Rankin for helping us move that along lately. Our ostrich study from earlier this year shows the best example we’ve done yet with this, but there’s plenty more to come.

I am incredibly excited that, now that my team has the tools and expertise built up to do what I’ve long wanted to do, we can finally deliver the goods on the aspirations I had back when I was a postdoc, and which we have put enormous effort into pushing forward since then. In addition to new analyses of horses and mice and other animals, we’ll be trying to push the envelope more with how well we can apply similar methods to extinct animals, which brings new challenges– and evolutionary questions that get me very, very fired up.

Here we are, then; time has brought some changes to my life and work and it will continue to as we pass this juncture. I suspect I’ll look back on 2016 and see it as transformative, but it hasn’t been an easy year either, to say the least. “Draining” is the word that leaps to mind right now—but also “Focused” applies, because I had to try to be that, and sometimes succeeded. I’ve certainly benefited a lot at work from having some talented staff, students and other collaborators cranking out cool papers with me.

I still have time to do other things, too. Once in a while, a cool critter manifests in The Freezers. Check out a hippo foot from a CT scan! It’s not my best scan ever (noisy data) but it shows the anatomy fairly well, and some odd pathologies such as tiny floating lumps of mineralized soft tissue here and there. Lots to puzzle over.