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Posts Tagged ‘publication’

Last year we finally, after about 14 years of slow work, released our biomechanical model of an ostrich’s hindleg. We showed how it informed us about the potential leverages (moment arms; contributions to mechanical advantage of the joints) of all of the muscles. It was a satisfying moment, to understate it, to finally publish this work from my postdoc at Stanford. Today, we begin to deliver on that model’s promise. And it only took 4 years or so, roughly? The journal Royal Society Interface has published our study of how we used this musculoskeletal model to simulate walking and running dynamics. Those simulations join an intimidatingly broad and complex literature using similar models to study human (and some other primate) locomotion or other functions at the level of individual muscles (for whole limbs/bodies) in vast detail and growing rigor. I have Dr. Jeffery Rankin, a research fellow finishing up his post with me after ~6 years of hard work on many projects, to thank for driving this work forward, and Dr. Jonas Rubenson (now at PennState) for his patient collaboration that has continued since the early 2000’s.

Stomach-Churning Rating: 2/10; computer models of muscle actions. The underlying anatomical data are goopy, as prior ostrich-dissection-focused posts show!

Our model; in right side view (on the left) and frontal view (on the right), with muscles in red and the leg's force as the blue arrow; frozen at the middle of a step.

Our model; in right side view (on the left) and frontal view (on the right), with muscles in red and the leg’s force as the blue arrow; frozen at the middle of a running step.

Simulations like these predict things that we can’t easily measure in living animals, such as how much force muscles and tendons generate, how quickly those tissues change length, how much mechanical energy they thus contribute to the joints, limbs and whole body, how much metabolic energy their actions cost, and much more. There are more ways to use these tools than I have space or time to explain, but simply put we forced our ostrich simulation to match experimental measurements of the motions and forces of a representative walking and running ostrich stride, from contact of one foot until the next time that foot hit the ground. It then used optimization methods (minimizing target criteria like muscle stress) to estimate how the muscles and tendons were used to generate those motions and forces. This is a ways ahead of some prior ostrich simulations such as this one that I recall from classes during my PhD studies.

Any modeller worth their salt knows that their models and simulations are wrong at some level. This is much as most science is “wrong”; i.e. a simplification of reality with some errors/noise introduced by assumptions, variation, methods and such. But generally these kinds of musculoskeletal dynamic simulations hold up pretty well against experimental data. A standard “validation” is to test how closely the simulations’ predictions of muscle activity match the “real” (measured in life, also with some uncertain error) activity of muscles. Science still lacks those data for ostriches, but fortunately measurements from other birds (by Steve Gatesy and colleagues) indicate that muscles tend to follow fairly conservative patterns. Grossly speaking, avian leg muscles tend to either be active mainly when the foot is on the ground (stance phase) or off the ground (swing phase). Some studies acknowledge that this is an oversimplification and other muscles do act across those two phases of a stride, either in multiple pulses or as “transitional” (stance-to-swing or swing-to-stance) switch-hitters in their activations. Our ostrich predictions matched the qualitative patterns for avian muscle activations measured to date, so that’s good. The results also reinforced the notion of transitional or multi-phasic muscle activation as still having some importance, which bears more study.

Yet what did the simulations with our ostrich model tell us that other ostrich experiments or other bird species didn’t? Three main things. First, we could calculate what the primary functions of muscles were; they can act as motors (generating energy), brakes (absorbing energy), springs (bouncing energy back and forth) or struts (just transmitting force). We could then sum up what whole muscle groups were doing overall. The image below shows how these broad functions of groups vary across the stance phase (swing phase is harder to condense here so I’ve left it out).

Positive work can speed things up; negative work can slow things down.

Positive work can speed things up; negative work can slow things down. Solid bars are running; striped bars are walking. (from our Fig. 13) You may need to click to em-broaden this image for the gory biomechanical details.

There’s a lot going on there but a few highlights from that plot are that the hip extensor (antigravity) muscles (biarticular hip/knee “hamstrings”) are acting like motors, the knee extensors (like our quadriceps) are mainly braking as in other animals and the ankle is fairly springy as its tendons (e.g. digital flexors; gastrocnemius) suggest. We often characterize birds as “knee-driven” but it’s more accurate biomechanically to say that their hips drive (power; i.e. act as motors) their motion, whereas their knees still act as brakes — in both cases as in many other land vertebrates. Thus in some ways bird legs don’t work so unusually. Birds like ostriches are, though, a little odd in how much they rely on their hamstring muscles to power locomotion (at the hip) rather than their caudofemoral muscles, which are reduced. Zooming in on some particular muscles such as parts of the hip or knee extensors, the functions sometimes weren’t as predictable as their similar anatomy might suggest. Some muscles had parts that turned on during swing phase and other parts used during stance phase. Neural control and mechanics can produce some unexpected patterns.

Second, we looked at one important methodological issue. Simulations of musculoskeletal dynamics can vary from simple static (assuming each instant of a motion is independent from the others; e.g. ignoring acceleration, inertia, tendon effects, etc.) to more complex grades of fully dynamic flavours (e.g. assuming rigid or flexible tendons). We looked across this spectrum of assumptions, for both walking and running gaits, with the expectation that more static assumptions would work less well (vs. more dynamic ones; by various criteria) for running vs. walking. This also showed us how much tendons influence our simulations’ estimates of muscle mechanics—a fully rigid tendon will make the muscle do all of the work (force times length change) whereas a flexible tendon can literally take up some (or even all) of that slack, allowing muscles to remain closer to their isometric (high force-generating, negligible length change) quasi-optimum.

Nicely, our predicted muscle functions weren’t influenced much by these methodological variations. However, static assumptions  clearly were in some ways less appropriate for running than for walking, as were flexible tendons. Somewhat surprisingly, making the simulations more dynamic didn’t lower the levels of activation (and thus presumably the metabolic costs) of muscles, but actually raised those levels. There are good reasons why this might be realistic but it needs further study. It does muddy the waters for the issue of whether assuming that rapid locomotion can be modelled as static is a “bad” thing such as for estimating maximal speeds—yes, tendons can do more (elastic energy storage, etc.) if more dynamic models are used, but co-contraction of antagonistic muscles against each other also brings in some added costs and might lead to slower speed estimates. We’ll see in future work…

Finally, one often overlooked (sometimes even undiscussed!) aspect of these simulations is that they may silently add in extra forces to help muscles that are struggling to support and move their joints. The justification is typically that these extra “reserve actuators” are passive tissues, bony articular forces and other non-muscular interactions. We found that the hip joint muscles of ostriches were very weak at resisting abduction (drawing the thigh away from the body) and this needed resisting during the stance phase, so our simulations had very high reserve actuators switched on there. That fits the anatomy pretty well and needs more investigation.

Want to know more? Happily, not only is the paper free for anyone to view but so are all of the data including the models (modified slightly from our last paper’s). So, although the software (Opensim) isn’t ideal for 4-year-olds to play with (it is fancy engineering stuff), if you have the interest and dilligence it is there to play with and re-use and all that. But also watch this space for future developments, as there is more to happen with our steadily improving models of ostriches and other beasties. Anyway, while this paper is very technical and challenging to explain I am not too bashful to say it’s one of the finer papers from my career; a big stride forward from what we’ve done before. I have been looking forward for a long time to us getting this paper out.

P.S. Our peer reviewers were splendid- tough but constructive and fair. The paper got a lot better thanks to them.

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Seeking adaptations for running and swimming in the vertebral columns of ancient crocs

A guest post by Dr. Julia Molnar, Howard University, USA (this comes from Julia’s PhD research at RVC with John & colleagues)

Recently, John and I with colleagues Stephanie Pierce, Bhart-Anjan Bhullar, and Alan Turner described morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs (Royal Society Open Science, doi 10.1098/rsos.150439). Our results shed light upon key aspects of the evolutionary history of these under-appreciated archosaurs.

Stomach-Churning Rating: 5/10; a juicy croc torso in one small photo but that’s all.

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

Phylogenetic relationships of the three crocodylomorph groups in the study and our functional hypotheses about their vertebrae. * Image credits: Hesperosuchus by Smokeybjb, Suchodus by Dmitry Bogdanov (vectorized by T. Michael Keesey) http://creativecommons.org/licenses/by-sa/3.0

As fascinating as modern crocodiles might be, in many ways they are overshadowed by their extinct, Mesozoic cousins and ancestors. The Triassic, Jurassic, and early Cretaceous periods saw the small, fast, hyper-carnivorous “sphenosuchians,” the giant, flippered marine thalattosuchians, and various oddballs like the duck-billed Anatosuchus and the aptly named Armadillosuchus. As palaeontologists/biomechanists, we looked at this wide variety of ecological specializations in those species, the Crocodylomorpha, and wanted to know, how did they do it?

Of course, we weren’t the first scientists to wonder about the locomotion of crocodylomorphs, but we did have some new tools in our toolbox; specifically, a couple of micro-CT scanners and some sophisticated imaging software. We took CT and micro-CT scans of five fossil crocodylomorphs: two presumably terrestrial early crocodylomorphs (Terrestrisuchus and Protosuchus), three aquatic thalattosuchians (Pelagosaurus, Steneosaurus, and Metriorhynchus) and a semi-aquatic modern crocodile (Crocodylus niloticus). Since we’re still stuck on vertebrae (see, e.g., here; and also here), we digitally separated out the vertebrae to make 3D models of individual joints and took measurements from each vertebra. Finally, we manipulated the virtual joint models to find out how far they could move before the bones bumped into each other or the joints came apart (osteological range of motion, or RoM).

 

Our methods: get fossil, scan fossil, make virtual fossil and play with it.

Our methods: get fossil (NHMUK), scan fossil, make virtual fossil and play with it.

Above: Video of a single virtual inter-vertebral joint from the trunk of Pelagosaurus typus (NHMUK) showing maximum osteological range of motion in the lateral direction (video). Note the very un-modern-croc-like flat surfaces of the vertebral bodies! (modern crocs have a ball-and-socket spinal joint with the socket on the front end)

While this was a lot of fun, what we really wanted to find out was whether, as crocodylomorphs became specialized for different types of locomotion, the shapes of their vertebrae changed similarly to those of mammalian lineages. For example, many terrestrial mammals have a lumbar region that is very flexible dorsoventrally to allow up-and-down movements during bounding and galloping. Did fast-running crocodylomorphs have similar dorsoventral flexibility? And did fast-swimming aquatic crocodylomorphs evolve a stiffer vertebral column like that of whales and dolphins?

Above: Video of how we modelled and took measurements from the early crocodylomorph Terrestrisuchus gracilis (NHMUK).

Our first results were puzzling. The Nile croc had greater RoM in side-to-side motions, which makes sense because crocodiles mostly use more sprawling postures and are semi-aquatic, using quite a bit of side-to-side motions in life. The part that didn’t make sense was that we found pretty much the same thing in all of the fossil crocodylomorphs, including the presumably very terrestrial Terrestrisuchus and Protosuchus. With their long limbs and hinge-like joints, these two are unlikely to have been sprawlers or swimmers!

So we started looking for other parts of the croc that might affect RoM. The obvious candidate was osteoderms, the bony scales that cover the back. We went back to John’s Freezer and got out a nice frozen crocodile to measure the stiffness of its trunk and found that, sure enough, it was a lot stiffer and less mobile without the osteoderms. If the fairly flexible arrangement of osteoderms in crocodiles had this effect on stiffness, it seemed likely that (as previous authors have suggested; Eberhard Frey and Steve Salisbury being foremost amongst them) the rigid, interlocking osteoderms running from head to tail in early crocodylomorphs would really have put the brakes on their ability to move their trunk in certain ways.

Testing stiffness of crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated.

Testing the stiffness of (Nile) crocodile trunks to learn the effects of osteoderms, skin, muscles, and ribs. We hung metric weights from the middle of the trunk and measured how much it flexed (Ɵ), then removed bits and repeated. Click to em-croccen.

Another cool thing we found was new evidence of convergent evolution to aquatic lifestyles in the spines of thalattosuchians. The more basal thalattosuchians, thought to have been near-shore predators, had stiffness and RoM patterns similar to Crocodylus. But Metriorhynchus, which probably was very good at chasing down fast fish in the open ocean, seems to have had greater stiffness. (The stiffness estimates come from morphometrics and are based on modern crocodiles; see here again, or just read the paper already!) A stiff vertebral column can be useful for a swimmer because it increases the body’s natural frequency of oscillation, and faster oscillation means faster swimming (think tuna, not eel). The same thing seems to have happened in other secondarily aquatic vertebrate lineages such as whales, ichthyosaurs, and mosasaurs.

So, our results were a mixed bag of adaptations particular to crocs and ones that seem like general vertebrate swimming specializations. Crocodylomorphs are important because they are the only group of large vertebrates other than mammals that has secondarily aquatic members and has living members with a reasonably similar body plan, allowing us to test hypotheses in ways that would arguably be impossible for, say, non-avian dinosaurs and birds. The take-home message: crocodylomorphs A) are awesome, and B) can teach us a lot about how vertebrates adapt to different modes of life.

Another take on this story is on our lab website here.

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If you’ve been working in science for long enough, perhaps not very long at all, you’ve heard about (or witnessed) scientists in your field who get listed as co-authors on papers for political reasons alone. They may be an uninvolved but domineering professor or a fellow co-worker, a friend, a political ally, an overly protective museum curator, or just a jerk of any stripe. I read this article recently and felt it was symptomatic of the harm that bad supervisors (or other collaborators) do to science, including damage to the general reputation of professors and other mentors. There are cultural differences not only between countries (e.g. more authoritative, hierarchical cultures probably tolerate behaviour like this more) but also within institutions because of individual variation and local culture, tradition or other precedent. But this kind of honorary co-authorship turns my stomach—it is co-authorship bloat and a blight upon science. Honorary co-authorship should offend any reasonable scientist who actually works, at any level of the scientific hierarchy. So here’s my rant about it. Marshmallows and popcorn are welcomed if you want to watch my raving, but I hope this post stimulates discussion. A brief version of this did do that on my personal Facebook account, which motivated me to finish this public post.

Stomach-Churning Rating: 0/10 but it may provoke indigestion if you’ve been a victim of co-author bloat.

At its root, honorary co-authorship (HONCO) shows disdain for others’ efforts in research. “I get something for nothing, unlike others.” It persists because of deference to pressures from politics (I need to add this co-author or they’ll cause me trouble), other social dynamics (this person is my buddy; here’s a freebie for them), careerism (oneself/ally/student needs to be on this paper to boost their CV and move up in their career; or else), or even laziness (a minimal publishable unit mentality- e.g. any minor excuse for being a co-author is enough). All of these reasons for tolerating it, and apathy about the status quo, keep the fires of HONCO burning. My feeling from my past 20 years of experience in academia is that, as science is getting increasingly complex and requiring more collaborators and co-authors, the fire is raging to a point where it is visibly charring the integrity of science too often to just keep quiet about it and hope it doesn’t cause much damage.

There’s a flip side to HONCO, too– it’s not that, as some might take the article above to imply, we all need to boot senior authors off of papers. Senior authors, like other collaborators, have a reason for existing that encompasses — but is not limited to — boosting the careers of those they mentor. We scientists all want the satisfaction of doing science, even if the nature of our involvement in research evolves (and varies widely). Part of that satisfaction comes from publishing papers as the coup de grace to each project, and it’s a privilege that should be open to being earned by anyone qualified. Indeed, if adding HONCOs to papers is fraud, then removing worthy contributors from papers can be seen as a similar kind of fraud (unless a result of mutually agreed I’ll-help-you-for-nothing generosity). The broader point is, authors should deserve to be authors, and non-authors should not deserve to be authors.

On that latter issue, I think back to my grad school days and how my mentors Kevin Padian, Rodger Kram, Bob Full and others often gave me valuable input on my early papers (~1998-2002) but never earned co-authorship on them (exception: mentor Steve Gatesy’s vital role in our 2000 “abductors, adductors” paper). And frankly I feel a little bad now about that. Some of those mentors might have deserved co-authorship, but even when asked they declined, and just appeared in the Acknowledgements. It was the culture in my department at Berkeley, like many other USA grad schools at the time and perhaps now, that PhD students often did not put their supervisors on their papers and thus published single-author work. I see that less often today — but still varying among fields; e.g. in biomechanics, less single-authorship globally; in palaeontology and morphology, more single-authored work, but perhaps reducing overall. That is my off-the-cuff impression from the past >10 years.

I was shocked to see less (or often no) single-authored papers by lab colleagues once I moved to the UK to take up my present post– the prevalence of supervisors as senior authors on papers was starkly evident. On reflection, I now think that many of those multi-authored papers deserved to be such. It was not solo work and involved some significant steering, with key ideas originating from supervisors and thus constituting valid intellectual input. Yet I wondered then if it was a good thing or not, especially after hearing student complaints like waiting six months for comments from their supervisor on a manuscript. But this gets into a grey area that is best considered on a paper-by-paper basis, following clear criteria for authorship and contributions, and it involves difficulties inherent to some supervisor-supervisee relationships that I will not cover here. Much as supervisors need to manage their team, their team needs to manage them. ‘Nuff said.

Many institutions and journals have clear criteria for co-authorship, and publications have “author contributions” sections that are intended to make it clear who did what for a given paper – and thus whose responsibility any problems might be, too. HONCOs take credit without responsibility or merit, and are blatant fraud. I say it’s time we stand up to this disease. The criteria and contributions aspects of paper are part of the immune system of science that is there to help defend against academic misconduct. We need to work together to give that system a fighting chance.

There are huge grey areas in what criteria are enough for co-authorship. I have to wrestle with this for almost every paper I’m involved in– I am always thinking about whether I truly deserve to be listed on a paper, or whether others do. I’ve been training myself to think, and talk, about co-authorship criteria early in the process of research— that’s essential in avoiding bad blood later on down the line when it’s time to write up the work, when it’s possibly too late for others to earn co-authorship. This is a critical process that is best handled explicitly and in writing, especially in larger collaborations. What will the topic of any future paper(s) be and who will be involved as co-authors, or not? It’s a good agenda item for research meetings.

There are also grey areas in author contributions. How much editing of a paper is enough for co-authorship justification? Certainly not just spellchecking or adding comments saying “Great point!”, although both can be a bit helpful. Is funding a study a criterion? Sometimes– how much and how directly/indirectly did the funding help? Is providing data enough? Sometimes. In these days of open data, it seems like the data-provision criterion, part of the very hull that science floats upon, is weakening as a justification for co-authorship. It is becoming increasingly common to cite others’ papers for data, provide little new data oneself, and churn out papers without those data-papers’ authors involved. And that’s a good thing, to a degree. It’s nicer to invite published-data-providers on board a paper as collaborators, and they can often provide insight into the nature (and limitations or faults!) of the data. But adding co-authors can easily slide down the slippery slope of hooray-everyone’s-a-co-author (e.g. genetics papers with 1000+ co-authors, anyone?). I wrote up explicit co-authorship criteria here (Figshare login needed; 2nd pdf in the list) and here (Academia.edu login needed) if you’re curious how I handle it, but standards vary. Dr. William Pérez recently shared a good example of criteria with me; linked here.

In palaeontology and other specimen-based sciences, we get into some rough terrain — who collected the fossil (i.e. was on that field season and truly helped), identified it, prepared and curated it, published on it, or otherwise has “authority” over it, and which of them if any deserve co-authorship? I go to palaeontology conferences every year and listen over coffee/beers to colleagues complain about how their latest paper had such-and-such (and their students, pals, etc.) added onto the paper as HONCOs. Some museums or other institutions even have policies like this, requiring external users to add internal co-authors as a strong-arm tactic. An egregious past example: a CT-scanning facility I used once, and never again, even had the guff to call their mandatory joint-authorship policy for usage “non-collaborative access”… luckily we signed no such policy, and so we got our data, paid a reasonable fee for it, and had no HONCOs. Every time I hear about HONCOs, I wonder “How long can this kind of injustice last?” Yet there’s also the reality that finding and digging up a good field site or specimen(s); or analogous processes in science; takes a lot of time and effort and you don’t want others prematurely jumping your claim, which can be intellectual property theft, a different kind of misconduct. And there is good cause for sensitivity about non-Western countries that might not have the resources and training of staff to earn co-authorship as easily; flexibility might be necessary to avoid imperialist pillaging of their science with minimal benefit to their home country.

Yet there’s hope for minimizing HONCO infections. A wise person once said (slightly altered) “I’d rather light a candle than curse the darkness.” Problems can have solutions, even though cultural change tends to be agonizingly slow. But it can be slower still, or retrograde, if met with apathy. What can we do about HONCOs? Can we beat the bloat? What have I done myself before and what would I do differently now? I’ll take an inward look here.

Tolerating HONCOs isn’t a solution. I looked back on my experiences with >70 co-authored papers and technical book chapters since 1998. Luckily there are few instances where I’d even need to contemplate if a co-author was a HONCO. Most scientists I’ve worked with have clearly pulled their weight on papers or understood why they’re not co-authors on a given paper. More about that below. In those few instances of possible HONCOs, about five papers from several years ago, some colleagues provided research material/data but never commented on the manuscripts or other aspects of the work. I was disgruntled but tolerated it. It was a borderline grey area and I was a young academic who needed allies, and the data/specimens were important. Since then, I’ve curtailed collaborations with those people. To be fair, there were some papers where I didn’t do a ton (but did satisfy basic criteria for co-authorship, especially commenting on manuscripts) and I got buried in Middle-Authorland, and that’s fine with me; it wasn’t HONCO hell I was in. There were a few papers where I played a minor role and it wasn’t clear what other co-authors were contributing, but I was comfortable giving them the benefit of the doubt.

One anti-HONCO solution was on a more recent paper that involved a person who I had heard was a vector of HONCO infection. I stated early on in an email that only one person from their group could be a co-author on the resulting paper, and they could choose who it was and that person would be expected to contribute something beyond basic data. They wrote back agreeing to it and (magnanimously) putting a junior student forward for it, who did help, although they never substantially commented on the manuscript so I was a little disappointed. But in the grand scheme of things, this strategy worked in beating the HONCO bloat. I may have cost myself some political points that may stifle future collaborations with that senior person, but I feel satisfied that I did the right thing under the constraints, and damn the consequences. Containment of HONCO has its attendant risks of course. HONCO-rejects might get honked off. Maybe one has to pick their battles and concede ground sometimes, but how much do the ethics of such concessions weigh?

Another solution I used recently involved my own input on a paper. I was asked to join a “meta-analysis” paper as a co-author but the main work had already been done for it, and conclusions largely reached. I read the draft and saw places where I could help in a meaningful way, so with trepidation I agreed to help and did. But during the review process it became clear that (1) there was too much overlap between this paper and others by the same lead author, which made me uncomfortable; and (2) sections that I had contributed to didn’t really meld well with the main thrust of the paper and so were removed. As a consequence, I felt like a reluctant HONCO and asked to be removed from the paper as a co-author, even though I’d helped write sections of the main text that remained in the paper (but this was more stylistic in my view than deeply intellectual). I ended up in the Acknowledgements and relieved about it. I am comfortable removing myself from papers in which I don’t get a sense of satisfaction that I did something meriting co-author status. But it’s easier for more senior researchers like me to do that, compared to the quandary that sink-or-swim early-career researchers may face.

More broadly in academia, a key matter at stake is the CVs of researchers, especially junior ones, which these days require more and more papers (even minimal publishable units) to be competitive for jobs, awards and funding. Adding HONCOs to papers does strengthen individuals’ CVs, but in a parasitic way from the dilution of co-author contributions. And it’s just unethical, full stop. One solution: It’s thus up to senior people to lead from the front, showing that they don’t accept HONCOs themselves and encouraging more junior researchers to do the same when they can—or even questioning the contributions that potential new staff/students made to past papers, if their CV seems bloated (but such questions probe dangerous territory!). Junior people, however, still need to make a judgement call on how they’ll handle HONCOs with themselves or others. There is the issue of reputation to think about; complicity in the HONCO pandemic at any career level might be looked upon unfavourably by others, and scientists can be as gossipy as any humans, so bad ethics can bite you back.

I try to revisit co-authorship and the criteria involved throughout a project, especially as we begin the writing-up stage, to reduce risks of HONCOs or other maladies. An important aspect of collaboration is to ensure that people that might deserve co-authorship get an early chance to earn it, or else are told that they won’t be on board and why. Then they are not asked for further input unless it is needed, which might shift the balance and put them back on the co-author list. Critically, co-authorship is negotiable and should be a negotiation. One should not take it personally if not on a paper, but should treat others fairly and stay open-minded about co-authorship whenever possible. This has to be balanced against the risk of co-authorship bloat. Sure, so-and-so might add a little to a paper, but each co-author added complicates the project, probably slows it down, and diminishes the credit given to each other co-author. So a line must be drawn at some point. Maybe some co-authors and their contributions are best saved for a future paper, for example. This is a decision that the first, corresponding and senior author(s) should agree on, in consultation with others. But I also feel that undergraduate students and technicians often are the first to get the heave-ho from co-author considerations, which I’ve been trying to avoid lately when I can, as they deserve as much as anyone to have their co-author criteria scrutinized.

The Acknowledgements section of a paper is there for a reason, and it’s nice to show up there when you’ve truly helped a paper out whether as quasi-collaborative colleague, friendly draft-commenter, editor, reviewer or in other capacities. It is a far cry from being a co-author but it also typically implies that those people acknowledged are not to blame if something is wrong with the paper. I see Acknowledgements as “free space” that should be packed with thank-you’s to everyone one can think of that clearly assisted in some way. No one lists Acknowledged status on their CVs or gets other concrete benefits from them normally, but it is good social graces to use it generously. HONCOs’ proper home, at best, is there in the Acknowledgements, safely quarantined.

The Author Contributions section of a paper is something to take very seriously these days. I used to fill it out without much thought, but I’ve now gotten in the habit of scrutinizing it (where feasible) with every paper I’m involved in. Did author X really contribute to data analysis or writing the paper? Did all authors truly check and approve the final manuscript? “No” answers there are worrying. It is good research practice nowadays to put careful detail into this section of every paper, and even to openly discuss it among all authors so everyone agrees. Editors and reviewers should also pay heed to it, and readers of papers might find it increasingly interesting to peruse that section. Why should we care about author contribution lists in papers? Well, sure, it’s interesting to know who did what, that’s the main reason! It can reveal what skills an individual has or lacks, or their true input on the project vs. what the co-author order implies.

But there’s a deeper value to Author Contributions lists that is part of the academic immune system against HONCOs and other fraud. Anyone contributing to a particular part of a paper should be able to prove their contribution if challenged. For example, if a problem was suspected in a section of a paper, any authors listed as contributing to that section would be the first points of contact to check with about that possible problem. In a formal academic misconduct investigation, those contributing authors would need to walk through their contributions and defend (or correct) their work. It would be unpleasant to be asked how one contributed to such work if one didn’t do it, or to find out that someone listed you as contributing when you didn’t, and wouldn’t have accepted it if you had known. Attention to detail can pay off in any part of a research publication.

Ultimately, beating the blight of HONCO bloat will need teamwork from real co-authors, at every career level. Too often these academic dilemmas are broken down into “junior vs. senior” researcher false dichotomies. Yes, there’s a power structure and status quo that we need to be mindful of. Co-authorships, however, require collaboration and thus communication and co-operation.

It’s a long haul before we might see real progress; the fight against HONCOs must proceed paper-by-paper. There are worse problems that science faces, too, but my feeling is that HONCOs have gone far enough and it’s time to push back, and to earn the credit we claim as scientific authors. Honorary co-authorship is a dishonourable practice that is very different from other “honorary” kudos like honorary professorships or awards. Complex and collaborative science can mean longer co-author lists, absolutely, but it doesn’t mean handing out freebies to chums, students needing a boost, or erstwhile allies. It means more care is needed in designing and writing up research. And it also means that science is progressing; a progress we should all feel proud of in the end.

Do you have abhorrent HONCO chronicles of your own (anonymized please; no lynch mobs here!) or from public record? Or ideas for handling HONCO hazards? Please share and discuss.

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Deck the ‘Nets With PeerJ Papers— please sing along!

♬Deck the ‘nets with PeerJ papers,
Fa la la la la, la la la la.
‘Tis the day to show our labours,
Fa la la la la, la la la la.

Downloads free; CC-BY license,
Fa la la, la la la, la la la.
Read the extant ratite science,
Fa la la la la, la la la la.

See the emu legs before you
Fa la la la la, la la la la.
Muscles allometric’ly grew.
Fa la la la la, la la la la.

Follow the evolvin’ kneecaps
Fa la la la la, la la la la.
While we dish out ratite recaps 
Fa la la la la, la la la la.

Soon ostrich patellar printing
Fa la la la la, la la la la.
Hail anat’my, don’t be squinting
Fa la la la la, la la la la.

Dissections done all together
Fa la la la la, la la la la.
Heedless of the flying feathers,
Fa la la la la, la la la la♪

(alternate rockin’ instrumental version)

Stomach-Churning Rating: 5/10: cheesy songs vs. fatty chunks of tissue; there are no better Crimbo treats!

Today is a special day for palaeognath publications, principally pertaining to the plethora of published PeerJ papers (well, three of them anyway) released today, featuring my team’s research! An early Crimbo comes this year in the form of three related studies of hind limb anatomy, development, evolution and biomechanics in those flightless feathered freaks of evolutionary whimsy, the ratites! And since the papers are all published online in PeerJ (gold open access), they are free for anyone with internet access to download and use with due credit. These papers include some stunning images of morphology and histology, evolutionary diagrams, and a special treat to be revealed below. Here I’ll summarize the papers we have written together (with thanks to Leverhulme Trust funding!):

1) Lamas, L., Main, R.P., Hutchinson, J.R. 2014. Ontogenetic scaling patterns and functional anatomy of the pelvic limb musculature in emus (Dromaius novaehollandiae). PeerJ 2:e716 http://dx.doi.org/10.7717/peerj.716 

My final year PhD student and “emu whisperer” Luis Lamas has published his first paper with co-supervisor Russ Main and I. Our paper beautifully illustrates the gross anatomy of the leg muscles of emus, and then uses exhaustive measurements (about 6524 of them, all done manually!) of muscle architecture (masses, lengths, etc.) to show how each of the 34 muscles and their tendons grew across a more than tenfold range of body mass (from 6 weeks to 18 months of age). We learned that these muscles get relatively, not just absolutely, larger as emus grow, and their force-generating ability increases almost as strongly, whereas their tendons tend to grow less quickly. As a result, baby emus have only about 22% of their body mass as leg muscles, vs. about 30% in adults. However, baby emus still are extremely athletic, more so than adults and perhaps even “overbuilt” in some ways.

This pattern of rapidly growing, enlarged leg muscles seems to be a general, ancestral pattern for living bird species, reflecting the precocial (more independent, less nest-bound), cursorial (long-legged, running-adapted) natural history and anatomy, considering other studies of ostriches, rheas, chickens and other species close to the root of the avian family tree. But because emus, like other ratites, invest more of their body mass into leg muscles, they can carry out this precocial growth strategy to a greater extreme than flying birds, trading flight prowess away for enhanced running ability. This paper adds another important dataset to the oft-neglected area of “ontogenetic scaling” of the musculoskeletal system, or how the locomotor apparatus adapts to size-/age-related functional/developmental demands as it grows. Luis did a huge amount of work for this paper, leading arduous dissections and analysis of a complex dataset.

Superficial layer of leg muscles in an emu, in right side view.

Superficial layer of leg muscles in an emu, in right side view. Click any image here to emu-biggen. The ILPO and IC are like human rectus femoris (“quads”); ILFB like our biceps femoris (“hams”); FL, GM and GL much like our fibularis longus and gastrocnemius (calf) muscles, but much much bigger! Or, perhaps FL stands for fa la la la la?

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grown than isometry (maintaining the same relative size), which is the dotted line at 1.0.

Data for an extra set of emus studied by coauthor Russ Main in the USA, which grew their muscles similarly to our UK group. The exponents (y-axis) show how much more strongly the muscles grew than isometry (maintaining the same relative size), which is the dotted line at 1. The numbers above each data point are the # of individuals measured. Muscle names are partly above; the rest are in the paper. If you want to know them, we might have been separated at birth!

2) Regnault, S., Pitsillides, A.A., Hutchinson, J.R. 2014. Structure, ontogeny and evolution of the patellar tendon in emus (Dromaius novaehollandiae) and other palaeognath birds. PeerJ 2:e711 http://dx.doi.org/10.7717/peerj.711

My second year PhD student Sophie Regnault (guest-blogger here before with her rhino feet post) has released her first PhD paper, on the evolution of kneecaps (patellae) in birds, with a focus on the strangeness of the region that should contain the patella in emus. This is a great new collaboration combining her expertise in all aspects of the research with coauthor Prof. Andy Pitsillides‘s on tissue histology and mine on evolution and morphology. This work stems from my own research fellowship on the evolution of the patella in birds, but Sophie has taken it in a bold new direction. First, we realized that emus don’t have a patella– they just keep that region of the knee extensor (~human quadriceps muscle) tendon as a fatty, fibrous tissue throughout growth, showing no signs of forming a bony patella like other birds do. This still blows my mind! Why they do this, we can only speculate meekly about so far. Then, we surveyed other ratites and related birds to see just how unusual the condition in emus was. We discovered, by mapping the form of the patella across an avian family tree, that this fatty tendon seems to be a thing that some ratites (emus, cassowaries and probably the extinct giant moas) do, whereas ostriches go the opposite direction and develop a giant double-boned kneecap in each knee (see below), whereas some other relatives like tinamous and kiwis develop a more “normal”, simple flake-like bit of bone, which is likely the state that the most recent common ancestor of all living birds had.

There’s a lot in this paper for anatomists, biomechanists, palaeontologists, ornithologists, evo-devo folks and more… plenty of food for thought. The paper hearkens back to my 2002 study of the evolution of leg tendons in tetrapods on the lineage that led to birds. In that study I sort of punted on the question of how a patella evolved in birds, because I didn’t quite understand that wonderful little sesamoid bone. And now, 12 years later, we do understand it, at least within the deepest branches of living birds. What happened further up the tree, in later branches, remains a big open subject. It’s clear there were some remarkable changes, such as enormous patellae in diving birds (which the Cretaceous Hesperornis did to an extreme) or losses in other birds (e.g., by some accounts, puffins… I am skeptical)– but curiously, patellae that are not lost in some other birds that you might expect (e.g., the very non-leggy hummingbirds).

Fatty knee extensor tendon of emus, lacking a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing over it. A is a schematic; B is a dissection.

Fatty knee extensor tendon of an emu, showing the absence of a patella. The fatty tissue is split into superficial (Sup) and deep regions, with a pad corresponding to the fat pad in other birds continuous with it and the knee joint meniscus (cushioning pad). The triceps femoris (knee extensor) muscle group inserts right into the fatty tendon, continuing on over it. A is a schematic; B is a dissection.

Sectioning of a Southern Cassowary's knee extensor tendon, showing: A Similar section  as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, with collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Sectioning of a Southern Cassowary’s knee extensor tendon, showing: A, Similar section as in the emu image above. revealing similar regions and fibrous tissue (arrow), with no patella, just fat; and B, With collagen fibre bundles (col), fat cells (a), and cartilage-like tissue (open arrows) labelled.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds, which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

Evolution of patellar form in birds. White branches indicate no patella, blue is a small flake of bone for a patella, green is something bigger, yellow is a double-patella in ostriches, black is a gigantic spar of bone in extinct Hesperornis and relatives, and grey is uncertain. Note the uncertainty and convergent evolution of the patella in ratite birds (Struthio down to Apteryx), which is remarkable but fits well with their likely convergent evolution of flightlessness and running adaptations.

3) Chadwick, K.P., Regnault, S., Allen, V., Hutchinson, J.R. 2014. Three-dimensional anatomy of the ostrich (Struthio camelus) knee joint. PeerJ 2:e706 http://dx.doi.org/10.7717/peerj.706

Finally, Kyle Chadwick came from the USA to do a technician post and also part-time Masters degree with me on our sesamoid grant, and proved himself so apt at research that he published a paper just ~3 months into that work! Vivian Allen (now a postdoc on our sesamoid bone grant) joined us in this work, along with Sophie Regnault. We conceived of this paper as fulfilling a need to explain how the major tissues of the knee joint in ostriches, which surround the double-patella noted above, all relate to each other and especially to the patellae. We CT and MRI scanned several ostrich knees and Kyle made a 3D model of a representative subject’s anatomy, which agrees well with the scattered reports of ostrich knee/patellar morphology in the literature but clarifies the complex relationships of all the key organs for the first time.

This ostrich knee model also takes Kyle on an important first step in his Masters research, which is analyzing how this morphology would interact with the potential loads on the patellae. Sesamoid bones like the patella are famously responsive to mechanical loads, so by studying this interaction in ostrich knees, along with other studies of various species with and without patellae, we hope to use to understand why some species evolved patellae (some birds, mammals and lizards; multiple times) and why some never did (most other species, including amphibians, turtles, crocodiles and dinosaurs). And, excitingly for those of you paying attention, this paper includes links to STL format 3D graphics so you can print your own ostrich knees, and a 3D pdf so you can interactively inspect the anatomy yourself!

(A) X-ray of an ostrich knee in side view, and (B) labelled schematic of the same.

Ostrich knee in side view: A, X-ray, and (B) labelled schematic.

3D model of an ostrich knee, showing: A, view looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, view looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

3D model of an ostrich knee, showing: A, View looking down onto the top of the tibia (shank), with the major collateral ligaments (CL), and B, View looking straight at the front of the knee joint, with major organs of interest near the patella, sans muscles.

You can view all the peer review history of the papers if you want, and that prompts me to comment that, as usual at PeerJ (full disclosure: I’m an associate editor but that brings me £0 conflict of interest), the peer review quality was as rigorous at a typical specialist journal, and faster reviewing+editing+production than any other journal I’ve experienced. Publishing there truly is fun!

Merry Christmas and Happy Holidays — and good Ratite-tidings to all!

And stay tuned- the New Year will bring at least three more papers from us on this subject of ratite locomotion and musculoskeletal anatomy!

♬Should auld palaeognathans be forgot, 
And never brought for scans? 
Should publications be soon sought, 
For auld ratite fans!♪

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I’ll let the poll (prior post) run for a while but as it winds down I wanted to explain why I posted it:

In the past, I’ve often run into scientists who, when defending their published or other research, respond something like this:

“Yeah those data (or methods) might be wrong but the conclusions are right regardless, so don’t worry.”

And I’ve said things like that before. However, I’ve since realized that this is a dangerous attitude, and in many contexts it is wrong.

If the data are guesses, as in the example I gave, then we might worry about them and want to improve them. The “data are guesses” context that I set the prior post in comes from Garland’s 1983 paper on the maximal speeds of mammals– you can download a pdf here if this link works (or Google it). Basically the analysis shows that, as mammals get bigger, they don’t speed up as a simple linear analysis might show you. Rather, at a moderate size of around 50-100kg body mass or so, they hit a plateau of maximal speed, then bigger mammals tend to move more slowly. However, all but a few of the data points in that paper are guesses, many coming from old literature. The elephant data points are excessively fast in the case of African elephants, and on a little blog-ish webpage from the early 2000s we chronicled the history of these data– it’s a fun read, I think. The most important, influential data plot from that paper by Garland is below, and I love it– this plot says a lot:

Garland1983

I’ve worried about the accuracy of those data points for a long time, especially as analyses keep re-using them– e.g. this paper, this one, and this one, by different authors. I’ve talked to several people about this paper over the past 20 years or so. The general feeling has been in agreement with Scientist 1 in the poll, or the quote above– it’s hard to imagine how the main conclusions of the paper would truly be wrong, despite the unavoidable flaws in the data. I’d agree with that statement still: I love that Garland paper after many years and many reads. It is a paper that is strongly related to hypotheses that my own research seeks out to test. I’ve also tried to fill in some real empirical data on maximal speeds for mammals (mainly elephants; others have been less attainable), to improve data that could be put into or compared with such an analysis. But it is very hard to get good data on even near-maximal speeds for most non-domesticated, non-trained species. So the situation seems to be tolerable. Not ideal, but tolerable. Since 1983, science seems to be moving slowly toward better understanding of the real-life patterns that the Garland paper first inferred, and that is good.

But…

My poll wasn’t really about that Garland paper. I could defend that paper- it makes the best of a tough situation, and it has stimulated a lot of research (197 citations according to Google; seems low actually, considering the influence I feel the paper has had).

I decided to do the poll because thinking about the Garland paper’s “(educated) guesses as data” led me to think of another context in which someone might say “Yeah those data might be wrong but the conclusions are right regardless, so don’t worry.” They might say it to defend their own work, such as to deflect concerns that the paper might be based on flawed data or methods that should be formally corrected. I’ve heard people say this a lot about their own work, and sometimes it might be defensible. But I think we should think harder about why we would say such things, and if we are justified in doing so.

We may not just be making the best of a tough situation in our own research. Yes, indeed, science is normally wrong to some degree. A more disconcerting situation is that our wrongs may be mistakes that others will proliferate in the future. Part of the reasoning for being strict stewards of our own data is this: It’s our responsibility as scientists to protect the integrity of the scientific record, particularly of our own published research because we may know that best. We’re not funded (by whatever source, unless we’re independently wealthy) just to further our own careers, although that’s important too, as we’re not robots. We’re funded to generate useful knowledge (including data) that others can use, for the benefit of the society/institution that funds us. All the more reason to share our critical data as we publish papers, but I won’t go off on that important tangent right now.

In the context described in the latter paragraph and the overly simplistic poll, I’d tend to favour data over conclusions, especially if forced to answer the question as phrased. The poll reveals that, like me, most (~58%) respondents also would tend to favour data over conclusions (yes, biased audience, perhaps- social media users might tend to be more savvy about data issues in science today? Small sample size, sure,  that too!). Whereas very few (~10%) would favour conclusions, in the context of the poll. The many excellent comments on the poll post reveal the trickier nuances behind the poll’s overly simplistic question, and why many (~32%) did not favour one answer over the other.

If you’ve followed this blog for a while, you may be familiar with a post in which I ruminated over my own responsibilities and conundrums we face in work-life balance, personal happiness, and our desires to protect ourselves or judge/shame others. And if you’ve closely followed me on Twitter or Facebook, you may have noticed we corrected a paper recently and retracted another. So I’ve stuck by my guns lately, as I long have, to correct my team’s work when I’m aware of problems. But along the way I’ve learned a lot, too, about myself, science, collaboration, humanity, how to improve research practice or scrutiny, and the pain of errors vs. the satisfaction of doing the right thing. I’ve had some excellent advice from senior management at the RVC along the way, which I am thankful for.

I’ve been realizing I should minimize my own usage of the phrase “The science may be flawed but the conclusions are right.” That can be a more-or-less valid defence, as in the case of the classic Garland paper. But it can also be a mask (unintentional or not) that hides fear that past science might have real problems (or even just minor ones that nonetheless deserve fixing) that could distract one away from the pressing issues of current science. Science doesn’t appreciate the “pay no attention to the person behind the curtain” defence, however. And we owe it to future science to tidy up past messes, ensuring the soundness of science’s data.

We’re used to moving forward in science, not backward. Indeed, the idea of moving backward, undoing one’s own efforts, can be terrifying to a scientist– especially an early career researcher, who may feel they have more at risk. But it is at the very core of science’s ethos to undo itself, to fix itself, and then to move on forward again.

I hope that this blog post inspires other scientists to think about their own research and how they balance the priorities of keeping their research chugging along but also looking backwards and reassessing it as they proceed. It should become less common to say “Yeah those data might be wrong but the conclusions are right regardless, so don’t worry.” Or it might more common to politely question such a response in others. As I wrote before, there often are no simple, one-size-fits-all answers for how to best do science. Yet that means we should be wary of letting our own simple answers slip out, lest they blind us or others.

Maybe this is all bloody obvious or tedious to blog readers but I found it interesting to think about, so I’m sharing it. I’d enjoy hearing your thoughts.

Coming soon: more Mystery Anatomy, and a Richard Owen post I’ve long intended to do.

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A short post that guest-tweeting at the  Biotweeps account on Twitter got me thinking about– featuring a poll.

Imagine this: two scientists (colleagues, if you’re a scientist) are arguing thusly. Say it’s an argument about a classic paper in which much of the data subjected to detailed statistical analyses are quantitative guesses, not hard measurements. This could be in any field of science.

Scientist 1: “Conclusions are what matter most in science. If the data are guesses, but still roughly right, we shouldn’t worry much. The conclusions will still be sound regardless. That’s the high priority, because science advances by ideas gleaned from conclusions, inspiring other scientists.”

Scientist 2: “Data are what matter most in science. If the data are guesses, or flawed in some other way, this is a big problem and scientists must fix it. That’s the high priority, because science advances by data that lead to conclusions, or to more science.”

Who’s right? Have your say in this anonymous poll (please vote first before viewing results!):

link: http://poll.fm/4xf5e

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

And if you have more to say and don’t mind being non-anonymous, say more in the Comments- can you convince others of your answer? Or figure out what you think by ruminating in the comments?

I’m genuinely curious what people think. I have my own opinion, which has changed a lot over the past year. And I think it is a very important question scientists should think about, and discuss. I’m not just interested in scientists’ views though; anyone science-interested should join in.

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[This is the original, unedited text of my shorter, tighter (and I think actually better) News & Views piece for Nature, on the paper described below)

Ambitious experimental and morphological studies of a modern fish show how a flexible phenotype may have helped early “fishapods” to make the long transition from finned aquatic animals into tetrapods able to walk on land.

Stomach-Churning Rating: 1/10. Cute fish. Good science. Happy stomachs!

Photo by Antoine Morin, showing Polypterus on land.

Photo by Antoine Morin, showing Polypterus on land.

Napoleon Bonaparte’s military excursions into Egypt in 1798-1799 led a young French naturalist, Ètienne Geoffroy Saint-Hilaire, to cross paths with a strange fish that had paired lungs and could “walk” across land on its stubby, lobelike fins. In 1802, he dubbed this fish “Polyptère bichir”1, today known as the Nile bichir, Polypterus bichir La Cepède 1803. The bichir’s mélange of primitive and advanced traits helped to catapult Geoffroy into scholarly conflict with the reigning naturalist Georges Cuvier back in France and to establish Ètienne as a leading anatomist, embryologist and early evolutionary researcher of repute even today2. Now, on their own excursion under the very “evo-devo” flag that the discoverer of Polypterus helped raise, Canadian scientists Standen et al.3 suggest how the remarkable plasticity of the skeleton of Polypterus (the smaller west African relative of P. bichir, P. senegalus or “Cuvier’s bichir”) reveals a key part of the mechanism that might have facilitated the gradual transition from water to land and thus from “fishapods” to tetrapods (four-limbed vertebrates).

In a bold experiment, the authors raised 149 young bichirs on land and in water for eight months, then studied how they moved on land vs. in water, and also how the ultimate shape of the skeletal elements of the paired front fin bases differed between the land- and water-raised bichirs. Standen et al.3 discovered that both the form and function of the fins’ foundations transformed to better satisfy the constraints of moving on land. Land-acclimated bichirs took faster steps on land, their fins slipped across the substrate less, they held their fins closer to their body, their noses stayed more aloft and their tails undulated less, with less variable motions overall—behaviours that the authors had predicted should appear to enhance walking abilities on land. In turn, the bones of the neck and shoulder region altered their shape to produce a more mobile fin base with greater independence of fin from neck motion, along with improved bracing of the ventral “collarbone” region. These environmentally-induced traits should have fostered the locomotor changes observed in “terrestrialized” fish and aided the animals in resisting gravity, and they represent a common biological phenomenon termed developmental plasticity4,5. Interestingly, the land-reared fish could still swim about as well as the wholly aquatic cohort, so there was not a clear trade-off between being a good swimmer and a good walker, which is surprising.

Considered alone, the developmental plasticity of bichir form and function shows how impressive these amphibious fish are. But Standen et al.’s study3  ventured further, to apply the lessons learned from bichir ontogeny to a phylogenetic context and macroevolutionary question. The phenotypic plasticity during bichir development, they infer, could have been harnessed during the evolutionary transformation of fins for swimming into limbs for walking, in the “fishapod” ancestors of tetrapods. Indeed, bichirs are close to the base of the family tree of fishes6, and other living relatives of tetrapods have reduced or lost their fins (lungfishes) or adapted to strange deep-sea swimming lifestyles, never walking on land (coelacanths). Thus perhaps bichirs and the “fishapod” lineage share what Geoffroy would have called “unity of type”, today termed homology, of their developmental plasticity in response to a land environment. Surveying the fossil record of early “fishapods” and tetrapods, Standen et al.3 found that the macroevolutionary changes of neck and shoulder anatomy in these gradually more land-adapted animals parallel those they observed in terrestrialized Polypterus, providing ancillary support for their hypothesis.

A further test of the application of Polypterus’s plasticity to fossil tetrapods is naturally difficult. However, the “fishapod” lineage has some exceptional examples of fossil preservation. With sufficient sample sizes (e.g. fossil beds that reveal growth series, such as the Late Devonian Miguasha site in Canada7) and palaeoenvironmental gradients in fish or tetrapods, one could imagine performing a rigorous indirect test. Even small samples could be helpful– for example, the early tetrapod Ichthyostega exhibits some developmental changes in its forelimb suggesting that it became more terrestrial as it grew, whereas the related Acanthostega does not evidence such changes8— this hints at some developmental plasticity in the former animal.

During the Devonian period (~360-420 million years ago), were the “fishapod” ancestors of tetrapods floundering about on land now and then, gradually shifting from anatomy and behaviours that were more developmentally plastic (as in bichirs) to ones that were more canalized into the terrestrialized forms and functions that more land-adapted tetrapods retained? An attractive possibility is that the developmental plasticity could have led to fixation (reduction of plasticity), an evolutionary phenomenon called genetic assimilation, which another intellectual descendant of Geoffroy, Conrad Hal Waddington, promoted from the 1950s onwards9, a concept that now enjoys numerous cases of empirical support10 that this one may eventually join.

The nature of the genetic and developmental mechanism that bichirs use to achieve the observed developmental plasticity is still unclear. If it has a high enough degree of heritability, then it could be selected for in cross-generational experiments with bichirs. With sufficient time and luck raising these unusual fish, the hypothesis that their plastic response to a terrestrial environment can become genetically assimilated could be directly tested. This study could thus become an epic exemplar of how genetic assimilation can contribute not only to microevolutionary change but also to major macroevolutionary events, as was presciently suggested in a seminal review of developmental plasticity4.

This genetic assimilation is the Polypterus study’s reasonable speculation, and one that Geoffroy likely would have applauded, all the more for involving his beloved bichirs. Much as Napoleon’s landfall in Egypt was not a lasting success, bichirs never left wholly terrestrial descendants despite their malleable locomotor system. But the same type of plastic developmental mechanism that bichirs use today to make tentative, floppy incursions of the terrestrial realm might have been harnessed by our own “fishapod” forebears, leaving a far more revolutionary dynasty upon the Earth.

 

References

  1.  Geoffroy, E. (1802). Histoire naturelle et description anatomique d’un nouveau genre de poisson du Nil, nommé polyptère. Annales du Muséum d’Histoire Naturelle 1:57-68.
  2. Le Guyader, H., & Grene, M. (2004) Geoffroy Saint-Hilaire: A Visionary Naturalist. Univ. Chicago Press.
  3. Standen, E. M., Du, T. Y., & Larsson, H. C. E. (2014). Developmental plasticity and the origin of tetrapods. Nature, published online.
  4. West-Eberhard, M. J. (1989). Phenotypic plasticity and the origins of diversity. Annual Review of Ecology and Systematics 20:249-278.
  5. Pigliucci, M., Murren, C. J., & Schlichting, C. D. (2006). Phenotypic plasticity and evolution by genetic assimilation. Journal of Experimental Biology 209(12):2362-2367.
  6. Near, T. J., Dornburg, A., Tokita, M., Suzuki, D., Brandley, M. C., & Friedman, M. (2014). Boom and bust: ancient and recent diversification in bichirs (Polypteridae: Actinopterygii), a relictual lineage of ray‐finned fishes. Evolution 68:1014-1026.
  7. Cloutier, R. (2013). Great Canadian Lagerstätten 4. The Devonian Miguasha Biota (Québec): UNESCO World Heritage Site and a Time Capsule in the Early History of Vertebrates.Geoscience Canada40:149-163.
  8. Callier, V., Clack, J. A., & Ahlberg, P. E. (2009). Contrasting developmental trajectories in the earliest known tetrapod forelimbs.Science324:364-367.
  9. Waddington, C. H. (1953). Genetic assimilation of an acquired character. Evolution 7:118-126.
  10. Crispo, E. (2007). The Baldwin effect and genetic assimilation: revisiting two mechanisms of evolutionary change mediated by phenotypic plasticity. Evolution 61:2469-2479.

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