Wednesday, 12 November 2014

Postdoctorate research

So having thought it through, my first blog post probably should have been on what I actually do for my living, not on a conference I attended... Oops. As such I will now be doing a quick catch up.

So it all started with the imminent end of my PhD almost a year ago. On the 7th October 2013 I had my interview for a position at University College London (UCL)  and the Royal Veterinary College (RVC). Whilst I thought it went well, I couldn't tell how it went (will discuss interview in another post as I think it would make an entertaining post and be fun to hear other people's experiences). Luckily 3 or 4 days later I had an offer that I couldn't refuse to work with Anjali Goswami and John Hutchinson on the biomechanics of felid postcrania. The Leverhulme grant would provide 2 years 4 months of funding for me to carry out the research. If you are wondering why 4 months, its because the grant was written for Stephanie Pierce, who with all of her experience deservedly would be paid more (and get the work done in 2 years). Thankfully for me, she is a bit of a big deal and now is an assistant professor over in Harvard. No pressure following her then (especially as her PhD supervisor was also mine in Bristol)...

So with a rapid transition from having planned my year with part-time work funding research time in Bristol, I had to get my thesis done and move to London. SVP 2013 marked the end of all research time, and from then on it was a rapid completion of my thesis (handed in on the 12th December - was aiming for Friday 13 but finished early). Quickly February 2014 rolls around, and I was starting all of my inductions within the two universities.

So what have I done for my work so far? The first month were mainly inductions plus finishing thesis corrections post-viva (they were very generous in giving me the time to do it, possibly because there were only a few). Since then there has been a big shift in work. Previous research on scaling patterns show that animals undergoing large increases in body size should have to change their posture and gaits to deal with the increases in muscular stresses and strains within their bones. Yet cats do not appear to follow this (almost) law of biomechanics and only seem to make their bones a bit more robust in larger species.

Femora and skulls from domestic cats compared to lion. This shows a size range of about 40 times body mass, to give an indication of how much different the largest and smallest could be.

So my project breaks down into several areas looking at investigating how cats manage to defy the norm:

1) How do felid muscles scale with their body size? If their muscles are doing something that can compensate for what the rest of the skeleton is doing (or in this case not doing), maybe that can explain the lack of apparent posture change in their limbs and backbones. To get at this there have been many many days of dissections looking at lions, tigers (no bears, oh my), snow leopard, jaguar, ocelot, domestic cat, and blackfooted cat. A(n?) European lynx is supposedly on route to round out the full body range. Each dissection involves removing every muscle in the arm, leg, and vertebral series and then bissecting the muscles to study the muscle architecture. Somehow my back has survived these dissections so far so I take that as a victory no matter what the results. (GRAPHIC IMAGES BELOW).

Jaguar dissection showing all of the forelimbs labelled.

Supraspinatus showing the muscle fibres after bissection

If you survived the gory images, well done.
2) How has body mass changed through the evolution of cats? There are about 39/40 living species which occupy a range of body sizes from 1-2kg in the blackfooted and rusty footed cats and up to 300kg in males of the largest tiger subspecies. However, we know from the fossil record there are many more cat species no longer with us, particularly those belonging to the Machairodontinae (the sabre toothed cats). Some of these species reached up to 400-500kg, with estimates from some papers reaching up to 700kg (the size of the largest male polar bear). Are there any trends, and do the fossil taxa change how we view the living ones as a whole?

3) How do certain bones perfom under loads, and can we accurately model them on computers? Taking a selection of limb bones from a small cat and big cat, and vertebral column, simple loads will be applied and then using finite element modelling compared to computer models to see if stress and strain patterns can be replicated.

4) How does the entire post-cranial skeleton perform under physiological loads? Using more complicated 3D modelling (SIMM), and using data from the muscle dissections and videos to validate the movement, can we replicate realistic movements, and how does this affect stress/strain loads on the muscles, tendons and bones under these conditions.

That's just the stuff for my specific work, however I will (hopefully) be publishing PhD things and work from my MSc student from last year (who carried out the project I had planned for my work year). My birthday present from John Hutchinson (one of the PIs) was to be involved in the BBC filming the Horizon series on the Secret Life of Cats. In addition I have a BSc student in the RVC who will be collecting and analysing data from filming of various felid species walking and running. There is also talk of keeping my fingers involved in dinosaur things with some neurocranial anatomy of a sauropod, but we shall see what comes of that.

Other members of "Team Cat" have posts about the project and work to date I have been involved in. Feel free to check out:!walking-the-cat-back/c1a4

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