Earlier this year (in June), Channel 4 television here in the UK broadcast series 2 of Inside Nature’s Giants (ING from hereon… titled Raw Anatomy in the US, you poor, poor people). You may have heard it here first. Hopefully you’re familiar with ING series 1 – it looked at the anatomy of elephants, baleen whales, crocodiles and giraffes – and, if you’re not, be sure to check out the Tet Zoo articles starting here. My praise for series 1 was extreme, by which I mean that I thought it was excellent: a real triumph and a major event in both the world of broadcasting, and in bringing good science to the masses.
I’m pleased to say that this was widely recognised: many TV critics said positive things about ING (very memorable example), and in June 2010 the team behind the series (Windfall Films) won a BAFTA award (= British Academy of Film and Television Arts). Nature featured an interview with anatomist Joy Reidenberg – the main [human] star of the series – in June (Gilbey 2010). The interview touched on the educational significance of the series, the importance of bringing evolutionary perspectives on nature to a wide audience, and the fact that anatomy is not a dead, Victorian science (far from it: we are in the midst of an anatomical revolution). Clearly, expectations for series 2 were pretty high.
WARNING: major spoiler for ep 1 ahead, and further spoilers to follow.
The three episodes did not disappoint. Once again, standards were high and a great deal of material that would have been totally novel to the majority of the audience was presented with flair and aplomb, and (admirably) without dumbing-down. Ep 1 looked at the Great white shark, ep 2 was called ‘Monster Python’, and ep 3 was titled ‘The Big Cats’. A 90 minute special episode, ‘Monsters of the Deep’ is due to be screened some time later this year. It’s devoted to giant squid: I’m sure it’ll be excellent, but I won’t be writing about it (hey, not because I don’t like squid).
I need to say at the outset that I failed to take notes while watching series 2, and that (except for the python episode) I haven’t been able to view the episodes online. This is my stupid fault for leaving the writing-up to too late (you know, because I’m lazy). The consequence of all this is that I’ve had to be a bit sparse on some of the details, and have missed the names of some of the experts. Apologies in advance. If you can help by filling in any of the missing data, please do so. I’ll then update the articles accordingly.
As was the case for series 1, some of ING series 2 was filmed at the Royal Veterinary College. The series was presented by Mark Evans (biologist Simon Watt also featured heavily). Richard Dawkins made occasional appearances and, among the several anatomists who featured, Joy Reidenberg was a regular face once again [image below provided by Joy Reidenberg, used with permission].
So, ep 1 covered Carcharodon carcharias. Even as an obviously dedicated, obsessive tetrapodophile I have to admit that I find sharks cool and fascinating, and lamnids like the White shark are among my favourites. I’m therefore going to break the tetrapods-only rule once again. The shark used in the episode was a particularly large female (4.5 m long and 900 kg in mass), killed following entanglement in a South African beach protection net (note that no animals were killed specifically for the series).
One of the highlights for me was seeing the jelly that occupies the ampullae of Lorenzini [shown here]. These flask-shaped, electroreceptive organs – well known and familiar to anyone who knows sharks – are distributed across the White shark’s snout and around its jaws, but while many sources show the organs in cross-section, I’ve never actually seen their contents before. That’s because I’m naïve: the jelly extrudes from a freshly dead shark should you squeeze the area around any of the ampullae, apparently. Also interesting (and not mentioned that often in the literature) is that the ampullae extend across the dorsal suface of the head, not just the nose.
The ING team began by discussing (and dissecting) the jaws and gills. One really bizarre and interesting fact is that the cartilaginous jaws are not solid, but flexible enough for the teeth to be wiggled back and forth. This makes it all the more remarkable – or, if you like, ridiculous – that the White shark has a bite force that can perhaps exceed 1.8 tons (Wroe et al. 2008). The jaws are mobile relative to the snout and braincase, and during biting the snout is lifted and the jaws are protruded forwards. This ‘lift and lunge’ biting process – which you might have seen on film (if you’ve seen it in real life, you’re either very lucky or very unlucky) – is very rapid, taking between 0.75 and 1.78 secs (Ellis & McCosker 1991). Like many animals assumed to have a homodont dentition, Carcharodon is actually quite heterodont: the upper jaw teeth are wider and stouter than the lower jaw teeth, the teeth decrease markedly in size towards the corners of the mouth, and the crown of the third upper jaw tooth is short compared to its neighbours, and has a peculiar curvature that directs its apex toward the midline. There are 26 upper and 24 lower jaw teeth, with numerous replacements lined up behind, of course [image of Carcharodon jaws below provided by Joy Reidenberg, used with permission]
Later in the dissection, they turned the animal onto its back and cut open its belly in order to reveal the liver. It’s well known (I hope) that sharks use a large, oily liver as a buoyancy organ (no swim bladder), but the size of this organ in Carcharodon has to be seen to be believed… it was enormous, bigger than a person [adjacent photo shows the extracted liver: people for scale]. The Carcharodon liver can constitute as much as a quarter of the shark’s weight (Ellis & McCosker 1991). The team also looked at the spiral valve intestine: the shark gut is short and looks like a simple tube, but when cut open it reveals a tightly spiralling structure that obviously maximises the absorption surface. Like the ampullae, the spiralling structure of the intestine is something you see referred to in every single shark book (frequently illustrated in diagrammatic form), but actually seeing it is a rare and wonderful thing… if, that is, you’re not a shark specialist (and I’ll admit here that I’ve never properly dissected a shark).
Something that should be more widely known about the Great white (and a few other lamnid sharks) is that it’s endothermic. More specifically, it exhibits regional endothermy; the ability to generate (and retain) heat in the viscera, brain, eyes and slow-twitch muscle fibres. This heat is transferred to the surrounding tissues, and Great whites and other endothermic fish are able to maintain internal temperatures as much as 14° C higher than the surrounding water (Carey et al. 1982, Dickson & Graham 2004, Bruce 2006). The heat-generating muscles in the tail were obvious (being deep red) in dissection, compared to the surrounding whiter muscles [image below: did I say that Great white sharks are among the most awesome creatures on the planet? South African breaching shark, photo © Chris Brunskill/Ardea.com].
Much more was covered – this is but the briefest of summaries. While there’s clearly no shortage of stuff to talk about when discussing animal anatomy, I’ve become increasingly impressed with how much information ING managed to pack into each episode. And, even to someone with a reasonable amount of prior knowledge about shark anatomy, seeing such things as the liver were memorable firsts. The episode also did a good job of showing what a wonderful, beautiful animal the Great white is when alive, and of how it deserves conservation status and legal protection. So – watch the episode if you can!
For the Tet Zoo reviews on series 1 of ING, see…
- Inside Nature’s Giants: a major television event worthy of praise and accolade. Part I!
- Inside Nature’s Giants part II: whale guts and hindlimbs ahoy
- Enough mammals for the time being: crocodiles on Inside Nature’s Giants (part III)
- Inside Nature’s Giants part IV: the incredible anatomy of the giraffe
Many thanks to Zach Buchan for invaluable assistance, to Joy Reidenberg, and to Tom Mustill at Windfall. More on ING series 2 coming soon.
Refs – -
Bruce, B. D. 2006. The Biology and Ecology of the White Shark, Carcharodon carcharias. In Camhi, M. D., Pikitch, E. K. & Babcock, E. A. (eds) Sharks of the Opean Ocean: Biology, Fisheries and Conservation. John Wiley & Sons, pp. 69-81.
Carey, F. G., Kanwisher, J. W., Brazier, O., Gabrielson, G., Casey, J. G. & Pratt, H. L. 1982. Temperature and activities of a white shark, Carcharodon carcharias. Copeia 1982, 254-260.
Dickson KA, & Graham JB (2004). Evolution and consequences of endothermy in fishes. Physiological and biochemical zoology : PBZ, 77 (6), 998-1018 PMID: 15674772
Ellis, R. & McCosker, J. E. 1991. Great White Shark. Stanford University Press (Stanford, California).
Gilbey, J. 2010. Q&A: Prime-time dissection with Joy Reidenberg. Nature 465, 1013.
Wroe, S., Huber, D. R., Lowry, M., McHenry, C., Moreno, K., Clausen, P., Ferrara, T. L., Cunningham, E., Dean, M. N. & Summers, A. P. 2008. Three-dimensional computer analysis of white shark jaw mechanics: how hard can a great white bite? Journal of Zoology 276, 336-342.