The second episode of Inside Nature’s Giants (read part I first) looked at whale anatomy: this time round, the autopsy was carried out on a Fin whale Balaenoptera physalus that had died off the coast of County Cork, southern Ireland.
Whereas the other dissections all took place in the RVC, this one was carried out in place on a beach, meaning that the weather, tides and light all intervened and spread the dissection out over two days (hence the rain spots on the image above; © Channel 4). The whole event was led by Joy Reidenberg, and toward the end of the episode she was literally standing thigh-deep in whale gloop, or slithering around on her belly while clambering around among viscera. Nice. Heavy machinery was involved: JCBs and all that. Bloating due to the build-up of gases meant that the whale was ready to burst, and that any over-enthusiatic incising would result in a humongous explosion of whale guts (they showed some video footage – taken in Denmark – where this is exactly what happened. A still from that footage is shown below). So Reidenberg carefully made numerous small incisions along the throat pleats; the gas rushed out with a loud whistling sound, as planned.
After cutting open (and successfully deflating) the pleated ventral skin on the belly and throat, Reidenberg extracted the larynx and hyoid, while teams used heavy machinery to peel away the skin (as shown at the top of the article; image © Channel 4), and to remove the guts and other abdominal tissue.
As you’ll know if you’ve ever looked at a whale skeleton from underneath, many whales have enormous hyoid bones (I’m referring to the basihyoid and thyrohyoids). I always thought this was all to do with the tongue and throat musculature, and it probably is in some species: sperm whales and beaked whales employ suction feeding, so need powerful throat musculature (Heyning & James 1996), and the rorqual tongue, used in manipulating prey, requires the support of large, robust hyoids (Werth 2007). However, in 2006, Reidenberg proposed that the hyoids might play a key role in pulling the head ventrally (as shown in the adjacent CG still; image © Channel 4), and hence in setting up the dorsoventral ‘body wave’ employed during swimming. This was discussed in the programme, and they used CG to show how it might work. So far as I can tell, this hasn’t yet been published (please tell me if you know otherwise). Reidenberg also explained how the expandable laryngeal sac allows rorquals like the Fin whale to make low-frequency noises (incidentally, the laryngeal sac of the Pygmy right whale Caperea marginata is asymmetrical, and I believe that humpbacks do some freaky stuff with their throat when bubble-netting). After removing the larynx she was able to manipulate the corniculate flaps – a pair of pliable lip-like, anterior structures located close to the epiglottis – and make the suggestion that they might be used in making pulsing infrasonic noises. I’d love to talk more about this sort of thing: for the relevant literature see Reidenberg & Laitman (2004, 2007, 2009).
Moving away from the throat and to the rest of the body, Reidenberg tried to get the heart out, but couldn’t reach far enough into the chest to get it. The team also worked hard to retrieve – successfully – one of the vestigial hindlimbs. If you know anything about whales, you’ll know all about the vestigial pelvic girdles and hindlimbs present in various members of the group. However, I suppose the presence of hindlimbs and pelvic girdles in modern whales is not well known to the public at large, and I even recall seeing scepticism about their presence being expressed by some (as if they’re rare or based on apocryphal accounts). So, if you’re going to talk about the terrestrial origins of cetaceans – and this is exactly what they did in Inside Nature’s Giants – it would be wrong not to get that vestigial pelvis or hindlimb out [adjacent
hindlimb pelvis pic © Channel 4].
All in all, outstanding. Coming next: the crocodile episode!
For previous Tet Zoo articles on cetacean anatomy see…
- A 3-m tooth that can bend 30 cm in any direction and is hypersentitive to salinity, temperature and pressure… and the sonic lance hypothesis
- Seriously frickin’ weird cetacean skulls: Kogia, shark-mouthed horror
- The dolphins with the massive jagged bony crests
- Inia: gnarly, heterodont, carries rocks for fun
- Killer sperm whales
- Blunt-nosed paedomorphic cutie
- Weird whales grand finale
- A 6 ton model, and a baby that puts on 90 kg a day: rorquals part I
- From cigar to elongated, bloated tadpole: rorquals part II
- Lunging is expensive, jaws can be noisy, and what’s with the asymmetry? Rorquals part III
Wow, that’s quite a lot.
Refs – –
Heyning, J. E. & Mead, J. G. 1996. Suction feeding in beaked whales: morphological and observational evidence. Contributions in Science, Natural History Museum of Los Angeles County 464, 1-12.
Reidenberg, J. S. & Laitman, J. T. 2004. Anatomy of infrasonic communication in baleen whales: divergent mechanisms of sound generation in mysticetes and odontocetes. Acoustical Society of America Journal 115, 2556-2556.
– . & Laitman, J. T. 2007. Discovery of a low frequency sound source in Mysticeti (baleen whales): anatomical establishment of a new vocal fold homolog. Anatomical Record 290, 745-759.
– . & Laitman, J. T. 2009. Sisters of the sinuses: cetacean air sacs. The Anatomical Record 291, 1389-1396.
Werth, A. J. 2007. Adaptations of the cetacean hyolingual apparatus for aquatic feeding and thermoregulation. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology 290, 546-568.