Just occasionally, I find it in me to write about some ecology (aka fluffy bunny biology). Lots of female biologists end up studying science because they just want to cuddle the world, but I’ve always been more of a molecular person. (In fact, I probably would have studied Chemistry or Physics if the teaching had been half as good as it was in the Biology department at my school). Nevertheless I do have brief lapses into wanting to stroke fluffy things, and I am always game for a cool story about animals.
You know what my favourite animal is?
An orca! Having seeing Free Willy as a six year old I became obsessed with orcas as a kid. I had a huge poster on my wall, and I actually have a cuddly orca instead of a teddy bear. This post isn’t actually about orcas, but it is about rorquals, which are almost as cool. (Rorquals, in case you were wondering – one group of baleen whales – are blue whales, minke whales and humpback whales).
Rorquals feed by this awesome process called ‘lunge feeding‘. They basically just engulf a ridiculous quantity of sea water (laden with their favourite, tasty krill) by swimming at high speed, and then push all of the water out again through a sort of sieve made of baleen plates using their tongue, so that just the krill is left over. Omnomnomnomnom. When I say ‘ridiculous quantity of water’, we’re talking 80 cubic metres. The whale has to have two separate jaw bones, and a pleat of blubbery flesh in the middle of its lower jaw that can open out to fit each gulp in. (In the article I’m about to tell you about they refer to this as ventral groove blubber, which for some reason just sounds hilarious to me.)
The journal Nature are talking about rorquals today, because a team of scientists from the States and Canada have figured out how the whale manages to co-ordinate all the actions required to pull off this ‘lunge’. They have discovered a sensory organ in the connective tissue behind the jaw, which is activated in the early stages of the lunge, and which they believe helps to co-ordinate the precise speed and angle of the rest of it. (If the rate of mouth opening and pouch expansion isn’t tightly controlled then the lunge is less efficient). Nicholas Pyenson (the lead author on the study) said the organ was a “gelatinous mess” (funnily enough, that’s not a quote from the Nature paper) so in the past it was probably assumed that it was a fluid-filled joint between the two bones that make up the lower jaw.
The scientists suggest that the whale uses specialised hairs, or vibrissae, on its chin to feel when there are high density prey around. The jaws then move apart and rotate. When the jaw starts to open, the connective tissue where this sensory organ is gets compressed, which acts as a ‘we’re lunging now!’ stimulus. The scientists believe that the organ then co-ordinates with the brain to control the mechanics of the lunge, though I think that’s a general hypothesis, rather than one they’re collecting data for yet.
This discovery is especially newsworthy because other species of baleen whale outside of the rorquals (like grey whales and right whales), who have the baleen plate sieve in their mouth, but don’t have this exclusively lunging method of feeding, don’t seem to have the sensory organ, which bodes well for the scientists’ predictions of its function.