It's possible that whales can sense things that no other living creatures can. Scientists have discovered a grapefruit-sized mass of vessels and nervous tissues located in whales' chins, and they believe it's an entirely new kind of sensory organ. It's possible the organ is what allows these massive creatures to eat using a lightning-fast mouth movement called "lunge feeding."
To find out more, we spoke with the study's lead researcher, paleobiologist Nick Pyenson. He says this sensory organ is just one more thing that makes whales like "mammals from space."
The first thing you need to understand about baleen whales is that they're enormous. The biggest of the baleen whales are known as rorqual whales, a group that includes humpback whales, fin whales and, of course, the blue whale — the largest animal to ever live.
Animals as large as rorquals obviously need plenty of food to survive. To acquire that food, they rely on their uncommonly large mouths and a technique known as lunge-feeding. When lunge-feeding, a hungry whale will accelerate to great speeds and open its mouth wide, allowing its pleated throat to expand like a parachute while taking in a giant gulp of water. The mouth then swings shut, and the whale begins the process of straining its prey through filter-like "mouth hairs" known as baleen. Fish, krill, and various other sea creatures are caught in the baleen, and water is expelled.
We know rorquals lunge-feed because we've seen them do it. What's less clear is how they go about orchestrating the behavior, which involves the careful cooperation of several enormous anatomical structures. The scale, quickness and precision of rorqual feeding behavior is nothing short of spectacular. In today's issue of Nature a team of researchers led by paleobiologist Nick Pyenson describes the discovery of a heretofore unknown sensory organ, located in the chin of rorqual whales, that they believe is responsible for coordinating that behavior.
"In blue whales, jaws can be up to six meters long, and those jaws open and close under water in les than ten seconds," explains Pyenson in an interview with io9. Speed is important, "especially if you want to capture a big swarm of krill before they disperse."
But lunge feeding-involves more than opening one's mouth and blindly rushing a group of prey. Pyenson says that a whale needs to be able to sense what's going on inside its mouth and respond to that sensation in turn, actively controlling both the state of its throat pleats and the positioning of its jaws in order to capture as much prey as possible.
So when Pyenson and his colleagues happened upon a large, nerve-laden mass positioned between the jaws and throat-pleats of dissected fin and minke whales (two rorqual species), it wasn't long before they realized that the fleshy structure might be implicated in the coordination of the whales' mouth movements.
The organ rests inside the whale's chin, in the gap between the whale's bony jaws (pictured above, click to enlarge). The structure is pinched by the jaws, explains Pyenson, "and compresses through the course of a lunge." But the organ also sits atop a y-shaped stem of fibrous cartilage that connects to the whale's throat pouch. All this is wired up to the whale's sensory nervous system. The result is an organ that is well-placed anatomically to help control both the flexible, blubbery tissue of the whale's throat, and the bony tissue of the jaws, "coordinating both hard and soft tissue together, and linked mechanically to both sets of tissue types."
What's really interesting about this find is that the organ appears to be missing from smaller whales, a fact that could point to the organ's evolutionary importance:
"In terms of evolution, the innovation of this sensory organ has a fundamental role in one of the most extreme feeding methods of aquatic creatures," said co-author Bob Shadwick.
"Because the physical features required to carry out lunge-feeding evolved before the extremely large body sizes observed in today's rorquals, it's likely that this sensory organ — and its role in coordinating successful lunging — is responsible for rorquals claiming the largest-animals-on-Earth status," he explained.
When we asked Pyenson if there was a human sensory process that he thought this organ could be most closely tied to, he said it was difficult to say, but was a good enough sport about it to take a shot. The nerves and connective tissue that comprise the organ, Pyenson says, show the hallmarks of what are known as mechanoreceptors:
[Humans] have different mechanoreceptors all throughout our skin and joints that relay information about position and pressure. It's an unusual structure, and what's really unusual about it is its position. But it's not about temperature, it's not taste, it's really about movement and pressure. That's probably the closest analogy we have.
The more we investigate the ocean's largest mammals, the more mind-boggling discoveries we seem to make. Pyenson notes that studies like this one are notoriously difficult to perform, and that whale anatomy is something that remains incredibly mysterious to researchers.
"Whales are like mammals from space," he explains. "they just have all these strange adaptations to living life in the water."
"It's a great irony that we've hunted and studied large baleen whales for well over 100 years, and for all those thousand and thousands of whales that have ben killed, nobody's ever looked at the anatomy at this level of detail. We are still only beginning to understand the anatomy of the largest ocean predators of all time."
The researchers' findings are published in today's issue of Nature.