For rorqual whales, some of the largest animals in the world,feeding is no simple task. In fact, some have described the act ofa blue or fin whale opening its jaws 90 degrees wide and taking agiant gulp of water as the largest biomechanical event on earth. Now, scientists at the University of British Columbia and theSmithsonian Institution in Washington, D.C., believe they'veidentified an organ that helps these huge mammals accomplish thegargantuan task of quickly opening and closing their giant mouthsunderwater while moving along relatively rapidly, a process knownas lunge feeding. "It really is pretty astonishing when you look at the fact that ablue whale, which has six-metre-long jaws, has to open and shut itsmouth in under 10 seconds to actually capture any prey," saidNicholas D. Pyenson, curator of fossil marine mammals at theSmithsonian. "In doing so, they engulf a volume of water that's about 100 cubicmetres. Imagine a city bus it's a volume of water that's largerthan that." Cavity filled with mechanoreceptors Pyenson and his colleagues at UBC discovered an oval, gel-filledcavity in the chin of rorqual whales filled with blood vessels andnerves that act as mechanoreceptors relaying information to thewhale's brain about the positioning of its enormous jaws. "It just gives it information about where the jaw is as it goesthrough this very rapid and very dramatic expansion of the mouth,"Pyenson said. The researchers suspect the as-yet-unnamed organ is an importantanatomical feature that enabled whales to evolve the very largebody size they have today. Their findings are published in the May 23 edition of the journal Nature. Scientists from the University of British Columbia and theSmithsonian Institution collecting field data in Iceland. Left toright: Robert E. Shadwick, Jeremy A. Goldbogen and Nicholas D.Pyenson. (A. Wayne Vogl and Nicholas D. Pyenson/Smithsonian Institution) Pyenson's collaborators on the study were Robert E. Shadwick, whoholds the Canada research chair in integrative animal physiology atUBC, A. Wayne Vogl, a professor of cell and developmental biologyat UBC, and Jeremy A. Goldbogen, now a postdoctoral researcher atthe Cascadia Research Collective in Olympia, Wash., but previouslya PhD student of Shadwick at UBC. Rorqual whales fall under the group known as baleen whales, whichinstead of teeth have a sieve-like substance called baleen hangingfrom their upper jaw that filters fish, krill and plankton out ofthe water. Unlike toothed whales and dolphins, rorqual whales don'tuse echolocation to pursue a single prey but take in a jumble of marine life in onegiant gulp of water with the help of a flexible accordion-likethroat pouch that allows their mouth to expand. They then let the water flow out through their baleen, which ismade up partly of keratin, the protein found in human hair andfingernails, which filters out the prey. "It's a very efficient form of feeding even though it's very costlyin the sense of the physics involved, because you're no longer veryhydrodynamic when you engulf a large volume of water, you're notvery streamlined," Pyenson said. Organ synched up with chin hairs Another peculiarity of baleen whales is that their right and leftjaws are not fused the way human jaws are. It is in the spacebetween the two jaws that the researchers found the sensory organ.From the outside, the cavity appears as a bump at the edge of thechin that can be glimpsed when a whale opens its jaws. The scientists discovered the organ while studying discarded tissueof dead whales caught at a commercial whaling station in Iceland.The species they studied were fin, minke and Bryde's whales, but,says Pyenson, they suspect the organ exists in all rorquals, whichalso include blue and humpback whales. Goldbogen, Vogl and their colleague Robert E. Shadwick point to aridge of tissue they sampled from the throat pouch a fin whale,part of which is seen in the background. (Nicholas D. Pyenson/Smithsonian Institution) Exactly how rorqual whales detect prey without the aid ofecholocation, the process of emitting a sound and using its echo tolocate and glean information about objects, is a question that hasstumped scientists, but Pyenson and his colleagues believe thesensory organ they've identified plays a role. Specifically, theorgan links up with the hairs that rorqual whales have on the tipof their chins to help them locate prey. "When we used MRI and CT data to look at the detailed anatomy, wediscovered the same nerves that are going in this organ are thosethat also connect up to the chin hairs, so we think the chin hairsare pretty important for detecting clouds of prey," Pyenson said. "Our hypothesis is that they likely detect a certain density ofobjects hitting it ... and that registers with the animal and says'OK, time to open your mouth.'" Pyenson and his fellow researchers are not the first to havespotted the organ, but previous research misidentified it as acartilaginous joint, Pyenson said. Pyenson said it's ironic that for most of the centuries that humanshave been hunting and later studying whales, the organ hasgone unnoticed. "I think it underscores how little we know about the anatomy of thelargest animals that are alive on the planet today," he said. The e-commerce company in China offers quality products such as Cable Stayed Bridge Manufacturer , China Truss Bridge, and more. For more , please visit Truss Bridge today!
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