A new sensory organ has been discovered in rorqual whales. The discovery may help explain the great success of their ‘lunge-feeding method’.
Rorqual whales are a subgroup of baleen whales that includes blue, fin, minke, and humpback whales. They are known for their enormous size, and an accordion-like layer of blubber extending from their snout to their navel. This blubber can expand to many times its resting size, allowing massive quantities of prey-filled water to be swallowed and then expelled back out while filtering the prey.
The newly discovered organ is at the tip of the whale’s chin, in the ligamentous tissue connecting their jaws.
It was discovered in samples that were taken from recently killed fin and minke whales from Iceland’s commercial whaling operations.
Scanning the chin revealed a grapefruit-sized sensory organ supplied by neurovascular tissue.
“We think this sensory organ sends information to the brain in order to coordinate the complex mechanism of lunge-feeding, which involves rotating the jaws, inverting the tongue and expanding the throat pleats and blubber layer,” says lead author Nick Pyenson, a paleobiologist at the Smithsonian Institution, who conducted the study while a postdoctoral fellow at UBC. “It probably helps rorquals feel prey density when initiating a lunge.”
Fin whales, the second-longest whales on the planet, can swallow as much as 80 cubic meters of water and prey, in each six-second-or-less gulp. A previous study has shown that they adults capture 10 kg or so of krill in each gulp, which they use to maintain their 50-ton bodies.
“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,” says co-author and UBC Zoology Prof. 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,” Shadwick adds.
“This also demonstrates how poorly we understand the basic functions of these top predators of the ocean and underlines the importance for biodiversity conservation.”
Source: University of British Columbia
Image Credits: dryoptera via flickr under a CC license; Carl Buell, arranged by Nicholas D. Pyenson / Smithsonian Institution; and Blue Whale via Shutterstock
