Like tree rings, these layered plates hold chemical clues to how the animals adapt to a changing world.
(From Smithsonian.com/ by Jennifer Holland)– Had he glanced over his shoulder just before the “great fish” swallowed him, biblical Jonah would have had an enviable view. Enviable, that is, if you’re Alex Werth, a landlocked biologist who studies the feeding anatomy of whales. “Ah, to be Jonah and watch baleen in action from a seat on a whale’s tongue,” he says.
Baleen is the apparatus toothless whales rely on to filter food from the sea. Hundreds of these flexible plates, made of the structural protein keratin, grow downward from a whale’s upper jaw, lined up like the slats of venetian blinds. Fitting the plates into the mouth requires a large upper jaw, giving baleen whales a sort of upside-down grin.
The feeding structure evolved stepwise some 30 million years ago when the oceans were full of toothed whales competing for limited food. Having developed a tool and taste for other kinds of prey, baleen whales—known collectively as mysticetes—eventually split off and diverged into 12 or more species including the blue whale, the largest animal ever to have lived, along with humpbacks, grays, and right whales. And, at least until American commercial whalers commenced heavy pursuit some 200 years ago, these relatively passive feeders gulping down little marine animals by the tonne did just fine.
“Baleen changed everything,” Werth says. “And yet our understanding of aspects of this anatomy is still tissue thin.” Many scientists concur that filter feeding found footing in the Oligocene (33.9 to 23 million years ago) as changes in Southern Ocean currents brought massive plankton blooms—a ready new food source. (Interestingly, the animals didn’t start out as giants. A new report published in May 2017 suggests that their gigantism came later, perhaps three million years ago, as prey became more tightly packed but patchier—the result of intense nutrient upwellings. This dining style favored whales that could both binge feed and were bulky enough to travel far between patches—baleen whales grew to meet the challenge.)
The estimated time of baleen whales’ arrival is where common ground among scientists ends. Few agree, Werth says, on the steps by which the filtration system evolved in whales, how intermediate forms fed (likely by suction, according to the latest fossil find), “or even how [baleen] works with the forces and flows of the sea.”
But while some of whales’ deep past continues to perplex, scientists today have discovered an unexpected source of clarity, a detailed treasure map hidden inside baleen. Information associated with keratin, either in the protein or alongside it, holds chemical timestamps and data on whales’ health, movements, and reproduction. “It’s as if these animals have been keeping a daily journal, and suddenly we can see what they’ve been writing,” says endocrinologist Kathleen Hunt of Northern Arizona University. And the narrative unfolding from the baleen could inform whale conservation in whole new ways.
Read the full story here: http://www.smithsonianmag.com/science-nature/history-toothless-whales-180964717/