Whales that give new meaning to longevity (fwd)

From: pita admininstrator (pita@www1.wheelock.edu)
Date: Tue Oct 24 2000 - 14:47:02 EDT


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Science News

   Week of Oct. 14, 2000; Vol. 158, No. 16

Cetacean Seniors

   By Janet Raloff

   Like a stream of massive torpedoes, thousands of blubbery dynamos are
   making a southwest migration through the icy Arctic Ocean. They're
   bowhead whales heading toward winter haunts in the Bering Sea, just
   north of the Aleutian Islands.

   Along the way, I=F1upiat Eskimos in Alaska will legally harvest severa=
l
   of these endangered mammals-30-to-60-foot-long behemoths that
   sometimes tip the scales at 50 tons or more.

   Having hunted these whales for centuries, the I=F1upiat are keen
   observers of the bowhead (Balaena mysticetus). Their tales recall
   whales that hunters had recognized by distinctive scars. In some
   cases, several generations of storytellers described encountering the
   same whale, leading to speculation that bowheads might live some 60
   years.

   Studies now suggest that these whales can actually outlive
   people-perhaps by a century.

   The new research was triggered by hunters finding ancient harpoon
   points in the foot-thick blubber of newly landed whales. Six points
   made of stone or ivory have turned up since 1981. None of the I=F1upia=
t
   subsistence whalers could remember having seen such primitive tools
   used.

                                                   ancient harpoon points

      Ancient harpoon points found in modern whales include two of slate,
      two of stone, a triangular metal blade, and an ivory head bearing a
      piercing metal blade, which perhaps represents a transitional type.
                            (George and Alaska Eskimo Whaling Commission)

   "You have to understand that [the I=F1upiat] are technological
   pickpockets," quips biologist David W. Norton, with a grin of respect.
   Now working in Fairbanks, he conducted research in Barrow, Alaska,
   over roughly 3 decades. During that time, he saw I=F1upiat hunters in
   Alaska's northernmost county, the North Slope Borough, quickly embrace
   any useful technology to which they were exposed. Indeed, history
   shows that as soon as I=F1upiat whalers gained access to metal, around
   1870, they swapped it for stone and ivory in their tools.

   Against that backdrop, the old harpoon points suggest that at least
   some contemporary bowheads are survivors of run-ins with whalers 100
   years earlier, observes biologist Todd M. O'Hara of the borough's
   Department of Wildlife Management in Barrow.

   To investigate this provocative possibility, O'Hara's colleague J.
   Craig George began looking for a way to determine the age of elder
   bowheads. A little research led him to Jeffrey L. Bada of the Scripps
   Institution of Oceanography in La Jolla, Calif.

   A geochemist, Bada has been refining a technique for dating fossils on
   the basis of changes in their aspartic acid. This amino acid can exist
   in either of two mirror-image forms. Living things make and use only
   the left-handed version. However, after death, a body's aspartic acid
   gradually converts to a 50-50 mix of the two forms. In fossils, that
   conversion takes about 1 million years.

   Bada's team had shown that this change in the ratio also occurs in
   living animals' body parts that are not undergoing metabolism, such as
   teeth and the lens of the eye. In such tissues, body heat sets the
   pace of change in the ratio of left-handed to right-handed aspartic
   acid.

   Indeed, the conversion rate appears to be identical in the lenses of
   all animals with the same basic body temperature. The scientists have
   tested more than 20 species, including people and bowhead whales. Bada
   offered to help calculate the age of North Slope bowheads from that
   ratio of the two forms of aspartic acid in eye lenses.

   George sent tissues from 48 bowhead whales to Bada without letting him
   know whether each had come from an infant, juvenile, young adult, or
   mature adult. The chemist's assays accurately dated the relative age
   of the young whales and indicated that most adults had been 20 to 60
   years old at death. However, the lens analyses from five large males
   suggested that at the time that I=F1upiat hunters harpooned them, one
   was 90, four were between 135 and 180, and one was more than 200 years
   old.

   O'Hara's group has recently recruited two other research teams to
   apply other techniques to estimate bowhead ages.

   Next month, for instance, Mark Baskaran of Wayne State University in
   Detroit expects to start measuring radioactive lead in samples of
   bowhead bone. The lead isotope forms during the decay of radium, a
   naturally occurring calciumlike radionuclide in seawater. Because both
   the radium and lead decay at known rates, Baskaran can use their ratio
   to determine the age of bones more than a year old.

   Cheryl Rosa of the University of Alaska, Fairbanks plans to assay
   pentosidine in samples of whales' skin. Aging leads to a progressive
   build-up of this chemical in many animals' skin. Rosa envisions
   eventually using it to determine the ages of living whales. A tethered
   dart can extract a small chunk of skin from a passing animal. Rosa
   notes, "The whale doesn't even seem to notice."

   Bada points out that these complementary studies are important to
   confirm the longevity indicated by his work. They might even provide
   further surprises. Unless whales' eyes are much warmer than people's
   and therefore have a faster aspartic acid conversion rate, Bada says,
   "what we have assigned the bowheads are only minimum ages-which is
   staggering! These are truly aged animals, perhaps the most long-lived
   mammals."

   However, he points out that other members of the whale family may also
   have the capacity to be centenarians, even if they don't live as long
   as bowheads. Bada claims to have "a bunch of pretty compelling data"
   to suggest several other whales can get "quite old."

   From Science News, [16]Vol. 158, No. 16, Oct. 14, 2000, p. 254.

   1. http://sciencenews.org/index.asp

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