African lungfish
walk in water
study suggests four-legged
locomotion began at sea
By Nick Bascom
African lungfish walk and bound along
the bottoms of water tanks on their slender, whiplike pelvic fins, a new study finds.
Lungfish are closely related to some of
the earliest four-legged terrestrial vertebrates, or tetrapods. The findings suggest
that these transitional creatures learned
to scuttle across the floors of ancient seas
before they took to land and developed
more complex limbs with digits, biologist Heather King and colleagues at the
University of Chicago suggest online
December 12 in the Proceedings of the
National Academy of Sciences.
“The cool thing about the lungfish is
that it’s walking underwater,” says King.
“And if lots of tetrapods were also doing
this, it could mean that the first step in
the evolution of vertebrate walking took
place underwater.”
Around 400 million years ago, certain
species of bony fish — called the lobe-
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finned fishes for their muscular, fleshy
fins — began to evolve features such as
larger limbs with digits, which allowed
them to move onto land. “We have a
whole series of fossils that show this
transition from lobe-finned fishes to tetrapods,” says King. Until now, however,
scientists didn’t have a clear idea of the
order in which these features emerged.
“The fossil record has limitations,”
says study coauthor Neil Shubin. “Liv-
ing organisms are far weirder than you
can imagine, and the more you look the
more you find.”
To get a closer look at one of the last
living species of lobe-finned fish, the
research team plopped African lungfish
of the species Protopterus annectans one
at a time into a tank with a plastic mesh
bottom and trained several cameras on
them. From various angles, the scientists
captured video of the lungfish ambling
and leaping using their pelvic fins.
“If you asked me to tell you what those
fins do just by looking at them, I’d give
you a thousand functions, and walking
wouldn’t be one of them,” says Shubin.
“But that’s what they do.”
Watching the strange aquatic critters
hop and hobble may be the best way to
study this important transition in the
history of vertebrate locomotion.
The near-vegan lifestyle of wild orangutans in Borneo’s
forests means the apes face recurring protein droughts
severe enough that their body tissues start to waste away.
The forests of Borneo, one of only two natural habitats for
wild orangutans, produce abundant fruit only about every
five years. in bad years, the animals make do with leaves
and bark. During such tough times, the apes average only
about 1. 4 grams of protein per kilogram of body mass per
day, a tenth of what mountain gorillas consume, nathaniel
Dominy of Dartmouth College and his colleagues report
online December 14 in Biology Letters. Knowing these
protein budgets is important for understanding how orangutans have adapted to survive in places with resources
that fluctuate so extremely, says mark e. harrison of the
university of Leicester in england, who also has studied
orangutan feeding ecology. — Susan Milius
Apes’ boom-bust diet
© Tim Laman
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