[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Not dinos, but interesting, in an evolutionary sense



Hi All -

A friend of mine on the other side of the pond sent me this, and I thought
that many of you'd be interested:


BBC News Online: Sci/Tech

  ------------------------------------------------------------------------
Front Page | World | UK | UK Politics | Business | Sci/Tech | Health |
Education | Sport | Entertainment | Talking Point | High Graphics |
Feedback | Help | Noticias | Newyddion |
  ------------------------------------------------------------------------
Tuesday, May 11, 1999 Published at 14:09 GMT 15:09 UK

Early elephants used 'swimming trunks'

Scientists believe they have discovered why elephants have trunks - they
used them as underwater snorkels.

New research suggests that the animals evolved from mammals like the sea
cow which is still found in some of the world's oceans.

The elephants' aquatic ancestry was revealed by the careful laboratory
study of one embryo and six foetuses, ranging in age from 58 to 166 days
old.

Ann Gaeth, at the University of Melbourne, Australia, had the rare
opportunity to look at the foetuses after her colleague, Roger Short, was
sent the specimens from the Kruger National Park in South Africa. The
foetuses were taken from elephants killed in a culling operation in 1993.

Ancestral features

She found that all the elephant foetuses contained a physiological
curiosity called a nephrostome. This is a funnel-shaped kidney duct found
only in freshwater fish, frogs and egg-laying reptiles and mammals.

"The elephant is so unusual," Ms Gaeth told BBC News Online. "No other
mammal that produces live offspring has these nephrostomes."

The nephrostomes appear very early in embryo development and then
disappear. "Something that appears early in gestation is much more likely
to be ancestral. Those features that appear later in development are likely
to be related to more recent adaptations," says Ms Gaeth.

Ms Gaeth says that fossil evidence indicates that elephants left behind
their aquatic life about 30m years ago. She has identified changes to their
bodies that have occurred to adapt them to life on land.

Up periscopes

Their lungs now allow the elephants to suck up a large amount of water in
their trunks and hold it there, before letting it gush into their mouths.]

The trunks themselves appear extremely early on in foetal development,
being shown in even the earliest embryo examined. This suggests that they
were used when the elephants' ancestors lived in water, probably as
snorkels.

Modern elephants still use their trunks in this way. When Asian elephants
used for logging are required to travel from one island to another, they
frequently swim.

Their necks are too short to allow them to breathe with their mouths, so
the trunk is pushed up like a periscope and used as a snorkel.

Internal testicles

Further embryonic evidence that elephants once swam is that, unlike other
land-living mammals, they have internal testicles and always have done.
Seals and whales also have internal testicles, but only acquired them when
their land-living ancestors took to the seas 60m years ago.

Fossil studies of elephant ancestry have been supplemented in recent years
by DNA, biochemical and immunological evidence, all of which show that
aquatic beginnings were likely. The modern elephants' nearest relatives are
the sea cows - dugongs and manatees.

This latest work, backing up these suggestions, is published in the
Proceedings of the National Academy of Sciences.
____________________________________________________
BBC News Online: Sci/Tech

  ------------------------------------------------------------------------
Front Page | World | UK | UK Politics | Business | Sci/Tech | Health |
Education | Sport | Entertainment | Talking Point | High Graphics |
Feedback | Help | Noticias | Newyddion |
  ------------------------------------------------------------------------