Science & Tech

Common aquatic animals show extreme resistance to radiation

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Harvard scientists have found that a common class of freshwater invertebrate animals called bdelloid rotifers are extraordinarily resistant to ionizing radiation, surviving and continuing to reproduce after doses of gamma radiation much greater than that tolerated by any other animal species studied to date.

Because free radicals such as those generated by radiation have been
implicated in inflammation, cancer, and aging in higher organisms, the
findings — published this week in the Proceedings of the National
Academy of Sciences
by Harvard’s Matthew Meselson and graduate student
Eugene Gladyshev — could stimulate new lines of research into these
medically important problems.

“Bdelloid rotifers are far more resistant to ionizing radiation than any
of the hundreds of other animal species for which radiation resistance
has been examined,” says Meselson, Thomas Dudley Cabot Professor of the
Natural Sciences in Harvard’s Faculty of Arts and Sciences. “They are
able to recover and resume normal reproduction after receiving a dose of
radiation that shatters their genomes, causing hundreds of DNA
double-strand breaks which they are nevertheless able to repair.”

Meselson and Gladyshev found that the bdelloid rotifers Adineta vaga and
Philodina roseola remained reproductively viable after doses of
radiation roughly five times greater than other classes of rotifers and
other animals could endure.

Such radiation resistance appears not to be the result of any special
protection of DNA itself against breakage, the researchers say, but
instead reflects bdelloid rotifers’ extraordinary ability to protect
their DNA-repairing machinery from radiation damage.

Roughly a half-millimeter in size and commonly observed under
microscopes in high-school biology classes, bdelloid rotifers are highly
unusual in several regards: They appear to be exclusively asexual, have
relatively few transposable genes, and can survive and reproduce after
complete desiccation at any stage of their life cycle. Meselson and
Gladyshev hypothesize that it’s this last property that explains
bdelloids’ apparently unique resistance to radiation.

Bdelloid rotifers have been widely studied since at least 1702, when the
renowned Dutch scientist and microscopy pioneer Antony van Leeuwenhoek added
water to dust retrieved from a rain gutter on his house and observed the
organisms in the resulting fluid. He subsequently described the
creatures in a letter to Britain’s Royal Society, which still counts an
envelope of van Leeuwenhoek’s rain-gutter dust among its holdings.

Meselson and Gladyshev’s work is supported by the National Science
‘s Eukaryotic Genetics Program.