Would you give up sex for eternal life? This little invertebrate, a bdelloid rotifer, has lived a celibate life for ~80 million years. The males have disappeared and the females reproduce by parthenogenesis. A drawback to this convenient scheme is that our DNA is usually repaired during meiosis, when we form gametes or germ cells.
• Scientists bombarded these little creatures with gamma rays that would typically shatter DNA into little bits. To their astonishment, the rotifers kept reproducing even at levels of radiation five times more than other animals can endure. Their secret lies in genetic redundancy: their genomes have duplicated, so that each gene is in 4 copies. When one is damaged, the others serve as template to copy off a new version (gene conversion).
• How did this resistance to radiation damage evolve? These animals live in fresh water pools that can dry up at any time. The rotifers can go dormant for weeks to years, springing back to life with water. Dessication has the same effect on DNA as radiation so the rotifers must have evolved to survive in their ephemeral habitats. “There could be some benefit to millions of years without sex after all”, says Dr. Alan Tunnacliffe, University of Cambridge 🙂
Live image of Philodina roseola , details at http://www.cellimagelibrary.org/images/41670
Refs: (1) Gladyshev, E., and M. Meselson. 2008. Extreme Resistance of Bdelloid Rotifers to Ionizing Radiation. Proc. Natl. Acad. Sci. 105 (13): 5139-5144.
(2) Mark Welch, D.B., J.L. Mark Welch and M. Meselson. 2008. Evidence for degenerate tetraploidy in bdelloid rotifers. Proc. Natl. Acad. Sci. 105 (13): 5145-5149.