Saturday, April 25, 2009
Spider "Resurrections" Take Scientists by Surprise
Charles Q. Choi
for National Geographic News
April 24, 2009
Spiders in a lab twitched back to life hours after "drowning"—and the scientists were as surprised as anyone.
The bugs, it seems, enter comas to survive for hours underwater, according to a new study. The unexpected discovery was made during investigations of spiders from salt marshes that are regularly flooded with seawater.
A number of spiders and insects have long been known to survive for hours underwater. But submersion experiments typically only test how long the bugs can withstand drowning—not whether they can revive themselves after their seeming deaths.
Scientists at the University of Rennes in France collected three species of wolf spider—two from salt marshes, one from a forest. The team immersed 120 females of each species in seawater, jostling the spiders with brushes every two hours to see if they responded. As expected, all the forest wolf spiders (Pardosa lugubris) apparently died after 24 hours. The two salt marsh-dwelling species took longer—28 hours for Pardosa purbeckensis and 36 hours for Arctosa fulvolineata.
After the "drownings," the researchers, hoping to weigh the spiders later, left them out to dry. That's when things began to get weird.
Hours later, the spiders began twitching and were soon back on their eight feet.
"This is the first time we know of arthropods returning to life from comas after submersion," said lead researcher Julien Pétillon, an arachnologist now at Ghent University in Belgium.
Marsh-dwelling A. fulvolineata, which took longest to "die," typically requires about two hours to recover, the researchers discovered. In the wild, the species doesn't avoid water during flooding, while the other salt marsh species generally climbs onto vegetation to avoid advancing water. The spiders' survival trick depends on a switch to a metabolic process that does not require air, the researchers speculate.
Whatever trick these spiders have mastered, Pétillon said, they may not be alone.
"There could be many other species that could do this that we do not know of yet."
Findings published April 22 in the journal Biology Letters.