Spider's Blood Found in Amber May Hold Prehistoric Secrets
for National Geographic News
|October 4, 2005|
A 20-million-year-old spider frozen in time with droplets of its own blood may offer important new clues to the past, says the scientist who found it in the Caribbean.
The discovery of the previously unknown spider, preserved in fossilized tree resin, or amber, has echoes of Jurassic Park.
In Michael Crichton's book, scientists brought T. rex and other Jurassic giants back to life using dinosaur DNA taken from bloodsucking mosquitoes encased in amber.
While scientists maintain that the fictional story line remains extremely far-fetched, paleontologist David Penney says the new spider represents the first known amber fossil containing traces of blood.
Penney, from the University of Manchester in England, says it may be possible to extract DNA from the extinct spider's blood. But the fossil could prove even more valuable by helping shed light on the origins of animals found in the Caribbean.
The specimen came from an amber mine in the Dominican Republic on the Caribbean island of Hispaniola.
"This is the first ever fossil record of the spider family Filistatidae," Penney said. "Nobody's ever seen this before."
The small spider's closest living relatives are found only in Brazil and Argentina, providing a possible clue as to how Hispaniola and other islands in its island chain formed and were colonized by animals.
Hispaniola is part of the Antilles island chain, which stretches from Cuba to Grenada.
"The geological past of that region is quite complicated and not fully understood," Penney said.
South American Connection
Some speculate that the Antilles were once attached to Central America. More recently scientists have proposed that the chain was briefly connected to South America some 35 million years ago.
"The fact that this specimen has its closest relatives in Brazil and Argentina lends weight to this argument," Penney said.
Dominican amber fossils suggest there has been relatively little change in climate and habitat in the Caribbean for tens of millions of years, he said.
"The Dominican Republic is the only place on Earth where the amber fauna [fossilized animals in amber] are almost identical to the recent fauna," he explained. "That tells us that [Hispaniola] was tropical at the time it was formed."
The island's amber fossil record may also help turn up previously unknown species still living today, Penney said.
"The fauna on the island is quite poorly known. Not all the species are described," he said. Descendants of the newly discovered fossil spider may well have survived on Hispaniola, he added.
The paleontologist used blood droplets visible in the amber fossil, which is 4 centimeters long and 2 centimeters wide (1.6 inches long and 0.8 inch wide), to determine how the spider met its end.
From the flow of the blood droplets, Penney says, the spider must have been struck head-on by tree resin as it flowed down a tree trunk.
When the resin engulfed the spider, blood oozed from the arachnid's legs, which broke at predetermined weak spots. Leg loss is a predator-escape mechanism that is not unique to spiders.
"[It's] a bit like when you catch a lizard's tail and it breaks off," Penney said. "The same happens with spider legs in some families."
But can DNA be extracted from amber-preserved blood? And could it be used to sequence the DNA of long-extinct animals?
Experts are highly skeptical on both counts.
Along with other researchers, a team at the Natural History Museum in London recently tried to replicate experiments of scientists who claimed to have extracted insect DNA from amber fossils. These attempts all failed.
As a result, said the museum's ancient DNA expert Jeremy Austin, "Most scientists now agree that DNA doesn't survive in fossilized insects in amber."
And even if insect DNA was recoverable from amber fossils, the team says the chances of getting dinosaur DNA from a Jurassic-era mosquito are "virtually nonexistent."
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