SYDNEY, May 14 -- It may very well be the sexiest discovery in global archeology sincesingle-celled amoeba's were caught asexually reproducing in steaming Triassic eddies --Australian researchers have identified fossilized giant sperm almost 17 million years old.
The giant sperm, found at the rich Riversleigh World Heritage Fossil Site, come from tinyshrimps and are thought to have been longer than the male's entire body.
The "ostracod" crustaceans have the impressive distinction of coiling their gigantic semento the extent that they are discernable to the naked eye almost 20 million years after,sadly, not being deployed.
"These are the oldest fossilized sperm ever found in the geological record," a delightedProfessor Mike Archer, of the UNSW School of Biological, Earth and EnvironmentalSciences, who has been excavating at Riversleigh for more than 35 years told Xinhua.
Riversleigh has been synonymous with fossils in Australia since the late 1800's. The site inQueensland north contains hundreds of fossil sites that span an age from about 25 millionyears ago to about 15 million years ago, revealing a narrative of an Australia very differentfrom the dry continent of today.
"The Riversleigh fossil deposits in remote northwestern Queensland have been the site ofthe discovery of many extraordinary prehistoric Australian animals, such as giant, toothedplatypuses and flesh-eating kangaroos. So we have become used to delightfully unexpectedsurprises in what turns up there.
"But the discovery of fossil sperm, complete with sperm nuclei, was totally unexpected. Itnow makes us wonder what other types of extraordinary preservation await discovery inthese deposits."
The study is published in the journal Proceedings of the Royal Society B.
A UNSW research team led by Professor Archer, Associate Professor Suzanne Hand andHenk Godthelp collected the fossil ostracods from Bitesantennary Site at Riversleigh in1988.
They were sent to John Neil, a specialist ostracod researcher at La Trobe University, whorealized they contained fossilized soft tissues.
He drew this to the attention of European specialists, including the lead author on thepaper, Dr. Renate Matzke-Karasz, from Ludwig Maximilian University of Munich,Germany, who examined the specimens with Dr. Paul Tafforeau at the EuropeanSynchrotron Radiation Facility in Grenoble, France.
The microscopic study revealed the fossils contain the preserved internal organs of theostracods, including their sexual organs. Within these are the almost perfectly preservedgiant sperm cells, and within them, the nuclei that once contained the animals'chromosomes and DNA.
The researchers estimate the fossil sperm are about 1.3 millimeters long, about the samelength or slightly longer than the ostracod itself.
"About 17 million years ago, Bitesantennary Site was a cave in the middle of a vastbiologically diverse rainforest. Tiny ostracods thrived in a pool of water in the cave thatwas continually enriched by the droppings of thousands of bats," said Professor Archer.
UNSW's Associate Professor Suzanne Hand, who is a specialist in extinct bats and theirecological role in Riversleigh's ancient environments, said the bats could have played a rolein the extraordinary preservation of the ostracod sperm cells.
The steady rain of poo from thousands of bats in the cave would have led to high levels ofphosphorous in the water, which could have aided mineralisation of the soft tissues.
"This amazing discovery at Riversleigh is echoed by a few examples of soft-tissuepreservation in fossil bat-rich deposits in France. So the key to eternal preservation of softtissues may indeed be some magic ingredient in bat droppings," said Associate ProfessorHand.
Previous discoveries of extraordinary preservation at Riversleigh include insects withinternal muscles that have been preserved because bacteria became fossilized as theyattempted to consume the soft tissues of these creatures.
Perfectly preserved cells of leaves have been found, as well as the preserved soft tissue ofeyeballs in the eye sockets of some of the extinct marsupials.
Research at Riversleigh is supported by the Australian Research Council, UNSW CREATEFund, Queensland Museum, Queensland Parks and Wildlife Service, EnvironmentAustralia, Xstrata, Mount Isa City Council, Outback at Isa and the Waanyi people ofnorthwestern Queensland.
