Genetic analysis places spiders and scorpions among world's oldest creatures

Washington, Nov 3 : New genetic research has found that arachnids like spiders and scorpions first emerged at least 400 to 450 million years ago, making them among the world's oldest creatures.

According to a report in Discovery News, the study extends the known world presence of these creepy crawlies by over 200 million years.

The oldest fossil spider is 125 to 135 million years old, while the oldest fossil scorpion is around 200 million years old.

These invertebrates could even have emerged much earlier than this latest study determined.

"A horseshoe crab dating to 475 million years ago provided one of our anchor dates, and this crab actually looked quite modern, as did a Devonian period (416 to 359 million years ago) mite that was one very modern-looking mite," co-author Marjorie Hoy, a University of Florida entomologist, told Discovery News.

"I don't think the individuals just suddenly appeared on Earth, so it's likely these invertebrates are even older than we estimated," she added.

For the research, Hoy and colleague Ayyamperumal Jeyaprakash, who is a University of Florida senior biological scientist, obtained complete genetic sequences for the mitochondria of 25 different invertebrates, including four spiders, two mites, three scorpions, soft and hard ticks, and other members of an arachnid group that's known as the Chelicerata lineage.

Jeyaprakash identified genetic sequences common to the organisms.

The researchers then used high tech computer programs to calculate how much time passed since the sequences evolved from a common origin.

Scientists hope that even more fossils and genetic information will further pinpoint when arachnids emerged, ideally providing specific time frames for particular species within the group.

The study represents the first large-scale attempt to use genetic methods to make projections about when arachnids first evolved.

"Ours is the first divergence time estimate for spiders, scorpions, mites and ticks, but it won't be the final word on the matter," Hoy said. "The main point is that these arachnids are far more ancient than any of us had ever before realized," she added.

ANI