Centipedes significantly outscore humans in the leg count but come up short on genes, say researchers who've mapped the complete genome of the creepy crawly creatures.

The first mapping of Strigamia maritima, a European centipede, shows it possesses around 15,000 genes, just around two-thirds of a human's 22,000 or so, they say.

Still, the findings are likely to provide more insight into how life evolved on Earth, the international research ream reported in the journal PLOS Biology.

Centipedes are arthropods, an invertebrate group that includes spiders, insects and crustaceans, and along with millipedes make up a class known as myriapods -- until now the only arthropod class that hadn't had its genome sequenced.

More surprising than the genes identified in the centipede are the genes that aren't there, researchers say.

Strigamia maritima seems to have lost the genes than can encode any of the known light receptors animals use, they say, and all the genes controlling the circadian rhythm, also known as the body clock.

"Strigamia live underground and have no eyes, so it's not surprising that many of the genes for light receptors are missing," say zoologist Michael Akam of the University of Cambridge in Britain. "But they behave as if they are hiding from the light. They must have some alternative way of detecting when they are exposed."

The lack of a body clock is also mysterious, Akam says, unless it's using some system completely different from that of any other animal.

The gene findings are clues to how different animals handled the evolutionary transition from the oceans to the land, says study co-author Ariel Chipman of the Hebrew University of Jerusalem's Alexander Silberman Institute of Life Science.

"The use of different evolutionary solutions to similar problems shows that myriapods and insects adapted to dry land independently of each other," he says. "For example, comparing the centipede and insect genomes shows that they independently evolved different solutions to the same problem shared by all land-dwelling creatures -- that of living in dry air."

While early genomic studies focused exclusively on humans, increasingly available sequencing equipment and the expertise in using it has made the entire world of biological life fair game -- to our benefit, Chipman says.

"If we have a better understanding of the biological world around us, how it operates, and how it came to be as it is, we will ultimately have a better understanding of ourselves," he says.

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