The first genome sequence of myriapod, Strigamia maritime, has been completed by an international collaboration of researchers that included collaborators from Baylor College of Medicine. The myriapod is a member of the venomous centipedes and this achievement will uncover new clues into its biological evolution, absence of vision, and circadian rhythm. About 100 researchers contributed to this project that is now published online in the PLOS Biology journal. This study was funded by the National Human Genome Research Institute.
Dr. Stephen Richards, assistant professor in the Human Genome Sequencing Center at Baylor said in a press release: “This is the first myriapod and the last of the four classes of arthropods to have its genome sequenced. Arthropods are particularly interesting for scientific study because they diverged into more species than any other animal group as they adapted in many ways to conquer the planet. The genome of the myriapod in comparison with previously completed genomes of the other arthropod classes gives us an important view of the evolutionary changes of these exciting species.”
Dr. Richards, along with Dr. Ariel Chipman, of the Hebrew University of Jerusalem in Israel, Dr. David Ferrier, of The University of St. Andrews in the United Kingdom, and Dr. Michael Akam of the University of Cambridge in the UK, were the core of this worldwide collaboration.
“The arthropods have been around for over 500 million years and the relationship between the different groups and early evolution of the species is not really well understood. We have good sampling of insects but this is the first time a centipede, one of the more simple arthropods – simple in terms of body plan, no wings, simple repetitive segments, etc. — has been sequenced. This is a more conservative genome, not necessarily ancient or primitive, but one that has retained ancient features more than other groups,” noted Chipman.
Richards went on to explain that, based on fossil evidence, scientists now know that myriapods are one of three independent arthropod invasions of the land who originally came from the sea, along with insects and spiders. “So they had to find a way to smell chemicals in air, rather then taste them in water. The team identified large gene expansions of the gustatory (taste) receptors suspected to fill the olfactory role that olfactory (smell) receptors play in insects. This is a nice example of parallel evolution where different group of genes expanded, providing a different solution to the same problem.”
In terms of their blindness, no genes related with their circadian clock were found and genes related with the vision. These creatures seem to have lost their vision 200 million years ago.
Chipman said: “This teaches us about how evolution works and how things change, how things can be conserved and others lost. In general, this just gives us a better understanding of biology and how it works over long periods of time.”
“Strigamia (centipedes) live underground and have no eyes, so it is not surprising that many of the genes for light receptors are missing, but they behave as if they are hiding from the light. They must have some alternative way of detecting when they are exposed. It’s curious, too, that this creature appears to have no body clock — or if it does, it must use a system very different to other animals,” said Akam.
Akam concluded saying that the sequencing of this genome is more than a scientific curiosity: “Some of its genes may be of direct use. All centipedes inject venom to paralyze their prey. Components of venom often make powerful drugs, and the centipede genome will help researchers find these venom genes.”