An article published in the journal “BMC Biology” describes a genetic research that shows a whole genome duplication (WGD) during the evolution of arachnids. An international team of researchers in collaboration with the Human Genome Sequencing Center at Baylor College of Medicine analyzed the DNA of the common house spider (Parasteatoda tepidariorum) (photo ©Calibas) and the Arizona bark scorpion, Centruroides sculpturatus (photo ©Musides), concluding that they descended from a common ancestor that lived more than 450 million years ago.
This genetic study is part of a pilot project for the i5K, a wider project for the genetic study of 5,000 arthropod species. These projects have various purposes, sometimes very practical such as the study of spider and scorpions’ venoms for pharmaceutical purposes and the research in the field of material science on spider web’s silk.
Other goals are linked to genetic studies to understand the evolution of arthropods and their adaptations to various ecological niches. These gave tremendous success to the survival of the arthropod phylum for over half a billion years through an extraordinary diversification.
The arthropod (Arthropoda) phylum includes the Arachnid (Arachnida) class, which includes spiders, Araneae order, and scorpions, Scorpiones order. To try to better understand the history of spiders and scorpions, the team of the Human Genome Sequencing Center led by Dr. Stephen Richards sequenced the DNA of two representatives of those orders, the common house spider, also called the American house spider (Parasteatoda Tepidariorum), and the most venomous North American scorpion, Centruroides sculpturatus.
The result of the genetic analysis of these two arachnids was the discovery of an ancient whole genome duplication. An arthropod that lived over 450 million years ago became what is called in jargon a polyploid after that duplication. That’s a phenomenon already known in other arthropods such as horseshoe crabs but what happened in the common ancestor of spiders and scorpions was probably an independent event.
In these cases, most of the genetic material generated by the whole genome duplication is subsequently lost but a part of it contributes to that species’ evolution. That’s because some gene copies mutate and assume new functions. For example, genes of the type called Hox were found, which are very important in the development of animals’ body structure and in spiders their copies show differences in their expression.
Further studies on the evolution of spiders and scorpions following various gene mutations will help to understand these arachnids’ diversification. This kind of genetic research can help better understand various genetic mechanisms that follow a whole genome duplication, even in other phyla. In the past, this also happened in vertebrates, so the study of these mechanisms also means understanding key events in the evolution of humans’ ancestors.