Monday, 10 October 2011

A New Living Fossil - A Living Species Of Beetle Preserved in Ancient Sediments

An image of a living specimen of Helophorus sibericus (top left)
and the 20 million year old fossils from the  Irtysh River, Siberia
The water scavenger beetle Helophorus sibericus is well known throughout Eurasia with small populations even existing as far afield as North America. It was described by the Russian entomologist Victor Motschulsky from specimens collected at Lake Baikal, Siberia. It lives in marshes and pools of standing water. Not much is known about its early life, but scientists believe that they have a larval stage which is terrestrial and preys upon small invertebrates.

Based upon genetic and fossil evidence, it is thought that it has a temporal range of around two to three million years old. Fossils discovered in the sediments of the Irtysh River, which is also in Siberia, have shown that this insect is far older and  sheds light upon the temporal range of arthropods. The fossils themselves were well preserved and easily identifiable due to the distinctive pits that cover the abdomen. The interesting thing is that they dated to around 20 million years old.

This shows that the species is more than 17 million years older than previously thought. It is a popular theory that many of the arthropod species in North America and North Eurasia all originated during or after the last great ice age. This shows two things. The first is that scientists have greatly oversimplified the problem of the effects of climate change on evolution, especially in arthropods. The second is that Helophorus sibericus lives in an extremely stable environment.

It could have easily lived in puddles of melt water from the winter snow and simply become locked in stasis during the colder half of the year. Insects are some of the most succesful animal groups on Earth. Since they first appeared, their body design has barely changed apart from in size simply because they are perfectly evolved to every habitat in which they live. Their armour can be sculpted into an infinite variety of forms and this, coupled with an incredible natural hardiness has made them the true lords of the planet.