Wednesday, 8 February 2012

The Ancient Song Of The Cricket

Crickets are some of the noisiest arthropods on Earth. Their nature as a global species means that their raspy calls, created by rubbing serrated sections on their front legs together, are heard over the grasslands on nearly all continents from the Americas, Europe to Asia. They are used to attract mates and communicate across vast distances. Yet 'calls' don't really do the Cricket justice. As each individual 'chirp' is part of a very complex and beautiful song.

Scientists from the University of Bristol, believe they have reconstructed the oldest cricket song on Earth. Palaeontologists, excavating a fossil bearing formation in North West China, discovered a series of 165 million year old fossil crickets of the species Archaboilus musicus. The team, led by Jun-Jie Gu and Professor Dong Ren from the Capital Normal University in Beijing, contacted Dr Fernando Montealegre-Zapata and Professor Daniel Robert from Bristol's School of Biological Sciences.

The remarkable 165 million year old grasshopper fossils and
diagrams indicating the location of the serrated structure
On examining the serrated sections on the arms and comparing these to 59 other species of cricket (all living), they concluded that it could have produced very pure frequencies of around 6.4 kHz in 16 millisecond bursts. 'This discovery indicates that pure tone communication was already exploited by animals in the middle Jurassic, some 165 million years ago.' said Professor Roberts.
A close up of the serrated structures

The louder and clearer the song, the more likely the caller is to attract a mate. Cricket songs are adapted to their various environments and it seems that this species is no different. 'Using a low-pitched song, Archaboilus musicus was acoustically adapted to long-distance communication in a lightly cluttered environment, such as a Jurassic forest' added Dr Montealegre-Zapata.

Most species of cricket are nocturnal and therefore such an ability would have been very useful for creatures living in the dark forests of the Jurassic Earth. Due to the fact that animals had to adapt to be able to detect the supersonic frequencies, the discovery has shed light upon the auditory capacity of other Jurassic animals and on the ambience of a long extinct world.

It is also likely that they evolved this ability 'for avoiding an increasingly relevant echolocating predator, but that only happened 100 million years later, possibly with the appearance of bats,' Dr Montealegre-Zapata added. It is studies such as these which reveal the fundamental connections which underpin the ecology of ecosystems, both marine and terrestrial, right back through time to the origins of life itself.