Planthopper bugs may be small, but they attract mates from afar by sending vibrational calls along plant stems and leaves
A study carried out by zoologists with help from researchers in the Department of Engineering Science highlights how small animals can communicate at a distance despite the constraints of small body size.
Producing vibrations that will travel well along plant material requires the sudden release of mechanical energy – many times faster than could be achieved through direct action of the planthoppers’ tiny muscles.
The secret lies in the fast release of stored elastic energy, rather like a catapult, but with the key difference that the stored energy is released cyclically, leading to a repetitive up-down motion of the abdomen. This is accomplished by a complex anatomical structure that the researchers call the “snapping organ”, because of the speed with which it snaps open and closed.
The discovery of the new organ was as unexpected as its mechanism. Lead author from the Department of Zoology, Leonidas-Romanos Davranoglou, said: "I was studying 3D images of planthoppers that I had collected using X-ray imaging in a particle accelerator, trying to understand the evolutionary relationships between different groups. But as I dissected the bugs in virtual reality on my computer, I immediately realised that I was looking at something entirely new, so decided to investigate further".
Researchers collected hundreds of live planthoppers from the hills around Athens, which they brought back to their Oxford lab to conduct experiments. To understand the vibration generation mechanism of the new snapping organ, they used microtomography, laser vibrometry, confocal microscopy, and high-speed video recordings.
The scientists then teamed up with the Dynamics, Vibration and Uncertainty Lab, led by Dr Alice Cicirello at the Department of Engineering Science, to understand the vibration generation mechanism and to build a mathematical model of it. The vibratory organ was found to be present in all of the many different families of planthoppers, showing that this entire group of bugs are specialists in this unusual form of communication.
The combination of our skillsets was the key to achieve these new insights
Dr Alice Cicirello says: "It was very fascinating to uncover this mechanism. In order to understand the parts of the snapping organ involved in the vibration generation and the different phases during one cycle of vibration, we looked together at the vibration data recorded, X-ray images, and high-speed video recordings, and we discussed the elements that needed to be included in the mathematical model. The combination of our skillsets was the key to achieve these new insights”.
Main Image: Planthoppers (Agalmatium bilobum). Credit: L.-R. Davranoglou