My research investigates the biophysical mechanisms used by organisms to sense their environment.

Using insects as model systems, my research contributes to understanding the foundations of hearing and electroreception. These senses are investigated at multiple levels, from the molecular basis of mechanoreception to the psychophysics of auditory behaviour. My research has unveiled a novel mechanism of directional sound detection used by a small parasitoid fly. Studying mosquitoes we discovered that the mosquito auditory system -its antennae- is sensitive to nanometre-range vibrations. This result led to the discovery that mosquitoes and fruitflies are endowed with active auditory mechanics. Much like the ears of mammals, these auditory systems use the motility of their mechanoreceptive cells, ciliated neurones in insects, to enhance their mechanical sensitivity and frequency selectivity (eg. Goepfert et al 2003 PNAS, Jackson&Robert 2006 PNAS). We have recently shown that in tree crickets, nonlinear active mechanisms rely on the action of a critical oscillator to generate frequency-selective signal amplification (Mhatre&Robert 2013, Current Biology).

Our research also showed that frequency selectivity in the locust is possible through the anisotropic characteristics of its eardrum. Phenomenologically, we demonstrated the build up of a travelling wave which is frequency-dependent, analogous to a propagating nanoscale tsunami. The travelling wave results in the spatial dispersion of frequencies as well as energy localisation. The physical mechanism was shown to rely on membrane mass distribution and tension alone, a mechanism likely to be useful for the bio-inspired design of sensitive analytical microphones (Malkin et al 2013, Royal Society Interface). The microscale ears of insects can be sophisticated; we showed that those of the Amazonian Copiphora bushcricket exhibit the three canonical steps of mammalian hearing, including pressure reception, impedance conversion and frequency selectivity (Montealegre-Z et al 2012 Science). This research established that it is possible to perform these biophysical tasks using microscale auditory organs. 

We have recently discovered that bumble bees can detect floral electric fields and learn their presence and structure to inform foraging decisions (Clarke et al. 2013. Science). My research team could demonstrate that bumblebees can be trained to distinguish between experimental feeding stations (simulating flowers) that are at different electrostatic potentials. In brief, the main findings are: 1. Flowers are surrounded by weak electrostatic fields arising by interaction with the natural atmospheric potential gradient. 2. Bees can detect the presence of these fields. 3. Floral electrostatic potential changes as bees approach and visit the flower. 4. Bees can learn differences in magnitude and structure of floral electrostatic fields. Remarkably, further experiments demonstrated that bees learn more readily the difference between two shades of green when electrostatic fields are present. This discovery leads to the conclusion that weak electrostatic potentials constitute a previously unsuspected form of information that plays a role in the complex interaction between plants and their pollinators.