Antennal morphology as a physical filter of olfaction: temporal tuning of the antennae of the honeybee, Apis mellifera.

There are many different antennal morphologies for insects, yet they all have the same functional role in olfaction. Chemical signals are dispersed through two physical forces; diffusion and fluid flow. The interaction between antennal morphology and fluid flow generates a region of changing flow velocity called the boundary layer. The boundary layer determines signal dispersion dynamics and therefore influences the signal structure and information that arrives at the receptor cells. To investigate how the boundary layer changes the information in the signals arriving at receptor cells, we measured chemical dynamics within the boundary layer around the bee antennae using microelectrodes. We used two types of chemical signals: pulsed and continuous. The results showed that the boundary layer increased the decay time of the chemical signal for the pulsatile stimuli and increased the peak height for the continuous data. Spectral analysis of continuous signals showed that the temporal aspects of the chemical signal are changed by the boundary layer. Particularly the temporal dynamics of the signal are dampened at the slowest flow speed and amplified at the intermediate and fast flow speeds. By altering the structure of the chemical signal, the morphology will function as a sensory filter.