Mechanism of object identification by means of detecting polarised light

The researchers have studied polarisation vision in horseflies; their findings are of fundamental importance for understanding animal vision, developmental biology of the nervous system, will serve in the fight against insect disease vectors, and also in the design of advanced systems for machine vision. 

Authors: Andrej Meglič, Primož Pirih, Aleš Škorjanc, Marko Kreft, Gregor Belušič, Marko Ilićan, Martin F. Wehling

The eyes of insects are composed of a random mosaic of two or more types of optical units or ommatidia. Some contain light-sensitive cells that detect polarised light, but their functional integration in the visual system has thus far not been explained.

Female horseflies are an excellent research model, since they seek their victims by detecting polarised reflections from the animal fur. For this reason the researchers from the Biotechnical Faculty of the University of Ljubljana (Andrej Meglič, Primož Pirih, Aleš Škorjanc, Marko Kreft, Gregor Belušič), the University Sokendai in Japan (Marko Ilić) and the Air Force Research Laboratory (AFRL) in the USA (Martin F. Wehling) studied the vision of horseflies using a combination of physiological, anatomical, photometric and behavioural methods.

They found that the horsefly retina contains two types of ommatidia, which separately analyse colour and polarisation of light. They discovered a functional specialisation of ommatidial types which goes beyond colour vision and is very likely a common feature of the eyes of numerous insects. Additionally, they explained why horseflies are drawn to shiny, and also to blue objects.

Understanding of the composition and function of retinal mosaic represents an important advance in the area of visual and developmental neurobiology. Knowing the mechanism will help in controlling biting flies that carry disease. The eyes of horseflies also represent a biological blueprint for a miniature hybrid image sensor, which will inspire the design of advanced systems for machine vision in autonomous vehicles.

Source: Meglič A., Ilić M., Pirih P., Škorjanc A., Wehling M. F., Kreft M., Belušič G. Horsefly object-directed polarotaxis is mediated by a stochastically distributed ommatidial subtype in the ventral retina. Proc. Natl. Acad. Sci. USA, 116 (2019), 21843-21853.

Image source: Meglič A., Ilić M., Pirih P., Škorjanc A., Wehling M. F., Kreft M., Belušič G. Horsefly object-directed polarotaxis is mediated by a stochastically distributed ommatidial subtype in the ventral retina. Proc. Natl. Acad. Sci. USA, 116 (2019), 21843-21853