Research Projects

Abstract

The overall aim of this project is to identify the visual and magnetic sensory mechanisms and cues, and establish their role in orientation and navigation in dim-light conditions. This will significantly advance our understanding of the sensory and navigational capabilities of nocturnal moths and enable the development of novel light-traps to mitigate crop damage due to pests. Additionally, the potential localization of the magnetic-sense in moths will open new research lines in ecology, physiology, and neurobiology of insects.

This project builds upon the recent discovery of sensitivity of nocturnal moths to a specific property of light, namely its polarization—the orientation of the light-wave oscillations with respect to its propagation direction. This finding is currently confined to a single species (Ostrinia nubilalis) and is yet to be validated with behavioural tests. Additionally, sensitivity to polarized light should be examined in other nocturnal species to see whether this sensory modality is shared among moths and butterflies. The research will focus on moth species Autographa gamma, O. nubilalis, Spodoptera littoralis and on butterflies Vanessa cardui and Danaus plexippus. However, the methodology developed during this project can be applied to any insect species.

Insect night vision has been severely understudied, in part due to the technical difficulty of the experiments. Night-active insects, including moths, possess compound eyes with superposition optics. This is a special optical design, independently evolved in many arthropod groups, which overcomes the limitations of small-lensed compound eyes by creating multi-faceted lens assemblages that focus light on the retina across a transparent clear zone. Integrated studies have revealed that sphingid moths can detect colours in dim-light conditions (i.e. starlight) where human colour vision fails. Moreover, a recent study indicates that moths are highly sensitive to polarized light. The PS receptors are located both in the DRA and in the ventral eye region. Those in the DRA are presumably dedicated to skylight-based navigation. However, no physiological or behavioural studies exist on the function and capabilities of the moth DRA. The rest of the retina contains a highly ordered array of a smaller class of photoreceptors with very high PS and possibly mediates ventral polarization vision (VPV).

The functional role of VPV in moths is currently completely unknown and might support polarization-based navigation or object detection. However, the retinal substrate for VPV in moths consists of photoreceptors with a single orientation that are exclusively sensitive to vertically polarized light. Such arrangement is not suitable for a proper analysis of linearly polarized light and alternative roles can be attributed to VPV. Specifically, the unidirectional photoreceptor orientation in the VPV seems ideal for harbouring magnetoreceptor molecules. The Earth’s magnetic field is a weak signal, but the multiple, spatially arranged sensors in the VPV might sum and average these weak signals, bringing them above detection threshold.

Researchers

• link to Sicris
  
   

The phases of the project and their realization

1. Identification of the retinal substrate for colour and polarization vision

1.1 Anatomical characterisation of the retinal photoreceptros

1.2 Electrophysiological characterization of the photoreceptors

1.3 Mapping between the anatomical and physiological characterisation and linking them to the to the sensory cues.

2. Develop the experimental setup for studying magnetoreception coupled to multimodal visual stimulation protocol (instensity, spectral, polarization cues).

3. Testing the magnetic sensitivity of the retinal substrate by exposing the PS photoreceptors to localized magnetic fields of varying intensity and studying the interaction between polarized light and magnetic field in electrophysiological experiments

 Citations for bibliographic records

• https://bib.cobiss.net/bibliographies/si/webBiblio/bib201_20221206_112015_54920.htmllink